Add support for Python 3.8.7

Closes @W-7791264@.

.dockerignore

@@ -0,0 +1 @@
+.git/

.git2gus/config.json

@@ -0,0 +1,6 @@
+{
+  "productTag": "a1aB0000000MR0RIAW",
+  "issueTypeLabels": { "gus: story": "USER STORY", "gus: bug": "BUG P3" },
+  "defaultBuild": "Heroku Unscheduled",
+  "statusWhenClosed": "CLOSED"
+}

.github/CODEOWNERS

@@ -0,0 +1 @@
+* @heroku/languages

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,8 @@
+<!-- Hi and welcome to the Heroku Python buildpack repository!
+
+If you meant to open a PR against a fork instead of upstream, please adjust the base branch:
+https://help.github.com/articles/changing-the-base-branch-of-a-pull-request/
+
+Otherwise thank you in advance for your Pull Request - just remember to
+include as much information as possible to help the reviewers :-)
+-->

.github/dependabot.yml

@@ -0,0 +1,15 @@
+version: 2
+updates:
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    labels:
+      - "c: dependencies"
+
+  - package-ecosystem: "bundler"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    labels:
+      - "c: dependencies"

.github/workflows/check_changelog.yml

@@ -0,0 +1,17 @@
+name: Check Changelog
+
+on:
+  pull_request:
+    types: [opened, reopened, edited, synchronize]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    if: |
+      !contains(github.event.pull_request.body, '[skip changelog]') &&
+      !contains(github.event.pull_request.body, '[changelog skip]') &&
+      !contains(github.event.pull_request.body, '[skip ci]')
+    steps:
+      - uses: actions/checkout@v1
+      - name: Check that CHANGELOG is touched
+        run: git diff remotes/origin/${{ github.base_ref }} --name-only | grep CHANGELOG.md

.gitignore

@@ -1,2 +1,14 @@
 *.pyc
 site
+.DS_Store
+
+/.envrc
+repos/*
+
+#Venv
+buildpack/*
+
+builds/dockerenv.staging*
+builds/dockerenv.production
+
+test/scratch

.travis.yml

@@ -1,2 +1,41 @@
-sudo: false
+language: minimal
-script: exit 0
+dist: focal
+branches:
+  only:
+  - main
+
+script:
+  - make test STACK="${STACK}" TEST_CMD="${TEST_CMD}"
+
+jobs:
+  include:
+  - name: Bash linting (shellcheck)
+    script: make check
+  - name: Hatchet integration tests
+    if: env(HEROKU_API_USER) IS present AND env(HEROKU_API_KEY) IS present
+    language: ruby
+    rvm:
+      - 2.7
+    before_script:
+      - bundle exec hatchet ci:setup
+    script:
+      - PARALLEL_SPLIT_TEST_PROCESSES=11 bundle exec parallel_split_test spec/hatchet/
+
+env:
+  jobs:
+    - STACK=heroku-16 TEST_CMD=test/run-deps
+    - STACK=heroku-16 TEST_CMD=test/run-versions
+    - STACK=heroku-16 TEST_CMD=test/run-features
+
+    - STACK=heroku-18 TEST_CMD=test/run-deps
+    - STACK=heroku-18 TEST_CMD=test/run-versions
+    - STACK=heroku-18 TEST_CMD=test/run-features
+
+    - STACK=heroku-20 TEST_CMD=test/run-deps
+    - STACK=heroku-20 TEST_CMD=test/run-versions
+    - STACK=heroku-20 TEST_CMD=test/run-features
+  global:
+    - HATCHET_RETRIES=3
+    - IS_RUNNING_ON_CI=true
+    - HATCHET_APP_LIMIT=80
+    - HATCHET_DEPLOY_STRATEGY=git

CHANGELOG.md

@@ -1,5 +1,510 @@
 # Python Buildpack Changelog
 
+## Unreleased
+
+- Python 3.8.7 is now available (CPython) (#1122).
+
+## v186 (2020-11-18)
+
+- Update the `BUILD_WITH_GEO_LIBRARIES` error message (#1121).
+- Switch NLTK feature detection away from `sp-grep` (#1119).
+- Switch Django collectstatic feature detection away from `sp-grep` (#1119).
+- Remove vendored `sp-grep` script (#1119).
+- Remove vendored `pip-diff` script (#1118).
+- Remove vendored `pip-grep` script (#1116).
+
+## v185 (2020-11-12)
+
+- Error if the unsupported `BUILD_WITH_GEO_LIBRARIES` env var is set (#1115).
+- Remove deprecated GDAL/GEOS/PROJ support (#1113).
+- Remove vendored `jq` binary (#1112).
+- Remove redundant Mercurial install step (#1111).
+- Remove support for the Cedar-14 stack (#1110).
+
+## v184 (2020-10-21)
+
+- Vendor buildpack-stdlib instead of fetching from S3 (#1100).
+- Fix metric names for metrics emitted within `sub_env` (#1099).
+
+## v183 (2020-10-12)
+
+- Add support for Heroku-20 (#968).
+
+## v182 (2020-10-06)
+
+- Python 3.9.0 is now available (CPython) (#1090).
+- Migrate from the `lang-python` S3 bucket to `heroku-buildpack-python` (#1089).
+- Remove `vendor/shunit2` (#1086).
+- Replace `BUILDPACK_VENDOR_URL` and `USE_STAGING_BINARIES` with `BUILDPACK_S3_BASE_URL` (#1085).
+
+## v181 (2020-09-29)
+
+- PyPy 2.7 and 3.6, version 7.3.2 are now available (Note: PyPy support is in beta) (#1081).
+
+## v180 (2020-09-24)
+
+- Python 3.8.6 is now available (CPython) (#1072).
+
+## v179 (2020-09-23)
+
+- Remove duplicate pipenv metric event (#1070).
+- Emit metrics for how the Python version was chosen for an app (#1069).
+- Emit Python version metric events for all builds, not just clean installs (#1066).
+
+## v178 (2020-09-07)
+
+- Python 3.5.10 is now available (CPython) (#1062).
+
+## v177 (2020-08-18)
+
+- Python 3.6.12 and 3.7.9 are now available (CPython) (#1054).
+- The default Python version for new apps is now 3.6.12 (previously 3.6.11) (#1054).
+
+## v176 (2020-08-12)
+
+- Rebuild the Python 3.4.10 archives with the correct version of Python (#1048).
+- Fix the security update version check message for apps using PyPy (#1040).
+- Remove `vendor/test-utils` (#1043).
+
+## v175 (2020-08-05)
+
+- Update pip from 20.0.2 to 20.1.1 for Python 2.7 and Python 3.5+ (#1030).
+- Update setuptools from 39.0.1 to: (#1024)
+  - 44.1.1 for Python 2.7
+  - 43.0.0 for Python 3.4
+  - 47.1.1 for Python 3.5+
+- Switch the `heroku-buildpack-python` repository default branch from `master` to `main` (#1029).
+
+## v174 (2020-07-30)
+
+- For repeat builds, also manage the installed versions of setuptools/wheel, rather than just that of pip (#1007).
+- Install an explicit version of wheel rather than the latest release at the time (#1007).
+- Output the installed version of pip, setuptools and wheel in the build log (#1007).
+- Errors installing pip/setuptools/wheel are now displayed in the build output and fail the build early (#1007).
+- Install pip using itself rather than `get-pip.py` (#1007).
+- Disable pip's version check + cache when installing pip/setuptools/wheel (#1007).
+- Install setuptools from PyPI rather than a vendored copy (#1007).
+- Reduce the number of environment variables exposed to `bin/{pre,post}_compile` and other subprocesses (#1011).
+
+## v173 (2020-07-21)
+
+- Python 3.8.5 is now available (CPython).
+
+## v172 (2020-07-17)
+
+- Python 3.8.4 is now available (CPython).
+
+## v171 (2020-07-07)
+
+- Python 3.6.11 and 3.7.8 are now available (CPython).
+
+## v170 (2020-05-19)
+
+- Python 2.7.18, 3.5.9, 3.7.7 and 3.8.3 are now available (CPython).
+- PyPy 2.7 and 3.6, version 7.3.1 are now available (Note: PyPy support is in beta).
+- Docs: Fix explanation of runtime.txt generation when using pipenv.
+- Bugfix: Correctly detect Python version when using a `python_version` of `3.8` in `Pipfile.lock`.
+
+## v169 (2020-04-22)
+
+- Add a Hatchet test for python 3.8.2
+- Set Code Owners to @heroku/langauges
+- Bugfix: Caching on subsequent redeploys
+- Update tests to support latest version of Python
+
+## v168 (2020-04-06)
+
+- Doc: Update Readme with version numbers
+- update Code Owners to include the Heroku Buildpack Maintainers team
+- Deprecation warning: `BUILD_WITH_GEO_LIBRARIES` is now deprecated. See warning for details.
+- Clean up build log output
+- Update Python versions in README to match docs
+- Django version detection fixed, link updated
+
+## v167 (2020-03-26)
+
+- Add failcase for cache busting
+- Bugfix: Clearing pip dependencies
+
+## v166 (2020-03-05)
+
+- Correct ftp to https in vendored file
+- Warn for Django 1.11 approaching EOL, provide link to roadmap
+
+## v165 (2020-02-27)
+
+- Python 3.8.2 now available.
+
+## v164 (2020-02-20)
+
+- Update requirements.txt builds to use Pip 20.0.2
+- Download get-pip.py to tmpdir instead of root dir
+
+## v163 (2019-12-23)
+
+- New pythons released:
+  Python 3.8.1, 3.7.6, 3.6.10 (CPython)
+  Beta Release: Pypy 2.7 and 3.6, version 7.2.0
+
+## v162 (2019-12-06)
+
+- Bug fix: fragile sqlite3 install
+
+## v161 (2019-12-2)
+
+- Bug fix: Sqlite3 version bump
+
+## v160 (2019-10-23)
+
+- Bugfix: Pipenv no longer installs twice in CI
+
+## v159 (2019-10-22)
+
+- Python 2.7.17 now available on Heroku 18 and 16.
+
+## v158 (2019-10-21)
+
+- Python 3.7.5 and 3.8.0 now available on Heroku 18 and 16.
+- Add support for Python 3.8 branch
+- Sqlite3 Update:
+  - Test Improvements
+- Add support for staging binary testing
+
+## v157 (2019-09-18)
+
+- Typo fixes
+
+## v156 (2019-09-12)
+
+- Python 3.6.9 and 3.7.4 now available.
+
+- Move get-pip utility to S3
+- Build utility and documentation updates
+- Bump Hatchet tests to point at new default python version.
+
+## v155 (2019-08-22)
+
+add docs and make target for heroku-18 bob builds
+
+## v154 (2019-07-17)
+
+Fix python 3.5.7 formula actually building 3.7.2
+
+## v153 (2019-06-21)
+
+Hotfix for broken heroku-16 deploys
+
+## v152 (2019-04-04)
+
+Python 3.7.3 now available.
+
+## v151 (2019-03-21)
+
+Python 3.5.7 and 3.4.10 now available on all Heroku stacks.
+
+## v150 (2019-03-13)
+
+Python 2.7.16 now available on all Heroku stacks.
+
+## v149 (2019-03-04)
+
+Hotfix for broken Cedar 14 deploys
+
+## v148 (2019-02-21)
+
+No user facing changes, improving internal metrics
+
+## v147 (2019-02-07)
+
+Python 3.7.2 and 3.6.8 now available on all Heroku stacks.
+
+## v146 (2018-11-11)
+
+Python 3.7.1, 3.6.7, 3.5.6 and 3.4.9 now available on all Heroku stacks.
+
+## v145 (2018-11-08)
+
+Testing and tooling expanded to better support new runtimes
+
+## v144 (2018-10-10)
+
+Switch to cautious upgrade for Pipenv install to ensure the pinned pip version
+is used with Pipenv
+
+## v143 (2018-10-09)
+
+Add support for detecting `SLUGIFY_USES_TEXT_UNIDECODE`, which is required to
+install Apache Airflow version 1.10 or higher.
+
+## v142 (2018-10-08)
+
+Improvements to Python install messaging
+
+## v139, 140, 141
+
+No user-facing changes, documenting for version clarity
+
+## v138 (2018-08-01)
+
+Use stack image SQLite3 instead of vendoring
+
+## v137 (2018-07-17)
+
+Prevent 3.7.0 from appearing as unsupported in buildpack messaging.
+
+## v136 (2018-06-28)
+
+Upgrade to 3.6.6 and support 3.7.0 on all runtimes.
+
+## v135 (2018-05-29)
+
+Upgrade Pipenv to v2018.5.18.
+
+## v134 (2018-05-02)
+
+Default to 3.6.5, bugfixes.
+
+## v133
+
+Fixes for Pip 10 release.
+
+## v132
+
+Improve pip installation, with the release of v9.0.2.
+
+## v131
+
+Fix bug with pip.
+
+## v130
+
+Better upgrade strategy for pip.
+
+## v129
+
+Don't upgrade pip (from v128).
+
+## v128
+
+Upgrade pip, pin to Pipenv v11.8.2.
+
+## v127
+
+Pin to Pipenv v11.7.1.
+
+## v126
+
+Bugfixes.
+
+## v125
+
+Bugfixes.
+
+## v124
+
+Update buildpack to automatically install `[dev-packages]` during Heroku CI Pipenv builds.
+
+- Skip installs if Pipfile.lock hasn't changed, and uninstall stale dependencies with Pipenv.
+- Set `PYTHONPATH` during collectstatic runs.
+- No longer warn if there is no `Procfile`.
+- Update Pipenv's "3.6" runtime specifier to point to "3.6.4".
+
+## v123
+
+Update gunicorn `init.d` script to allow overrides.
+
+## v122
+
+Update default Python to v3.6.4.
+
+## v121
+
+Update default Python to v3.6.3.
+
+## v120
+
+Use `$ pipenv --deploy`.
+
+## v119
+
+Improvements to Pipenv support, warning on unsupported Python versions.
+
+- We now warn when a user is not using latest 2.x or 3.x Python.
+- Heroku now supports `[requires]` `python_full_version` in addition to `python_version`.
+
+## v118
+
+Improvements to Pipenv support.
+
+## v117
+
+Bug fix.
+
+## v116
+
+Vendoring improvements.
+
+- Geos libraries should work on Heroku-16 now.
+- The libffi/libmemcached vendoring step is now skipped on Heroku-16 (since they are installed in the base image).
+
+## v115
+
+Revert a pull request.
+
+- No longer using `sub_env` for `pip install` step.
+
+## v114
+
+- Bugfixes.
+
+Blacklisting `PYTHONHOME` and `PYTHONPATH` for older apps. Upgrades to nltk support.
+
+## v113
+
+Updates to Pipenv support.
+
+## v112
+
+Bugfix.
+
+- Fixed grep output bug.
+
+## v111
+
+Linting, bugfixes.
+
+## v110
+
+Update default Python to 3.6.2.
+
+## v109
+
+Update Default Python to 3.6.1, bugfixes.
+
+- Fixed automatic pip uninstall of dependencies removed from requirements.txt.
+
+## v108
+
+Fix output for collectstatic step.
+
+## v107
+
+Bugfix for C dependency installation.
+
+## v106
+
+Don't install packages that could mess up packaging.
+
+ - The Python buildpack will automatically remove `six`, `pyparsing`, `appdirs`,
+   `setuptools`, and `distribute` from a `requirements.txt` file now, as these
+   packages are provided by the Python buildpack.
+
+## v105
+
+Improvements to output messaging.
+
+## v104
+
+General improvements.
+
+- Fix for Heroku CI.
+- Use `pkg_resources` to check if a distribution is installed instead of
+  parsing `requirements.txt`. ([#395][395])
+
+[395]: https://github.com/heroku/heroku-buildpack-python/pull/395
+
+## v103
+
+Bug fixes and improvements.
+
+- Fix for Pipenv.
+- Fix for Heroku CI.
+- Improve handling of `WEB_CONCURRENCY` when using multiple buildpacks.
+- Adjust environment variables set during the build to more closely match those in the dyno environment (`DYNO` is now available, `STACK` is not).
+- Restore the build cache prior to running bin/pre_compile.
+
+## v102
+
+Buildpack code cleanup.
+
+- Improved messaging around NLTK.
+
+## v101
+
+Updated setuptools installation method.
+
+- Improved pipenv support.
+
+## v100
+
+Preliminary pipenv support.
+
+## v99
+
+Cleanup.
+
+## v98
+
+Official NLTK support and other improvements.
+
+- Support for `nltk.txt` file for declaring corpora to be downloaded.
+- Leading zeros for auto-set `WEB_CONCURRENCY`.
+
+## v97
+
+Improved egg-link functionality.
+
+## v96
+
+Bugfix.
+
+## v95
+
+Improved output support.
+
+## v94
+
+Improved support for PyPy.
+
+## v93
+
+Improved support for PyPy.
+
+## v92
+
+Improved cache functionality and fix egg-links regression.
+
+## v91
+
+Bugfix, rolled back to v88.
+
+## v90
+
+Bugfix.
+
+## v89
+
+Improved cache functionality and fix egg-links regression.
+
+## v88
+
+Fixed bug with editable pip installations.
+
+## v87
+
+Updated default Python 2.7.13.
+
+- Python 2.7.13 uses UCS-4 build, more compatible with linux wheels.
+- Updated setuptools to v32.1.0.
+
+## v86
+
+Refactor and multi-buildpack compatibility.
+
+## v85
+
+Packaging fix.
+
 ## v84
 
 Updated pip and setuptools.
@@ -15,7 +520,7 @@ Support for Heroku CI.
 
 ## v82 (2016-08-22)
 
-Update to library detection mechnisms (pip-pop).
+Update to library detection mechanisms (pip-pop).
 
 - Updated setuptools to v25.5.0
 
@@ -23,8 +528,8 @@ Update to library detection mechnisms (pip-pop).
 
 Updated default Python to 2.7.11.
 
-- Updated setuptools to v8.1.2.
+- Updated pip to v8.1.2.
-- Updated pip to v23.1.0.
+- Updated setuptools to v23.1.0.
 
 ## v80 (2016-04-05)
 
@@ -89,7 +594,7 @@ Revert to v66.
 
 ## v68 (2015-10-12)
 
-Fixed .heroku/venv error with modern apps.
+Fixed `.heroku/venv` error with modern apps.
 
 ## v67 (2015-10-12)
 
@@ -114,7 +619,6 @@ Updated Pip and Setuptools.
 - Setuptools updated to v18.3.2
 - Pip updated to v7.1.2
 
-
 ## v62 (2015-08-07)
 
 Updated Pip and Setuptools.

Gemfile

@@ -0,0 +1,8 @@
+source "https://rubygems.org"
+
+gem "rspec"
+gem "heroku_hatchet"
+gem "rspec-retry"
+gem "rake"
+gem "parallel_split_test"
+

Gemfile.lock

@@ -0,0 +1,60 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    diff-lcs (1.4.4)
+    erubis (2.7.0)
+    excon (0.78.0)
+    heroics (0.1.1)
+      erubis (~> 2.0)
+      excon
+      moneta
+      multi_json (>= 1.9.2)
+    heroku_hatchet (7.3.3)
+      excon (~> 0)
+      platform-api (~> 3)
+      rrrretry (~> 1)
+      thor (~> 1)
+      threaded (~> 0)
+    moneta (1.0.0)
+    multi_json (1.15.0)
+    parallel (1.19.2)
+    parallel_split_test (0.8.0)
+      parallel (>= 0.5.13)
+      rspec (>= 3.1.0)
+    platform-api (3.0.0)
+      heroics (~> 0.1.1)
+      moneta (~> 1.0.0)
+      rate_throttle_client (~> 0.1.0)
+    rake (13.0.1)
+    rate_throttle_client (0.1.2)
+    rrrretry (1.0.0)
+    rspec (3.10.0)
+      rspec-core (~> 3.10.0)
+      rspec-expectations (~> 3.10.0)
+      rspec-mocks (~> 3.10.0)
+    rspec-core (3.10.0)
+      rspec-support (~> 3.10.0)
+    rspec-expectations (3.10.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.10.0)
+    rspec-mocks (3.10.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.10.0)
+    rspec-retry (0.6.2)
+      rspec-core (> 3.3)
+    rspec-support (3.10.0)
+    thor (1.0.1)
+    threaded (0.0.4)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  heroku_hatchet
+  parallel_split_test
+  rake
+  rspec
+  rspec-retry
+
+BUNDLED WITH
+   2.1.4

LICENSE

@@ -1,6 +1,6 @@
 MIT License:
 
-Copyright (C) 2016 Heroku, Inc.
+Copyright (C) 2017 Heroku, Inc.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 

Makefile

@@ -1,10 +1,61 @@
 # These targets are not files
-.PHONY: tests
+.PHONY: check test compile builder-image buildenv deploy-runtimes tools
 
-tests:
+STACK ?= heroku-18
-	./bin/test
+STACKS ?= heroku-16 heroku-18 heroku-20
+TEST_CMD ?= test/run-versions && test/run-features && test/run-deps
+FIXTURE ?= test/fixtures/requirements-standard
+ENV_FILE ?= builds/dockerenv.default
+BUILDER_IMAGE_PREFIX := heroku-python-build
 
-tools:
+# Converts a stack name of `heroku-NN` to its build Docker image tag of `heroku/heroku:NN-build`.
-	git clone https://github.com/kennethreitz/pip-pop.git
+STACK_IMAGE_TAG := heroku/$(subst -,:,$(STACK))-build
-	mv pip-pop/bin/* vendor/pip-pop/
+
-	rm -fr pip-pop
+check:
+	@shellcheck -x bin/compile bin/detect bin/release bin/test-compile bin/utils bin/warnings bin/default_pythons
+	@shellcheck -x bin/steps/collectstatic bin/steps/eggpath-fix  bin/steps/eggpath-fix2 bin/steps/nltk bin/steps/pip-install bin/steps/pipenv bin/steps/pipenv-python-version bin/steps/python
+	@shellcheck -x bin/steps/hooks/*
+
+test:
+	@echo "Running tests using: STACK=$(STACK) TEST_CMD='$(TEST_CMD)'"
+	@echo
+	@docker run --rm -it -v $(PWD):/buildpack:ro -e "STACK=$(STACK)" "$(STACK_IMAGE_TAG)" bash -c 'cp -r /buildpack /buildpack_test && cd /buildpack_test && $(TEST_CMD)'
+	@echo
+
+compile:
+	@echo "Running compile using: STACK=$(STACK) FIXTURE=$(FIXTURE)"
+	@echo
+	@docker run --rm -it -v $(PWD):/src:ro -e "STACK=$(STACK)" -w /buildpack "$(STACK_IMAGE_TAG)" \
+		bash -c 'cp -r /src/{bin,vendor} /buildpack && cp -r /src/$(FIXTURE) /build && mkdir /cache /env && bin/compile /build /cache /env'
+	@echo
+
+builder-image:
+	@echo "Generating binary builder image for $(STACK)..."
+	@echo
+	@docker build --pull -f builds/$(STACK).Dockerfile -t "$(BUILDER_IMAGE_PREFIX)-$(STACK)" .
+	@echo
+
+buildenv: builder-image
+	@echo "Starting build environment for $(STACK)..."
+	@echo
+	@echo "Usage..."
+	@echo
+	@echo "  $$ bob build runtimes/python-X.Y.Z"
+	@echo
+	@docker run --rm -it --env-file="$(ENV_FILE)" -v $(PWD)/builds:/app/builds "$(BUILDER_IMAGE_PREFIX)-$(STACK)" bash
+
+deploy-runtimes:
+ifndef RUNTIMES
+	$(error No runtimes specified! Use: "make deploy-runtimes RUNTIMES='python-X.Y.Z ...' [STACKS='heroku-18 ...'] [ENV_FILE=...]")
+endif
+	@echo "Using: RUNTIMES='$(RUNTIMES)' STACKS='$(STACKS)' ENV_FILE='$(ENV_FILE)'"
+	@echo
+	@set -eu; for stack in $(STACKS); do \
+		$(MAKE) builder-image STACK=$${stack}; \
+		for runtime in $(RUNTIMES); do \
+			echo "Generating/deploying $${runtime} for $${stack}..."; \
+			echo; \
+			docker run --rm -it --env-file="$(ENV_FILE)" "$(BUILDER_IMAGE_PREFIX)-$${stack}" bob deploy "runtimes/$${runtime}"; \
+			echo; \
+		done; \
+	done

NOTICE

@@ -0,0 +1,65 @@
+This buildpack includes some vendorized packages to ease installation.
+
+shunit2 license
+---------------
+
+Copyright © 2007 Free Software Foundation, Inc. <http://fsf.org/>
+
+Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
+
+This version of the GNU Lesser General Public License incorporates the terms and conditions of version 3 of the GNU General Public License, supplemented by the additional permissions listed below.
+
+0. Additional Definitions.
+
+As used herein, “this License” refers to version 3 of the GNU Lesser General Public License, and the “GNU GPL” refers to version 3 of the GNU General Public License.
+
+“The Library” refers to a covered work governed by this License, other than an Application or a Combined Work as defined below.
+
+An “Application” is any work that makes use of an interface provided by the Library, but which is not otherwise based on the Library. Defining a subclass of a class defined by the Library is deemed a mode of using an interface provided by the Library.
+
+A “Combined Work” is a work produced by combining or linking an Application with the Library. The particular version of the Library with which the Combined Work was made is also called the “Linked Version”.
+
+The “Minimal Corresponding Source” for a Combined Work means the Corresponding Source for the Combined Work, excluding any source code for portions of the Combined Work that, considered in isolation, are based on the Application, and not on the Linked Version.
+
+The “Corresponding Application Code” for a Combined Work means the object code and/or source code for the Application, including any data and utility programs needed for reproducing the Combined Work from the Application, but excluding the System Libraries of the Combined Work.
+
+1. Exception to Section 3 of the GNU GPL.
+
+You may convey a covered work under sections 3 and 4 of this License without being bound by section 3 of the GNU GPL.
+
+2. Conveying Modified Versions.
+
+If you modify a copy of the Library, and, in your modifications, a facility refers to a function or data to be supplied by an Application that uses the facility (other than as an argument passed when the facility is invoked), then you may convey a copy of the modified version:
+
+a) under this License, provided that you make a good faith effort to ensure that, in the event an Application does not supply the function or data, the facility still operates, and performs whatever part of its purpose remains meaningful, or
+b) under the GNU GPL, with none of the additional permissions of this License applicable to that copy.
+3. Object Code Incorporating Material from Library Header Files.
+
+The object code form of an Application may incorporate material from a header file that is part of the Library. You may convey such object code under terms of your choice, provided that, if the incorporated material is not limited to numerical parameters, data structure layouts and accessors, or small macros, inline functions and templates (ten or fewer lines in length), you do both of the following:
+
+a) Give prominent notice with each copy of the object code that the Library is used in it and that the Library and its use are covered by this License.
+b) Accompany the object code with a copy of the GNU GPL and this license document.
+4. Combined Works.
+
+You may convey a Combined Work under terms of your choice that, taken together, effectively do not restrict modification of the portions of the Library contained in the Combined Work and reverse engineering for debugging such modifications, if you also do each of the following:
+
+a) Give prominent notice with each copy of the Combined Work that the Library is used in it and that the Library and its use are covered by this License.
+b) Accompany the Combined Work with a copy of the GNU GPL and this license document.
+c) For a Combined Work that displays copyright notices during execution, include the copyright notice for the Library among these notices, as well as a reference directing the user to the copies of the GNU GPL and this license document.
+d) Do one of the following:
+0) Convey the Minimal Corresponding Source under the terms of this License, and the Corresponding Application Code in a form suitable for, and under terms that permit, the user to recombine or relink the Application with a modified version of the Linked Version to produce a modified Combined Work, in the manner specified by section 6 of the GNU GPL for conveying Corresponding Source.
+1) Use a suitable shared library mechanism for linking with the Library. A suitable mechanism is one that (a) uses at run time a copy of the Library already present on the user's computer system, and (b) will operate properly with a modified version of the Library that is interface-compatible with the Linked Version.
+e) Provide Installation Information, but only if you would otherwise be required to provide such information under section 6 of the GNU GPL, and only to the extent that such information is necessary to install and execute a modified version of the Combined Work produced by recombining or relinking the Application with a modified version of the Linked Version. (If you use option 4d0, the Installation Information must accompany the Minimal Corresponding Source and Corresponding Application Code. If you use option 4d1, you must provide the Installation Information in the manner specified by section 6 of the GNU GPL for conveying Corresponding Source.)
+5. Combined Libraries.
+
+You may place library facilities that are a work based on the Library side by side in a single library together with other library facilities that are not Applications and are not covered by this License, and convey such a combined library under terms of your choice, if you do both of the following:
+
+a) Accompany the combined library with a copy of the same work based on the Library, uncombined with any other library facilities, conveyed under the terms of this License.
+b) Give prominent notice with the combined library that part of it is a work based on the Library, and explaining where to find the accompanying uncombined form of the same work.
+6. Revised Versions of the GNU Lesser General Public License.
+
+The Free Software Foundation may publish revised and/or new versions of the GNU Lesser General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Library as you received it specifies that a certain numbered version of the GNU Lesser General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that published version or of any later version published by the Free Software Foundation. If the Library as you received it does not specify a version number of the GNU Lesser General Public License, you may choose any version of the GNU Lesser General Public License ever published by the Free Software Foundation.
+
+If the Library as you received it specifies that a proxy can decide whether future versions of the GNU Lesser General Public License shall apply, that proxy's public statement of acceptance of any version is permanent authorization for you to choose that version for the Library.

README.md

@@ -2,38 +2,57 @@
 
 # Heroku Buildpack: Python
 
-This is the official [Heroku buildpack](https://devcenter.heroku.com/articles/buildpacks) for Python apps, powered by [pip](https://pip.pypa.io/) and other excellent software.
+[![Build Status](https://travis-ci.com/heroku/heroku-buildpack-python.svg?branch=main)](https://travis-ci.com/heroku/heroku-buildpack-python)
 
-Recommended web frameworks include **Django** and **Flask**. The recommended webserver is **Gunicorn**. There are no restrictions around what software can be used (as long as it's pip-installable). Web processes must bind to `$PORT`, and only the HTTP protocol is permitted for incoming connections.
+This is the official [Heroku buildpack](https://devcenter.heroku.com/articles/buildpacks) for Python apps.
 
-Some Python packages with obscure C dependencies (e.g. scipy) are [not compatible](https://devcenter.heroku.com/articles/python-c-deps). 
+Recommended web frameworks include **Django** and **Flask**, among others. The recommended webserver is **Gunicorn**. There are no restrictions around what software can be used (as long as it's pip-installable). Web processes must bind to `$PORT`, and only the HTTP protocol is permitted for incoming connections.
+
+Python packages with C dependencies that are not [available on the stack image](https://devcenter.heroku.com/articles/stack-packages) are generally not supported, unless `manylinux` wheels are provided by the package maintainers (common). For recommended solutions, check out [this article](https://devcenter.heroku.com/articles/python-c-deps) for more information.
 
 See it in Action
 ----------------
-
+```
-Deploying a Python application couldn't be easier:
-
 $ ls
-    Procfile  requirements.txt  web.py
+my-application		requirements.txt	runtime.txt
 
-    $ heroku create --buildpack heroku/python
+$ git push heroku main
+Counting objects: 4, done.
+Delta compression using up to 8 threads.
+Compressing objects: 100% (2/2), done.
+Writing objects: 100% (4/4), 276 bytes | 276.00 KiB/s, done.
+Total 4 (delta 0), reused 0 (delta 0)
+remote: Compressing source files... done.
+remote: Building source:
+remote:
+remote: -----> Python app detected
+remote: -----> Installing python
+remote: -----> Installing pip
+remote: -----> Installing SQLite3
+remote: -----> Installing requirements with pip
+remote:        Collecting flask (from -r /tmp/build_c2c067ef79ff14c9bf1aed6796f9ed1f/requirements.txt (line 1))
+remote:          Downloading ...
+remote:        Installing collected packages: Werkzeug, click, MarkupSafe, Jinja2, itsdangerous, flask
+remote:        Successfully installed Jinja2-2.10 MarkupSafe-1.1.0 Werkzeug-0.14.1 click-7.0 flask-1.0.2 itsdangerous-1.1.0
+remote:
+remote: -----> Discovering process types
+remote:        Procfile declares types -> (none)
+remote:
+```
 
-    $ git push heroku master
+A `requirements.txt` must be present at the root of your application's repository to deploy.
-    ...
-    -----> Python app detected
-    -----> Installing python-2.7.12
-         $ pip install -r requirements.txt
-           Collecting requests (from -r requirements.txt (line 1))
-             Downloading requests-2.10.0-py2.py3-none-any.whl (501kB)
-           Installing collected packages: requests
-           Successfully installed requests-2.10.0
 
-    -----> Discovering process types
+To specify your python version, you also need a `runtime.txt` file - unless you are using the default Python runtime version.
-           Procfile declares types -> (none)
 
-A `requirements.txt` file must be present at the root of your application's repository.
+Current default Python Runtime: Python 3.6.12
 
-You can also specify the latest production release of this buildpack for upcoming builds of an existing application:
+Alternatively, you can provide a `setup.py` file, or a `Pipfile`.
+Using `pipenv` will generate `runtime.txt` at build time if one of the field `python_version` or `python_full_version` is specified in the `requires` section of your `Pipfile`.
+
+Specify a Buildpack Version
+---------------------------
+
+You can specify the latest production release of this buildpack for upcoming builds of an existing application:
 
     $ heroku buildpacks:set heroku/python
 
@@ -41,14 +60,37 @@ You can also specify the latest production release of this buildpack for upcomin
 Specify a Python Runtime
 ------------------------
 
-Specific versions of the Python runtime can be specified with a `runtime.txt` file:
+Supported runtime options include:
 
-    $ cat runtime.txt
+- `python-3.9.0`
-    python-3.5.2
+- `python-3.8.7`
+- `python-3.7.9`
+- `python-3.6.12`
+- `python-2.7.18`
 
-Runtime options include:
+## Tests
 
-- `python-2.7.12`
+The buildpack tests use [Docker](https://www.docker.com/) to simulate
-- `python-3.5.2`
+Heroku's [stack images.](https://devcenter.heroku.com/articles/stack)
-- `pypy-5.3.1` (unsupported, experimental)
+
-- `pypy3-2.4.0` (unsupported, experimental)
+To run the test suite against the default stack:
+
+```
+make test
+```
+
+Or to test against a particular stack:
+
+```
+make test STACK=heroku-16
+```
+
+To run only a subset of the tests:
+
+```
+make test TEST_CMD=tests/versions
+```
+
+The tests are run via the vendored
+[shunit2](https://github.com/kward/shunit2)
+test framework.

Rakefile

@@ -0,0 +1 @@
+require 'hatchet/tasks'

bin/compile

@@ -15,258 +15,364 @@
 # Fail fast and fail hard.
 set -eo pipefail
 
+# Used by buildpack-stdlib's metrics features.
+export BPLOG_PREFIX="buildpack.python"
+export BUILDPACK_LOG_FILE=${BUILDPACK_LOG_FILE:-/dev/null}
+
 [ "$BUILDPACK_XTRACE" ] && set -o xtrace
 
-# Prepend proper path for virtualenv hackery. This will be deprecated soon.
+# Prepend proper path for old-school virtualenv hackery.
+# This may not be neccessary.
 export PATH=:/usr/local/bin:$PATH
 
-# Paths.
+# Setup Path variables, for later use in the Buildpack.
-BIN_DIR=$(cd $(dirname $0); pwd) # absolute path
+BIN_DIR=$(cd "$(dirname "$0")"; pwd) # absolute path
-ROOT_DIR=$(dirname $BIN_DIR)
+ROOT_DIR=$(dirname "$BIN_DIR")
 BUILD_DIR=$1
 CACHE_DIR=$2
 ENV_DIR=$3
 
-# Static configurations for virtualenv caches.
+# Export Path variables, for use in sub-scripts.
-VIRTUALENV_LOC=".heroku/venv"
+export BUILD_DIR CACHE_DIR ENV_DIR
-LEGACY_TRIGGER="lib/python2.7"
 
-DEFAULT_PYTHON_VERSION="python-2.7.12"
+# Set the base URL for downloading buildpack assets like Python runtimes.
-DEFAULT_PYTHON_STACK="cedar-14"
+# The user can provide BUILDPACK_S3_BASE_URL to specify a custom target.
-PYTHON_EXE="/app/.heroku/python/bin/python"
+# Note: this is designed for non-Heroku use, as it does not use the user-provided
-PIP_VERSION="8.1.2"
+# environment variable mechanism (the ENV_DIR).
-SETUPTOOLS_VERSION="25.2.0"
+S3_BASE_URL="${BUILDPACK_S3_BASE_URL:-"https://heroku-buildpack-python.s3.amazonaws.com"}"
+# This has to be exported since it's used by the geo-libs step which is run in a subshell.
 
-# Common Problem Warnings
+# Default Python Versions
-export WARNINGS_LOG=$(mktemp)
+# shellcheck source=bin/default_pythons
-export RECOMMENDED_PYTHON_VERSION=$DEFAULT_PYTHON_VERSION
+source "$BIN_DIR/default_pythons"
 
-# Setup bpwatch
+# Supported Python Branches
-export PATH=$PATH:$ROOT_DIR/vendor/bpwatch
+PY39="python-3.9"
-LOGPLEX_KEY="t.b90d9d29-5388-4908-9737-b4576af1d4ce"
+PY38="python-3.8"
-export BPWATCH_STORE_PATH=$CACHE_DIR/bpwatch.json
+PY37="python-3.7"
-BUILDPACK_VERSION=v28
+PY36="python-3.6"
+PY35="python-3.5"
+PY34="python-3.4"
+PY27="python-2.7"
+PYPY27="pypy2.7"
+PYPY36="pypy3.6"
 
-# Setup pip-pop (pip-diff)
+# Which stack is used (for binary downloading), if none is provided (e.g. outside of Heroku)?
-export PATH=$PATH:$ROOT_DIR/vendor/pip-pop
+# TODO: Remove this and require that STACK be set explicitly.
+DEFAULT_PYTHON_STACK="heroku-18"
 
-# Support Anvil Build_IDs
+# Common Problem Warnings:
-[ ! "$SLUG_ID" ] && SLUG_ID="defaultslug"
+# This section creates a temporary file in which to stick the output of `pip install`.
-[ ! "$REQUEST_ID" ] && REQUEST_ID=$SLUG_ID
+# The `warnings` subscript then greps through this for common problems and guides
+# the user towards resolution of known issues.
+WARNINGS_LOG=$(mktemp)
+RECOMMENDED_PYTHON_VERSION=$DEFAULT_PYTHON_VERSION
+
+# The buildpack ships with a few executable tools.
+# This installs them into the path, so we can execute them directly.
+export PATH=$PATH:$ROOT_DIR/vendor/
+
+# Set environment variables if they weren't set by the platform.
 [ ! "$STACK" ] && STACK=$DEFAULT_PYTHON_STACK
-[[ $BUILD_DIR == "/app" ]] && SKIP_MOVE_BUILD=1
 
-# Sanitizing environment variables.
+# Sanitize externally-provided environment variables:
-unset GIT_DIR PYTHONHOME PYTHONPATH
+# The following environment variables are either problematic or simply unneccessary
-unset RECEIVE_DATA RUN_KEY BUILD_INFO DEPLOY LOG_TOKEN DYNO
+# for the buildpack to have knowledge of, so we unset them, to keep the environment
-unset CYTOKINE_LOG_FILE GEM_PATH
+# as clean and pristine as possible.
+unset PYTHONHOME PYTHONPATH
 
-# Setup buildpack instrumentation.
+# Import the utils script, which contains helper functions used throughout the buildpack.
-bpwatch init $LOGPLEX_KEY
+# shellcheck source=bin/utils
-bpwatch build python $BUILDPACK_VERSION $REQUEST_ID
+source "$BIN_DIR/utils"
-TMP_APP_DIR=$CACHE_DIR/tmp_app_dir
 
-bpwatch start compile
+# Import the warnings script, which contains the `pip install` user warning mechanisms
+# (mentioned and explained above)
+# shellcheck source=bin/warnings
+source "$BIN_DIR/warnings"
 
-# Syntax sugar.
+if [[ "${STACK}" == "cedar-14" ]]; then
-source $BIN_DIR/utils
+  mcount "failure.unsupported.cedar-14"
-
+  puts-warn "The Cedar-14 stack is no longer supported by the latest release of this buildpack."
-# Import collection of warnings.
+  puts-warn
-source $BIN_DIR/warnings
+  puts-warn "Please switch to the Cedar-14 support branch by using this buildpack URL:"
-
+  puts-warn "https://github.com/heroku/heroku-buildpack-python#cedar-14"
-# Directory Hacks for path consistency.
+  puts-warn
-APP_DIR='/app'
+  puts-warn "For instructions on how to change the buildpacks used by an app, see:"
-TMP_APP_DIR=$CACHE_DIR/tmp_app_dir
+  puts-warn "https://devcenter.heroku.com/articles/buildpacks#setting-a-buildpack-on-an-application"
-
+  exit 1
-# Skip these steps for Docker.
-if [[ ! "$SKIP_MOVE_BUILD" ]]; then
-
-  # Copy Anvil app dir to temporary storage...
-  bpwatch start anvil_appdir_stage
-  if [ "$SLUG_ID" ]; then
-    mkdir -p $TMP_APP_DIR
-    deep-mv $APP_DIR $TMP_APP_DIR
-  else
-    deep-rm $APP_DIR
-  fi
-  bpwatch stop anvil_appdir_stage
-
-  # Copy Application code in.
-  bpwatch start appdir_stage
-    deep-cp $BUILD_DIR $APP_DIR
-  bpwatch stop appdir_stage
 fi
 
+if [[ -f "${ENV_DIR}/BUILD_WITH_GEO_LIBRARIES" ]]; then
+  mcount "failure.unsupported.BUILD_WITH_GEO_LIBRARIES"
+  puts-warn "The Python buildpack's legacy BUILD_WITH_GEO_LIBRARIES functonality is"
+  puts-warn "no longer supported:"
+  puts-warn "https://devcenter.heroku.com/changelog-items/1947"
+  puts-warn
+  puts-warn "To continue to use GDAL, GEOS or PROJ support, see the migration guide:"
+  puts-warn "https://help.heroku.com/D5INLB1A/python-s-build_with_geo_libraries-legacy-feature-is-no-longer-supported"
+  puts-warn
+  puts-warn "Or if you no longer need those libraries, this message can be hidden by"
+  puts-warn "unsetting the BUILD_WITH_GEO_LIBRARIES environment variable, using:"
+  puts-warn "heroku config:unset BUILD_WITH_GEO_LIBRARIES"
+  exit 1
+fi
 
-# Set new context.
+# Make the directory in which we will create symlinks from the temporary build directory
-ORIG_BUILD_DIR=$BUILD_DIR
+# to `/app`.
-BUILD_DIR=$APP_DIR
+# Symlinks are required, since Python is not a portable installation.
+# More on this topic later.
+mkdir -p /app/.heroku
 
-# Set up outputs under new context
+# This buildpack programatically generates (or simply copies) a number of files for
+# buildpack machinery: an export script, and a number of `.profile.d` scripts. This
+# section declares the locations of those files and targets.
 PROFILE_PATH="$BUILD_DIR/.profile.d/python.sh"
 EXPORT_PATH="$BIN_DIR/../export"
 GUNICORN_PROFILE_PATH="$BUILD_DIR/.profile.d/python.gunicorn.sh"
+WEB_CONCURRENCY_PROFILE_PATH="$BUILD_DIR/.profile.d/WEB_CONCURRENCY.sh"
 
 # We'll need to send these statics to other scripts we `source`.
 export BUILD_DIR CACHE_DIR BIN_DIR PROFILE_PATH EXPORT_PATH
 
-# Prepend proper environment variables for Python use.
+# Python Environment Variables
-export PATH=$BUILD_DIR/.heroku/python/bin:$BUILD_DIR/.heroku/vendor/bin:$PATH
+# Set Python-specific environment variables, for running Python within the buildpack.
+# Notes on each variable included.
+
+# PATH is relatively obvious, we need to be able to execute 'python'.
+export PATH=/app/.heroku/python/bin:/app/.heroku/vendor/bin:$PATH
+# Tell Python to not buffer it's stdin/stdout.
 export PYTHONUNBUFFERED=1
+# Set the locale to a well-known and expected standard.
 export LANG=en_US.UTF-8
-export C_INCLUDE_PATH=/app/.heroku/vendor/include:$BUILD_DIR/.heroku/vendor/include:/app/.heroku/python/include:$C_INCLUDE_PATH
+# `~/.heroku/vendor` is an place where the buildpack may stick pre-build binaries for known
-export CPLUS_INCLUDE_PATH=/app/.heroku/vendor/include:$BUILD_DIR/.heroku/vendor/include:/app/.heroku/python/include:$CPLUS_INCLUDE_PATH
+# C dependencies. This section configures Python (GCC, more specifically)
-export LIBRARY_PATH=/app/.heroku/vendor/lib:$BUILD_DIR/.heroku/vendor/lib:/app/.heroku/python/lib:$LIBRARY_PATH
+# and pip to automatically include these paths when building binaries.
-export LD_LIBRARY_PATH=/app/.heroku/vendor/lib:$BUILD_DIR/.heroku/vendor/lib:/app/.heroku/python/lib:$LD_LIBRARY_PATH
+# TODO: Stop adding .heroku/vendor here now that the buildpack no longer vendors anything.
-export PKG_CONFIG_PATH=/app/.heroku/vendor/lib/pkg-config:$BUILD_DIR/.heroku/vendor/lib/pkg-config:/app/.heroku/python/lib/pkg-config:$PKG_CONFIG_PATH
+export C_INCLUDE_PATH=/app/.heroku/vendor/include:/app/.heroku/python/include:$C_INCLUDE_PATH
+export CPLUS_INCLUDE_PATH=/app/.heroku/vendor/include:/app/.heroku/python/include:$CPLUS_INCLUDE_PATH
+export LIBRARY_PATH=/app/.heroku/vendor/lib:/app/.heroku/python/lib:$LIBRARY_PATH
+export LD_LIBRARY_PATH=/app/.heroku/vendor/lib:/app/.heroku/python/lib:$LD_LIBRARY_PATH
+export PKG_CONFIG_PATH=/app/.heroku/vendor/lib/pkg-config:/app/.heroku/python/lib/pkg-config:$PKG_CONFIG_PATH
+
+# Global pip options (https://pip.pypa.io/en/stable/user_guide/#environment-variables).
+# Disable pip's warnings about EOL Python since we show our own.
+export PIP_NO_PYTHON_VERSION_WARNING=1
+
+# The Application Code
+# --------------------
 
 # Switch to the repo's context.
-cd $BUILD_DIR
+cd "$BUILD_DIR"
 
-# Warn for lack of Procfile.
+# The Cache
-if [[ ! -f Procfile ]]; then
+# ---------
-  puts-warn 'Warning: Your application is missing a Procfile. This file tells Heroku how to run your application.'
+
-  puts-warn 'Learn more: https://devcenter.heroku.com/articles/procfile'
+# The workflow for the Python Buildpack's cache is as follows:
+#
+# - `~/.heroku/{known-paths}` are copied from the cache into the slug.
+# - The build is executed, modifying `~/.heroku/{known-paths}`.
+# - Once the build is complete, `~/.heroku/{known-paths}` is copied back into the cache.
+
+# Create the cache directory, if it doesn't exist.
+mkdir -p "$CACHE_DIR/.heroku"
+
+# Restore old artifacts from the cache.
+mkdir -p .heroku
+
+# The Python installation.
+cp -R "$CACHE_DIR/.heroku/python" .heroku/ &> /dev/null || true
+# A plain text file which contains the current stack being used (used for cache busting).
+cp -R "$CACHE_DIR/.heroku/python-stack" .heroku/ &> /dev/null || true
+# A plain text file which contains the current python version being used (used for cache busting).
+cp -R "$CACHE_DIR/.heroku/python-version" .heroku/ &> /dev/null || true
+# A plain text file which contains the current sqlite3 version being used (used for cache busting).
+cp -R "$CACHE_DIR/.heroku/python-sqlite3-version" .heroku/ &> /dev/null || true
+# "editable" installations of code repositories, via pip or pipenv.
+if [[ -d "$CACHE_DIR/.heroku/src" ]]; then
+  cp -R "$CACHE_DIR/.heroku/src" .heroku/ &> /dev/null || true
 fi
 
-# Experimental pre_compile hook.
+# The pre_compile hook. Customers rely on this. Don't remove it.
-bpwatch start pre_compile
+# This part of the code is used to allow users to customize their build experience
-  source $BIN_DIR/steps/hooks/pre_compile
+# without forking the buildpack by providing a `bin/pre_compile` script, which gets
-bpwatch stop pre_compile
+# run inline with the buildpack automatically.
 
-# If no requirements.txt file given, assume `setup.py develop` is intended.
+# shellcheck source=bin/steps/hooks/pre_compile
-if [ ! -f requirements.txt ]; then
+source "$BIN_DIR/steps/hooks/pre_compile"
-  echo "-e ." > requirements.txt
+
+# Sticky runtimes. If there was a previous build, and it used a given version of Python,
+# continue to use that version of Python in perpituity (warnings will be raised if
+# they are out–of–date).
+if [ -f "$CACHE_DIR/.heroku/python-version" ]; then
+  CACHED_PYTHON_VERSION=$(cat "$CACHE_DIR/.heroku/python-version")
 fi
 
-
+# We didn't always record the stack version. This code is in place because of that.
-# Sticky runtimes.
+if [ -f "$CACHE_DIR/.heroku/python-stack" ]; then
-if [ -f $CACHE_DIR/.heroku/python-version ]; then
+  CACHED_PYTHON_STACK=$(cat "$CACHE_DIR/.heroku/python-stack")
-  DEFAULT_PYTHON_VERSION=$(cat $CACHE_DIR/.heroku/python-version)
-fi
-
-# Stack fallback for non-declared caches.
-if [ -f $CACHE_DIR/.heroku/python-stack ]; then
-  CACHED_PYTHON_STACK=$(cat $CACHE_DIR/.heroku/python-stack)
 else
   CACHED_PYTHON_STACK=$STACK
 fi
 
-# If no runtime given, assume default version.
+# Pipenv Python version support.
-if [ ! -f runtime.txt ]; then
+# Detect the version of Python requested from a Pipfile (e.g. python_version or python_full_version).
-  echo $DEFAULT_PYTHON_VERSION > runtime.txt
+# Convert it to a runtime.txt file.
+
+# shellcheck source=bin/steps/pipenv-python-version
+source "$BIN_DIR/steps/pipenv-python-version"
+
+if [[ -f runtime.txt ]]; then
+  mcount "version.reason.python.specified"
+elif [[ -n "${CACHED_PYTHON_VERSION:-}" ]]; then
+  mcount "version.reason.python.cached"
+  echo "${CACHED_PYTHON_VERSION}" > runtime.txt
+else
+  mcount "version.reason.python.default"
+  echo "${DEFAULT_PYTHON_VERSION}" > runtime.txt
 fi
 
-# Prepare the cache.
+# Create the directory for .profile.d, if it doesn't exist.
-mkdir -p $CACHE_DIR
+mkdir -p "$(dirname "$PROFILE_PATH")"
+# Create the directory for editable source code installation, if it doesn't exist.
+mkdir -p /app/.heroku/src
 
-# Purge "old-style" virtualenvs.
+# On Heroku CI, builds happen in `/app`. Otherwise, on the Heroku platform,
-bpwatch start clear_old_venvs
+# they occur in a temp directory. Beacuse Python is not portable, we must create
-  [ -d $CACHE_DIR/$LEGACY_TRIGGER ] && rm -fr $CACHE_DIR/.heroku/bin $CACHE_DIR/.heroku/lib $CACHE_DIR/.heroku/include
+# symlinks to emulate that we are operating in `/app` during the build process.
-  [ -d $CACHE_DIR/$VIRTUALENV_LOC ] && rm -fr $CACHE_DIR/.heroku/venv $CACHE_DIR/.heroku/src
+# This is (hopefully obviously) because apps end up running from `/app` in production.
-bpwatch stop clear_old_venvs
+if [[ $BUILD_DIR != '/app' ]]; then
+    # python expects to reside in /app, so set up symlinks
+    # we will not remove these later so subsequent buildpacks can still invoke it
+    ln -nsf "$BUILD_DIR/.heroku/python" /app/.heroku/python
+    ln -nsf "$BUILD_DIR/.heroku/vendor" /app/.heroku/vendor
+    # Note: .heroku/src is copied in later.
+fi
 
-# Restore old artifacts from the cache.
+# Download / Install Python, from pre-build binaries available on Amazon S3.
-bpwatch start restore_cache
+# This step also bootstraps pip / setuptools.
-    mkdir -p .heroku
+(( start=$(nowms) ))
+# shellcheck source=bin/steps/python
+source "$BIN_DIR/steps/python"
+mtime "python.install.time" "${start}"
 
-    cp -R $CACHE_DIR/.heroku/python .heroku/ &> /dev/null || true
+# Install Pipenv dependencies, if a Pipfile was provided.
-    cp -R $CACHE_DIR/.heroku/python-stack .heroku/ &> /dev/null || true
+# shellcheck source=bin/steps/pipenv
-    cp -R $CACHE_DIR/.heroku/python-version .heroku/ &> /dev/null || true
+source "$BIN_DIR/steps/pipenv"
-    cp -R $CACHE_DIR/.heroku/vendor .heroku/ &> /dev/null || true
-    cp -R $CACHE_DIR/.heroku/venv .heroku/ &> /dev/null || true
 
-bpwatch stop restore_cache
+# If no requirements.txt file given, assume `setup.py develop` is intended.
+# This allows for people to ship a setup.py application to Heroku
 
-set +e
+if [ ! -f requirements.txt ] && [ ! -f Pipfile ]; then
-# Create set-aside `.heroku` folder.
+  echo "-e ." > requirements.txt
-mkdir .heroku &> /dev/null
+fi
-set -e
 
-mkdir -p $(dirname $PROFILE_PATH)
+# Fix egg-links.
+# Because we're installing things into a different path than we're running them (temp dir vs app dir),
+# We must re-write all of Python's eggpath links to target the proper directory.
+# shellcheck source=bin/steps/eggpath-fix
+source "$BIN_DIR/steps/eggpath-fix"
 
-# Install Python.
+# SQLite3 support.
-source $BIN_DIR/steps/python
+# This sets up and installs sqlite3 dev headers and the sqlite3 binary but not the
+# libsqlite3-0 library since that exists on the stack image.
+# Note: This only applies to Python 2.7.15+ and Python 3.6.6+
+(( start=$(nowms) ))
+# shellcheck source=bin/steps/sqlite3
+source "$BIN_DIR/steps/sqlite3"
+buildpack_sqlite3_install
+mtime "sqlite3.install.time" "${start}"
 
-# Sanity check for setuptools/distribute.
+# pip install
-source $BIN_DIR/steps/setuptools
+# -----------
 
-# Uninstall removed dependencies with Pip.
+# Install dependencies with pip (where the magic happens).
-source $BIN_DIR/steps/pip-uninstall
+(( start=$(nowms) ))
+# shellcheck source=bin/steps/pip-install
+source "$BIN_DIR/steps/pip-install"
+mtime "pip.install.time" "${start}"
 
-# Mercurial support.
+# Support for NLTK corpora.
-source $BIN_DIR/steps/mercurial
+# Note: this may only work on Python 2.7. I don't think many customers use this functionality,
+# and it should probably be undocumented.
+# (there's an import error on 3.6 that should hopefully be fixed upstream at some point)
+(( start=$(nowms) ))
+sub_env "$BIN_DIR/steps/nltk"
+mtime "nltk.download.time" "${start}"
 
-# Pylibmc support.
+# Support for editable installations. Here, we are copying pip–created src directory,
-source $BIN_DIR/steps/pylibmc
+# and copying it into the proper place (the logical place to do this was early, but it must be done here).
+# In CI, $BUILD_DIR is /app.
+if [[ ! "$BUILD_DIR" == "/app" ]]; then
+  rm -rf "$BUILD_DIR/.heroku/src"
+  deep-cp /app/.heroku/src "$BUILD_DIR/.heroku/src"
+fi
 
-# Libffi support.
-source $BIN_DIR/steps/cryptography
-
-# Support for Geo libraries.
-sub-env $BIN_DIR/steps/geo-libs
-
-# GDAL support.
-source $BIN_DIR/steps/gdal
-
-# Install dependencies with Pip.
-source $BIN_DIR/steps/pip-install
 
 # Django collectstatic support.
-sub-env $BIN_DIR/steps/collectstatic
+# The buildpack automatically runs collectstatic for Django applications.
+# This is the cause for the majority of build failures on the Python platform.
+# These failures are intentional — if collectstatic (which can be tricky, at times) fails,
+# your build fails.
+(( start=$(nowms) ))
+sub_env "$BIN_DIR/steps/collectstatic"
+mtime "collectstatic.time" "${start}"
 
 
-# Create .profile script for application runtime environment variables.
+# Progamatically create .profile.d script for application runtime environment variables.
-set-env PATH '$HOME/.heroku/python/bin:$PATH'
+
-set-env PYTHONUNBUFFERED true
+# Set the PATH to include Python / pip / pipenv / etc.
-set-env PYTHONHOME /app/.heroku/python
+set_env PATH "\$HOME/.heroku/python/bin:\$PATH"
-set-env LIBRARY_PATH '/app/.heroku/vendor/lib:/app/.heroku/python/lib:$LIBRARY_PATH'
+# Tell Python to run in unbuffered mode.
-set-env LD_LIBRARY_PATH '/app/.heroku/vendor/lib:/app/.heroku/python/lib:$LD_LIBRARY_PATH'
+set_env PYTHONUNBUFFERED true
-set-default-env LANG en_US.UTF-8
+# Tell Python where it lives.
-set-default-env PYTHONHASHSEED random
+set_env PYTHONHOME "\$HOME/.heroku/python"
-set-default-env PYTHONPATH /app/
+# Set variables for C libraries.
+set_env LIBRARY_PATH "\$HOME/.heroku/vendor/lib:\$HOME/.heroku/python/lib:\$LIBRARY_PATH"
+set_env LD_LIBRARY_PATH "\$HOME/.heroku/vendor/lib:\$HOME/.heroku/python/lib:\$LD_LIBRARY_PATH"
+# Locale.
+set_default_env LANG en_US.UTF-8
+# The Python hash seed is set to random.
+set_default_env PYTHONHASHSEED random
+# Tell Python to look for Python modules in the /app dir. Don't change this.
+set_default_env PYTHONPATH "\$HOME"
+
+# Python expects to be in /app, if at runtime, it is not, set
+# up symlinks… this can occur when the subdir buildpack is used.
+cat <<EOT >> "$PROFILE_PATH"
+if [[ \$HOME != "/app" ]]; then
+    mkdir -p /app/.heroku
+    ln -nsf "\$HOME/.heroku/python" /app/.heroku/python
+    ln -nsf "\$HOME/.heroku/vendor" /app/.heroku/vendor
+fi
+EOT
 
 # Install sane-default script for $WEB_CONCURRENCY and $FORWARDED_ALLOW_IPS.
-cp $ROOT_DIR/vendor/python.gunicorn.sh $GUNICORN_PROFILE_PATH
+cp "$ROOT_DIR/vendor/WEB_CONCURRENCY.sh" "$WEB_CONCURRENCY_PROFILE_PATH"
+cp "$ROOT_DIR/vendor/python.gunicorn.sh" "$GUNICORN_PROFILE_PATH"
 
+# Experimental post_compile hook. Don't remove this.
+# shellcheck source=bin/steps/hooks/post_compile
+source "$BIN_DIR/steps/hooks/post_compile"
 
-# Experimental post_compile hook.
+# Fix egg-links, again.
-bpwatch start post_compile
+# shellcheck source=bin/steps/eggpath-fix2
-  source $BIN_DIR/steps/hooks/post_compile
+source "$BIN_DIR/steps/eggpath-fix2"
-bpwatch stop post_compile
 
-# Store new artifacts in cache.
+# Store new artifacts in the cache.
-bpwatch start dump_cache
+rm -rf "$CACHE_DIR/.heroku/python"
+rm -rf "$CACHE_DIR/.heroku/python-version"
+rm -rf "$CACHE_DIR/.heroku/python-stack"
+rm -rf "$CACHE_DIR/.heroku/vendor"
+rm -rf "$CACHE_DIR/.heroku/src"
 
-  rm -rf $CACHE_DIR/.heroku/python
+mkdir -p "$CACHE_DIR/.heroku"
-  rm -rf $CACHE_DIR/.heroku/python-version
+cp -R .heroku/python "$CACHE_DIR/.heroku/"
-  rm -rf $CACHE_DIR/.heroku/python-stack
+cp -R .heroku/python-version "$CACHE_DIR/.heroku/"
-  rm -rf $CACHE_DIR/.heroku/vendor
+cp -R .heroku/python-stack "$CACHE_DIR/.heroku/" &> /dev/null || true
-  rm -rf $CACHE_DIR/.heroku/venv
+if [[ -d .heroku/src ]]; then
-
+  cp -R .heroku/src "$CACHE_DIR/.heroku/" &> /dev/null || true
-  mkdir -p $CACHE_DIR/.heroku
-  cp -R .heroku/python $CACHE_DIR/.heroku/
-  cp -R .heroku/python-version $CACHE_DIR/.heroku/
-  cp -R .heroku/python-stack $CACHE_DIR/.heroku/ &> /dev/null || true
-  cp -R .heroku/vendor $CACHE_DIR/.heroku/ &> /dev/null || true
-  cp -R .heroku/venv $CACHE_DIR/.heroku/ &> /dev/null || true
-
-bpwatch stop dump_cache
-
-# Fin.
-if [[ ! "$SKIP_MOVE_BUILD" ]]; then
-
-  bpwatch start appdir_commit
-    deep-rm $ORIG_BUILD_DIR
-    deep-mv $BUILD_DIR $ORIG_BUILD_DIR
-  bpwatch stop appdir_commit
-
-  bpwatch start anvil_appdir_commit
-  if [ "$SLUG_ID" ]; then
-    deep-mv $TMP_APP_DIR $APP_DIR
-  fi
-
-  bpwatch stop anvil_appdir_commit
-  bpwatch stop compile
 fi
 
+# Measure the size of the Python installation.
+# shellcheck disable=SC2119
+mmeasure 'python.size' "$(measure-size)"

bin/default_pythons

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+
+# Disable unused env var warning, since shellcheck doesn't take into account
+# that this file is sourced. We don't want to use export since it exposes
+# the env vars to subprocesses.
+# shellcheck disable=2034
+
+DEFAULT_PYTHON_VERSION="python-3.6.12"
+LATEST_39="python-3.9.0"
+LATEST_38="python-3.8.7"
+LATEST_37="python-3.7.9"
+LATEST_36="python-3.6.12"
+LATEST_35="python-3.5.10"
+LATEST_34="python-3.4.10"
+LATEST_27="python-2.7.18"
+LATEST_PYPY_36="pypy3.6-7.3.2"
+LATEST_PYPY_27="pypy2.7-7.3.2"

bin/detect

@@ -15,7 +15,7 @@
 BUILD_DIR=$1
 
 # Exit early if app is clearly not Python.
-if [ ! -f $BUILD_DIR/requirements.txt ] && [ ! -f $BUILD_DIR/setup.py ]; then
+if [ ! -f "$BUILD_DIR/requirements.txt" ] && [ ! -f "$BUILD_DIR/setup.py" ] && [ ! -f "$BUILD_DIR/Pipfile" ]; then
   exit 1
 fi
 

bin/release

@@ -1,10 +1,9 @@
 #!/usr/bin/env bash
 # bin/release <build-dir>
 
-BIN_DIR=$(cd $(dirname $0); pwd) # absolute path
 BUILD_DIR=$1
 
-MANAGE_FILE=$(cd $BUILD_DIR && find . -maxdepth 3 -type f -name 'manage.py' | head -1)
+MANAGE_FILE=$(cd "$BUILD_DIR" && find . -maxdepth 3 -type f -name 'manage.py' | head -1)
 MANAGE_FILE=${MANAGE_FILE:2}
 
 cat <<EOF

bin/steps/README.MD

@@ -0,0 +1,21 @@
+# Python Buildpack Install Steps
+
+TODO: Add context on Python install steps, such as why symlinking vs copying
+
+## Installing Python packages using Pip
+
+### Convention: Use `python` process to invoke Pip
+
+We don't use this convention (yet) but this is an upcoming change being considered.
+
+This is a bigger concern on Windows than it is in Linux environments, but an
+emerging convention in the Python community is to invoke pip using:
+
+```
+python3 -m pip [options]
+```
+
+Invoking pip this way ensures correct location - python knows where these
+packages are stored because it put them there (defaults to Python's pathing info).
+
+All normal command line options are available using this method.

bin/steps/collectstatic

@@ -10,7 +10,8 @@
 #   - $DISABLE_COLLECTSTATIC: disables this functionality.
 #   - $DEBUG_COLLECTSTATIC: upon failure, print out environment variables.
 
-source $BIN_DIR/utils
+# shellcheck source=bin/utils
+source "$BIN_DIR/utils"
 
 # Location of 'manage.py', if it exists.
 MANAGE_FILE=$(find . -maxdepth 3 -type f -name 'manage.py' -printf '%d\t%P\n' | sort -nk1 | cut -f2 | head -1)
@@ -19,24 +20,45 @@ MANAGE_FILE=${MANAGE_FILE:-fakepath}
 # Legacy file-based support for $DISABLE_COLLECTSTATIC
 [ -f .heroku/collectstatic_disabled ] && DISABLE_COLLECTSTATIC=1
 
-# Ensure that Django is explicitly specified in requirements.txt
+# Ensure that Django is actually installed.
-pip-grep -s requirements.txt django Django && DJANGO_INSTALLED=1
+is_module_available 'django' && DJANGO_INSTALLED=1
 
-bpwatch start collectstatic  # metrics collection
 
 if [ ! "$DISABLE_COLLECTSTATIC" ] && [ -f "$MANAGE_FILE" ] && [ "$DJANGO_INSTALLED" ]; then
     set +e
 
-    puts-cmd "python $MANAGE_FILE collectstatic --noinput"
+    puts-step "$ python $MANAGE_FILE collectstatic --noinput"
 
     # Run collectstatic, cleanup some of the noisy output.
-    python $MANAGE_FILE collectstatic --noinput --traceback 2>&1 | sed '/^Post-processed/d;/^Copying/d;/^$/d' | indent
+    PYTHONPATH=${PYTHONPATH:-.}
+    export PYTHONPATH
+
+    # Create a temporary file for collecting the collectstaic logs.
+    COLLECTSTATIC_LOG=$(mktemp)
+
+    python "$MANAGE_FILE" collectstatic --noinput --traceback 2>&1 | tee "$COLLECTSTATIC_LOG" | sed '/^Post-processed/d;/^Copying/d;/^$/d' | indent
     COLLECTSTATIC_STATUS="${PIPESTATUS[0]}"
 
     set -e
 
     # Display a warning if collectstatic failed.
-    [ $COLLECTSTATIC_STATUS -ne 0 ] && {
+    [ "$COLLECTSTATIC_STATUS" -ne 0 ] && {
+
+        if grep -q 'SyntaxError' "$COLLECTSTATIC_LOG"; then
+            mcount "failure.collectstatic.syntax-error"
+
+        elif grep -q 'ImproperlyConfigured' "$COLLECTSTATIC_LOG"; then
+            mcount "failure.collectstatic.improper-configuration"
+
+        elif grep -q 'The CSS file' "$COLLECTSTATIC_LOG"; then
+            mcount "failure.collectstatic.fancy-references"
+
+        elif grep -q 'OSError' "$COLLECTSTATIC_LOG"; then
+            mcount "failure.collectstatic.missing-file"
+
+        else
+            mcount "failure.collectstatic.other"
+        fi
 
         echo
         echo " !     Error while running '$ python $MANAGE_FILE collectstatic --noinput'."
@@ -63,5 +85,3 @@ if [ ! "$DISABLE_COLLECTSTATIC" ] && [ -f "$MANAGE_FILE" ] && [ "$DJANGO_INSTALL
 
     echo
 fi
-
-bpwatch stop collectstatic  # metrics collection

bin/steps/cryptography

@@ -1,35 +0,0 @@
-#!/usr/bin/env bash
-
-# This script serves as the Cryptography build step of the
-# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python)
-# compiler.
-#
-# A [buildpack](https://devcenter.heroku.com/articles/buildpacks) is an
-# adapter between a Python application and Heroku's runtime.
-#
-# This script is invoked by [`bin/compile`](/).
-
-# The location of the pre-compiled libffi binary.
-VENDORED_LIBFFI="https://lang-python.s3.amazonaws.com/$STACK/libraries/vendor/libffi.tar.gz"
-
-PKG_CONFIG_PATH="/app/.heroku/vendor/lib/pkgconfig:$PKG_CONFIG_PATH"
-
-# Syntax sugar.
-source $BIN_DIR/utils
-
-bpwatch start libffi_install
-
-# If a package using cffi exists within requirements, use vendored libffi.
-if (pip-grep -s requirements.txt argon2-cffi bcrypt cffi cryptography django[argon2] Django[argon2] django[bcrypt] Django[bcrypt] PyNaCl pyOpenSSL PyOpenSSL requests[security] misaka &> /dev/null) then
-
-  if [ ! -d ".heroku/vendor/lib/libffi-3.1" ]; then
-    echo "-----> Noticed cffi. Bootstrapping libffi."
-    mkdir -p .heroku/vendor
-    # Download and extract libffi into target vendor directory.
-    curl $VENDORED_LIBFFI -s | tar zxv -C .heroku/vendor &> /dev/null
-  fi
-
-  export LIBFFI=$(pwd)/vendor
-fi
-
-bpwatch stop libffi_install

bin/steps/eggpath-fix

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+set +e
+# delete any existing egg links, to uninstall exisisting installations.
+find .heroku/python/lib/python*/site-packages/ -name "*.egg-link" -delete 2> /dev/null
+find .heroku/python/lib/python*/site-packages/ -name "*.pth" -print0 2> /dev/null | xargs -r -0 -n 1 sed -i -e "s#/app/#/$(pwd)/#" &> /dev/null
+set -e
+
+set +e
+# Support for the above, for PyPy.
+find .heroku/python/lib-python/*/site-packages/ -name "*.egg-link" -print0 2> /dev/null | xargs -r -0 -n 1 sed -i -e "s#/app/#$(pwd)/#" &> /dev/null
+find .heroku/python/lib-python/*/site-packages/ -name "*.pth" -print0 2> /dev/null | xargs -r -0 -n 1 sed -i -e "s#/app/#/$(pwd)/#" &> /dev/null
+set -e

bin/steps/eggpath-fix2

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set +e
+# rewrite build dir in egg links to /app so things are found at runtime
+find .heroku/python/lib/python*/site-packages/ -name "*.pth" -print0 2> /dev/null | xargs -r -0 -n 1 sed -i -e "s#$(pwd)#/app#" &> /dev/null
+set -e
+
+set +e
+# Support for PyPy
+find .heroku/python/lib-python/*/site-packages/  -name "*.pth" -print0 2> /dev/null | xargs -r -0 -n 1 sed -i -e "s#$(pwd)#/app#" &> /dev/null
+set -e

bin/steps/gdal

@@ -1,35 +0,0 @@
-#!/usr/bin/env bash
-
-# This script serves as the GDAL build step of the
-# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python)
-# compiler.
-#
-# A [buildpack](https://devcenter.heroku.com/articles/buildpacks) is an
-# adapter between a Python application and Heroku's runtime.
-#
-# This script is invoked by [`bin/compile`](/).
-
-# The location of the pre-compiled cryptography binary.
-VENDORED_GDAL="https://lang-python.s3.amazonaws.com/$STACK/libraries/vendor/gdal.tar.gz"
-
-PKG_CONFIG_PATH="/app/.heroku/vendor/lib/pkgconfig:$PKG_CONFIG_PATH"
-
-# Syntax sugar.
-source $BIN_DIR/utils
-
-bpwatch start gdal_install
-
-# If GDAL exists within requirements, use vendored gdal.
-if (pip-grep -s requirements.txt GDAL gdal pygdal &> /dev/null) then
-
-  if [ ! -f ".heroku/vendor/bin/gdalserver" ]; then
-    echo "-----> Noticed GDAL. Bootstrapping gdal."
-    mkdir -p .heroku/vendor
-    # Download and extract cryptography into target vendor directory.
-    curl $VENDORED_GDAL -s | tar zxv -C .heroku/vendor &> /dev/null
-  fi
-
-  export GDAL=$(pwd)/vendor
-fi
-
-bpwatch stop gdal_install

bin/steps/geo-libs

@@ -1,39 +0,0 @@
-#!/usr/bin/env bash
-
-# This script serves as the GDAL build step of the
-# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python)
-# compiler.
-#
-# A [buildpack](https://devcenter.heroku.com/articles/buildpacks) is an
-# adapter between a Python application and Heroku's runtime.
-#
-# This script is invoked by [`bin/compile`](/).
-
-# The location of the pre-compiled cryptography binary.
-VENDORED_GDAL="https://lang-python.s3.amazonaws.com/$STACK/libraries/vendor/gdal.tar.gz"
-VENDORED_GEOS="https://lang-python.s3.amazonaws.com/$STACK/libraries/vendor/geos.tar.gz"
-VENDORED_PROJ="https://lang-python.s3.amazonaws.com/$STACK/libraries/vendor/proj.tar.gz"
-
-PKG_CONFIG_PATH="/app/.heroku/vendor/lib/pkgconfig:$PKG_CONFIG_PATH"
-
-# Syntax sugar.
-source $BIN_DIR/utils
-
-bpwatch start geo_libs_install
-
-# If GDAL exists within requirements, use vendored gdal.
-if [[ "$BUILD_WITH_GEO_LIBRARIES" ]]; then
-
-  if [ ! -f ".heroku/vendor/bin/proj" ]; then
-    echo "-----> Bootstrapping gdal, geos, proj."
-    mkdir -p .heroku/vendor
-    # Download and extract cryptography into target vendor directory.
-    curl $VENDORED_GDAL -s | tar zxv -C .heroku/vendor &> /dev/null
-    curl $VENDORED_GEOS -s | tar zxv -C .heroku/vendor &> /dev/null
-    curl $VENDORED_PROJ -s | tar zxv -C .heroku/vendor &> /dev/null
-  fi
-
-  export GDAL=$(pwd)/vendor
-fi
-
-bpwatch stop geo_libs_install

bin/steps/hooks/post_compile

@@ -3,5 +3,5 @@
 if [ -f bin/post_compile ]; then
     echo "-----> Running post-compile hook"
     chmod +x bin/post_compile
-    sub-env bin/post_compile
+    sub_env bin/post_compile
 fi

bin/steps/hooks/pre_compile

@@ -3,5 +3,5 @@
 if [ -f bin/pre_compile ]; then
     echo "-----> Running pre-compile hook"
     chmod +x bin/pre_compile
-    sub-env bin/pre_compile
+    sub_env bin/pre_compile
 fi

bin/steps/mercurial

@@ -1,6 +0,0 @@
-# Install Mercurial if it appears to be required.
-if (grep -Fiq "hg+" requirements.txt) then
-  bpwatch start mercurial_install
-    /app/.heroku/python/bin/pip install  mercurial | cleanup | indent
-  bpwatch stop mercurial_install
-fi

bin/steps/nltk

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+# This script serves as the NLTK build step of the
+# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python)
+# compiler.
+#
+# A [buildpack](https://devcenter.heroku.com/articles/buildpacks) is an
+# adapter between a Python application and Heroku's runtime.
+#
+# This script is invoked by [`bin/compile`](/).
+
+# Syntax sugar.
+# shellcheck source=bin/utils
+source "$BIN_DIR/utils"
+
+# Check that nltk was installed by pip, otherwise obviously not needed
+if is_module_available 'nltk'; then
+    puts-step "Downloading NLTK corpora…"
+
+    nltk_packages_definition="$BUILD_DIR/nltk.txt"
+
+    if [ -f "$nltk_packages_definition" ]; then
+
+        readarray -t nltk_packages < "$nltk_packages_definition"
+        puts-step "Downloading NLTK packages: ${nltk_packages[*]}"
+
+        python -m nltk.downloader -d "$BUILD_DIR/.heroku/python/nltk_data" "${nltk_packages[@]}" | indent
+        set_env NLTK_DATA "/app/.heroku/python/nltk_data"
+
+        mcount "buildvar.NLTK_PACKAGES_DEFINITION"
+        mcount "steps.nltk"
+    else
+        puts-warn "'nltk.txt' not found, not downloading any corpora"
+        puts-warn "Learn more: https://devcenter.heroku.com/articles/python-nltk"
+    fi
+fi

bin/steps/pip-install

@@ -1,26 +1,72 @@
-# Install dependencies with Pip.
+#!/usr/bin/env bash
-puts-cmd "pip install -r requirements.txt"
 
-[ ! "$FRESH_PYTHON" ] && bpwatch start pip_install
+# shellcheck source=bin/utils
-[ "$FRESH_PYTHON" ] && bpwatch start pip_install_first
+source "$BIN_DIR/utils"
+
+if [ ! "$SKIP_PIP_INSTALL" ]; then
+
+    # Install dependencies with Pip.
+    puts-step "Installing requirements with pip"
+
+    # Set Pip env vars
+    # This reads certain environment variables set on the Heroku app config
+    # and makes them accessible to the pip install process.
+    #
+    # PIP_EXTRA_INDEX_URL allows for an alternate pypi URL to be used.
+    if [[ -r "$ENV_DIR/PIP_EXTRA_INDEX_URL" ]]; then
+        PIP_EXTRA_INDEX_URL="$(cat "$ENV_DIR/PIP_EXTRA_INDEX_URL")"
+        export PIP_EXTRA_INDEX_URL
+        mcount "buildvar.PIP_EXTRA_INDEX_URL"
+    fi
 
     set +e
-/app/.heroku/python/bin/pip install -r requirements.txt --exists-action=w --src=./.heroku/src --disable-pip-version-check --no-cache-dir 2>&1 | tee $WARNINGS_LOG | cleanup | indent
+
+    # Set SLUGIFY_USES_TEXT_UNIDECODE, required for Airflow versions >=1.10
+    if [[ -r "$ENV_DIR/SLUGIFY_USES_TEXT_UNIDECODE" ]]; then
+        SLUGIFY_USES_TEXT_UNIDECODE="$(cat "$ENV_DIR/SLUGIFY_USES_TEXT_UNIDECODE")"
+        export SLUGIFY_USES_TEXT_UNIDECODE
+        mcount "buildvar.SLUGIFY_USES_TEXT_UNIDECODE"
+    fi
+
+    set +e
+
+    # Measure that we're using pip.
+    mcount "tool.pip"
+
+    # Count expected build failures.
+    if grep -q '==0.0.0' requirements.txt; then
+        mcount "failure.none-version"
+    fi
+
+    if grep -qi '^django==1.*' requirements.txt; then
+        puts-warn "Your Django version is nearing the end of its community support."
+        puts-warn "Upgrade to continue to receive security updates and for the best experience with Django."
+        puts-warn "For more information, check out https://www.djangoproject.com/download/#supported-versions"
+    fi
+
+    if [ ! -f "$BUILD_DIR/.heroku/python/bin/pip" ]; then
+        exit 1
+    fi
+
+    /app/.heroku/python/bin/pip install -r "$BUILD_DIR/requirements.txt" --exists-action=w --src=/app/.heroku/src --disable-pip-version-check --no-cache-dir 2>&1 | tee "$WARNINGS_LOG" | cleanup | indent
     PIP_STATUS="${PIPESTATUS[0]}"
     set -e
 
     show-warnings
 
     if [[ ! $PIP_STATUS -eq 0 ]]; then
+        mcount "failure.pip-install"
         exit 1
     fi
 
-
-# Smart Requirements handling
     cp requirements.txt .heroku/python/requirements-declared.txt
     /app/.heroku/python/bin/pip freeze --disable-pip-version-check > .heroku/python/requirements-installed.txt
 
-[ ! "$FRESH_PYTHON" ] && bpwatch stop pip_install
+    # Install test dependencies, for CI.
-[ "$FRESH_PYTHON" ] && bpwatch stop pip_install_first
+    if [ "$INSTALL_TEST" ]; then
-
+        if [[ -f "$1/requirements-test.txt" ]]; then
-echo
+            puts-step "Installing test dependencies…"
+            /app/.heroku/python/bin/pip install -r "$1/requirements-test.txt" --exists-action=w --src=./.heroku/src --disable-pip-version-check --no-cache-dir 2>&1 | cleanup | indent
+        fi
+    fi
+fi

bin/steps/pip-uninstall

@@ -1,18 +0,0 @@
-set +e
-# Install dependencies with Pip.
-bpwatch start pip_uninstall
-if [[ -f .heroku/python/requirements-declared.txt ]]; then
-
-  cp .heroku/python/requirements-declared.txt requirements-declared.txt
-
-  pip-diff --stale requirements-declared.txt requirements.txt --exclude setuptools pip wheel > .heroku/python/requirements-stale.txt
-
-  rm -fr requirements-declared.txt
-
-  if [[ -s .heroku/python/requirements-stale.txt ]]; then
-    puts-step "Uninstalling stale dependencies"
-    /app/.heroku/python/bin/pip uninstall -r .heroku/python/requirements-stale.txt -y --exists-action=w | cleanup | indent
-  fi
-fi
-bpwatch stop pip_uninstall
-set -e

bin/steps/pipenv

@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+
+# export CLINT_FORCE_COLOR=1
+# export PIPENV_FORCE_COLOR=1
+# shellcheck source=bin/utils
+source "$BIN_DIR/utils"
+set -e
+
+if [[ -f Pipfile.lock ]]; then
+    if [[ -f .heroku/python/Pipfile.lock.sha256 ]]; then
+        if [[ $(openssl dgst -sha256 Pipfile.lock) == $(cat .heroku/python/Pipfile.lock.sha256) ]]; then
+            # Don't skip installation if there are git deps.
+            if ! grep -q 'git' Pipfile.lock; then
+                echo "Skipping installation, as Pipfile.lock hasn't changed since last deploy." | indent
+
+                mcount "tool.pipenv"
+                export SKIP_PIPENV_INSTALL=1
+                export SKIP_PIP_INSTALL=1
+            fi
+        fi
+    fi
+fi
+
+
+if [ ! "$SKIP_PIPENV_INSTALL" ]; then
+    # Pipenv support (Generate requirements.txt with pipenv).
+    if [[ -f Pipfile ]]; then
+        # Measure that we're using Pipenv.
+        mcount "tool.pipenv"
+
+        # Skip pip install, later.
+        export SKIP_PIP_INSTALL=1
+
+        # Set Pip env vars
+        # This reads certain environment variables set on the Heroku app config
+        # and makes them accessible to the pip install process.
+        #
+        # PIP_EXTRA_INDEX_URL allows for an alternate pypi URL to be used.
+        if [[ -r "$ENV_DIR/PIP_EXTRA_INDEX_URL" ]]; then
+            PIP_EXTRA_INDEX_URL="$(cat "$ENV_DIR/PIP_EXTRA_INDEX_URL")"
+            export PIP_EXTRA_INDEX_URL
+            mcount "buildvar.PIP_EXTRA_INDEX_URL"
+        fi
+
+        # Set SLUGIFY_USES_TEXT_UNIDECODE, required for Airflow versions >=1.10
+        if [[ -r "$ENV_DIR/SLUGIFY_USES_TEXT_UNIDECODE" ]]; then
+            SLUGIFY_USES_TEXT_UNIDECODE="$(cat "$ENV_DIR/SLUGIFY_USES_TEXT_UNIDECODE")"
+            export SLUGIFY_USES_TEXT_UNIDECODE
+            mcount "buildvar.SLUGIFY_USES_TEXT_UNIDECODE"
+        fi
+
+        export PIPENV_VERSION="2018.5.18"
+
+        # Install pipenv.
+        # Due to weird old pip behavior and pipenv behavior, pipenv upgrades pip
+        # to latest if only --upgrade is specified. Specify upgrade strategy to
+        # avoid this eager behavior.
+        /app/.heroku/python/bin/pip install pipenv==$PIPENV_VERSION --upgrade --upgrade-strategy only-if-needed &> /dev/null
+
+        # Install the test dependencies, for CI.
+        if [ "$INSTALL_TEST" ]; then
+            puts-step "Installing test dependencies…"
+            /app/.heroku/python/bin/pipenv install --dev --system --deploy 2>&1 | cleanup | indent
+
+        # Install the dependencies.
+        elif [[ ! -f Pipfile.lock ]]; then
+            puts-step "Installing dependencies with Pipenv $PIPENV_VERSION…"
+            /app/.heroku/python/bin/pipenv install --system --skip-lock 2>&1 | indent
+
+        else
+            pipenv-to-pip Pipfile.lock > requirements.txt
+            cp requirements.txt .heroku/python/requirements-declared.txt
+            openssl dgst -sha256 Pipfile.lock > .heroku/python/Pipfile.lock.sha256
+
+            puts-step "Installing dependencies with Pipenv $PIPENV_VERSION…"
+            /app/.heroku/python/bin/pipenv install --system --deploy 2>&1 | indent
+        fi
+    fi
+else
+    export SKIP_PIP_INSTALL=1
+    pipenv-to-pip Pipfile.lock > requirements.txt
+fi

bin/steps/pipenv-python-version

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+
+# Detect Python-version with Pipenv.
+
+if [[ -f $BUILD_DIR/Pipfile ]]; then
+
+    if [[ ! -f $BUILD_DIR/runtime.txt ]]; then
+        if [[ ! -f $BUILD_DIR/Pipfile.lock ]]; then
+            puts-warn "No 'Pipfile.lock' found! We recommend you commit this into your repository."
+        fi
+        if [[ -f $BUILD_DIR/Pipfile.lock ]]; then
+            set +e
+            PYTHON=$(jq -r '._meta.requires.python_full_version' "$BUILD_DIR/Pipfile.lock")
+            if [[ "$PYTHON" != "null" ]]; then
+                echo "python-$PYTHON" > "$BUILD_DIR/runtime.txt"
+            fi
+            set -e
+
+            if [[ "$PYTHON" == "null" ]]; then
+                PYTHON=$(jq -r '._meta.requires.python_version' "$BUILD_DIR/Pipfile.lock")
+                if [ "$PYTHON" = 2.7 ]; then
+                    echo "$LATEST_27" > "$BUILD_DIR/runtime.txt"
+                fi
+                if [ "$PYTHON" = 3.6 ]; then
+                    echo "$LATEST_36" > "$BUILD_DIR/runtime.txt"
+                fi
+                if [ "$PYTHON" = 3.7 ]; then
+                    echo "$LATEST_37" > "$BUILD_DIR/runtime.txt"
+                fi
+                if [ "$PYTHON" = 3.8 ]; then
+                    echo "$LATEST_38" > "$BUILD_DIR/runtime.txt"
+                fi
+                if [ "$PYTHON" = 3.9 ]; then
+                    echo "$LATEST_39" > "$BUILD_DIR/runtime.txt"
+                fi
+            fi
+
+
+        fi
+    fi
+fi

bin/steps/pylibmc

@@ -1,34 +0,0 @@
-#!/usr/bin/env bash
-
-# This script serves as the Pylibmc build step of the
-# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python)
-# compiler.
-#
-# A [buildpack](https://devcenter.heroku.com/articles/buildpacks) is an
-# adapter between a Python application and Heroku's runtime.
-#
-# This script is invoked by [`bin/compile`](/).
-
-# The location of the pre-compiled libmemcached binary.
-VENDORED_MEMCACHED="https://lang-python.s3.amazonaws.com/$STACK/libraries/vendor/libmemcache.tar.gz"
-
-# Syntax sugar.
-source $BIN_DIR/utils
-
-
-bpwatch start pylibmc_install
-
-# If pylibmc exists within requirements, use vendored libmemcached.
-if (pip-grep -s requirements.txt pylibmc &> /dev/null) then
-
-  if [ ! -d ".heroku/vendor/lib/sasl2" ]; then
-    echo "-----> Noticed pylibmc. Bootstrapping libmemcached."
-    mkdir -p .heroku/vendor
-    # Download and extract libmemcached into target vendor directory.
-    curl $VENDORED_MEMCACHED -s | tar zxv -C .heroku/vendor &> /dev/null
-  fi
-
-  export LIBMEMCACHED=$(pwd)/vendor
-fi
-
-bpwatch stop pylibmc_install

bin/steps/python

@@ -1,78 +1,193 @@
+#!/usr/bin/env bash
+
 set +e
+runtime-fixer runtime.txt
 PYTHON_VERSION=$(cat runtime.txt)
 
-# Install Python.
+# The location of the pre-compiled python binary.
-if [ -f .heroku/python-version ]; then
+VENDORED_PYTHON="${S3_BASE_URL}/${STACK}/runtimes/${PYTHON_VERSION}.tar.gz"
-  if [ ! $(cat .heroku/python-version) = $PYTHON_VERSION ]; then
+
-    bpwatch start uninstall_python
+SECURITY_UPDATE="Python has released a security update! Please consider upgrading to"
-      puts-step "Found $(cat .heroku/python-version), removing"
+SECURITY_UPDATE_PYPY="The PyPy project has released a security update! Please consider upgrading to"
-      rm -fr .heroku/python
+
-    bpwatch stop uninstall_python
+ONLY_SUPPORTED_2_VERSION="Only the latest version of Python 2 is supported on the platform. Please consider upgrading to"
+
+PYTHON_2_EOL_UPDATE="Python 2 has reached it's community EOL. Upgrade your Python runtime to maintain a secure application as soon as possible."
+
+# check if runtime exists
+if curl --output /dev/null --silent --head --fail "$VENDORED_PYTHON"; then
+  if [[ "$PYTHON_VERSION" == $PY39* ]]; then
+    if [ "$PYTHON_VERSION" != "$LATEST_39" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_39"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PY38* ]]; then
+    # do things to alert the user of security release available
+    if [ "$PYTHON_VERSION" != "$LATEST_38" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_38"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PY37* ]]; then
+    # do things to alert the user of security release available
+    if [ "$PYTHON_VERSION" != "$LATEST_37" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_37"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PY36* ]]; then
+    # security update note
+    if [ "$PYTHON_VERSION" != "$LATEST_36" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_36"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PY35* ]]; then
+    # security update note
+    if [ "$PYTHON_VERSION" != "$LATEST_35" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_35"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PY34* ]]; then
+    # security update note
+    if [ "$PYTHON_VERSION" != "$LATEST_34" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_34"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PY27* ]]; then
+    puts-warn "$PYTHON_2_EOL_UPDATE"
+    echo "       Learn More: https://devcenter.heroku.com/articles/python-2-7-eol-faq"
+    # security update note
+    if [ "$PYTHON_VERSION" != "$LATEST_27" ]; then
+      puts-warn "$ONLY_SUPPORTED_2_VERSION" "$LATEST_27"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PYPY27* ]]; then
+    # security update note
+    if [ "$PYTHON_VERSION" != "$LATEST_PYPY_27" ]; then
+      puts-warn "$SECURITY_UPDATE_PYPY" "$LATEST_PYPY_27"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
+  if [[ "$PYTHON_VERSION" == $PYPY36* ]]; then
+    # security update note
+    if [ "$PYTHON_VERSION" != "$LATEST_PYPY_36" ]; then
+      puts-warn "$SECURITY_UPDATE_PYPY" "$LATEST_PYPY_36"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
 else
-    SKIP_INSTALL=1
-  fi
-fi
-
-if [ ! $STACK = $CACHED_PYTHON_STACK ]; then
-  bpwatch start uninstall_python
-    rm -fr .heroku/python .heroku/python-stack .heroku/vendor
-    unset SKIP_INSTALL
-  bpwatch stop uninstall_python
-fi
-
-
-if [ ! "$SKIP_INSTALL" ]; then
-  bpwatch start install_python
-    puts-step "Installing $PYTHON_VERSION"
-
-    # Prepare destination directory.
-    mkdir -p .heroku/python
-
-    curl https://lang-python.s3.amazonaws.com/$STACK/runtimes/$PYTHON_VERSION.tar.gz -s | tar zxv -C .heroku/python &> /dev/null
-    if [[ $? != 0 ]] ; then
   puts-warn "Requested runtime ($PYTHON_VERSION) is not available for this stack ($STACK)."
   puts-warn "Aborting.  More info: https://devcenter.heroku.com/articles/python-support"
   exit 1
 fi
 
-  bpwatch stop install_python
+mcount "version.python.${PYTHON_VERSION}"
 
-  # Record for future reference.
+if [[ "$STACK" != "$CACHED_PYTHON_STACK" ]]; then
-  echo $PYTHON_VERSION > .heroku/python-version
+    puts-step "Stack has changed from $CACHED_PYTHON_STACK to $STACK, clearing cache"
-  echo $STACK > .heroku/python-stack
+    rm -rf .heroku/python-stack .heroku/python-version .heroku/python .heroku/vendor .heroku/python .heroku/python-sqlite3-version
-  FRESH_PYTHON=true
-
-  hash -r
 fi
 
-# If Pip isn't up to date:
+if [ -f .heroku/python-version ]; then
-if [ "$FRESH_PYTHON" ] || [[ ! $(pip --version) == *$PIP_VERSION* ]]; then
+  if [ ! "$(cat .heroku/python-version)" = "$PYTHON_VERSION" ]; then
-  WORKING_DIR=$(pwd)
+      puts-step "Found $(cat .heroku/python-version), removing"
+      rm -rf .heroku/python
+  else
+    SKIP_INSTALL=1
+  fi
+fi
 
-  bpwatch start prepare_environment
+# Check if we should reinstall python dependencies
+if [[ ! -f "$CACHE_DIR/.heroku/requirements.txt" ]]; then
+  # IF there's no cached dependencies, update cached version of requirements.txt
+  # This should only run for new apps and first deploys after this update
+  cp -R "$BUILD_DIR/requirements.txt" "$CACHE_DIR/.heroku/requirements.txt"
+else
+  # IF there IS a cached directory, check for differences with the new one
+  if ! diff "$BUILD_DIR/requirements.txt" "$CACHE_DIR/.heroku/requirements.txt" &> /dev/null; then
+    puts-step "Requirements file has been changed, clearing cached dependencies"
+    # if there are any differences, clear the Python cache
+    # Installing Python over again does not take noticably more time
+    cp -R "$BUILD_DIR/requirements.txt" "$CACHE_DIR/.heroku/requirements.txt"
+    rm -rf .heroku/python
+    unset SKIP_INSTALL
+  else
+    puts-step "No change in requirements detected, installing from cache"
+  fi
+fi
 
-  TMPTARDIR=$(mktemp -d)
+if [ ! "$SKIP_INSTALL" ]; then
-  trap "rm -rf $TMPTARDIR" RETURN
+    puts-step "Installing $PYTHON_VERSION"
 
-  bpwatch start install_setuptools
+    # Prepare destination directory.
-    # Prepare it for the real world
+    mkdir -p .heroku/python
-    # puts-step "Installing Setuptools ($SETUPTOOLS_VERSION)"
-    tar zxf $ROOT_DIR/vendor/setuptools-$SETUPTOOLS_VERSION.tar.gz -C $TMPTARDIR
-    cd $TMPTARDIR/setuptools-$SETUPTOOLS_VERSION/
-    python setup.py install &> /dev/null
-    cd $WORKING_DIR
-  bpwatch stop install_setuptoools
 
-  bpwatch start install_pip
+    if ! curl "${VENDORED_PYTHON}" -s | tar zxv -C .heroku/python &> /dev/null; then
-    # puts-step "Installing Pip ($PIP_VERSION)"
+      puts-warn "Requested runtime ($PYTHON_VERSION) is not available for this stack ($STACK)."
-    tar zxf $ROOT_DIR/vendor/pip-$PIP_VERSION.tar.gz -C $TMPTARDIR
+      puts-warn "Aborting.  More info: https://devcenter.heroku.com/articles/python-support"
-    cd $TMPTARDIR/pip-$PIP_VERSION/
+      exit 1
-    python setup.py install &> /dev/null
+    fi
-    cd $WORKING_DIR
 
-  bpwatch stop install_pip
+  # Record for future reference.
-  bpwatch stop prepare_environment
+  echo "$PYTHON_VERSION" > .heroku/python-version
+  echo "$STACK" > .heroku/python-stack
+
+  hash -r
 fi
 
 set -e
+
+PIP_VERSION='20.1.1'
+# Must use setuptools <47.2.0 until we fix:
+# https://github.com/heroku/heroku-buildpack-python/issues/1006
+SETUPTOOLS_VERSION='47.1.1'
+WHEEL_VERSION='0.34.2'
+
+if [[ "${PYTHON_VERSION}" == ${PY34}* ]]; then
+  # Python 3.4 support was dropped in pip 19.2+, setuptools 44+ and wheel 0.34+.
+  PIP_VERSION='19.1.1'
+  SETUPTOOLS_VERSION='43.0.0'
+  WHEEL_VERSION='0.33.6'
+elif [[ "${PYTHON_VERSION}" == ${PY27}* || "${PYTHON_VERSION}" == ${PYPY27}* ]]; then
+  # Python 2.7 support was dropped in setuptools 45+.
+  SETUPTOOLS_VERSION='44.1.1'
+fi
+
+# We don't use get-pip.py, since:
+#  - it uses `--force-reinstall`, which is unnecessary here and slows down repeat builds
+#  - it means downloading pip twice (once embedded in get-pip.py, and again during
+#    the install, since get-pip.py can't install the embedded version directly)
+#  - we would still have to manage several versions of get-pip.py, to support older Pythons.
+# Instead, we use the pip wheel to install itself, using the method described here:
+# https://github.com/pypa/pip/issues/2351#issuecomment-69994524
+PIP_WHEEL_FILENAME="pip-${PIP_VERSION}-py2.py3-none-any.whl"
+PIP_WHEEL_URL="${S3_BASE_URL}/common/${PIP_WHEEL_FILENAME}"
+PIP_WHEEL="${TMPDIR:-/tmp}/${PIP_WHEEL_FILENAME}"
+
+if ! curl -sSf "${PIP_WHEEL_URL}" -o "$PIP_WHEEL"; then
+  mcount "failure.python.download-pip"
+  puts-warn "Failed to download pip"
+  exit 1
+fi
+
+if [[ -f "$BUILD_DIR/Pipfile" ]]; then
+  # The buildpack is pinned to old pipenv, which requires older pip.
+  # Pip 9.0.2 doesn't support installing itself from a wheel, so we have to use split
+  # versions here (ie: installer pip version different from target pip version).
+  PIP_VERSION='9.0.2'
+  PIP_TO_INSTALL="pip==${PIP_VERSION}"
+else
+  PIP_TO_INSTALL="${PIP_WHEEL}"
+fi
+
+puts-step "Installing pip ${PIP_VERSION}, setuptools ${SETUPTOOLS_VERSION} and wheel ${WHEEL_VERSION}"
+
+/app/.heroku/python/bin/python "${PIP_WHEEL}/pip" install --quiet --disable-pip-version-check --no-cache \
+  "${PIP_TO_INSTALL}" "setuptools==${SETUPTOOLS_VERSION}" "wheel==${WHEEL_VERSION}"
+
 hash -r

bin/steps/setuptools

@@ -1,11 +0,0 @@
-#!/usr/bin/env bash
-
-# Syntax sugar.
-source $BIN_DIR/utils
-
-if (pip-grep -s requirements.txt setuptools distribute &> /dev/null) then
-
-  puts-warn 'The package setuptools/distribute is listed in requirements.txt.'
-  puts-warn 'Please remove to ensure expected behavior. '
-
-fi

bin/steps/sqlite3

@@ -0,0 +1,77 @@
+#!/usr/bin/env bash
+
+# shellcheck source=bin/utils
+source "$BIN_DIR/utils"
+
+sqlite3_install() {
+  HEROKU_PYTHON_DIR="$1"
+  HEADERS_ONLY="$3"
+
+  mkdir -p "$HEROKU_PYTHON_DIR"
+
+  APT_CACHE_DIR="$HEROKU_PYTHON_DIR/apt/cache"
+  APT_STATE_DIR="$HEROKU_PYTHON_DIR/apt/state"
+
+  mkdir -p "$APT_CACHE_DIR/archives/partial"
+  mkdir -p "$APT_STATE_DIR/lists/partial"
+
+  APT_OPTIONS="-o debug::nolocking=true"
+  APT_OPTIONS="$APT_OPTIONS -o dir::cache=$APT_CACHE_DIR"
+  APT_OPTIONS="$APT_OPTIONS -o dir::state=$APT_STATE_DIR"
+  APT_OPTIONS="$APT_OPTIONS -o dir::etc::sourcelist=/etc/apt/sources.list"
+
+  apt-get $APT_OPTIONS update > /dev/null 2>&1
+  if [ -z "$HEADERS_ONLY" ]; then
+    apt-get $APT_OPTIONS -y -d --reinstall install libsqlite3-dev sqlite3 > /dev/null 2>&1
+  else
+    apt-get $APT_OPTIONS -y -d --reinstall install libsqlite3-dev
+  fi
+
+  find "$APT_CACHE_DIR/archives/" -name "*.deb" -exec dpkg -x {} "$HEROKU_PYTHON_DIR/sqlite3/" \;
+
+  mkdir -p "$HEROKU_PYTHON_DIR/include"
+  mkdir -p "$HEROKU_PYTHON_DIR/lib"
+
+  # remove old sqlite3 libraries/binaries
+  find "$HEROKU_PYTHON_DIR/include/" -name "sqlite3*.h" -exec rm -f {} \;
+  find "$HEROKU_PYTHON_DIR/lib/" -name "libsqlite3.*" -exec rm -f {} \;
+  rm -f "$HEROKU_PYTHON_DIR/lib/pkgconfig/sqlite3.pc"
+  rm -f "$HEROKU_PYTHON_DIR/bin/sqlite3"
+
+  # copy over sqlite3 headers & bins and setup linking against the stack image library
+  mv "$HEROKU_PYTHON_DIR/sqlite3/usr/include/"* "$HEROKU_PYTHON_DIR/include/"
+  mv "$HEROKU_PYTHON_DIR/sqlite3/usr/lib/x86_64-linux-gnu"/libsqlite3.*a "$HEROKU_PYTHON_DIR/lib/"
+  mkdir -p "$HEROKU_PYTHON_DIR/lib/pkgconfig"
+  # set the right prefix/lib directories
+  sed -e 's/prefix=\/usr/prefix=\/app\/.heroku\/python/' -e 's/\/x86_64-linux-gnu//' "$HEROKU_PYTHON_DIR/sqlite3/usr/lib/x86_64-linux-gnu/pkgconfig/sqlite3.pc" > "$HEROKU_PYTHON_DIR/lib/pkgconfig/sqlite3.pc"
+  # need to point the libsqlite3.so to the stack image library for /usr/bin/ld -lsqlite3
+  SQLITE3_LIBFILE="/usr/lib/x86_64-linux-gnu/$(readlink -n "$HEROKU_PYTHON_DIR/sqlite3/usr/lib/x86_64-linux-gnu/libsqlite3.so")"
+  ln -s "$SQLITE3_LIBFILE" "$HEROKU_PYTHON_DIR/lib/libsqlite3.so"
+  if [ -z "$HEADERS_ONLY" ]; then
+    mv "$HEROKU_PYTHON_DIR/sqlite3/usr/bin"/* "$HEROKU_PYTHON_DIR/bin/"
+  fi
+
+  # cleanup
+  rm -rf "$HEROKU_PYTHON_DIR/sqlite3/"
+  rm -rf "$HEROKU_PYTHON_DIR/apt/"
+}
+
+buildpack_sqlite3_install() {
+  HEROKU_PYTHON_DIR="$BUILD_DIR/.heroku/python"
+
+  SQLITE3_VERSION_FILE="$BUILD_DIR/.heroku/python-sqlite3-version"
+  if [ -f "$SQLITE3_VERSION_FILE" ]; then
+    INSTALLED_SQLITE3_VERSION=$(cat "$SQLITE3_VERSION_FILE")
+  fi
+
+  puts-step "Installing SQLite3"
+
+  if sqlite3_install "$BUILD_DIR/.heroku/python" ; then
+    mcount "success.python.sqlite3"
+  else
+    echo "Sqlite3 failed to install."
+    mcount "failure.python.sqlite3"
+  fi
+
+  mkdir -p "$CACHE_DIR/.heroku/"
+}

bin/test-compile

@@ -1,11 +1,13 @@
 #!/usr/bin/env bash
 
 # Syntax sugar.
-BIN_DIR=$(cd $(dirname $0); pwd) # absolute path
+BIN_DIR=$(cd "$(dirname "$0")" || return; pwd) # absolute path
-source $BIN_DIR/utils
 
-DISABLE_COLLECTSTATIC=1 "$(dirname ${0:-})/compile" "$1" "$2" "$3"
+# shellcheck source=bin/utils
+source "$BIN_DIR/utils"
 
-if [[ -f "$1/requirements-test.txt" ]]; then
+# Locale support for Pipenv.
-    /app/.heroku/python/bin/pip install -r "$1/requirements-test.txt" --exists-action=w --src=./.heroku/src --disable-pip-version-check --no-cache-dir 2>&1 | cleanup | indent
+export LC_ALL=C.UTF-8
-fi
+export LANG=C.UTF-8
+
+DISABLE_COLLECTSTATIC=1 INSTALL_TEST=1 "$(dirname "${0:-}")/compile" "$1" "$2" "$3"

bin/utils

@@ -1,6 +1,16 @@
+#!/usr/bin/env bash
 shopt -s extglob
+shopt -s nullglob
 
-if [ $(uname) == Darwin ]; then
+# This is necessary since this script is sometimes sourced from
+# subshells that don't have the variables from bin/compile.
+# Remove this once we no longer wrap all the things in `sub_env`.
+BIN_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+ROOT_DIR=$(dirname "${BIN_DIR}")
+# shellcheck source=vendor/buildpack-stdlib_v8.sh
+source "${ROOT_DIR}/vendor/buildpack-stdlib_v8.sh"
+
+if [ "$(uname)" == Darwin ]; then
     sed() { command sed -l "$@"; }
 else
     sed() { command sed -u "$@"; }
@@ -11,46 +21,20 @@ indent() {
   sed "s/^/       /"
 }
 
+
 # Clean up pip output
 cleanup() {
-  sed -e 's/\.\.\.\+/.../g' | sed -e '/already satisfied/Id' | sed -e '/Overwriting/Id' | sed -e '/python executable/Id' | sed -e '/no previously-included files/Id'
+  sed -e 's/\.\.\.\+/.../g' | sed -e '/already satisfied/Id' | sed -e '/No files were found to uninstall/Id' | sed -e '/Overwriting/Id' | sed -e '/python executable/Id' | sed -e '/no previously-included files/Id'
-}
-
-# Buildpack Indented line.
-puts-line() {
-  echo "       $@"
 }
 
 # Buildpack Steps.
 puts-step() {
-  echo "-----> $@"
+  echo "-----> $*"
 }
 
 # Buildpack Warnings.
 puts-warn() {
-  echo " !     $@"
+  echo " !     $*"
-}
-
-# Buildpack Commands.
-puts-cmd() {
-  echo "     $ $@"
-}
-
-# Usage: $ set-env key value
-set-env() {
-  echo "export $1=$2" >> $PROFILE_PATH
-  echo "export $1=$2" >> $EXPORT_PATH
-}
-
-# Usage: $ set-default-env key value
-set-default-env() {
-  echo "export $1=\${$1:-$2}" >> $PROFILE_PATH
-  echo "export $1=\${$1:-$2}" >> $EXPORT_PATH
-}
-
-# Usage: $ un-set-env key
-un-set-env() {
-  echo "unset $1" >> $PROFILE_PATH
 }
 
 # Does some serious copying.
@@ -69,42 +53,54 @@ deep-cp() {
   )
 }
 
-# Does some serious moving.
+
-deep-mv() {
+# Measure the size of the Python installation.
-  deep-cp "$1" "$2"
+measure-size() {
-  deep-rm "$1"
+  echo "$(du -s .heroku/python 2>/dev/null || echo 0) | awk '{print $1}')"
 }
 
-# Does some serious deleting.
+# Python version operator >
-deep-rm() {
+version_gt() {
-  # subshell to avoid surprising caller with shopts.
+  test "$(printf '%s\n' "$@" | sort -V | head -n 1)" != "$1";
-  (
-    shopt -s dotglob
-    rm -rf "$1"/!(.curlrc|.netrc|tmp|.|..)
-  )
 }
 
-
+# Python verison operator >=
-sub-env() {
+version_gte() {
-
+  if [ "$1" == "$2" ]; then
-  WHITELIST=${2:-''}
+    return 0
-  BLACKLIST=${3:-'^(GIT_DIR|PYTHONHOME|LD_LIBRARY_PATH|LIBRARY_PATH|PATH)$'}
-
-  # Python-specific variables.
-  export PYHONHOME=$BUILD_DIR/.heroku/python
-  export PYTHONPATH=$BUILD_DIR/
-
-  (
-    if [ -d "$ENV_DIR" ]; then
-      for e in $(ls $ENV_DIR); do
-        echo "$e" | grep -E "$WHITELIST" | grep -qvE "$BLACKLIST" &&
-        export "$e=$(cat $ENV_DIR/$e)"
-        :
-      done
   fi
 
-    $1
+  version_gt "$1" "$2"
-
-  )
 }
 
+# Check if Python 2
+python2_check() {
+  VERSION="$1"
+
+  version_gte "$VERSION" "python-2.7.0" && version_gt "python-3.0.0" "$VERSION"
+}
+
+# Check if Python 3
+python3_check() {
+  VERSION="$1"
+
+  version_gte "$VERSION" "python-3.0.0" && version_gt "python-4.0.0" "$VERSION"
+}
+
+# Check if Python version needs to install SQLite3
+python_sqlite3_check() {
+  VERSION="$1"
+  MIN_PYTHON_3="python-3.5.6"
+  MIN_PYTHON_2="python-2.7.15"
+
+  ( python2_check "$VERSION" && version_gte "$VERSION" "$MIN_PYTHON_2" ) \
+    || ( python3_check "$VERSION" && version_gte "$VERSION" "$MIN_PYTHON_3" )
+}
+
+is_module_available() {
+  # Returns 0 is the specified module exists, otherwise returns 1.
+  # Uses pkgutil rather than pkg_resources or pip's CLI, since pkgutil exists
+  # in the stdlib, and doesn't depend on the choice of package manager.
+  local module_name="${1}"
+  python -c "import sys, pkgutil; sys.exit(0 if pkgutil.find_loader('${module_name}') else 1)"
+}

bin/warnings

@@ -1,3 +1,4 @@
+#!/usr/bin/env bash
 shopt -s extglob
 
 old-platform() {
@@ -7,15 +8,7 @@ old-platform() {
     puts-warn "This caused the security warning you saw above during the 'pip install' step."
     puts-warn "We recommend '$RECOMMENDED_PYTHON_VERSION', which you can specify in a 'runtime.txt' file."
     puts-warn "  -- Much Love, Heroku."
-  fi
+    mcount 'warnings.python.old'
-}
-
-pylibmc-missing() {
-  if grep -qi 'fatal error: libmemcached/memcached.h: No such file or directory' "$WARNINGS_LOG"; then
-    echo
-    puts-warn "Hello! There was a problem with your build related to libmemcache."
-    puts-warn "The Python library 'pylibmc' must be explicitly specified in 'requirements.txt' in order to build correctly."
-    puts-warn "Once you do that, everything should work as expected.   -- Much Love, Heroku."
   fi
 }
 
@@ -27,6 +20,7 @@ scipy-included() {
     puts-warn "There is, however, a buildpack available that makes it possible to use it on Heroku."
     puts-warn "You can learn more here:  https://devcenter.heroku.com/articles/python-c-deps"
     puts-warn "Sorry for the inconvenience.   -- Much Love, Heroku."
+    mcount 'warnings.scipy'
   fi
 }
 
@@ -37,13 +31,37 @@ distribute-included() {
     puts-warn "This library is automatically installed by Heroku and shouldn't be in"
     puts-warn "Your requirements.txt file. This can cause unexpected behavior."
     puts-warn "  -- Much Love, Heroku."
+    mcount 'warnings.distribute'
+  fi
+}
+
+six-included() {
+  if grep -qi 'Running setup.py install for six' "$WARNINGS_LOG"; then
+    echo
+    puts-warn "Hello! Your requirements.txt file contains the six package."
+    puts-warn "This library is automatically installed by Heroku and shouldn't be in"
+    puts-warn "Your requirements.txt file. This can cause unexpected behavior."
+    puts-warn "  -- Much Love, Heroku."
+    mcount 'warnings.six'
+  fi
+}
+
+gdal-missing() {
+  if grep -qi 'Could not find gdal-config' "$WARNINGS_LOG"; then
+    mcount 'warnings.gdal'
+    echo
+    puts-warn "Hello! Package installation failed since the GDAL library was not found."
+    puts-warn "For GDAL, GEOS and PROJ support, use the Geo buildpack alongside the Python buildpack:"
+    puts-warn "https://github.com/heroku/heroku-geo-buildpack"
+    puts-warn "  -- Much Love, Heroku."
   fi
 }
 
 show-warnings() {
   old-platform
-  pylibmc-missing
   scipy-included
   distribute-included
+  six-included
+  gdal-missing
 }
 

buildpack.toml

@@ -0,0 +1,13 @@
+[buildpack]
+name = "Python"
+
+  [publish.Ignore]
+  files = [
+    "test/",
+    ".gitignore",
+    ".dockerignore",
+    ".github/",
+    "Dockerfile",
+    "Pipfile",
+    "Pipfile.lock"
+  ]

builds/README.md

@@ -1,31 +1,80 @@
 # Python Buildpack Binaries
 
+The binaries for this buildpack are built in Docker containers based on the Heroku stack image.
 
-To get started with it, create an app on Heroku inside a clone of this repository, and set your S3 config vars:
+## Configuration
 
-    $ heroku create --buildpack https://github.com/heroku/heroku-buildpack-python#not-heroku
+In order to publish binaries AWS credentials must be passed to the build container.
-    $ heroku config:set WORKSPACE_DIR=builds
+If you are testing only the build (ie: `bob build`), these are optional.
-    $ heroku config:set AWS_ACCESS_KEY_ID=<your_aws_key>
-    $ heroku config:set AWS_SECRET_ACCESS_KEY=<your_aws_secret>
-    $ heroku config:set S3_BUCKET=<your_s3_bucket_name>
 
+In addition, unless you are building the official binaries for Heroku (which use the defaults
+specified in each `Dockerfile`), you will need to override `S3_BUCKET` and `S3_PREFIX` to
+match your own S3 bucket/use case.
 
-Then, shell into an instance and run a build by giving the name of the formula inside `builds`:
+If you only need to set AWS credentials, you can do so by setting the environment variables
+`AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` before calling the make commands.
 
-    $ heroku run bash
+For example:
-    Running `bash` attached to terminal... up, run.6880
-    ~ $ bob build runtimes/python-2.7.6
 
-    Fetching dependencies... found 2:
+```bash
-      - libraries/sqlite
+set +o history # Disable bash history
+export AWS_ACCESS_KEY_ID=...
+export AWS_SECRET_ACCESS_KEY=...
+set -o history # Re-enable bash history
+make ...
+```
 
-    Building formula runtimes/python-2.7.6:
+If you need to override the default S3 bucket, or would prefer not to use credentials via
-        === Building Python 2.7.6
+environment variables, then you need to instead use a Docker env file like so:
-        Fetching Python v2.7.6 source...
-        Compiling...
 
-If this works, run `bob deploy` instead of `bob build` to have the result uploaded to S3 for you.
+1. Copy the `builds/dockerenv.default` env file to a location outside the buildpack repository.
+2. Edit the new file, adding at a minimum the values for the variables
+   `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` (see Docker
+   [env-file documentation](https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file)).
+3. Pass the path of the file to the make commands using `ENV_FILE`. For example:
 
-To speed things up drastically, it'll usually be a good idea to `heroku run bash --size PX` instead.
+   ```bash
+   make ... ENV_FILE=~/.dockerenv.python-buildpack
+   ```
 
-Enjoy :)
+## Launching an interactive build environment
+
+To start an interactive version of the build environment (ideal for development) use the
+`buildenv` make target, passing in the desired `STACK` name. For example:
+
+```bash
+make buildenv STACK=heroku-18
+```
+
+This will create the builder docker image based on the latest image for that stack, and
+then start a bash shell where you can run `bob build`, `bob deploy`, and so forth.
+
+The `builds/` directory is bind-mounted into the running container, so local build formula
+changes will appear there immediately without the need to rebuild the image.
+
+## Bulk deploying runtimes
+
+When a new Python version is released, binaries have to be generated for multiple stacks.
+To automate this, use the `deploy-runtimes` make target, which will ensure the builder
+image is up to date, and then run `bob deploy` for each runtime-stack combination.
+
+The build formula name(s) are passed using `RUNTIMES`, like so:
+
+```bash
+make deploy-runtimes RUNTIMES='python-X.Y.Z'
+```
+
+By default this will deploy to all supported stacks (see `STACKS` in `Makefile`),
+but this can be overridden using `STACKS`:
+
+```bash
+make deploy-runtimes RUNTIMES='python-X.Y.Z' STACKS='heroku-16 heroku-18'
+```
+
+Multiple runtimes can also be specified (useful for when adding a new stack), like so:
+
+```bash
+make deploy-runtimes RUNTIMES='python-A.B.C python-X.Y.Z' STACKS='heroku-20'
+```
+
+Note: Both `RUNTIMES` and `STACKS` are space delimited.

builds/dockerenv.default

@@ -0,0 +1,8 @@
+# Since no values are specified here, these variables will be read from the environment at run time:
+# https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file
+AWS_ACCESS_KEY_ID
+AWS_SECRET_ACCESS_KEY
+
+# Uncomment these if you need to override the default S3 bucket and/or path prefixes.
+# S3_BUCKET
+# S3_PREFIX

builds/heroku-16.Dockerfile

@@ -0,0 +1,20 @@
+FROM heroku/heroku:16-build
+
+ENV WORKSPACE_DIR="/app/builds" \
+    S3_BUCKET="heroku-buildpack-python" \
+    S3_PREFIX="heroku-16/" \
+    STACK="heroku-16"
+
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt /app/
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+
+COPY . /app

builds/heroku-18.Dockerfile

@@ -0,0 +1,20 @@
+FROM heroku/heroku:18-build
+
+ENV WORKSPACE_DIR="/app/builds" \
+    S3_BUCKET="heroku-buildpack-python" \
+    S3_PREFIX="heroku-18/" \
+    STACK="heroku-18"
+
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt /app/
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+
+COPY . /app

builds/heroku-20.Dockerfile

@@ -0,0 +1,20 @@
+FROM heroku/heroku:20-build
+
+ENV WORKSPACE_DIR="/app/builds" \
+    S3_BUCKET="heroku-buildpack-python" \
+    S3_PREFIX="heroku-20/" \
+    STACK="heroku-20"
+
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt /app/
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+
+COPY . /app

builds/libraries/autoconf

@@ -1,15 +0,0 @@
-#!/usr/bin/env bash
-# Build Path: /app/.heroku/python/
-
-OUT_PREFIX=$1
-
-echo "Building autoconf..."
-
-
-SOURCE_TARBALL='https://ftp.gnu.org/gnu/autoconf/autoconf-2.68.tar.gz'
-curl -L $SOURCE_TARBALL | tar xz
-
-cd autoconf-2.68
-./configure --prefix=$OUT_PREFIX
-make
-make install

builds/libraries/sqlite

@@ -3,7 +3,7 @@
 
 OUT_PREFIX=$1
 
-echo "Building SQLite..."
+echo "Building SQLite…"
 
 
 SOURCE_TARBALL='https://www.sqlite.org/sqlite-autoconf-3070900.tar.gz'
@@ -19,4 +19,4 @@ make install
 
 # Cleanup
 cd ..
-rm -fr sqlite
+rm -rf sqlite

builds/libraries/vendor/gdal

@@ -1,23 +0,0 @@
-#!/usr/bin/env bash
-# Build Path: /app/.heroku/vendor/
-
-OUT_PREFIX=$1
-
-# Use new path, containing autoconf.
-export PATH="/app/.heroku/python/bin/:$PATH"
-hash -r
-
-
-echo "Building gdal..."
-
-SOURCE_TARBALL='http://download.osgeo.org/gdal/1.11.1/gdal-1.11.1.tar.gz'
-
-curl -L $SOURCE_TARBALL | tar zx
-
-cd gdal-1.11.1
-./configure --prefix=$OUT_PREFIX  &&
-make
-make install
-
-# Cleanup
-cd ..

builds/libraries/vendor/geos

@@ -1,23 +0,0 @@
-#!/usr/bin/env bash
-# Build Path: /app/.heroku/vendor/
-
-OUT_PREFIX=$1
-
-# Use new path, containing autoconf.
-export PATH="/app/.heroku/python/bin/:$PATH"
-hash -r
-
-
-echo "Building geos..."
-
-SOURCE_TARBALL='http://download.osgeo.org/geos/geos-3.4.2.tar.bz2'
-
-curl -L $SOURCE_TARBALL | tar xj
-
-cd geos-3.4.2
-./configure --prefix=$OUT_PREFIX  &&
-make
-make install
-
-# Cleanup
-cd ..

builds/libraries/vendor/libffi

@@ -1,23 +0,0 @@
-#!/usr/bin/env bash
-# Build Path: /app/.heroku/vendor/
-
-OUT_PREFIX=$1
-
-# Use new path, containing autoconf.
-export PATH="/app/.heroku/python/bin/:$PATH"
-hash -r
-
-
-echo "Building libffi..."
-
-SOURCE_TARBALL='ftp://sourceware.org/pub/libffi/libffi-3.1.tar.gz'
-
-curl -L $SOURCE_TARBALL | tar x
-
-cd libffi-3.1
-./configure --prefix=$OUT_PREFIX --disable-static &&
-make
-make install
-
-# Cleanup
-cd ..

builds/libraries/vendor/libmemcache

@@ -1,40 +0,0 @@
-#!/usr/bin/env bash
-# Build Path: /app/.heroku/vendor/
-
-OUT_PREFIX=$1
-
-# fail hard
-set -o pipefail
-# fail harder
-set -eux
-
-DEFAULT_VERSION="1.0.18"
-dep_version=${VERSION:-$DEFAULT_VERSION}
-dep_dirname=libmemcached-${dep_version}
-dep_archive_name=${dep_dirname}.tar.gz
-dep_url=https://launchpad.net/libmemcached/1.0/${dep_version}/+download/${dep_archive_name}
-
-# SASL Support.
-echo "-----> Building cyrus-sasl 2.1.26..."
-
-curl -LO ftp://ftp.cyrusimap.org/cyrus-sasl/cyrus-sasl-2.1.26.tar.gz
-# FTP doesn't play well with piping into tar xz
-tar xzf cyrus-sasl-2.1.26.tar.gz
-
-pushd cyrus-sasl-2.1.26
-./configure --prefix=${OUT_PREFIX} --with-plugindir=${OUT_PREFIX}lib/sasl2 --with-configdir=${OUT_PREFIX}lib/sasl2
-
-make -s -j 9
-make install -s
-popd
-
-echo "-----> Building libmemcached ${dep_version}..."
-
-curl -L ${dep_url} | tar xz
-pushd ${dep_dirname}
-CPPFLAGS=-I${OUT_PREFIX}/include LDFLAGS=-L${OUT_PREFIX}/lib ./configure --prefix=${OUT_PREFIX} --without-memcached
-make -s -j 9
-make install -s
-popd
-
-echo "-----> Done."

builds/libraries/vendor/proj

@@ -1,23 +0,0 @@
-#!/usr/bin/env bash
-# Build Path: /app/.heroku/vendor/
-
-OUT_PREFIX=$1
-
-# Use new path, containing autoconf.
-export PATH="/app/.heroku/python/bin/:$PATH"
-hash -r
-
-
-echo "Building gdal..."
-
-SOURCE_TARBALL='http://download.osgeo.org/proj/proj-4.8.0.tar.gz'
-
-curl -L $SOURCE_TARBALL | tar zx
-
-cd proj-4.8.0
-./configure --prefix=$OUT_PREFIX  &&
-make
-make install
-
-# Cleanup
-cd ..

builds/runtimes/pypy

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+# fail hard
+set -o pipefail
+# fail harder
+set -eu
+
+OUT_PREFIX=$1
+
+dep_formula=${0#$WORKSPACE_DIR/} # this is the original script, e.g. pypy-5.3.1
+dep_name=$(basename $BASH_SOURCE) # this is us
+dep_version=${dep_formula##*"/${dep_name}-"} # "subtract" our name from full version name
+dep_package=${dep_name}2-v${dep_version} # it's always "pypy2-…"
+dep_dirname=${dep_package}-linux64
+dep_archive_name=${dep_dirname}.tar.bz2
+dep_url=https://bitbucket.org/pypy/pypy/downloads/${dep_archive_name}
+
+echo "Building PyPy…"
+
+curl -L "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name
+
+ln "$OUT_PREFIX/bin/pypy" "$OUT_PREFIX/bin/python"

builds/runtimes/pypy-5.3.1

@@ -2,13 +2,4 @@
 # Build Path: /app/.heroku/python/
 # Build Deps: libraries/sqlite
 
-# NOTICE: This formula only works for the cedar-14 stack, not cedar.
+source $(dirname $0)/pypy
-
-OUT_PREFIX=$1
-
-echo "Building PyPy..."
-SOURCE_TARBALL='https://bitbucket.org/pypy/pypy/downloads/pypy2-v5.3.1-linux64.tar.bz2'
-curl -L $SOURCE_TARBALL | tar jx
-cp -R pypy2-v5.3.1-linux64/* $OUT_PREFIX
-
-ln $OUT_PREFIX/bin/pypy $OUT_PREFIX/bin/python

builds/runtimes/pypy-5.6.0

@@ -2,13 +2,4 @@
 # Build Path: /app/.heroku/python/
 # Build Deps: libraries/sqlite
 
-# NOTICE: This formula only works for the cedar-14 stack, not cedar.
+source $(dirname $0)/pypy
-
-OUT_PREFIX=$1
-
-echo "Building PyPy..."
-SOURCE_TARBALL='https://bitbucket.org/pypy/pypy/downloads/pypy2-v5.6.0-linux64.tar.bz2'
-curl -L $SOURCE_TARBALL | tar jx
-cp -R pypy2-v5.6.0-linux64/* $OUT_PREFIX
-
-ln $OUT_PREFIX/bin/pypy $OUT_PREFIX/bin/python

builds/runtimes/pypy-5.7.0

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+# Build Deps: libraries/sqlite
+
+source $(dirname $0)/pypy

builds/runtimes/pypy-5.7.1

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+# Build Deps: libraries/sqlite
+
+source $(dirname $0)/pypy

builds/runtimes/pypy-5.8.0

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+# Build Deps: libraries/sqlite
+
+source $(dirname $0)/pypy

builds/runtimes/pypy2.7

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+# fail hard
+set -o pipefail
+# fail harder
+set -eu
+
+OUT_PREFIX=$1
+
+dep_formula=${0#$WORKSPACE_DIR/} # this is the original script, e.g. pypy-5.3.1
+dep_name=$(basename $BASH_SOURCE) # this is us
+dep_version=${dep_formula##*"/${dep_name}-"} # "subtract" our name from full version name
+dep_package=${dep_name}-v${dep_version} # it's always "pypy2-…"
+dep_dirname=${dep_package}-linux64
+dep_archive_name=${dep_dirname}.tar.bz2
+dep_url="https://downloads.python.org/pypy/${dep_archive_name}"
+
+echo "Building PyPy…"
+echo "${dep_url}"
+
+curl -fL "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name
+
+ln "$OUT_PREFIX/bin/pypy" "$OUT_PREFIX/bin/python"

builds/runtimes/pypy2.7-7.2.0

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy2.7

builds/runtimes/pypy2.7-7.3.1

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy2.7

builds/runtimes/pypy2.7-7.3.2

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy2.7

builds/runtimes/pypy3

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+# fail hard
+set -o pipefail
+# fail harder
+set -eu
+
+OUT_PREFIX=$1
+
+dep_formula=${0#$WORKSPACE_DIR/} # this is the original script, e.g. pypy-5.3.1
+dep_name=$(basename $BASH_SOURCE) # this is us
+dep_version=${dep_formula##*"/${dep_name}-"} # "subtract" our name from full version name
+dep_package=${dep_name}${dep_version_prefix:-}-v${dep_version}${dep_version_suffix:-}
+dep_dirname=${dep_package}-linux64
+dep_archive_name=${dep_dirname}.tar.bz2
+dep_url=https://bitbucket.org/pypy/pypy/downloads/${dep_archive_name}
+
+echo "Building PyPy3…"
+
+curl -L "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name
+
+ln "$OUT_PREFIX/bin/pypy3" "$OUT_PREFIX/bin/python"

builds/runtimes/pypy3-2.4.0

@@ -2,13 +2,4 @@
 # Build Path: /app/.heroku/python/
 # Build Deps: libraries/sqlite
 
-# NOTICE: This formula only works for the cedar-14 stack, not cedar.
+source $(dirname $0)/pypy3
-
-OUT_PREFIX=$1
-
-echo "Building PyPy..."
-SOURCE_TARBALL='https://bitbucket.org/pypy/pypy/downloads/pypy3-2.4.0-linux64.tar.bz2'
-curl -L $SOURCE_TARBALL | tar jx
-cp -R pypy3-2.4.0-linux64/* $OUT_PREFIX
-
-ln $OUT_PREFIX/bin/pypy3 $OUT_PREFIX/bin/python

builds/runtimes/pypy3-5.5.0

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+# Build Deps: libraries/sqlite
+
+# version pypy3-5.5.0 is really called pypy3.3-v5.5.0-alpha
+dep_version_prefix=".3"
+dep_version_suffix="-alpha"
+source $(dirname $0)/pypy3

builds/runtimes/pypy3-5.7.1

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+# Build Deps: libraries/sqlite
+
+source $(dirname $0)/pypy3

builds/runtimes/pypy3-5.8.0

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+# Build Deps: libraries/sqlite
+
+source $(dirname $0)/pypy3

builds/runtimes/pypy3.6

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+# fail hard
+set -o pipefail
+# fail harder
+set -eu
+
+OUT_PREFIX=$1
+
+dep_formula=${0#$WORKSPACE_DIR/} # this is the original script, e.g. pypy-5.3.1
+dep_name=$(basename $BASH_SOURCE) # this is us
+dep_version=${dep_formula##*"/${dep_name}-"} # "subtract" our name from full version name
+dep_package=${dep_name}${dep_version_prefix:-}-v${dep_version}${dep_version_suffix:-}
+dep_dirname=${dep_package}-linux64
+dep_archive_name=${dep_dirname}.tar.bz2
+dep_url="https://downloads.python.org/pypy/${dep_archive_name}"
+
+echo "Building PyPy3…"
+echo "${dep_url}"
+
+curl -fL "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name
+
+ln "$OUT_PREFIX/bin/pypy3" "$OUT_PREFIX/bin/python"

builds/runtimes/pypy3.6-7.2.0

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy3.6

builds/runtimes/pypy3.6-7.3.1

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy3.6

builds/runtimes/pypy3.6-7.3.2

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy3.6

builds/runtimes/python-2.7.10

@@ -1,15 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/
-# Build Deps: libraries/sqlite
 
-OUT_PREFIX=$1
+source $(dirname $0)/python2
-
-echo "Building Python..."
-SOURCE_TARBALL='https://python.org/ftp/python/2.7.10/Python-2.7.10.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-2.7.10 src
-cd src
-
-./configure --prefix=$OUT_PREFIX  --with-ensurepip=no
-make
-make install

builds/runtimes/python-2.7.11

@@ -1,15 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/
-# Build Deps: libraries/sqlite
 
-OUT_PREFIX=$1
+source $(dirname $0)/python2
-
-echo "Building Python..."
-SOURCE_TARBALL='https://python.org/ftp/python/2.7.11/Python-2.7.11.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-2.7.11 src
-cd src
-
-./configure --prefix=$OUT_PREFIX  --with-ensurepip=no
-make
-make install

builds/runtimes/python-2.7.12

@@ -1,15 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/
-# Build Deps: libraries/sqlite
 
-OUT_PREFIX=$1
+source $(dirname $0)/python2
-
-echo "Building Python..."
-SOURCE_TARBALL='https://python.org/ftp/python/2.7.12/Python-2.7.12.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-2.7.12 src
-cd src
-
-./configure --prefix=$OUT_PREFIX  --with-ensurepip=no
-make
-make install

builds/runtimes/python-2.7.13

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python2

builds/runtimes/python-2.7.14

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python2

builds/runtimes/python-2.7.15

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python2

builds/runtimes/python-2.7.16

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python2

builds/runtimes/python-2.7.17

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python2

builds/runtimes/python-2.7.18

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python2

builds/runtimes/python-2.7.9

@@ -1,15 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/
-# Build Deps: libraries/sqlite
 
-OUT_PREFIX=$1
+source $(dirname $0)/python2
-
-echo "Building Python..."
-SOURCE_TARBALL='https://python.org/ftp/python/2.7.9/Python-2.7.9.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-2.7.9 src
-cd src
-
-./configure --prefix=$OUT_PREFIX  --with-ensurepip=no
-make
-make install

builds/runtimes/python-3.4.10

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.4.9

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.0

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.1

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.10

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.2

@@ -1,18 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/
-# Build Deps: libraries/sqlite
-
-OUT_PREFIX=$1
-
-echo "Building Python..."
-SOURCE_TARBALL='https://python.org/ftp/python/3.5.2/Python-3.5.2.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-3.5.2 src
-cd src
-
-./configure --prefix=$OUT_PREFIX --with-ensurepip=no
-make
-make install
-
-# ln $OUT_PREFIX/bin/python3 $OUT_PREFIX/bin/python
 
+source $(dirname $0)/python3

builds/runtimes/python-3.5.3

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.4

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.5

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.6

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.7

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.5.9

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.6.0

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.6.1

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.6.10

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3

builds/runtimes/python-3.6.11

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3