Leverage pip to access installed packages

- Use `get_installed_distributions` from pip
- This cascades to `pkg_resources.working_set` which relies on
  `sys.path` to uncover packages
- Consequently I implemented `temp_path()` as a contextmanager in the
  style of `temp_environ()`
- This requires us to know the environment's `sys.path`, so
  `load_path(python)` will do a `json.dumps` of `sys.path` to stdout
  which then gets loaded and returned
- Allows us to avoid trying to hack around `pip freeze` output to parse
  out names from comments etc
- Provides other potential uses

Signed-off-by: Dan Ryan <dan@danryan.co>

pipenv/core.py

@@ -2543,23 +2543,10 @@ def do_clean(
     pypi_mirror=None,
 ):
     # Ensure that virtualenv is available.
-    from .vendor.requirementslib import Requirement
 
     ensure_project(three=three, python=python, validate=False, pypi_mirror=pypi_mirror)
     ensure_lockfile(pypi_mirror=pypi_mirror)
-    installed_package_names = []
-    pip_freeze_command = delegator.run("{0} freeze".format(which_pip()))
-    for line in pip_freeze_command.out.split("\n"):
-        installed = line.strip()
-        if not installed or installed.startswith("#"):  # Comment or empty.
-            continue
-        r = Requirement.from_line(installed).requirement
-        # Ignore editable installations.
-        if not r.editable:
-            installed_package_names.append(r.name.lower())
-        else:
-            if verbose:
-                click.echo("Ignoring {0}.".format(repr(r.name)), err=True)
+    installed_package_names = [pkg.project_name for pkg in project.get_installed_packages()]
     # Remove known "bad packages" from the list.
     for bad_package in BAD_PACKAGES:
         if bad_package in installed_package_names:

pipenv/project.py

@@ -269,6 +269,20 @@ class Project(object):
             return os.path.join(self.project_directory, ".venv")
         return str(get_workon_home().joinpath(self.virtualenv_name))
 
+    def get_installed_packages(self):
+        from . import PIPENV_ROOT, PIPENV_VENDOR, PIPENV_PATCHED
+        from .utils import temp_path, load_path, temp_environ
+        if self.virtualenv_exists:
+            with temp_path(), temp_environ():
+                new_path = load_path(self.which("python"))
+                new_path = [new_path[0], PIPENV_ROOT, PIPENV_PATCHED, PIPENV_VENDOR] + new_path[1:]
+                sys.path = new_path
+                os.environ['VIRTUAL_ENV'] = self.virtualenv_location
+                from .patched.notpip._internal.utils.misc import get_installed_distributions
+                return get_installed_distributions(local_only=True)
+        else:
+            return []
+
     @classmethod
     def _sanitize(cls, name):
         # Replace dangerous characters into '_'. The length of the sanitized

pipenv/utils.py

@@ -934,6 +934,28 @@ def temp_environ():
         os.environ.update(environ)
 
 
+@contextmanager
+def temp_path():
+    """Allow the ability to set os.environ temporarily"""
+    path = [p for p in sys.path]
+    try:
+        yield
+    finally:
+        sys.path = [p for p in path]
+
+
+def load_path(python):
+    import delegator
+    import json
+    python = escape_grouped_arguments(python)
+    json_dump_commmand = "'import json, sys; print(json.dumps(sys.path));'"
+    c = delegator.run("{0} -c {1}".format(python, json_dump_commmand))
+    if c.return_code == 0:
+        return json.loads(c.out.strip())
+    else:
+        return []
+
+
 def is_valid_url(url):
     """Checks if a given string is an url"""
     pieces = urlparse(url)