Make sure to consider existing .venv directory

Fix #1993. I made it more general than the issue, so the .venv directory
is honoured in all situations.

pipenv/core.py

@@ -53,7 +53,6 @@ from .environments import (
     PIPENV_COLORBLIND,
     PIPENV_NOSPIN,
     PIPENV_SHELL_FANCY,
-    PIPENV_VENV_IN_PROJECT,
     PIPENV_TIMEOUT,
     PIPENV_SKIP_VALIDATION,
     PIPENV_HIDE_EMOJIS,
@@ -878,7 +877,7 @@ def do_create_virtualenv(python=None, site_packages=False):
         err=True,
     )
     # The user wants the virtualenv in the project.
-    if PIPENV_VENV_IN_PROJECT:
+    if project.is_venv_in_project():
         cmd = [
             'virtualenv',
             project.virtualenv_location,
@@ -928,7 +927,7 @@ def do_create_virtualenv(python=None, site_packages=False):
             sys.exit(1)
     click.echo(crayons.blue(c.out), err=True)
     # Enable site-packages, if desired...
-    if not PIPENV_VENV_IN_PROJECT and site_packages:
+    if not project.is_venv_in_project() and site_packages:
         click.echo(
             crayons.normal(u'Making site-packages available…', bold=True),
             err=True,
@@ -2145,7 +2144,7 @@ def do_shell(three=None, python=False, fancy=False, shell_args=None):
         args = []
     # Standard (properly configured shell) mode:
     else:
-        if PIPENV_VENV_IN_PROJECT:
+        if project.is_venv_in_project():
             # use .venv as the target virtualenv name
             workon_name = '.venv'
         else:
@@ -2157,7 +2156,7 @@ def do_shell(three=None, python=False, fancy=False, shell_args=None):
     terminal_dimensions = get_terminal_size()
     try:
         with temp_environ():
-            if PIPENV_VENV_IN_PROJECT:
+            if project.is_venv_in_project():
                 os.environ['WORKON_HOME'] = project.project_directory
             c = pexpect.spawn(
                 cmd,
@@ -2171,7 +2170,7 @@ def do_shell(three=None, python=False, fancy=False, shell_args=None):
         # import subprocess
         # Tell pew to use the project directory as its workon_home
         with temp_environ():
-            if PIPENV_VENV_IN_PROJECT:
+            if project.is_venv_in_project():
                 os.environ['WORKON_HOME'] = project.project_directory
             pew.workon_cmd([workon_name])
             sys.exit(0)

pipenv/project.py

@@ -197,6 +197,12 @@ class Project(object):
     def requirements_exists(self):
         return bool(self.requirements_location)
 
+    def is_venv_in_project(self):
+        return (
+            PIPENV_VENV_IN_PROJECT or
+            os.path.exists(os.path.join(self.project_directory, '.venv'))
+        )
+
     @property
     def virtualenv_exists(self):
         # TODO: Decouple project from existence of Pipfile.
@@ -252,7 +258,7 @@ class Project(object):
         # This should work most of the time, for non-WIndows, in-project venv,
         # or "proper" path casing (on Windows).
         if (os.name != 'nt' or
-                PIPENV_VENV_IN_PROJECT or
+                self.is_venv_in_project() or
                 self._get_virtualenv_location(venv_name)):
             return clean_name, encoded_hash
 
@@ -287,11 +293,9 @@ class Project(object):
         # Use cached version, if available.
         if self._virtualenv_location:
             return self._virtualenv_location
-        venv_in_project = PIPENV_VENV_IN_PROJECT or \
-            os.path.exists(os.path.join(self.project_directory, '.venv'))
 
         # Default mode.
-        if not venv_in_project:
+        if not self.is_venv_in_project():
             loc = self._get_virtualenv_location(self.virtualenv_name)
         # The user wants the virtualenv in the project.
         else: