Assume PIPENV_VENV_IN_PROJECT when a local virtual environment exists

HISTORY.txt

@@ -1,3 +1,5 @@
+next:
+ - Assume `PIPENV_VENV_IN_PROJECT` if `./.venv/` already exists.
 10.1.0:
  - Default dependencies now take precidence over Develop dependencies when
    creating a Pipfile.lock.

pipenv/environments.py

@@ -11,7 +11,7 @@
 PIPENV_SHELL_FANCY = bool(os.environ.get('PIPENV_SHELL_FANCY'))
 
 # Create the virtualenv in the project, instead of with pew.
-PIPENV_VENV_IN_PROJECT = bool(os.environ.get('PIPENV_VENV_IN_PROJECT'))
+PIPENV_VENV_IN_PROJECT = bool(os.environ.get('PIPENV_VENV_IN_PROJECT')) or os.path.isdir('.venv')
 
 # No color mode, for unfun people.
 PIPENV_COLORBLIND = bool(os.environ.get('PIPENV_COLORBLIND'))

tests/test_pipenv.py

@@ -663,6 +663,15 @@ def test_venv_in_project(self):
 
                 assert normalize_drive(p.path) in p.pipenv('--venv').out
 
+    @pytest.mark.dotvenv
+    def test_reuse_previous_venv(self):
+        with PipenvInstance(chdir=True) as p:
+            os.mkdir('.venv')
+            c = p.pipenv('install requests')
+            assert c.return_code == 0
+
+            assert normalize_drive(p.path) in p.pipenv('--venv').out
+
     @pytest.mark.dotvenv
     @pytest.mark.install
     @pytest.mark.complex