From 9477a9135183c347b7ffc957ddf6eb5e1b18f978 Mon Sep 17 00:00:00 2001
From: Chad Smith <chad@grassfedcode.com>
Date: Sun, 11 Aug 2019 19:00:53 -0700
Subject: [PATCH] Add venv as an option for venv_backend (#231)

* add venv as an option for venv_backend

* remove python resolution changes

* update tests

* run black

* use different interpreters for venv vs virtualenv

* update test
---
 nox/sessions.py          |  9 ++++++++-
 nox/virtualenv.py        | 25 ++++++++++++++++---------
 tests/test_sessions.py   |  1 +
 tests/test_virtualenv.py |  6 ++++++
 4 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/nox/sessions.py b/nox/sessions.py
index 2affcf7e..ccf59935 100644
--- a/nox/sessions.py
+++ b/nox/sessions.py
@@ -375,9 +375,16 @@ def _create_venv(self):
             self.venv = CondaEnv(
                 path, interpreter=self.func.python, reuse_existing=reuse_existing
             )
+        elif self.func.venv_backend == "venv":
+            self.venv = VirtualEnv(
+                path,
+                interpreter=self.func.python,
+                reuse_existing=reuse_existing,
+                venv=True,
+            )
         else:
             raise ValueError(
-                "Expected venv_backend one of ('virtualenv', 'conda'), but got '{}'.".format(
+                "Expected venv_backend one of ('virtualenv', 'conda', 'venv'), but got '{}'.".format(
                     self.func.venv_backend
                 )
             )
diff --git a/nox/virtualenv.py b/nox/virtualenv.py
index 9063b2b5..836b6420 100644
--- a/nox/virtualenv.py
+++ b/nox/virtualenv.py
@@ -196,12 +196,13 @@ class VirtualEnv(ProcessEnv):
 
     is_sandboxed = True
 
-    def __init__(self, location, interpreter=None, reuse_existing=False):
+    def __init__(self, location, interpreter=None, reuse_existing=False, *, venv=False):
         self.location_name = location
         self.location = os.path.abspath(location)
         self.interpreter = interpreter
         self._resolved = None
         self.reuse_existing = reuse_existing
+        self.venv_or_virtualenv = "venv" if venv else "virtualenv"
         super(VirtualEnv, self).__init__()
 
     _clean_location = _clean_location
@@ -275,21 +276,27 @@ def bin(self):
             return os.path.join(self.location, "bin")
 
     def create(self):
-        """Create the virtualenv."""
+        """Create the virtualenv or venv."""
         if not self._clean_location():
             logger.debug(
-                "Re-using existing virtualenv at {}.".format(self.location_name)
+                "Re-using existing virtual environment at {}.".format(
+                    self.location_name
+                )
             )
             return False
 
-        cmd = [sys.executable, "-m", "virtualenv", self.location]
-
-        if self.interpreter:
-            cmd.extend(["-p", self._resolved_interpreter])
+        if self.venv_or_virtualenv == "virtualenv":
+            cmd = [sys.executable, "-m", "virtualenv", self.location]
+            if self.interpreter:
+                cmd.extend(["-p", self._resolved_interpreter])
+        else:
+            cmd = [self._resolved_interpreter, "-m", "venv", self.location]
 
         logger.info(
-            "Creating virtualenv using {} in {}".format(
-                os.path.basename(self._resolved_interpreter), self.location_name
+            "Creating virtual environment ({}) using {} in {}".format(
+                self.venv_or_virtualenv,
+                os.path.basename(self._resolved_interpreter),
+                self.location_name,
             )
         )
         nox.command.run(cmd, silent=True, log=False)
diff --git a/tests/test_sessions.py b/tests/test_sessions.py
index 0b9559aa..dbe72bb1 100644
--- a/tests/test_sessions.py
+++ b/tests/test_sessions.py
@@ -514,6 +514,7 @@ def test__create_venv(self, create):
                 "virtualenv",
                 nox.virtualenv.VirtualEnv,
             ),
+            ("nox.virtualenv.VirtualEnv.create", "venv", nox.virtualenv.VirtualEnv),
             ("nox.virtualenv.CondaEnv.create", "conda", nox.virtualenv.CondaEnv),
         ],
     )
diff --git a/tests/test_virtualenv.py b/tests/test_virtualenv.py
index 04296e23..61b246d3 100644
--- a/tests/test_virtualenv.py
+++ b/tests/test_virtualenv.py
@@ -117,6 +117,7 @@ def test_constructor_defaults(make_one):
     assert venv.location
     assert venv.interpreter is None
     assert venv.reuse_existing is False
+    assert venv.venv_or_virtualenv == "virtualenv"
 
 
 @pytest.mark.skipif(IS_WINDOWS, reason="Not testing multiple interpreters on Windows.")
@@ -213,6 +214,11 @@ def test_create(make_one):
     assert dir_.join("test.txt").check()
 
 
+def test_create_venv_backend(make_one):
+    venv, dir_ = make_one(venv=True)
+    venv.create()
+
+
 @pytest.mark.skipif(IS_WINDOWS, reason="Not testing multiple interpreters on Windows.")
 def test_create_interpreter(make_one):
     venv, dir_ = make_one(interpreter="python3")