don't pass through -p if using the default version

asottile · asottile · commit 58a190fd69d4 · 2020-09-23T17:44:18.000-07:00
diff --git a/pre_commit/languages/python.py b/pre_commit/languages/python.py
@@ -132,13 +132,11 @@ def _sys_executable_matches(version: str) -> bool:
     return sys.version_info[:len(info)] == info
 
 
-def norm_version(version: str) -> str:
-    if version == C.DEFAULT:
-        return os.path.realpath(sys.executable)
-
-    # first see if our current executable is appropriate
-    if _sys_executable_matches(version):
-        return sys.executable
+def norm_version(version: str) -> Optional[str]:
+    if version == C.DEFAULT:  # use virtualenv's default
+        return None
+    elif _sys_executable_matches(version):  # virtualenv defaults to our exe
+        return None
 
     if os.name == 'nt':  # pragma: no cover (windows)
         version_exec = _find_by_py_launcher(version)
@@ -194,8 +192,10 @@ def install_environment(
         additional_dependencies: Sequence[str],
 ) -> None:
     envdir = prefix.path(helpers.environment_dir(ENVIRONMENT_DIR, version))
+    venv_cmd = [sys.executable, '-mvirtualenv', envdir]
     python = norm_version(version)
-    venv_cmd = (sys.executable, '-mvirtualenv', envdir, '-p', python)
+    if python is not None:
+        venv_cmd.extend(('-p', python))
     install_cmd = ('python', '-mpip', 'install', '.', *additional_dependencies)
 
     with clean_path_on_failure(envdir):
diff --git a/tests/languages/python_test.py b/tests/languages/python_test.py
@@ -36,13 +36,14 @@ def test_norm_version_expanduser():
 
 
 def test_norm_version_of_default_is_sys_executable():
-    assert python.norm_version('default') == os.path.realpath(sys.executable)
+    assert python.norm_version('default') is None
 
 
 @pytest.mark.parametrize('v', ('python3.6', 'python3', 'python'))
 def test_sys_executable_matches(v):
     with mock.patch.object(sys, 'version_info', (3, 6, 7)):
         assert python._sys_executable_matches(v)
+        assert python.norm_version(v) is None
 
 
 @pytest.mark.parametrize('v', ('notpython', 'python3.x'))
