GH-126985: move pyvenv.cfg detection from site to getpath (#126987)

5 files changed, 33 insertions, 99 deletions

diff --git a/Lib/site.py b/Lib/site.py
index abf4b52..92bd1cc 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -94,6 +94,12 @@ def _trace(message):
         print(message, file=sys.stderr)
 
 
+def _warn(*args, **kwargs):
+    import warnings
+
+    warnings.warn(*args, **kwargs)
+
+
 def makepath(*paths):
     dir = os.path.join(*paths)
     try:
@@ -619,7 +625,10 @@ def venv(known_paths):
                     elif key == 'home':
                         sys._home = value
 
-        sys.prefix = sys.exec_prefix = site_prefix
+        if sys.prefix != site_prefix:
+            _warn(f'Unexpected value in sys.prefix, expected {site_prefix}, got {sys.prefix}', RuntimeWarning)
+        if sys.exec_prefix != site_prefix:
+            _warn(f'Unexpected value in sys.exec_prefix, expected {site_prefix}, got {sys.exec_prefix}', RuntimeWarning)
 
         # Doing this here ensures venv takes precedence over user-site
         addsitepackages(known_paths, [sys.prefix])
diff --git a/Lib/sysconfig/__init__.py b/Lib/sysconfig/__init__.py
index 67a0719..ee52700 100644
--- a/Lib/sysconfig/__init__.py
+++ b/Lib/sysconfig/__init__.py
@@ -173,7 +173,9 @@ _SCHEME_KEYS = ('stdlib', 'platstdlib', 'purelib', 'platlib', 'include',
 _PY_VERSION = sys.version.split()[0]
 _PY_VERSION_SHORT = f'{sys.version_info[0]}.{sys.version_info[1]}'
 _PY_VERSION_SHORT_NO_DOT = f'{sys.version_info[0]}{sys.version_info[1]}'
+_PREFIX = os.path.normpath(sys.prefix)
 _BASE_PREFIX = os.path.normpath(sys.base_prefix)
+_EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
 _BASE_EXEC_PREFIX = os.path.normpath(sys.base_exec_prefix)
 # Mutex guarding initialization of _CONFIG_VARS.
 _CONFIG_VARS_LOCK = threading.RLock()
@@ -465,10 +467,8 @@ def _init_config_vars():
     # Normalized versions of prefix and exec_prefix are handy to have;
     # in fact, these are the standard versions used most places in the
     # Distutils.
-    _PREFIX = os.path.normpath(sys.prefix)
-    _EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
-    _CONFIG_VARS['prefix'] = _PREFIX  # FIXME: This gets overwriten by _init_posix.
-    _CONFIG_VARS['exec_prefix'] = _EXEC_PREFIX  # FIXME: This gets overwriten by _init_posix.
+    _CONFIG_VARS['prefix'] = _PREFIX
+    _CONFIG_VARS['exec_prefix'] = _EXEC_PREFIX
     _CONFIG_VARS['py_version'] = _PY_VERSION
     _CONFIG_VARS['py_version_short'] = _PY_VERSION_SHORT
     _CONFIG_VARS['py_version_nodot'] = _PY_VERSION_SHORT_NO_DOT
@@ -541,7 +541,6 @@ def get_config_vars(*args):
     With arguments, return a list of values that result from looking up
     each argument in the configuration variable dictionary.
     """
-    global _CONFIG_VARS_INITIALIZED
 
     # Avoid claiming the lock once initialization is complete.
     if not _CONFIG_VARS_INITIALIZED:
@@ -552,15 +551,6 @@ def get_config_vars(*args):
             # don't re-enter init_config_vars().
             if _CONFIG_VARS is None:
                 _init_config_vars()
-    else:
-        # If the site module initialization happened after _CONFIG_VARS was
-        # initialized, a virtual environment might have been activated, resulting in
-        # variables like sys.prefix changing their value, so we need to re-init the
-        # config vars (see GH-126789).
-        if _CONFIG_VARS['base'] != os.path.normpath(sys.prefix):
-            with _CONFIG_VARS_LOCK:
-                _CONFIG_VARS_INITIALIZED = False
-                _init_config_vars()
 
     if args:
         vals = []
diff --git a/Lib/test/test_embed.py b/Lib/test/test_embed.py
index bf861ef..5c38b28 100644
--- a/Lib/test/test_embed.py
+++ b/Lib/test/test_embed.py
@@ -1649,14 +1649,14 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
             config = {
                 'base_prefix': sysconfig.get_config_var("prefix"),
                 'base_exec_prefix': exec_prefix,
-                'exec_prefix': exec_prefix,
+                'exec_prefix': tmpdir,
+                'prefix': tmpdir,
                 'base_executable': base_executable,
                 'executable': executable,
                 'module_search_paths': paths,
             }
             if MS_WINDOWS:
                 config['base_prefix'] = pyvenv_home
-                config['prefix'] = pyvenv_home
                 config['stdlib_dir'] = os.path.join(pyvenv_home, 'Lib')
                 config['use_frozen_modules'] = bool(not support.Py_DEBUG)
             else:
diff --git a/Lib/test/test_getpath.py b/Lib/test/test_getpath.py
index d5dcdad..7e5c4a3 100644
--- a/Lib/test/test_getpath.py
+++ b/Lib/test/test_getpath.py
@@ -92,8 +92,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable=r"C:\venv\Scripts\python.exe",
-            prefix=r"C:\Python",
-            exec_prefix=r"C:\Python",
+            prefix=r"C:\venv",
+            exec_prefix=r"C:\venv",
             base_executable=r"C:\Python\python.exe",
             base_prefix=r"C:\Python",
             base_exec_prefix=r"C:\Python",
@@ -339,8 +339,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/usr/bin/python",
             base_prefix="/usr",
             base_exec_prefix="/usr",
@@ -371,8 +371,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/usr/bin/python3",
             base_prefix="/usr",
             base_exec_prefix="/usr",
@@ -404,8 +404,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/path/to/non-installed",
-            exec_prefix="/path/to/non-installed",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/path/to/non-installed/bin/python",
             base_prefix="/path/to/non-installed",
             base_exec_prefix="/path/to/non-installed",
@@ -435,8 +435,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/usr/bin/python9",
             base_prefix="/usr",
             base_exec_prefix="/usr",
@@ -652,8 +652,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable=f"{venv_path}/bin/python",
-            prefix="/Library/Frameworks/Python.framework/Versions/9.8",
-            exec_prefix="/Library/Frameworks/Python.framework/Versions/9.8",
+            prefix=venv_path,
+            exec_prefix=venv_path,
             base_executable="/Library/Frameworks/Python.framework/Versions/9.8/bin/python9.8",
             base_prefix="/Library/Frameworks/Python.framework/Versions/9.8",
             base_exec_prefix="/Library/Frameworks/Python.framework/Versions/9.8",
@@ -697,8 +697,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable=f"{venv_path}/bin/python",
-            prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
-            exec_prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
+            prefix=venv_path,
+            exec_prefix=venv_path,
             base_executable="/Library/Frameworks/DebugPython.framework/Versions/9.8/bin/python9.8",
             base_prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
             base_exec_prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
@@ -734,8 +734,8 @@ class MockGetPathTests(unittest.TestCase):
         ])
         expected = dict(
             executable="/framework/Python9.8/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/framework/Python9.8",
+            exec_prefix="/framework/Python9.8",
             base_executable="/usr/bin/python",
             base_prefix="/usr",
             base_exec_prefix="/usr",
diff --git a/Lib/test/test_sysconfig.py b/Lib/test/test_sysconfig.py
index 9bbf8d0..a705dd0 100644
--- a/Lib/test/test_sysconfig.py
+++ b/Lib/test/test_sysconfig.py
@@ -110,6 +110,7 @@ class TestSysConfig(unittest.TestCase):
             **venv_create_args,
         )
 
+
     def test_get_path_names(self):
         self.assertEqual(get_path_names(), sysconfig._SCHEME_KEYS)
 
@@ -592,71 +593,6 @@ class TestSysConfig(unittest.TestCase):
         self.assertTrue(suffix.endswith('-darwin.so'), suffix)
 
     @requires_subprocess()
-    def test_config_vars_depend_on_site_initialization(self):
-        script = textwrap.dedent("""
-            import sysconfig
-
-            config_vars = sysconfig.get_config_vars()
-
-            import json
-            print(json.dumps(config_vars, indent=2))
-        """)
-
-        with self.venv() as venv:
-            site_config_vars = json.loads(venv.run('-c', script).stdout)
-            no_site_config_vars = json.loads(venv.run('-S', '-c', script).stdout)
-
-        self.assertNotEqual(site_config_vars, no_site_config_vars)
-        # With the site initialization, the virtual environment should be enabled.
-        self.assertEqual(site_config_vars['base'], venv.prefix)
-        self.assertEqual(site_config_vars['platbase'], venv.prefix)
-        #self.assertEqual(site_config_vars['prefix'], venv.prefix)  # # FIXME: prefix gets overwriten by _init_posix
-        # Without the site initialization, the virtual environment should be disabled.
-        self.assertEqual(no_site_config_vars['base'], site_config_vars['installed_base'])
-        self.assertEqual(no_site_config_vars['platbase'], site_config_vars['installed_platbase'])
-
-    @requires_subprocess()
-    def test_config_vars_recalculation_after_site_initialization(self):
-        script = textwrap.dedent("""
-            import sysconfig
-
-            before = sysconfig.get_config_vars()
-
-            import site
-            site.main()
-
-            after = sysconfig.get_config_vars()
-
-            import json
-            print(json.dumps({'before': before, 'after': after}, indent=2))
-        """)
-
-        with self.venv() as venv:
-            config_vars = json.loads(venv.run('-S', '-c', script).stdout)
-
-        self.assertNotEqual(config_vars['before'], config_vars['after'])
-        self.assertEqual(config_vars['after']['base'], venv.prefix)
-        #self.assertEqual(config_vars['after']['prefix'], venv.prefix)  # FIXME: prefix gets overwriten by _init_posix
-        #self.assertEqual(config_vars['after']['exec_prefix'], venv.prefix)  # FIXME: exec_prefix gets overwriten by _init_posix
-
-    @requires_subprocess()
-    def test_paths_depend_on_site_initialization(self):
-        script = textwrap.dedent("""
-            import sysconfig
-
-            paths = sysconfig.get_paths()
-
-            import json
-            print(json.dumps(paths, indent=2))
-        """)
-
-        with self.venv() as venv:
-            site_paths = json.loads(venv.run('-c', script).stdout)
-            no_site_paths = json.loads(venv.run('-S', '-c', script).stdout)
-
-        self.assertNotEqual(site_paths, no_site_paths)
-
-    @requires_subprocess()
     def test_makefile_overwrites_config_vars(self):
         script = textwrap.dedent("""
             import sys, sysconfig
@@ -689,7 +625,6 @@ class TestSysConfig(unittest.TestCase):
         self.assertNotEqual(data['prefix'], data['base_prefix'])
         self.assertNotEqual(data['exec_prefix'], data['base_exec_prefix'])
 
-
 class MakefileTests(unittest.TestCase):
 
     @unittest.skipIf(sys.platform.startswith('win'),