Set 'home' to parent directory of system_executable

PEP 405 says of the "home" key:

"If a home key is found, this signifies that the Python binary belongs
to a virtual environment, and the value of the home key is the directory
containing the Python executable used to create this virtual
environment."

And:

"In this case, prefix-finding continues as normal using the value of the
home key as the effective Python binary location, which finds the prefix
of the base installation."

Previously, "home" was being set to `interpreter.system_exec_prefix`
which does not abide by the PEP specification.

In Python 3.11, the "home" directory is used to determine the value of
`sys._base_executable`, so if the path specified is incorrect, the
path + interpreter returned will be invalid. This can cause headaches
later when trying to probe info via the discovery module.

Now, set this to the parent directory of `interpreter.system_executable`.

Signed-off-by: Vincent Fazio <vfazio@gmail.com>

docs/changelog/2440.bugfix.rst

@@ -0,0 +1 @@
+Use parent directory of python executable for pyvenv.cfg "home" value per PEP 405 - by :user:`vfazio`.

src/virtualenv/create/creator.py

@@ -157,7 +157,7 @@ def run(self):
 
     def set_pyenv_cfg(self):
         self.pyenv_cfg.content = OrderedDict()
-        self.pyenv_cfg["home"] = self.interpreter.system_exec_prefix
+        self.pyenv_cfg["home"] = os.path.dirname(os.path.abspath(self.interpreter.system_executable))
         self.pyenv_cfg["implementation"] = self.interpreter.implementation
         self.pyenv_cfg["version_info"] = ".".join(str(i) for i in self.interpreter.version_info)
         self.pyenv_cfg["virtualenv"] = __version__

tests/unit/create/test_creator.py

@@ -318,6 +318,28 @@ def test_prompt_set(tmp_path, creator, prompt):
             assert cfg["prompt"] == actual_prompt
 
 
+@pytest.mark.parametrize("creator", CURRENT_CREATORS)
+def test_home_path_is_exe_parent(tmp_path, creator):
+    cmd = [str(tmp_path), "--seeder", "app-data", "--without-pip", "--creator", creator]
+
+    result = cli_run(cmd)
+    cfg = PyEnvCfg.from_file(result.creator.pyenv_cfg.path)
+
+    # Cannot assume "home" path is a specific value as path resolution may change
+    # between versions (symlinks, framework paths, etc) but we can check that a
+    # python executable is present from the configured path per PEP 405
+    if sys.platform == "win32":
+        exes = ("python.exe",)
+    else:
+        exes = (
+            "python",
+            f"python{sys.version_info.major}",
+            f"python{sys.version_info.major}.{sys.version_info.minor}",
+        )
+
+    assert any(os.path.exists(os.path.join(cfg["home"], exe)) for exe in exes)
+
+
 @pytest.mark.slow()
 @pytest.mark.usefixtures("current_fastest")
 def test_cross_major(cross_python, coverage_env, tmp_path, session_app_data):