calculate zip path from prefix when in a venv

Before python3.11, when in a venv the zip path is calculated
from prefix. In python3.11 the behavior is accidentally changed
to calculating from default prefix. This change will break venv
created from a non-installed python with a stdlib zip file. This
commit restore the behavior back to before python3.11.

Lib/test/test_getpath.py

@@ -382,6 +382,39 @@ def test_venv_changed_name_posix(self):
         actual = getpath(ns, expected)
         self.assertEqual(expected, actual)
 
+    def test_venv_non_installed_zip_path_posix(self):
+        "Test a venv created from non-installed python has correct zip path."""
+        ns = MockPosixNamespace(
+            argv0="/venv/bin/python",
+            PREFIX="/usr",
+            ENV_PATH="/venv/bin:/usr/bin",
+        )
+        ns.add_known_xfile("/path/to/non-installed/bin/python")
+        ns.add_known_xfile("/venv/bin/python")
+        ns.add_known_link("/venv/bin/python",
+                          "/path/to/non-installed/bin/python")
+        ns.add_known_file("/path/to/non-installed/lib/python9.8/os.py")
+        ns.add_known_dir("/path/to/non-installed/lib/python9.8/lib-dynload")
+        ns.add_known_file("/venv/pyvenv.cfg", [
+            r"home = /path/to/non-installed"
+        ])
+        expected = dict(
+            executable="/venv/bin/python",
+            prefix="/path/to/non-installed",
+            exec_prefix="/path/to/non-installed",
+            base_executable="/path/to/non-installed/bin/python",
+            base_prefix="/path/to/non-installed",
+            base_exec_prefix="/path/to/non-installed",
+            module_search_paths_set=1,
+            module_search_paths=[
+                "/path/to/non-installed/lib/python98.zip",
+                "/path/to/non-installed/lib/python9.8",
+                "/path/to/non-installed/lib/python9.8/lib-dynload",
+            ],
+        )
+        actual = getpath(ns, expected)
+        self.assertEqual(expected, actual)
+
     def test_venv_changed_name_copy_posix(self):
         "Test a venv --copies layout on *nix that lacks a distributed 'python'"
         ns = MockPosixNamespace(

Lib/test/test_venv.py

@@ -537,6 +537,69 @@ def test_pathsep_error(self):
         self.assertRaises(ValueError, venv.create, bad_itempath)
         self.assertRaises(ValueError, venv.create, pathlib.Path(bad_itempath))
 
+    @unittest.skipIf(os.name == 'nt', 'not relevant on Windows')
+    @requireVenvCreate
+    def test_zippath_from_non_installed_posix(self):
+        """
+        Test that when create venv from non-installed python, the zip path
+        value is as expected.
+        """
+        rmtree(self.env_dir)
+        # First try to create a non-installed python. It's not a real full
+        # functional non-installed python, but enough for this test.
+        non_installed_dir = os.path.realpath(tempfile.mkdtemp())
+        try:
+            bindir = os.path.join(non_installed_dir, self.bindir)
+            os.mkdir(bindir)
+            shutil.copy2(sys.executable, bindir)
+            libdir = os.path.join(non_installed_dir, *self.lib)
+            os.makedirs(libdir)
+            landmark = os.path.join(libdir, "os.py")
+            stdlib_zip = "python%d%d.zip" % sys.version_info[:2]
+            zip_landmark = os.path.join(non_installed_dir,
+                                        self.lib[0],
+                                        stdlib_zip)
+            additional_pythonpath_for_non_installed = []
+            # Copy stdlib files to the non-installed python so venv can
+            # correctly calculate the prefix.
+            for eachpath in sys.path:
+                if eachpath.endswith(".zip"):
+                    if os.path.isfile(eachpath):
+                        shutil.copyfile(
+                            eachpath,
+                            os.path.join(non_installed_dir, self.lib[0]))
+                elif os.path.isfile(os.path.join(eachpath, "os.py")):
+                    for name in os.listdir(eachpath):
+                        if name == "site-packages":
+                            continue
+                        fn = os.path.join(eachpath, name)
+                        if os.path.isfile(fn):
+                            shutil.copy(fn, libdir)
+                        elif os.path.isdir(fn):
+                            shutil.copytree(fn, os.path.join(libdir, name))
+                else:
+                    additional_pythonpath_for_non_installed.append(
+                        eachpath)
+            cmd = [os.path.join(non_installed_dir, self.bindir, self.exe),
+                   "-m",
+                   "venv",
+                   "--without-pip",
+                   self.env_dir]
+            # Our fake non-installed python is not fully functional because
+            # it cannot find the extensions. Set PYTHONPATH so it can run the
+            # venv module correctly.
+            pythonpath = os.pathsep.join(
+                additional_pythonpath_for_non_installed)
+            subprocess.check_call(cmd, env={"PYTHONPATH": pythonpath})
+            envpy = os.path.join(self.env_dir, self.bindir, self.exe)
+            # Now check the venv created from the non-installed python has
+            # correct zip path in pythonpath.
+            cmd = [envpy, '-S', '-c', 'import sys; print(sys.path)']
+            out, err = check_output(cmd)
+            self.assertTrue(zip_landmark.encode() in out)
+        finally:
+            rmtree(non_installed_dir)
+
 @requireVenvCreate
 class EnsurePipTest(BaseTest):
     """Test venv module installation of pip."""

Modules/getpath.py

@@ -679,9 +679,8 @@ def search_up(prefix, *landmarks, test=isfile):
         else:
             library_dir = executable_dir
         pythonpath.append(joinpath(library_dir, ZIP_LANDMARK))
-    elif build_prefix or venv_prefix:
+    elif build_prefix:
         # QUIRK: POSIX uses the default prefix when in the build directory
-        # or a venv
         pythonpath.append(joinpath(PREFIX, ZIP_LANDMARK))
     else:
         pythonpath.append(joinpath(prefix, ZIP_LANDMARK))