rework _abspath_resolve_leaf to _getpath_realpath

Author: mayeut

Lib/test/test_venv.py

@@ -895,6 +895,7 @@ def test_venvwlauncher(self):
     @requires_subprocess()
     @unittest.skipIf(os.name == 'nt', 'not relevant on Windows')
     @unittest.skipUnless(can_symlink(), 'Needs symlinks')
+    @unittest.skipUnless(sysconfig.get_config_var('HAVE_READLINK'), "Requires HAVE_READLINK support")
     def test_executable_symlink(self):
         """
         Test creation using a symlink to python executable.
@@ -908,7 +909,7 @@ def test_executable_symlink(self):
             cmd = [exe_symlink, "-m", "venv", "--without-pip", self.env_dir]
             subprocess.check_call(cmd)
         data = self.get_text_file_contents('pyvenv.cfg')
-        path = os.path.dirname(sys._base_executable)
+        path = os.path.dirname(os.path.abspath(sys._base_executable))
         self.assertIn('home = %s' % path, data)
         self.assertIn('executable = %s' % exe.resolve(), data)
 

Lib/venv/__init__.py

@@ -134,23 +134,37 @@ def _same_path(cls, path1, path2):
             return path1 == path2
 
     @classmethod
-    def _abspath_resolve_leaf(cls, path):
-        """Returns the absolute path, resolving links to the last component.
-
-        If there's a cycle, os.path.abspath(path) is returned
+    def _getpath_realpath(cls, path):
+        """Mimics getpath.realpath
+
+        It only mimics it for HAVE_READLINK.
+        There are a few differences listed here:
+        - we ensure that we have a resolvable abspath first
+          (i.e. exists and no symlink loop)
+        - we stop if a candidate does not resolve to the same file
+          (this can happen with normpath)
         """
-        path = os.path.abspath(path)
-        result = path
-        while os.path.islink(result):
-            link = os.readlink(result)
-            if os.path.isabs(link):
-                result = link
-            else:
-                result = os.path.join(os.path.dirname(result), link)
-                result = os.path.abspath(result)
-            if result == path:
-                # circular links
-                break
+        result = os.path.abspath(path)
+        try:
+            real_path = os.path.realpath(result, strict=True)
+        except OSError:
+            logger.warning('Unable to resolve %r real path', result)
+            return result
+        if sysconfig.get_config_var('HAVE_READLINK'):
+            while os.path.islink(result):
+                link = os.readlink(result)
+                if os.path.isabs(link):
+                    candidate = link
+                else:
+                    candidate = os.path.join(os.path.dirname(result), link)
+                    candidate = os.path.normpath(candidate)
+                # shall exists and be the same file as the original one
+                valid = os.path.exists(candidate) and os.path.samefile(real_path, candidate)
+                if not valid:
+                    logger.warning('Stopped resolving %r because %r is not the same file',
+                                   result, candidate)
+                    break
+                result = candidate
         return result
 
     def ensure_directories(self, env_dir):
@@ -184,7 +198,7 @@ def create_if_needed(d):
                              'check that your PATH environment variable is '
                              'correctly set.')
         # only resolve executable symlinks, not the full chain, see gh-106045
-        dirname, exename = os.path.split(self._abspath_resolve_leaf(executable))
+        dirname, exename = os.path.split(self._getpath_realpath(executable))
         if sys.platform == 'win32':
             # Always create the simplest name in the venv. It will either be a
             # link back to executable, or a copy of the appropriate launcher