Fix distutils uninstallation error

Author: uranusjr

src/pip/_internal/metadata/base.py

@@ -148,7 +148,7 @@ def info_location(self) -> Optional[str]:
         raise NotImplementedError()
 
     @property
-    def installed_by_legacy_distutils(self) -> bool:
+    def installed_by_distutils(self) -> bool:
         """Whether this distribution is installed with legacy distutils format.
 
         A distribution installed with "raw" distutils not patched by setuptools
@@ -173,19 +173,22 @@ def installed_as_egg(self) -> bool:
         return info_location.endswith(".egg")
 
     @property
-    def installed_with_egg_info(self) -> bool:
+    def installed_with_setuptools_egg_info(self) -> bool:
         """Whether this distribution is installed with the ``.egg-info`` format.
 
         This usually indicates the distribution was installed with setuptools
         with an old pip version or with ``single-version-externally-managed``.
 
-        Note that this *does not* ensure ``.egg-info`` is a directory. It can
-        be a file when ``installed_by_legacy_distutils`` is also True.
+        Note that this ensure the metadata store is a directory. distutils can
+        also installs an ``.egg-info``, but as a file, not a directory. This
+        property is *False* for that case. Also see ``installed_by_distutils``.
         """
         info_location = self.info_location
         if not info_location:
             return False
-        return info_location.endswith(".egg-info")
+        if not info_location.endswith(".egg-info"):
+            return False
+        return pathlib.Path(info_location).is_dir()
 
     @property
     def installed_with_dist_info(self) -> bool:

src/pip/_internal/req/req_uninstall.py

@@ -423,7 +423,7 @@ def commit(self) -> None:
     def from_dist(cls, dist: BaseDistribution) -> "UninstallPathSet":
         dist_location = dist.location
         info_location = dist.info_location
-        if dist_location is None or info_location is None:
+        if dist_location is None:
             logger.info(
                 "Not uninstalling %s since it is not installed",
                 dist.canonical_name,
@@ -457,10 +457,11 @@ def from_dist(cls, dist: BaseDistribution) -> "UninstallPathSet":
 
         # Uninstall cases order do matter as in the case of 2 installs of the
         # same package, pip needs to uninstall the currently detected version
-        if dist.installed_with_egg_info and not dist.editable:
+        if dist.installed_with_setuptools_egg_info and not dist.editable:
             # if dist is editable and the location points to a ``.egg-info``,
             # we are in fact in the ``.egg_link`` case.
-            paths_to_remove.add(info_location)
+            if info_location is not None:
+                paths_to_remove.add(info_location)
             installed_files = dist.iter_declared_entries()
             if installed_files is not None:
                 for installed_file in installed_files:
@@ -486,7 +487,7 @@ def from_dist(cls, dist: BaseDistribution) -> "UninstallPathSet":
                     paths_to_remove.add(f"{path}.pyc")
                     paths_to_remove.add(f"{path}.pyo")
 
-        elif dist.installed_by_legacy_distutils:
+        elif dist.installed_by_distutils:
             raise UninstallationError(
                 "Cannot uninstall {!r}. It is a distutils installed project "
                 "and thus we cannot accurately determine which files belong "