Fix editable-or-not egg-info uninstallation

Author: uranusjr

src/pip/_internal/metadata/base.py

@@ -214,6 +214,14 @@ def canonical_name(self) -> NormalizedName:
     def version(self) -> DistributionVersion:
         raise NotImplementedError()
 
+    @property
+    def setuptools_filename(self) -> str:
+        """Convert a project name to its setuptools-compatible filename.
+
+        This is a copy of ``pkg_resources.to_filename()`` for compatibility.
+        """
+        return self.raw_name.replace("-", "_")
+
     @property
     def direct_url(self) -> Optional[DirectUrl]:
         """Obtain a DirectUrl from this distribution.

src/pip/_internal/req/req_uninstall.py

@@ -455,13 +455,22 @@ def from_dist(cls, dist: BaseDistribution) -> "UninstallPathSet":
         paths_to_remove = cls(dist)
         develop_egg_link = egg_link_path_from_location(dist.raw_name)
 
+        # Distribution is installed with metadata in a "flat" .egg-info
+        # directory. This means it is not a modern .dist-info installation, an
+        # egg, or legacy editable.
+        setuptools_flat_installation = (
+            dist.installed_with_setuptools_egg_info
+            and info_location is not None
+            and os.path.exists(info_location)
+            # If dist is editable and the location points to a ``.egg-info``,
+            # we are in fact in the legacy editable case.
+            and not info_location.endswith(f"{dist.setuptools_filename}.egg-info")
+        )
+
         # 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_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.
-            if info_location is not None:
-                paths_to_remove.add(info_location)
+        if setuptools_flat_installation:
+            paths_to_remove.add(info_location)
             installed_files = dist.iter_declared_entries()
             if installed_files is not None:
                 for installed_file in installed_files:
@@ -512,15 +521,16 @@ def from_dist(cls, dist: BaseDistribution) -> "UninstallPathSet":
             for path in uninstallation_paths(dist):
                 paths_to_remove.add(path)
 
-        elif dist.editable and develop_egg_link:
+        elif develop_egg_link:
             # PEP 660 modern editable is handled in the ``.dist-info`` case
             # above, so this only covers the setuptools-style editable.
             with open(develop_egg_link) as fh:
                 link_pointer = os.path.normcase(fh.readline().strip())
             assert (
                 link_pointer == dist_location
-            ), "Egg-link {} does not match installed location of {} (at {})".format(
-                link_pointer, dist.raw_name, dist_location
+            ), (
+                f"Egg-link {link_pointer} does not match installed location of "
+                f"{dist.raw_name} (at {dist_location})"
             )
             paths_to_remove.add(develop_egg_link)
             easy_install_pth = os.path.join(