Search weels for .dist-info directories

Some wheels don't use canonicalized names for their .dist-info
directories, so search the wheel for them.

Fixes: pypa#134

src/installer/sources.py

@@ -145,6 +145,22 @@ def open(cls, path: "os.PathLike[str]") -> Iterator["WheelFile"]:
         with zipfile.ZipFile(path) as f:
             yield cls(f)
 
+    @property
+    def dist_info_dir(self) -> str:
+        """Name of the dist-info directory."""
+        if not hasattr(self, "_dist_info_dir"):
+            top_level_directories = {
+                path.split("/", 1)[0] for path in self._zipfile.namelist()
+            }
+            dist_infos = [
+                name for name in top_level_directories if name.endswith(".dist-info")
+            ]
+            assert (
+                len(dist_infos) == 1
+            ), "Wheel doesn't contain exactly one .dist-info directory"
+            self._dist_info_dir = dist_infos[0]
+        return self._dist_info_dir
+
     @property
     def dist_info_filenames(self) -> List[str]:
         """Get names of all files in the dist-info directory."""

tests/test_sources.py

@@ -99,6 +99,11 @@ def test_provides_correct_contents(self, fancy_wheel):
         assert sorted(got_records) == sorted(expected_records)
         assert got_files == files
 
+    def test_finds_dist_info(self, fancy_wheel):
+        denorm = fancy_wheel.rename(fancy_wheel.parent / "Fancy-1.0.0-py3-none-any.whl")
+        with WheelFile.open(denorm) as source:
+            assert source.dist_info_filenames
+
 
 def replace_file_in_zip(path: str, filename: str, content: "bytes | None") -> None:
     """Helper function for replacing a file in the zip.