installer_canonicalize_wheel_name.diff

diff --git installer/sources.py installer/sources.py
index fa0bc34..03c16f9 100644
--- installer/sources.py
+++ installer/sources.py
@@ -122,6 +122,33 @@ 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"
+            dist_info_dir = dist_infos[0]
+
+            # NAME-VER.dist-info
+            di_dname = dist_info_dir.rsplit("-", 2)[0]
+            norm_di_dname = installer.utils.normalize_distribution_name(di_dname)
+            norm_file_dname = installer.utils.normalize_distribution_name(self.distribution)
+            assert (
+                norm_di_dname == norm_file_dname
+            ), "Wheel .dist-info directory doesn't match wheel filename"
+
+            self._dist_info_dir = dist_info_dir
+        return self._dist_info_dir
+
     @property
     def dist_info_filenames(self) -> List[str]:
         """Get names of all files in the dist-info directory."""
diff --git installer/utils.py installer/utils.py
index 3da89e4..cb412d7 100644
--- installer/utils.py
+++ installer/utils.py
@@ -93,6 +93,14 @@ def parse_metadata_file(contents: str) -> Message:
     return feed_parser.close()
 
 
+def normalize_distribution_name(name: str) -> str:
+    """Normalize a project name according to PEP-503.
+
+    :param name: The project name to normalize
+    """
+    return re.sub(r"[-_.]+", "-", name).lower()
+
+
 def parse_wheel_filename(filename: str) -> WheelFilename:
     """Parse a wheel filename, into it's various components.