Attempt to fix issue with symlinked packages

Author: jherland

importlib_metadata/__init__.py

@@ -31,7 +31,7 @@
 from importlib import import_module
 from importlib.abc import MetaPathFinder
 from itertools import starmap
-from typing import List, Mapping, Optional, cast
+from typing import Iterable, Iterator, List, Mapping, Optional, cast
 
 
 __all__ = [
@@ -961,10 +961,32 @@ def _top_level_declared(dist):
     return (dist.read_text('top_level.txt') or '').split()
 
 
+def _walk_dirs(package_paths: Iterable[PackagePath]) -> Iterator[PackagePath]:
+    for package_path in package_paths:
+
+        def make_file(name):
+            result = PackagePath(name)
+            result.hash = None
+            result.size = None
+            result.dist = package_path.dist
+            return result
+
+        real_path = package_path.locate()
+        real_sitedir = package_path.dist.locate_file("")  # type: ignore
+        if real_path.is_dir() and real_path.is_symlink():
+            # .files only mentions symlink, we must recurse into it ourselves:
+            for root, dirs, files in os.walk(real_path):
+                for filename in files:
+                    real_file = pathlib.Path(root, filename)
+                    yield make_file(real_file.relative_to(real_sitedir))
+        else:
+            yield package_path
+
+
 def _top_level_inferred(dist):
     opt_names = {
         f.parts[0] if len(f.parts) > 1 else inspect.getmodulename(f)
-        for f in always_iterable(dist.files)
+        for f in _walk_dirs(always_iterable(dist.files))
     }
 
     @pass_none