Re-implement _block_standard as a wrapper function around _adapters.TraversableResourcesLoader and ensure that the known standard readers are replaced by readers from importlib_resources.

Author: jaraco

importlib_resources/future/adapters.py

@@ -1,11 +1,44 @@
-import contextlib
+import functools
 import pathlib
 from contextlib import suppress
 from types import SimpleNamespace
 
 from .. import readers, _adapters
 
 
+def _block_standard(reader_getter):
+    """
+    Wrap _adapters.TraversableResourcesLoader.get_resource_reader
+    and intercept any standard library readers.
+    """
+
+    @functools.wraps(reader_getter)
+    def wrapper(*args, **kwargs):
+        """
+        If the reader is from the standard library, return None to allow
+        allow likely newer implementations in this library to take precedence.
+        """
+        try:
+            reader = reader_getter(*args, **kwargs)
+        except NotADirectoryError:
+            # MultiplexedPath may fail on zip subdirectory
+            return
+        # Python 3.10+
+        if reader.__class__.__module__.startswith('importlib.resources.'):
+            return
+        # Python 3.8, 3.9
+        if isinstance(reader, _adapters.CompatibilityFiles) and (
+            reader.spec.loader.__class__.__module__.startswith('zipimport')
+            or reader.spec.loader.__class__.__module__.startswith(
+                '_frozen_importlib_external'
+            )
+        ):
+            return
+        return reader
+
+    return wrapper
+
+
 class TraversableResourcesLoader(_adapters.TraversableResourcesLoader):
     """
     Adapt loaders to provide TraversableResources and other
@@ -16,18 +49,10 @@ class TraversableResourcesLoader(_adapters.TraversableResourcesLoader):
     """
 
     def get_resource_reader(self, name):
-        with contextlib.suppress(Exception):
-            return self._block_standard(super().get_resource_reader(name))
-        return self._standard_reader()
-
-    def _block_standard(self, reader):
-        """
-        If the reader is from the standard library, raise an exception to
-        allow likely newer implementations in this library to take precedence.
-        """
-        if reader.__class__.__module__.startswith('importlib.resources.'):
-            raise RuntimeError("Reader blocked to be superseded.")
-        return reader
+        return (
+            _block_standard(super().get_resource_reader)(name)
+            or self._standard_reader()
+        )
 
     def _standard_reader(self):
         return self._zip_reader() or self._namespace_reader() or self._file_reader()