`importlib.abc.SourceLoader` issues `DeprecationWarning` because it inherits from `ResourceLoader`

[TTsangSC]

Bug report

Bug description:

Problem

• importlib.abc.SourceLoader itself does not seem to be deprecated as far as the docs go, either in 3.14 or 3.15.
• However, since it inherits from the deprecated importlib.abc.ResourceLoader, a DeprecationWarning is issued at instantiation time since 3.14.

Example

import os
import sys
import warnings
from collections.abc import Iterable
from importlib.abc import SourceLoader
from importlib.machinery import ModuleSpec
from typing import Protocol


class FinderLike(Protocol):
 def find_spec(self, fullname: str) -> ModuleSpec | None: ...


class MyLoader(SourceLoader):
 """Bare-bone `SourceLoader` subclass, only providing implementations for the abstract methods."""
 @staticmethod
 def get_data(path: os.PathLike | str) -> bytes:
 with open(path, mode='rb') as fobj:
 return fobj.read()

 @staticmethod
 def get_filename(fullname: str, finders: Iterable[FinderLike] | None = None) -> str:
 if finders is None:
 finders = (
 f for f in sys.meta_path
 if callable(getattr(f, 'find_spec', None))
 if not isinstance(f, MyLoader) # Avoid circular dependence
 )
 for finder in finders:
 try:
 spec = finder.find_spec(fullname)
 if spec is None: raise TypeError
 except (TypeError, ImportError):
 continue
 if spec.origin is not None and os.path.isfile(spec.origin):
 return str(spec.origin)
 raise ImportError(f'cannot find filename for `{fullname}`')


with warnings.catch_warnings():
 warnings.filterwarnings('error', category=DeprecationWarning)
 loader = MyLoader() # DeprecationWarning: importlib.abc.ResourceLoader is deprecated in favour of supporting resource loading through importlib.resources.abc.TraversableResources.

Questions

• Is this to be considered a bug? Or is SourceLoader supposed to be deprecated too?
• If the former, how can it be fixed? If the latter, should the docs be updated?

Possibly related issues

#89710, #121604

CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs

• GH-137426: Remove code deprecation of importlib.abc.ResourceLoader #137567
• [3.14] GH-137426: Remove code deprecation of importlib.abc.ResourceLoader (GH-137567) #137654

[brettcannon]

• Is this to be considered a bug? Or is SourceLoader supposed to be deprecated too?

It's a bug in so much as SourceLoader isn't deprecated.

• If the former, how can it be fixed?

One option is for SourceLoader to stop inheriting from ResourceLoader and copy over the abstract method from it (as well as update the docstring and documentation).

What I'm wondering about, though, is why didn't the tests catch this?

[brettcannon]

@hugovk not sure if this should be a release blocker, made it one just in case since the fix might be annoying in a point release if we change the inheritance structure.

[brettcannon]

I found my mistake: I merged 27494dd probably thinking the warning suppression was for tests of ResourceLoader instead of SourceLoader.

[brettcannon]

Another option is to drop the warning on ResourceLoader since it has no removal date and it isn't hurting anything having it there.

[brettcannon]

#137567 reverts the deprecation of ResourceLoader if that's the direction we choose to go.