gh-121190: A better error message from `importlib.resources.files()` when module spec is None by whitphx · Pull Request #138531 · python/cpython · GitHub

importlib.resources.files(package) raises an error when package.__spec__ is None because the code below refers to spec.name but spec is None.

cpython/Lib/importlib/resources/_common.py

Line 117 in f19f1d8

reader = spec.loader.get_resource_reader(spec.name)

The error would be

AttributeError: 'NoneType' object has no attribute 'name'`

and #121190 said it's not helpful.

This PR adds a None-check to handle such a case and raise an error with a specific message.

(This is from PyConTW 2025 sprint)

Issue: Different output from importlib.resources.files() in REPL in 3.12 versus 3.13 #121190

…es() when module spec is not available

Thanks for working on this! 👏

Python stdlib is not typed (that's what typeshed is for) so you'll likely be asked to revert these changes

Yes, please revert all type annotation changes.

Thanks updated!

I wonder is the error can be a bit more specific. I think most Python users will not know what a "spec" is? (I don't :-) )

Thanks. I proposed a new message. wdyt?

Why was the default adapter removed? Isn't this a breaking change?

For the simplicity sake, because it seems not to be used anywhere.
This default value was defined since this mechanism was introduced in #24670 but it was not used even in that commit.

As it does not pertain to the issue that's addressed in this PR I'd recommend reverting this change anyway.

Thanks, got it 👍

By the way, importlib.resources module is somewhat special as its development is mainly in importlib_resources package which is then backported here, see https://github.com/python/importlib_metadata/wiki/Development-Methodology

So I am not sure if this PR should be merged here or moved over to the importlib_resources repo (CC @jaraco)

As it does not pertain to the issue that's addressed in this PR I'd recommend reverting this change anyway.

…apter.__init__()

By the way, importlib.resources module is somewhat special as its development is mainly in importlib_resources package which is then backported here, see https://github.com/python/importlib_metadata/wiki/Development-Methodology

So I am not sure if this PR should be merged here or moved over to the importlib_resources repo (CC @jaraco)

It can be merged here, but we prefer to merge changes in importlib_resources to make it easier to keep the code in sync.

@whitphx, thank you so much for this PR!

It looks good to me, but I'd like @jaraco to have a look too.

Co-authored-by: Daniel Hollas <danekhollas@gmail.com>

…pec is None from python/cpython#138531

Thank you, I created a PR to python/importlib_resources as well: python/importlib_resources#331

Thanks for this change. I made some changes in the importlib_resources port, so I'd rather apply that here. This work will happen in gh-148460.

…pec is None from python/cpython#138531

Raise an exception with a better message from importlib.resources.fil…

078c801

…es() when module spec is not available

whitphx requested review from FFY00, jaraco and warsaw as code owners September 5, 2025 08:16

bedevere-app Bot added the awaiting review label Sep 5, 2025

bedevere-app Bot mentioned this pull request Sep 5, 2025

Different output from importlib.resources.files() in REPL in 3.12 versus 3.13 #121190

Closed

blurb-it Bot and others added 2 commits September 5, 2025 08:26

📜🤖 Added by blurb_it.

c79a7cc

Fix Blurb

5ed2652

danielhollas reviewed Sep 5, 2025

View reviewed changes

whitphx added 2 commits September 6, 2025 17:04

Remove type annotations

847d8df

Modify the error message

e25491e

whitphx force-pushed the gh-121190 branch from 4dedeeb to e25491e Compare September 7, 2025 05:08

whitphx requested review from ZeroIntensity and danielhollas September 7, 2025 08:51

Merge branch 'main' into pythongh-121190

06b8233

danielhollas reviewed Sep 14, 2025

View reviewed changes

whitphx requested a review from danielhollas September 18, 2025 15:20

danielhollas reviewed Sep 18, 2025

View reviewed changes

Revert a change removing the default adapter argument on SpecLoaderAd…

7dc7e46

…apter.__init__()

FFY00 approved these changes Oct 4, 2025

View reviewed changes

bedevere-app Bot added awaiting merge and removed awaiting review labels Oct 4, 2025

whitphx and others added 2 commits October 22, 2025 22:03

Apply suggestion from @danielhollas

9e98cfc

Co-authored-by: Daniel Hollas <danekhollas@gmail.com>

fix the error message

d3ec82a

whitphx added a commit to whitphx/importlib_resources that referenced this pull request Oct 22, 2025

A better error message from importlib.resources.files() when module s…

47b3f09

…pec is None from python/cpython#138531

whitphx mentioned this pull request Oct 22, 2025

A better error message from importlib.resources.files() when module spec is None python/importlib_resources#331

Merged

jaraco self-assigned this Apr 12, 2026

jaraco closed this Apr 12, 2026

hswong3i pushed a commit to alvistack/python-importlib_resources that referenced this pull request Apr 13, 2026

A better error message from importlib.resources.files() when module s…

f51c057

…pec is None from python/cpython#138531

+              TYPE_CHECKING = False
+              if TYPE_CHECKING:
+                  from ..machinery import ModuleSpec

-                  spec = wrap_spec(package)
+                  if package.__spec__ is None:
+                      raise TypeError(f"Can't access resources on a module with no spec: {package}")

                   Adapt a package spec to adapt the underlying loader.
                   """
-                  def __init__(self, spec, adapter=lambda spec: spec.loader):

gh-121190: A better error message from `importlib.resources.files()` when module spec is None by whitphx · Pull Request #138531 · python/cpython · GitHub

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gh-121190: A better error message from importlib.resources.files() when module spec is None - #138531

gh-121190: A better error message from importlib.resources.files() when module spec is None#138531whitphx wants to merge 9 commits intopython:mainpython/cpython:mainfrom whitphx:gh-121190whitphx/cpython:gh-121190Copy head branch name to clipboard

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gh-121190: A better error message from importlib.resources.files() when module spec is None#138531
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