[rigen1048]

What does this PR do?

This PR fixes a distributed race condition in dynamic_module_utils.py that causes intermittent ModuleNotFoundError: No module named 'transformers_modules' failures when running tests with pytest-xdist, ffaced in #45687 pr ci/cd test

Root Cause

When running in parallel (e.g., -n 8), each worker process has an isolated sys.path.

Worker A downloads a dynamic model and initializes the cache (init_hf_modules()), updating its own sys.path.
Worker B requires the same model, sees the files already exist on disk, and skips initialization.
Worker B fails to import the model because its sys.path does not contain the cache directory, preventing it from resolving the transformers_modules namespace used in relative imports.

fix:

I have added a call to init_hf_modules() at the start of get_class_in_module. This ensures every worker process correctly configures its environment before attempting an import, regardless of which worker performed the initial download.

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@Rocketknight1
@Cyrilvallez

[Rocketknight1]

cc @ydshieh @tarekziade - I'm not sure we want to modify the actual code for this, but maybe there's some way we can fix it in the tests?

[tarekziade]

I don't think this change will help, this call is a no-op for the worker once sys.path is updated, the real bug is the conditional invalidate_caches()

The cleanest place to neutralize this is conftest.py because it's loaded once per xdist worker process before any test runs, so we can pre-warm each worker's environment.

so we could call :

from transformers.dynamic_module_utils import init_hf_modules
import importlib

init_hf_modules()
importlib.invalidate_caches()

at the top of conftest

WDYT @ydshieh

[rigen1048]

@tarekziade Thanks for the valuable feedback. My original solution worked, but it seems it violates architectural purity. I tested your suggestion against my reproducible script/test and it worked well.
Thanks to @Rocketknight1 for forwarding the pr to the right people. We should wait for @ydshieh ’s insight on this — it can help us move us forward to the right direction