# Sentry SDK thread-metadata test isolation

The fallback tests globally mock `threading.current_thread` while a worker
is running. Python 3.14's `Thread.join()` also calls that function. A one-use
mock can therefore be consumed by the wrong caller or raise `StopIteration`
when the main thread joins the worker.

## Scope and behavior

`isolate-threading-mocks.patch` changes three neighboring thread-metadata
tests in `tests/test_utils.py`, including the formerly excluded
`test_get_current_thread_meta_main_thread`.

Each test replaces only `sentry_sdk.utils.threading`, wraps the real module
for unmocked operations, and sets the SDK lookup's return value. The real
`Thread.join()` continues using Python's unmodified `threading` module.
The fallback-result assertions remain; SDK production code is unchanged.

## Reproduction and focused checks

Use a disposable Sentry SDK 2.66.0 checkout and its Python test dependencies.
From this directory:

```sh
patch --fuzz=0 -d /path/to/sentry-python -p1 < isolate-threading-mocks.patch
cd /path/to/sentry-python
python -m pytest tests/test_utils.py -k get_current_thread_meta -q
```

To reproduce the race, hold the worker inside its mock just after
`get_current_thread_meta()` returns, signal that point to the main thread,
and call `Thread.join()` before releasing the worker. Use an independent
bounded release so the patched join can finish. The original test raises
`StopIteration` in `join`; the patched test passes under the same schedule.
Perform this scheduling instrumentation only in a disposable checkout.

## Upstream status

This is a standalone test patch for Sentry SDK 2.66.0. No upstream submission
was made during this work. Recheck mock isolation and Python threading
behavior when upgrading the SDK or interpreter.

## Local NixOS integration and build results

[`../default.nix`](../default.nix) loads `default.nix` through
`pythonPackagesExtensions`. From the repository root:

```sh
nix build --no-link -L .#nixosConfigurations.jeeves.pkgs.python314Packages.sentry-sdk
```

The patched package passed 2,356 tests with 116 existing skips on Python
3.14.7. The controlled join reproduction failed before the fix and passed
after it.

That package build used the preceding dependency set with this patch to avoid
unrelated rebuilds after pytest-xdist changed. The integrated host derivation
was evaluated; a complete NixOS rebuild was not performed.