aio-libs / multidict / 33975467489

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Do not swallow non-TypeError exceptions in feature-detection fallbacks (#1382)

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## What do these changes do?

Several feature-detection fallbacks cleared *every* pending exception
when a fallback path was taken:
view richcompare and items-view `__contains__` measuring `len(other)`,
items-view `__contains__`
computing the identity, `MultiDict.__eq__` probing `keys()`, and
`extend()`/constructor probing
`items()`. A `MemoryError` or `KeyboardInterrupt` raised by the user
object was silently discarded. Each
is now guarded with `PyErr_ExceptionMatches()` so only the expected
`TypeError`/`AttributeError` is
cleared and anything else propagates — the same pattern the sibling
sites in `views.h` already use.
C-extension-only; the pure-Python backend propagates naturally.

## Are there changes in behavior for the user?

Yes (edge case): an exception other than `TypeError`/`AttributeError`
(notably `MemoryError`,
`KeyboardInterrupt`) raised by an object being probed now propagates
instead of being swallowed. The
normal fallbacks (a non-sized or non-mapping object) are unchanged.

## Is it a substantial burden for the maintainers to support this?

No. It applies the module's existing guard pattern to the few sites that
missed it.

## Related issue number

Findings from the C-extension analysis report #1306.

## Checklist

- [x] I think the code is well written
- [x] Unit tests for the changes exist
(`test_non_typeerror_exceptions_are_not_swallowed`)
- [x] Documentation reflects the changes (no public API change)
- [ ] N/A — no `CONTRIBUTORS.txt` in this repo
- [x] Add a new news fragment into the `CHANGES/` folder

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Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

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