handle PEP 639 License-Expression in test metadata#46
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thrau merged 1 commit intolocalstack:mainfrom Apr 2, 2026
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pytest >= 9.0 is built with setuptools >= 77, which emits License-Expression instead of the legacy License header. Use .get() to support both old-style and PEP 639 metadata. AI-assisted: OpenCode (Claude Opus 4.6)
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I didn't go as far as upgrading pytest, but on a local test I can confirm the entire test suite works with pytest-9.0.2 |
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nice catch Alessio @nolith, thanks for the contribution!
this change looks good to me. i would also have been ok with just removing the assert. but this makes it much clearer. i was vaguely aware that the license metadata field had been changed, but hadn't connected the dots to plux, so thanks!
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test_resolve_distribution_information fails with pytest >= 9.0.2 because pytest now uses PEP 639 License-Expression metadata instead of the legacy License field. Upstream pins pytest==8.4.1 in CI and has not encountered this yet. Upstream fix: localstack/plux#46
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Problem
test_resolve_distribution_informationassertsdist.metadata["License"] == "MIT"against the installed pytest package. This fails when pytest is built with PEP 639 metadata (setuptools >= 77), because theLicenseheader no longer exists — it is replaced byLicense-Expression.Why upstream CI doesn't catch it
The dev dependencies pin
pytest==8.4.1, which was built with older setuptools and still has the legacyLicense: MITheader in its METADATA. The test only fails with pytest >= 9.0, which requiressetuptools>=77and emits PEP 639 metadata (License-Expression: MITwith noLicensefield).Any environment that doesn't use the pinned pytest version (e.g. nixpkgs, conda, other distros) hits this failure.
Fix
Use
.get()to checkLicense-Expressionfirst, then fall back toLicense. This handles both old-style and PEP 639 metadata:Using
.get()instead of[]also avoids theDeprecationWarningfromimportlib.metadataabout implicitNonereturns on missing keys, which will become aKeyErrorin a future Python version.