fix(config): keep rxconfig dependencies on same-root reload

[benedikt-bartscher]

Summary

Fixes #7028

_get_config() evicts every project-local module that rxconfig.py imported before each load. rx.App() calls reload_config(), so every backend worker loads rxconfig.py twice and re-executes those modules in between. The app code imported before rx.App() keeps the first copies, sys.modules holds the second ones, and every class defined in an evicted module now exists twice.

For state-defining modules that is the StateValueError from #7028. For plain modules it is quieter and worse: pickle.dumps() of an instance of the app's copy fails with Can't pickle <class 'myapp.routes.Route'>: it's not the same object as myapp.routes.Route, because the qualified name resolves to the re-imported class. In our production app that made the auth substate unserializable, so it was never persisted to redis and clients got stuck on hydrate.

Changes

• Record the project root the dependencies were captured under and only evict them when a load comes from a different root. A same-root load still re-reads rxconfig.py from disk; only its project-local imports are kept. This is option 1 from Reloading a config whose rxconfig.py imports a state-defining module raises StateValueError #7028.
• Tests: same-root reload keeps the module object and pickling of a pre-reload instance works; a load from another project root still evicts and each project resolves its own same-named helper; the Reloading a config whose rxconfig.py imports a state-defining module raises StateValueError #7028 reproduction passes for both a plain reload_config() and a reload in a forked context (the AppHarness shape).

Testing

• tests/units/test_config.py: 134 passed. The two same-root tests fail on main (one with the Reloading a config whose rxconfig.py imports a state-defining module raises StateValueError #7028 StateValueError).
• ruff, pyright, codespell pass.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge with no outstanding correctness, security, or repository-rule issues.

Summary

• Tracks the project root associated with recorded rxconfig.py dependencies.
• Keeps dependency module identities stable during same-root reloads, avoiding duplicate state classes and pickle identity failures.
• Restricts rxconfig discovery to the explicitly requested project root.
• Adds regression coverage for successful reloads, failed loads, cross-root switching, state registration, and serialization.
• Adds a user-facing bugfix news fragment.

_{Reviews (6) · Last reviewed commit: "Merge remote-tracking branch 'upstream/m..."}

[cubic-dev-ai]

All reported issues were addressed

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[codspeed-hq]

Merging this PR will not alter performance

✅ 40 untouched benchmarks
⏩ 8 skipped benchmarks¹

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_{Comparing benedikt-bartscher:config-deps-evict-on-root-change (b46485c) with main (9165dc6)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed across 2 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>