GeezerVison

What does this implement/fix? Explain your changes.

When BinaryFormatter cannot run, RuntimeData.Stash falls back to NoopFormatter and still published a zero-length sys.clr_data capsule. NoopFormatter.Serialize writes nothing. The next PythonEngine.Initialize saw that capsule and called Deserialize, which throws.

Stash now returns before building or publishing the capsule when the formatter is a NoopFormatter. An existing capsule is cleared so a later Initialize builds a fresh runtime instead of restoring an empty one. Runtimes where BinaryFormatter still works, including .NET Framework, keep the real stash.

Does this close any currently open issues?

#2282

Any other comments?

#2639 already catches the BinaryFormatter failure and returns NoopFormatter, so Shutdown itself no longer throws NotSupportedException. This change stops that fallback from leaving a capsule the next Initialize cannot read.

The new embed test calls Py_Finalize after the assertion, then Initialize. A second Shutdown in the same process deallocates types from the previous runtime and hits MetaType.tp_dealloc in a debug build. GlobalTestsSetup would do that second shutdown.

Local run, with PYTHONNET_PYDLL set:

dotnet test src/embed_tests/Python.EmbeddingTest.csproj -f net10.0

242 passed, 5 skipped, 0 failed. net472 was not run here. This machine has no mono.

Checklist

• Make sure to include one or more tests for your change
• If an enhancement PR, please create docs and at best an example
• Ensure you have signed the .NET Foundation CLA
• Add yourself to AUTHORS
• Updated the CHANGELOG