Make _store_schema_list thread safe

[jtilly]

I'm using jsonschema through altair and as of version 4.17.1 I've been occasionally running into issues when generating plots in parallel (using threading): The commit that broke things for me is 4f8f3, where it makes a difference for me if I'm calling .append(...) in a loop or .extend(...) only once. The reason is that some of my threads end up with an incomplete list of _VOCABULARIES.

I understand that jsonschema is not advertising to be threadsafe (xref #464), but would you still consider merging this patch? I'm imitating the style of _store_schema_list from before 4f8f346.

I should add that my patch doesn't make the function thread safe, just a little bit thread safer.

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📚 Documentation preview 📚: https://python-jsonschema--1032.org.readthedocs.build/en/1032/

[Julian]

Hi there! I appreciate you sending this PR -- in general my philosophy is not to merge it because it sets wrong expectations -- I may change this area, again not think about thread-safety, and if it breaks may not feel like merging a future PR, and especially so given it needs tests.

In this specific case though I do know this area is very likely to change by the next release of jsonschema -- specifically the next release will likely make use of entirely different code paths for reference resolution using the referencing library I'm working on, which should improve compliance with the spec whilst making the interfaces better for downstream users.

I'm going to close this for the latter reason more so than the former, since this function is near certain to change or go away, but I'll say if you keep an eye out, it's possible that the way this will look shortly will work already for how you're using it (though yes I still won't really ever promise thread-safety as I personally am a fan of other ways of parallelization). But let's have that conversation again in a few weeks if need be.

[jtilly]

Got it, thank you for the explanation!