[1.0 backport] Adjust SCC setup to enable earlier collections.abc import in typeshed #14531
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…python#14088) Fixes python#11860 (?) Typeshed is currently unable to import Sequence, MutableSequence, or ByteString from collections.abc within builtins.pyi. It seems this is because: 1. In order to analyze `collections.abc`, we first need to analyze `collections`. 2. Since `collections` is a package containing an `__init__.pyi` file, the `add_implicit_module_attrs` function will try adding the `__path__` variable to the symboltable. 3. The `__path__` variable has type `builtins.str`. But str is a subclass of Sequence, which we have not analyzed yet since we're still in the middle of analyzing `collections` and `collections.abc`. This diff tries repairing this by: 1. Adding `_collections_abc` and `collections.abc` to the set of special-cased core modules we deliberately process early. 2. Modifying `add_implicit_module_attrs` so it does the same trick we do for the `__doc__` symbol and fall back to using an UnboundType if `builtins.str` is not defined yet. To be 100% honest, I'm not really sold on this PR for a few reasons: - I was able to test these changes manually, but wasn't sure how to write tests for them. - We have 3-4 subtly different lists of "core modules" scattered throughout mypy. For example, see `CORE_BUILTIN_MODULES` in mypy/build.py or try grepping for the string `"typing"` in the mypy dir. Arguably, we should defer landing this PR until we've had a chance to consolidate these lists and confirm there are no additional places where we need to special-case `_collections_abc`, `collections`, and `collections.abc`. - PEP 585 attempted to declare that we should one day remove entries like Sequence from `typing` module, but this realistically doesn't seem ever achievable given that (a) it would break backwards compat and (b) there doesn't seem to be any incentives for users to proactively switch. In that case, is there any pressing reason to change typeshed? Regardless, this is a crash and my goal atm is to de-crash mypy, so I'm throwing this over the wall.
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
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A backport of #14088 to the
release-1.0branch.