"No Buffer in module typing, referenced from 'inferred + unknowns'" when importing from typing_extensions #1772
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saschazepter
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Nov 28, 2024
…sue6940) Since Python 2.7 and 3.5, `typing.ByteString` was defined as an alias for `bytes | bytearray | memoryview`, and `bytes` was also accepted as a shorthand for this, so we have `bytes` sprinkled all over the codebase. But then PEP-688 reversed all of that by deprecating `typing.ByteString` and its successor `collections.abc.ByteString` in Python 3.12 (as well as the `bytes` shorthand)[1], and removing it completely in Python 3.14. That leaves us with a couple of problems, namely defining something useful that spans py3.8-py3.13 and keeps pytype happy, and finding all of the instances where `bytes` doesn't really mean `bytes`. The current successor to all of this is `collections.abc.Buffer` in Python 3.12 (or `typing_extensions.Buffer` in previous versions). However, the current CI does type checking using Python 3.11 (so the former is not avaiable), and pytype has issues with importing `typing_extensions.Buffer`[2]. The good news is we don't need to deal with this mess immediately, since the type annotation evaluation is delayed to the type checking phase, and we're making no effort at supporting it in all supported versions of Python. So by delaying the import of this particular symbol, we can still use it for type checking purposes, but can start assessing Python 3.14 problems without doing a lot of extra work. Putting this on stable will allow people interested in 3.14 to work on it 4-5 extra months earlier (and apparently there's some interest). [1] https://peps.python.org/pep-0688/#no-special-meaning-for-bytes [2] google/pytype#1772
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Recent versions of pytype seem to have settled on
from typing_extensions import Bufferand then usingBufferfor things that can bebytesormemoryview, or... Here's the baseline file where it generates such a *.pyi:node_py-start.zip
That runs successfully as part of a larger project, so I ran
merge-pyion it, and had to manually add the typing definitions for a few of the functions that usedBuffer, due to the fact they're just aliased here instead of defined as functions. (We also want to narrow the allowed usage to disallowstrand the extra arguments):node_py-annotated.zip
That generates a huge error output in the
*.pyifile:node_pyi-error.zip
I first noticed this with pytype==2023.11.21, but it looks like the same error in 2024.09.13, both running Python 3.10.11. But when pytype annotates similar to this on its own, everything seems to work. The idea behind delaying the
typing_extensionsimport is so that we don't have to vendor a copy of it for production builds, and can rely on whatever pytype provides when it is run.The text was updated successfully, but these errors were encountered: