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Fix a crash when inferring a typing.TypeVar call. #2239

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mbyrnepr2
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Closes pylint-dev/pylint#8802

Type of Changes

Type
βœ“ πŸ› Bug fix
✨ New feature
βœ“ πŸ”¨ Refactoring
πŸ“œ Docs

Description

Closes pylint-dev/pylint#8802

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@mbyrnepr2 mbyrnepr2 Jul 6, 2023

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Created this module since it felt like all brain_typing tests were going into brain/test_brain.py - let me know what you think.

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codecov bot commented Jul 6, 2023

Codecov Report

Merging #2239 (ea5dd00) into main (cdeb259) will not change coverage.
The diff coverage is 100.00%.

Additional details and impacted files

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@@           Coverage Diff           @@
##             main    #2239   +/-   ##
=======================================
  Coverage   92.80%   92.80%           
=======================================
  Files          94       94           
  Lines       10941    10941           
=======================================
  Hits        10154    10154           
  Misses        787      787           
Flag Coverage Ξ”
linux 92.61% <100.00%> (ΓΈ)
pypy 90.89% <100.00%> (ΓΈ)
windows 92.37% <100.00%> (ΓΈ)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files Coverage Ξ”
astroid/brain/brain_typing.py 86.66% <100.00%> (ΓΈ)

@mbyrnepr2 mbyrnepr2 marked this pull request as ready for review July 6, 2023 14:53
@jacobtylerwalls jacobtylerwalls added this to the 2.15.6 milestone Jul 6, 2023
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Let's backport. Shall we then move the changelog to 2.15.6?

@@ -134,7 +134,14 @@ def infer_typing_typevar_or_newtype(node, context_itton=None):
raise UseInferenceDefault

typename = node.args[0].as_string().strip("'")
node = extract_node(TYPING_TYPE_TEMPLATE.format(typename))
node = ClassDef(
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Shall we add the Meta class as base? Then we still have the __getitem__ inference correctly.

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Thanks for such quick feedbackπŸ‘.
I started a short vacation right after opening this so I’ll think about a test case when I can.

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Hey @DanielNoord I've taken a look finally :)

It seems to me there is no need for __getitem__ to be attached to the astroid node representing either typing.TypeVar or typing.NewType since neither of these are subscriptable. What do you think?
Similar point for __args__ since that is used to fetch the arguments used in subscripting.

As a sidenote - __getitem__ is already part of nodes.ClassDef since it inherits that method from LocalsDictNodeNG.

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Okay! Can we then remove that code?

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I took a look into that just now. The template is used by this function which needs the __args__ member since the function is inferring subscriptable types.
As an illustration, If I were to remove the code and use a similar ClassDef construction for the code above, this unitest fails:
FAILED astroid/tests/brain/test_brain.py::TypingBrain::test_has_dunder_args - astroid.exceptions.InferenceError: StopIteration raised without any error information.
In other words, running Pylint on this code:

from typing import Union
NumericTypes = Union[int, float]
NumericTypes.__args__ #@

...gives: E1101: Class 'Union' has no '__args__' member (no-member)

ChangeLog Outdated Show resolved Hide resolved
@mbyrnepr2 mbyrnepr2 force-pushed the pylint_issue_8802_typing_typevar_crash branch from e845e19 to 017c218 Compare July 13, 2023 13:01
@mbyrnepr2 mbyrnepr2 force-pushed the pylint_issue_8802_typing_typevar_crash branch 2 times, most recently from f8562cb to 5b671d3 Compare July 14, 2023 11:18
@mbyrnepr2 mbyrnepr2 force-pushed the pylint_issue_8802_typing_typevar_crash branch from 5b671d3 to ea5dd00 Compare July 16, 2023 12:03
@jacobtylerwalls jacobtylerwalls removed their request for review July 16, 2023 16:23
@mbyrnepr2 mbyrnepr2 merged commit 89dfb48 into pylint-dev:main Jul 17, 2023
20 checks passed
@mbyrnepr2 mbyrnepr2 deleted the pylint_issue_8802_typing_typevar_crash branch July 17, 2023 10:39
github-actions bot pushed a commit that referenced this pull request Jul 17, 2023
Pierre-Sassoulas pushed a commit that referenced this pull request Jul 17, 2023
…peVar` call. (#2254)

* Fix a crash when inferring a `typing.TypeVar` call. (#2239)

Closes pylint-dev/pylint#8802

(cherry picked from commit 89dfb48)

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Mark Byrne <31762852+mbyrnepr2@users.noreply.github.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
mbyrnepr2 added a commit to mbyrnepr2/astroid that referenced this pull request Sep 25, 2023
@Pierre-Sassoulas Pierre-Sassoulas added backported Assigned once the backport is done and removed backport maintenance/2.15.x labels Feb 4, 2024
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Pylint crashes with an invalid TypeVar definition
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