gh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` #102722

sobolevn · 2023-03-15T10:26:20Z

Two main changes:

More pickle tests with different callables
Passing things like 0 is not allowed, so I think testing this behaviour won't hurt. The test is quite simple

All tests work for both typing.Callable and _collections_abc.Callable.

I also went ahead and remove this suspicious if from #102681 (comment)

Moreover, all tests pass without it.
I cannot find any examples where it is needed. Please, prove me wrong.

CC @AlexWaygood

Issue: Improve coverage of _collections_abc._CallableGenericAlias #102721

…icAlias`

Lib/test/test_typing.py

Co-authored-by: Alex Waygood <[email protected]>

AlexWaygood · 2023-03-15T14:39:54Z

Lib/_collections_abc.py

-        # A special case in PEP 612 where if X = Callable[P, int],
-        # then X[int, str] == X[[int, str]].
-        if (len(self.__parameters__) == 1
-                and _is_param_expr(self.__parameters__[0])
-                and item and not _is_param_expr(item[0])):
-            item = (item,)


This makes me slightly nervous, but I can't find any changes in behaviour from removing this code.

@Fidget-Spinner and @serhiy-storchaka, can either of you think of anything bad that could happen if we remove this code? The whole test suite passes with it removed.

Yes, me too. Let's wait for others to comment.

It makes me nervous too. In case you're looking for an example that triggers this path, here's one:

from typing import ParamSpec P = ParamSpec("P") from collections.abc import Callable C = Callable[[P], int] print(C[str])

However I agree that if I just comment this out, the output is the same. It's possible that @serhiy-storchaka fixed the issue in the C code (the super() method) -- the code here is from Aug 4th, 2021, while he touched _Py_subs_parameters on May 8th, 2022.

Yes, I found examples that triggered this code path, but for all of the examples I found, I couldn't find any differences in behaviour with this code deleted (repr, __args__, __parameters__, equality)

Someone could trace through the C code that gets called and see if it does the right thing.

Looks like _unpack_args C function which was added in May now handles this case: https://github.com/python/cpython/blame/2dc94634b50f0e5e207787e5ac1d56c68b22c3ae/Objects/genericaliasobject.c#L361

It unpacks nested tuples to a flat format, so - this code is not needed anymore.

I don't suppose the pure-Python code could be useful for PyPy, could it? (Don't see how it could, just throwing that out there)

Sorry, the only other iterperter I worked on is RustPython.

AlexWaygood

Looks good to me other than my nervousness about https://github.com/python/cpython/pull/102722/files#r1137196475

Lib/_collections_abc.py

gvanrossum

Don’t worry about PyPy.

AlexWaygood · 2023-03-16T14:48:13Z

Thanks @sobolevn! I'd like to backport the coverage improvements, but not the code changes.

sobolevn · 2023-03-16T14:49:42Z

I'd like to backport the coverage improvements, but not the code changes.

Do you want me to do that? Or do you want to do that yourself?

I am fine with both :)

AlexWaygood · 2023-03-16T14:50:49Z

Would be great if you could take care of it, thanks!

sobolevn · 2023-03-16T14:53:38Z

Scheduled for tomorrow then :)

* main: (34 commits) pythongh-102701: Fix overflow in dictobject.c (pythonGH-102750) pythonGH-78530: add support for generators in `asyncio.wait` (python#102761) Increase stack reserve size for Windows debug builds to avoid test crashes (pythonGH-102764) pythongh-102755: Add PyErr_DisplayException(exc) (python#102756) Fix outdated note about 'int' rounding or truncating (python#102736) pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (python#102760) pythongh-99726: Improves correctness of stat results for Windows, and uses faster API when available (pythonGH-102149) pythongh-102192: remove redundant exception fields from ssl module socket (python#102466) pythongh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (python#102743) pythongh-102737: Un-ignore ceval.c in the CI globals check (pythongh-102745) pythonGH-102748: remove legacy support for generator based coroutines from `asyncio.iscoroutine` (python#102749) pythongh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` (python#102722) pythonGH-102653: Make recipe docstring show the correct distribution (python#102742) Add comments to `{typing,_collections_abc}._type_repr` about each other (python#102752) pythongh-102594: PyErr_SetObject adds note to exception raised on normalization error (python#102675) pythongh-94440: Fix issue of ProcessPoolExecutor shutdown hanging (python#94468) pythonGH-100112: avoid using iterable coroutines in asyncio internally (python#100128) pythongh-102690: Use Edge as fallback in webbrowser instead of IE (python#102691) pythongh-102660: Fix Refleaks in import.c (python#102744) pythongh-102738: remove from cases generator the code related to register instructions (python#102739) ...

…ricAlias` (GH-102788) This is a backport of #102722 without the `typing.py` changes. Automerge-Triggered-By: GH:AlexWaygood

…ricAlias` (GH-102790) This is a manual backport of #102722 but without `typing.py` changes and without `TypeVarTuple` case, because it was added in 3.11 Automerge-Triggered-By: GH:AlexWaygood

…icAlias` (python#102722) Co-authored-by: Alex Waygood <[email protected]>

pythongh-102721: Improve coverage of `_collections_abc._CallableGener…

8ed3dd8

…icAlias`

sobolevn requested review from gvanrossum, Fidget-Spinner, JelleZijlstra, AlexWaygood and rhettinger as code owners March 15, 2023 10:26

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Improve coverage of _collections_abc._CallableGenericAlias #102721

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This was referenced Mar 17, 2023

[3.11] gh-102721: Improve coverage of _collections_abc._CallableGenericAlias #102788

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[3.10] gh-102721: Improve coverage of _collections_abc._CallableGenericAlias #102790

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miss-islington pushed a commit that referenced this pull request Mar 17, 2023

[3.11] gh-102721: Improve coverage of `_collections_abc._CallableGene…

045c8a1

…ricAlias` (GH-102788) This is a backport of #102722 without the `typing.py` changes. Automerge-Triggered-By: GH:AlexWaygood

Fidget-Spinner pushed a commit to Fidget-Spinner/cpython that referenced this pull request Mar 27, 2023

pythongh-102721: Improve coverage of `_collections_abc._CallableGener…

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…icAlias` (python#102722) Co-authored-by: Alex Waygood <[email protected]>

warsaw pushed a commit to warsaw/cpython that referenced this pull request Apr 11, 2023

pythongh-102721: Improve coverage of `_collections_abc._CallableGener…

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…icAlias` (python#102722) Co-authored-by: Alex Waygood <[email protected]>

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gh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` #102722

gh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` #102722

sobolevn commented Mar 15, 2023 •

edited by AlexWaygood

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gh-102721: Improve coverage of _collections_abc._CallableGenericAlias #102722

gh-102721: Improve coverage of _collections_abc._CallableGenericAlias #102722

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gh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` #102722

gh-102721: Improve coverage of `_collections_abc._CallableGenericAlias` #102722

sobolevn commented Mar 15, 2023 •

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