Add additional Unpack/kwargs conformance test cases by yangdanny97 · Pull Request #1918 · python/typing · GitHub

These two examples from the typing spec don't appear to have corresponding cases in the conformance suite:

EXAMPLE 1

The reverse situation where the destination callable contains **kwargs: Unpack[TypedDict] and the source callable doesn’t contain **kwargs should be disallowed. This is because, we cannot be sure that additional keyword arguments are not being passed in when an instance of a subclass had been assigned to a variable with a base class type and then unpacked in the destination callable invocation

https://typing.readthedocs.io/en/latest/spec/callables.html#source-contains-kwargs-and-destination-doesn-t

EXAMPLE 2

Therefore, kwargs hinted with an unpacked TypedDict can only be passed to another function if the function to which unpacked kwargs are being passed to has **kwargs in its signature as well, because then additional keywords would not cause errors at runtime during function invocation. Otherwise, the type checker should generate an error.

https://typing.readthedocs.io/en/latest/spec/callables.html#passing-kwargs-inside-a-function-to-another-function

This PR adds 2 new test cases and updates the generated conformance output.

Pyre's output is super fishy here, it emits an error message on line 138, but it's not what I would expect. If we agree that these tests should be added, I'll dig into Pyre's behavior some more.

Example 2 I have some questions about. At a glance it seems reasonable, but I thought it was really weird to specify this requirement just for unpacked kwargs, but not typed dicts in other argument positions (which should still be susceptible to these issues due to structural typing). For example:

def func7(*, v1: int, v3: str, v2: str = "") -> None: ...

def func9(x: TD2, **kwargs: Unpack[TD2]) -> None:
    func7(**kwargs)  # not OK
    func7(**x)  # OK according to the spec, but not safe

Co-authored-by: Rebecca Chen <rchen152@gmail.com>

… suppression formats section

Removed repeated example, fixed formatting, removed stray "the".

Thanks for the contribution! Overall, it looks good. Just a few minor changes needed for consistency with existing tests and test results.

LGTM

@yangdanny97, this PR looks good to me. If you think it's complete, I can merge it.

@yangdanny97, looking at this closer, I agree with you that Example 2 seems inconsistent. It doesn't make any sense that there should be a difference between the two cases in your code snippet above. I'm not sure what to do about this. Implementing this behavior inconsistently will require some ugly special-casing within pyright's logic — and presumably in the other type checkers as well.

Rather than add Example 2 to the conformance tests, perhaps we should amend the typing spec to remove this inconsistency. Thoughts? If that sounds good to you, please update the PR to remove Example 2, and then either you or I can start a discussion in the typing forum to propose changing the spec.

I had a look at Pyre's implementation. I think the error emitted for the second example is a different bug, and Pyre doesn't implement the desired behavior of banning unpacked kwargs in this situation.

I'll update the results to mark Pyre as partial here, and then we should be good to go.

Edit: just saw your earlier response

@yangdanny97, looking at this closer, I agree with you that Example 2 seems inconsistent. It doesn't make any sense that there should be a difference between the two cases in your code snippet above. I'm not sure what to do about this. Implementing this behavior inconsistently will require some ugly special-casing within pyright's logic — and presumably in the other type checkers as well.

Rather than add Example 2 to the conformance tests, perhaps we should amend the typing spec to remove this inconsistency. Thoughts? If that sounds good to you, please update the PR to remove Example 2, and then either you or I can start a discussion in the typing forum to propose changing the spec.

Sure, I can update the PR to remove the second example until we sort out the spec. Ideally we have this check apply to all typed dict spreads, or none of them.

Posted https://discuss.python.org/t/typing-spec-inconsistency-for-unpacking-typed-dict-kwargs/79640

Summary: Handle a case that gave a weird error in python/typing#1918 Keyword only parameters were always treated as not having defaults, which made them incompatible with notrequired typeddict items. Reviewed By: rchen152 Differential Revision: D69222079 fbshipit-source-id: 5f4ac60d5bc3f7fa5da4b3709f0364f21f8d94aa

Danny Yang and others added 17 commits November 7, 2024 12:48

add content from typeshed/CONTRIBUTING.md

13678bd

fix build errors

9db1d7c

Merge branch 'main' into main

6ccbd65

resolve conflicts

958bb7e

address review comments

cfc2827

Update docs/guides/writing_stubs.rst

5c33d20

Co-authored-by: Rebecca Chen <rchen152@gmail.com>

Update docs/guides/writing_stubs.rst

d61da81

Co-authored-by: Rebecca Chen <rchen152@gmail.com>

add Incomplete vs Any, the Any trick sections; add reference to error…

f253587

… suppression formats section

fix ref

076d101

format and fix link

0cc549e

fix backticks, add Docstrings section

d3a652a

fix one more backtick

3e405f9

fix typo

830f247

fix label

fbd2031

Minor style and formatting fixes

cc9cdf0

Removed repeated example, fixed formatting, removed stray "the".

Merge branch 'main' of https://github.com/yangdanny97/typing

b5a44f1

Add additional callable kwargs conformance tests

45500fd

erictraut reviewed Feb 3, 2025

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Comment thread conformance/tests/callables_kwargs.py

Comment thread conformance/results/mypy/callables_kwargs.toml

add comments and notes

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erictraut approved these changes Feb 3, 2025

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This was referenced Feb 3, 2025

Assignability rule for unpacked kwargs is not enforced microsoft/pyright#9807

Closed

Parameter matching for unpacked TypedDict not enforced microsoft/pyright#9808

Closed

yangdanny97 added 2 commits February 5, 2025 22:55

remove 2nd example

a3df774

merge upstream

a9cea83

erictraut merged commit 53daf3c into python:main Feb 6, 2025

yangdanny97 mentioned this pull request Apr 5, 2025

Delete "Passing kwargs inside a function to another function section" #1960

Closed

carljm mentioned this pull request Apr 24, 2026

conformance: allow consistent treatment of kwargs: Unpack[TD] #2272

Merged

Add additional Unpack/kwargs conformance test cases by yangdanny97 · Pull Request #1918 · python/typing · GitHub

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Add additional Unpack/kwargs conformance test cases by yangdanny97 · Pull Request #1918 · python/typing · GitHub

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Add additional Unpack/kwargs conformance test cases#1918
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