[ty] Consider keyword arguments when unpacking a variadic argument#22796
Merged
dhruvmanila merged 1 commit intomainfrom Jan 26, 2026
Merged
[ty] Consider keyword arguments when unpacking a variadic argument#22796dhruvmanila merged 1 commit intomainfrom
dhruvmanila merged 1 commit intomainfrom
Conversation
dhruvmanila
added
bug
Typing conformance resultsNo changes detected ✅ |
|
dhruvmanila
requested review from
AlexWaygood,
carljm,
dcreager and
sharkdp
as code owners
dhruvmanila
force-pushed
the
dhruv/unpack-arg
branch
from
992fc8a to
b175d81
Compare
dhruvmanila
force-pushed
the
dhruv/unpack-arg
branch
from
b175d81 to
802bb74
Compare
|
| Lint rule | Added | Removed | Changed |
|---|---|---|---|
parameter-already-assigned |
0 | 120 | 0 |
unused-ignore-comment |
21 | 0 | 0 |
no-matching-overload |
0 | 13 | 0 |
invalid-argument-type |
0 | 7 | 3 |
invalid-await |
0 | 2 | 6 |
invalid-return-type |
4 | 0 | 4 |
invalid-assignment |
0 | 0 | 5 |
possibly-missing-attribute |
0 | 3 | 1 |
unresolved-attribute |
0 | 0 | 2 |
| Total | 25 | 145 | 21 |
AlexWaygood
approved these changes
Jan 23, 2026
Comment on lines
+795
to
+798
| # Explicit keyword argument takes precedence over variable-length variadic expansion. | ||
| # The list unpacking should only fill `a` and `b`, leaving `c` for the keyword argument. | ||
| def _(args: list[str]) -> None: | ||
| f(*args, c=1.0) |
Member
There was a problem hiding this comment.
I guess we could consider still flagging this as a separate error code? Since the length of the args iterable is unknown, we cannot verify that the call will definitely succeed; some users who want very strict typing might still want to know about that.
I agree that we should err on the side of leniency here, though -- if we did have a separate error code for that, it should definitely be disabled by default. It's too strict for most users.
Contributor
There was a problem hiding this comment.
I think if we were being consistent about the strict version, it would go beyond what main currently does -- really any * unpacking of anything other than a fixed-length tuple, to any function which doesn't take *args, is a call we can't verify is correct, which the strict diagnostic should be emitted on. I definitely think this is a separate (and low priority) feature, not something we should do in this PR.
Member
Author
There was a problem hiding this comment.
Yeah, that makes sense. I'll open a separate tracking issue for this.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
fixes: astral-sh/ty#1584
This PR fixes a bug where ty would unpack a variadic argument consuming all the remaining unmatched parameters. The way this fix is implemented is by collecting the parameters for which an argument is provided via keyword e.g.,
func(foo=1). For example,In the above example,
mainwould currently raiseparameter-already-assignedbecause we don't know how many elements wouldargsunpack into so we consider assigning the type to all the remaining parameters. But, in the above caseyhas been provided as keyword argument explicitly.Now, there are other cases like
foo(*args, 1)orfoo(*args, *(1,))which is not considered in this PR i.e., this PR only handles explicit keyword argument and we would still emit diagnostic for positional, variadic, and keyword-variadic. Pyright behaves in the same way i.e., it only handles keyword argument while other type checkers (mypy, pyrefly) does not handle any cases. Refer to the new mdtest cases for all the cases.Test Plan
Add new mdtests.