gh-127750: Fix annotations in singledispatchmethod signature tests #143571
+12
−12
Conversation
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
… the right params See https://github.com/python/cpython/pull/130309/changes#r2663516538. These functions don't annotate parameters for values used in single-dispatching (`item`), they annotate parameters one later (`arg`). This being legal relies on a bug -- pythonGH-84644, which is that `singledispatch` doesn't verify the annotation is on the "first" parameter. I think these functions should look like ```diff @functools.singledispatchmethod - def func(self, item, arg: int) -> str: + def func(self, item: int, arg) -> str: return str(item) @func.register - def _(self, item, arg: bytes) -> str: + def _(self, item: bytes, arg) -> str: return str(item) ``` (and signature tests updated accordingly) In practice, it doesn't matter how you annotate `func` here, because it's a default callback. But what matters is that any function passed to `register()` annotates the target parameter (always first positional in `singledispatch` and always second positional in `singledispatchmethod` (unless staticmethod, then the first) etc.) for the value to single-dispatch on; not some other, unrelated parameter (or return type, as presented in pythonGH-84644). Let's have a class with the same registree signature as these from the test: ```py class A: @functools.singledispatchmethod def func(self, item, arg: int) -> str: return 'argint' @func.register def _(self, item, arg: bytes) -> str: return 'argbytes' a = A() print(a.func(b'', 1)) ``` For this code, the output would be `argbytes`, even though `arg` is an integer `1`.
johnslavik
added
tests
Comment on lines
+3451
to
3455
| def m(self, item: int, arg) -> str: | ||
| return str(item) | ||
| @classmethod | ||
| def cm(cls, item, arg: int) -> str: | ||
| def cm(cls, item: int, arg) -> str: | ||
| return str(item) |
Member
There was a problem hiding this comment.
I think we can remove these methods if they are not used.
| return str(item) | ||
| @functools.singledispatchmethod | ||
| def func(self, item, arg: int) -> str: | ||
| def func(self, item: int, arg) -> str: |
Member
There was a problem hiding this comment.
Leave item not annotated here. This is the generic variant. But keep annotation for arg, so it will be seen in the result.
| return str(item) | ||
| @func.register | ||
| def _(self, item, arg: bytes) -> str: | ||
| def _(self, item: bytes, arg) -> str: |
Member
There was a problem hiding this comment.
Keep annotation for arg.
Suggested change
| def _(self, item: bytes, arg) -> str: | |
| def _(self, item: int, arg: bytes) -> str: |
See test_signatures above. These examples should be similar.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 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.
Follow-up to gh-130309.
See https://github.com/python/cpython/pull/130309/changes#r2663516538.
Details
These functions don't annotate parameters for values used in single-dispatching (
item), they annotate parameters one later (arg).This being legal relies on a bug -- GH-84644, which is that
singledispatchdoesn't verify the annotation is on the "first" parameter.In practice, it doesn't matter how you annotate
funchere, because it's a default callback. But what matters is that any function passed toregister()annotates the target parameter (always first positional insingledispatchand always second positional insingledispatchmethod(unless staticmethod, then the first) etc.) for the value to single-dispatch on; not some other, unrelated parameter (or return type, as presented in GH-84644).Let's have a class with the same registree signature as these from the test:
For this code, the output would be
argbytes, even thoughargis an integer1.