ruff/crates/ty_python_semantic/resources/mdtest/diagnostics
Andrii Turov 957320c0f1
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[ty] Add diagnostics for invalid await expressions (#19711)
## Summary

This PR adds a new lint, `invalid-await`, for all sorts of reasons why
an object may not be `await`able, as discussed in astral-sh/ty#919.
Precisely, `__await__` is guarded against being missing, possibly
unbound, or improperly defined (expects additional arguments or doesn't
return an iterator).

Of course, diagnostics need to be fine-tuned. If `__await__` cannot be
called with no extra arguments, it indicates an error (or a quirk?) in
the method signature, not at the call site. Without any doubt, such an
object is not `Awaitable`, but I feel like talking about arguments for
an *implicit* call is a bit leaky.
I didn't reference any actual diagnostic messages in the lint
definition, because I want to hear feedback first.

Also, there's no mention of the actual required method signature for
`__await__` anywhere in the docs. The only reference I had is the
`typing` stub. I basically ended up linking `[Awaitable]` to ["must
implement
`__await__`"](https://docs.python.org/3/library/collections.abc.html#collections.abc.Awaitable),
which is insufficient on its own.

## Test Plan

The following code was tested:
```python
import asyncio
import typing


class Awaitable:
    def __await__(self) -> typing.Generator[typing.Any, None, int]:
        yield None
        return 5


class NoDunderMethod:
    pass


class InvalidAwaitArgs:
    def __await__(self, value: int) -> int:
        return value


class InvalidAwaitReturn:
    def __await__(self) -> int:
        return 5


class InvalidAwaitReturnImplicit:
    def __await__(self):
        pass


async def main() -> None:
    result = await Awaitable()  # valid
    result = await NoDunderMethod()  # `__await__` is missing
    result = await InvalidAwaitReturn()  # `__await__` returns `int`, which is not a valid iterator 
    result = await InvalidAwaitArgs()  # `__await__` expects additional arguments and cannot be called implicitly
    result = await InvalidAwaitReturnImplicit()  # `__await__` returns `Unknown`, which is not a valid iterator


asyncio.run(main())
```

---------

Co-authored-by: Carl Meyer <carl@astral.sh>
2025-08-14 14:38:33 -07:00
..
attribute_assignment.md
invalid_argument_type.md
invalid_await.md [ty] Add diagnostics for invalid await expressions (#19711) 2025-08-14 14:38:33 -07:00
no_matching_overload.md [ty] Improve invalid method calls for unmatched overloads (#18122) 2025-05-15 11:39:14 -04:00
semantic_syntax_errors.md [ty] simplify return type of place_from_declarations (#19884) 2025-08-13 14:17:08 +00:00
shadowing.md
single_matching_overload.md [ty] Surface matched overload diagnostic directly (#18452) 2025-06-20 08:36:49 +05:30
union_call.md [ty] Surface matched overload diagnostic directly (#18452) 2025-06-20 08:36:49 +05:30
unpacking.md
unresolved_import.md
unresolved_reference.md [ty] Add a note to the diagnostic if a new builtin is used on an old Python version (#18068) 2025-05-13 10:08:04 -04:00
unsupported_bool_conversion.md
version_related_syntax_errors.md