Fix asyncio.gather regression (#8271)

Adding the empty-tuple overload caused major problems for pyright, and that overload only deals with an unlikely edge case anyway. Get rid of it, and replace the fallback overload with a more general overload. Fixes #8270.
2025-12-08 21:14:48 +08:00 · 2022-07-16 18:56:58 +01:00
parent de1a79bd00
commit 1ebe1b463e
2 changed files with 58 additions and 44 deletions
--- a/stdlib/asyncio/tasks.pyi
+++ b/stdlib/asyncio/tasks.pyi
@@ -66,17 +66,18 @@ def ensure_future(coro_or_future: Awaitable[_T], *, loop: AbstractEventLoop | No
 # of tasks passed; however, Tuple is used similar to the annotation for
 # zip() because typing does not support variadic type variables.  See
 # typing PR #1550 for discussion.
+#
+# The many type: ignores here are because the overloads overlap,
+# but having overlapping overloads is the only way to get acceptable type inference in all edge cases.
 if sys.version_info >= (3, 10):
    @overload
-    def gather(*, return_exceptions: bool = ...) -> Future[tuple[()]]: ...
+    def gather(__coro_or_future1: _FutureLike[_T1], *, return_exceptions: Literal[False] = ...) -> Future[tuple[_T1]]: ...  # type: ignore[misc]
    @overload
-    def gather(__coro_or_future1: _FutureLike[_T1], *, return_exceptions: Literal[False] = ...) -> Future[tuple[_T1]]: ...
-    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1], __coro_or_future2: _FutureLike[_T2], *, return_exceptions: Literal[False] = ...
    ) -> Future[tuple[_T1, _T2]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -84,7 +85,7 @@ if sys.version_info >= (3, 10):
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2, _T3]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -93,7 +94,7 @@ if sys.version_info >= (3, 10):
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2, _T3, _T4]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -103,13 +104,13 @@ if sys.version_info >= (3, 10):
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2, _T3, _T4, _T5]]: ...
    @overload
-    def gather(__coro_or_future1: _FutureLike[_T1], *, return_exceptions: bool) -> Future[tuple[_T1 | BaseException]]: ...
+    def gather(__coro_or_future1: _FutureLike[_T1], *, return_exceptions: bool) -> Future[tuple[_T1 | BaseException]]: ...  # type: ignore[misc]
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1], __coro_or_future2: _FutureLike[_T2], *, return_exceptions: bool
    ) -> Future[tuple[_T1 | BaseException, _T2 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -117,7 +118,7 @@ if sys.version_info >= (3, 10):
        return_exceptions: bool,
    ) -> Future[tuple[_T1 | BaseException, _T2 | BaseException, _T3 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -126,7 +127,7 @@ if sys.version_info >= (3, 10):
        return_exceptions: bool,
    ) -> Future[tuple[_T1 | BaseException, _T2 | BaseException, _T3 | BaseException, _T4 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -138,26 +139,15 @@ if sys.version_info >= (3, 10):
        tuple[_T1 | BaseException, _T2 | BaseException, _T3 | BaseException, _T4 | BaseException, _T5 | BaseException]
    ]: ...
    @overload
-    def gather(
-        __coro_or_future1: _FutureLike[Any],
-        __coro_or_future2: _FutureLike[Any],
-        __coro_or_future3: _FutureLike[Any],
-        __coro_or_future4: _FutureLike[Any],
-        __coro_or_future5: _FutureLike[Any],
-        __coro_or_future6: _FutureLike[Any],
-        *coros_or_futures: _FutureLike[Any],
-        return_exceptions: bool = ...,
-    ) -> Future[list[Any]]: ...
+    def gather(*coros_or_futures: _FutureLike[Any], return_exceptions: bool = ...) -> Future[list[Any]]: ...  # type: ignore[misc]

 else:
    @overload
-    def gather(*, loop: AbstractEventLoop | None = ..., return_exceptions: bool = ...) -> Future[tuple[()]]: ...
-    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1], *, loop: AbstractEventLoop | None = ..., return_exceptions: Literal[False] = ...
    ) -> Future[tuple[_T1]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        *,
@@ -165,7 +155,7 @@ else:
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -174,7 +164,7 @@ else:
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2, _T3]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -184,7 +174,7 @@ else:
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2, _T3, _T4]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -195,11 +185,11 @@ else:
        return_exceptions: Literal[False] = ...,
    ) -> Future[tuple[_T1, _T2, _T3, _T4, _T5]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1], *, loop: AbstractEventLoop | None = ..., return_exceptions: bool
    ) -> Future[tuple[_T1 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        *,
@@ -207,7 +197,7 @@ else:
        return_exceptions: bool,
    ) -> Future[tuple[_T1 | BaseException, _T2 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -216,7 +206,7 @@ else:
        return_exceptions: bool,
    ) -> Future[tuple[_T1 | BaseException, _T2 | BaseException, _T3 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -226,7 +216,7 @@ else:
        return_exceptions: bool,
    ) -> Future[tuple[_T1 | BaseException, _T2 | BaseException, _T3 | BaseException, _T4 | BaseException]]: ...
    @overload
-    def gather(
+    def gather(  # type: ignore[misc]
        __coro_or_future1: _FutureLike[_T1],
        __coro_or_future2: _FutureLike[_T2],
        __coro_or_future3: _FutureLike[_T3],
@@ -239,16 +229,8 @@ else:
        tuple[_T1 | BaseException, _T2 | BaseException, _T3 | BaseException, _T4 | BaseException, _T5 | BaseException]
    ]: ...
    @overload
-    def gather(
-        __coro_or_future1: _FutureLike[Any],
-        __coro_or_future2: _FutureLike[Any],
-        __coro_or_future3: _FutureLike[Any],
-        __coro_or_future4: _FutureLike[Any],
-        __coro_or_future5: _FutureLike[Any],
-        __coro_or_future6: _FutureLike[Any],
-        *coros_or_futures: _FutureLike[Any],
-        loop: AbstractEventLoop | None = ...,
-        return_exceptions: bool = ...,
+    def gather(  # type: ignore[misc]
+        *coros_or_futures: _FutureLike[Any], loop: AbstractEventLoop | None = ..., return_exceptions: bool = ...
    ) -> Future[list[Any]]: ...

 def run_coroutine_threadsafe(coro: _FutureLike[_T], loop: AbstractEventLoop) -> concurrent.futures.Future[_T]: ...
--- a/test_cases/stdlib/asyncio/test_gather.py
+++ b/test_cases/stdlib/asyncio/test_gather.py
@@ -0,0 +1,32 @@
+import asyncio
+from typing import Any, Awaitable, List, Tuple, Union
+from typing_extensions import assert_type
+
+
+async def coro1() -> int:
+    return 42
+
+
+async def coro2() -> str:
+    return "spam"
+
+
+async def test_gather(awaitable1: Awaitable[int], awaitable2: Awaitable[str]) -> None:
+    a = await asyncio.gather(awaitable1)
+    assert_type(a, Tuple[int])
+
+    b = await asyncio.gather(awaitable1, awaitable2, return_exceptions=True)
+    assert_type(b, Tuple[Union[int, BaseException], Union[str, BaseException]])
+
+    c = await asyncio.gather(awaitable1, awaitable2, awaitable1, awaitable1, awaitable1, awaitable1)
+    assert_type(c, List[Any])
+
+    awaitables_list: List[Awaitable[int]] = [awaitable1]
+    d = await asyncio.gather(*awaitables_list)
+    assert_type(d, List[Any])
+
+    e = await asyncio.gather()
+    assert_type(e, List[Any])
+
+
+asyncio.run(test_gather(coro1(), coro2()))