Update comments for operator.itemgetter.__call__ generic following mypy 1.11 fix (#13489)

Author: Avasam

stdlib/@tests/test_cases/check_SupportsGetItem.py

@@ -0,0 +1,38 @@
+from __future__ import annotations
+
+from _typeshed import SupportsDunderGT, SupportsDunderLT, SupportsGetItem
+from collections.abc import Callable
+from operator import itemgetter
+from typing import Any, TypeVar
+from typing_extensions import assert_type
+
+_T = TypeVar("_T")
+
+
+# This should be equivalent to itemgetter().__call__
+def standalone_call(obj: SupportsGetItem[Any, _T]) -> _T: ...
+
+
+# Expected type of itemgetter(1).__call__
+expected_type_itemgetter_call: Callable[[SupportsGetItem[int, _T]], _T]  # pyright: ignore[reportGeneralTypeIssues]
+
+# Expecting itemgetter(1) to be assignable to this
+# based on the example below: min({"first": 1, "second": 2}.items(), key=itemgetter(1))
+# That example and assigning to this variable are what failed in https://github.com/python/mypy/issues/14032
+expected_assignable_to: Callable[[tuple[str, int]], SupportsDunderLT[Any] | SupportsDunderGT[Any]]
+
+
+# Regression tests for https://github.com/python/mypy/issues/14032
+# assert_type(itemgetter("first")({"first": 1, "second": 2}), int) # See comment on itemgetter.__call__
+assert_type(min({"first": 1, "second": 2}, key=itemgetter(1)), str)
+assert_type(min({"first": 1, "second": 2}.items(), key=itemgetter(1)), tuple[str, int])
+assert_type(standalone_call({"first": 1, "second": 2}), int)
+assert_type(min({"first": 1, "second": 2}, key=standalone_call), str)
+assert_type(min({"first": 1, "second": 2}.items(), key=standalone_call), tuple[str, int])
+
+expected_itemgetter_call_type = itemgetter(1).__call__
+expected_itemgetter_call_type = itemgetter(1)
+expected_assignable_to = itemgetter(1)
+
+expected_itemgetter_call_type = standalone_call
+expected_assignable_to = standalone_call

stdlib/operator.pyi

@@ -205,8 +205,10 @@ class itemgetter(Generic[_T_co]):
     #   "tuple[int, int]" is incompatible with protocol "SupportsIndex"
     # preventing [_T_co, ...] instead of [Any, ...]
     #
-    # A suspected mypy issue prevents using [..., _T] instead of [..., Any] here.
-    # https://github.com/python/mypy/issues/14032
+    # If we can't infer a literal key from __new__ (ie: `itemgetter[Literal[0]]` for `itemgetter(0)`),
+    # then we can't annotate __call__'s return type or it'll break on tuples
+    #
+    # These issues are best demonstrated by the `itertools.check_itertools_recipes.unique_justseen` test.
     def __call__(self, obj: SupportsGetItem[Any, Any]) -> Any: ...
 
 @final

stubs/six/@tests/stubtest_allowlist.txt

@@ -14,7 +14,7 @@ six.get_method_self
 six.viewitems
 six.viewkeys
 six.viewvalues
-# Should be `operator.itemgetter[int]`. But a bug in mypy prevents using TypeVar in itemgetter__call__
+# Should be `byte2int: operator.itemgetter[int]`. But `itemgetter.__call__` returns `Any`
 six.byte2int
 
 # Utils

stubs/six/six/__init__.pyi

@@ -61,7 +61,7 @@ unichr = chr
 
 def int2byte(i: int) -> bytes: ...
 
-# Should be `byte2int: operator.itemgetter[int]`. But a bug in mypy prevents using TypeVar in itemgetter.__call__
+# Should be `byte2int: operator.itemgetter[int]`. But `itemgetter.__call__` returns `Any`
 def byte2int(obj: SupportsGetItem[int, _T]) -> _T: ...
 
 indexbytes = operator.getitem