Fix type hint of Field.default to be compatible with Python 3.8 and 3.9 (#10972)

Viicos · sydney-runkle · commit a9cf39c32a78 · 2024-11-26T07:20:30.000-05:00
For Python &lt; 3.10, we define `EllipsisType = type(Ellipsis)` in
`_typing_extra`. `EllipsisType` is then used in a type expression
but pyright raises an error because `EllipsisType` is defined as
variable.

Instead, we make use of the `ellipsis` builtin, only available
for type checkers (defined in typeshed) as a compatibility hack.
diff --git a/pydantic/fields.py b/pydantic/fields.py
@@ -734,7 +734,7 @@ class _EmptyKwargs(typing_extensions.TypedDict):
 # to understand the magic that happens at runtime with the following overloads:
 @overload  # type hint the return value as `Any` to avoid type checking regressions when using `...`.
 def Field(
-    default: _typing_extra.EllipsisType,
+    default: ellipsis,  # noqa: F821  # TODO: use `_typing_extra.EllipsisType` when we drop Py3.9
     *,
     alias: str | None = _Unset,
     alias_priority: int | None = _Unset,
