Properly rebuild the FieldInfo when a forward ref gets evaluated (#7698)

pydantic/_internal/_generate_schema.py

@@ -897,7 +897,9 @@ def _generate_dc_field_schema(
             metadata=common_field['metadata'],
         )
 
-    def _common_field_schema(self, name: str, field_info: FieldInfo, decorators: DecoratorInfos) -> _CommonField:
+    def _common_field_schema(  # noqa C901
+        self, name: str, field_info: FieldInfo, decorators: DecoratorInfos
+    ) -> _CommonField:
         # Update FieldInfo annotation if appropriate:
         if has_instance_in_type(field_info.annotation, (ForwardRef, str)):
             types_namespace = self._types_namespace
@@ -910,6 +912,14 @@ def _common_field_schema(self, name: str, field_info: FieldInfo, decorators: Dec
             if evaluated is not field_info.annotation and not has_instance_in_type(evaluated, PydanticRecursiveRef):
                 field_info.annotation = evaluated
 
+                # Handle any field info attributes that may have been obtained from now-resolved annotations
+                new_field_info = FieldInfo.from_annotation(evaluated)
+                for k, v in new_field_info._attributes_set.items():
+                    # If an attribute is already set, it means it was set by assigning to a call to Field (or just a
+                    # default value), and that should take the highest priority. So don't overwrite existing attributes.
+                    if k not in field_info._attributes_set:
+                        setattr(field_info, k, v)
+
         source_type, annotations = field_info.annotation, field_info.metadata
 
         def set_discriminator(schema: CoreSchema) -> CoreSchema:

tests/test_annotated.py

@@ -373,3 +373,30 @@ def test_predicate_error_python() -> None:
             'input': -1,
         }
     ]
+
+
+def test_annotated_field_info_not_lost_from_forwardref():
+    from pydantic import BaseModel
+
+    class ForwardRefAnnotatedFieldModel(BaseModel):
+        foo: 'Annotated[Integer, Field(alias="bar", default=1)]' = 2
+        foo2: 'Annotated[Integer, Field(alias="bar2", default=1)]' = Field(default=2, alias='baz')
+
+    Integer = int
+
+    ForwardRefAnnotatedFieldModel.model_rebuild()
+
+    assert ForwardRefAnnotatedFieldModel(bar=3).foo == 3
+    assert ForwardRefAnnotatedFieldModel(baz=3).foo2 == 3
+
+    with pytest.raises(ValidationError) as exc_info:
+        ForwardRefAnnotatedFieldModel(bar='bar')
+    assert exc_info.value.errors() == [
+        {
+            'input': 'bar',
+            'loc': ('bar',),
+            'msg': 'Input should be a valid integer, unable to parse string as an integer',
+            'type': 'int_parsing',
+            'url': 'https://errors.pydantic.dev/2.4/v/int_parsing',
+        }
+    ]