Fix bug with schema generation with Field(...) in a forward ref (#8494)

pydantic/_internal/_generate_schema.py

@@ -991,16 +991,21 @@ def _common_field_schema(  # C901
 
             evaluated = _typing_extra.eval_type_lenient(field_info.annotation, types_namespace, None)
             if evaluated is not field_info.annotation and not has_instance_in_type(evaluated, PydanticRecursiveRef):
-                field_info.annotation = evaluated
+                new_field_info = FieldInfo.from_annotation(evaluated)
+                field_info.annotation = new_field_info.annotation
 
                 # 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:
+                    # We skip over "attributes" that are present in the metadata_lookup dict because these won't
+                    # actually end up as attributes of the `FieldInfo` instance.
+                    if k not in field_info._attributes_set and k not in field_info.metadata_lookup:
                         setattr(field_info, k, v)
 
+                # Finally, ensure the field info also reflects all the `_attributes_set` that are actually metadata.
+                field_info.metadata = [*new_field_info.metadata, *field_info.metadata]
+
         source_type, annotations = field_info.annotation, field_info.metadata
 
         def set_discriminator(schema: CoreSchema) -> CoreSchema:

tests/test_annotated.py

@@ -424,3 +424,49 @@ class AnnotatedPrivateFieldModel(BaseModel):
 
     with pytest.raises(AttributeError):
         assert model.bar
+
+
+def test_min_length_field_info_not_lost():
+    class AnnotatedFieldModel(BaseModel):
+        foo: 'Annotated[String, Field(min_length=3)]' = Field(description='hello')
+
+    String = str
+
+    AnnotatedFieldModel.model_rebuild()
+
+    assert AnnotatedFieldModel(foo='000').foo == '000'
+
+    with pytest.raises(ValidationError) as exc_info:
+        AnnotatedFieldModel(foo='00')
+
+    assert exc_info.value.errors(include_url=False) == [
+        {
+            'loc': ('foo',),
+            'input': '00',
+            'ctx': {'min_length': 3},
+            'msg': 'String should have at least 3 characters',
+            'type': 'string_too_short',
+        }
+    ]
+
+    # Ensure that the inner annotation does not override the outer, even for metadata:
+    class AnnotatedFieldModel2(BaseModel):
+        foo: 'Annotated[String, Field(min_length=3)]' = Field(description='hello', min_length=2)
+
+    AnnotatedFieldModel2(foo='00')
+
+    class AnnotatedFieldModel4(BaseModel):
+        foo: 'Annotated[String, Field(min_length=3)]' = Field(description='hello', min_length=4)
+
+    with pytest.raises(ValidationError) as exc_info:
+        AnnotatedFieldModel4(foo='00')
+
+    assert exc_info.value.errors(include_url=False) == [
+        {
+            'loc': ('foo',),
+            'input': '00',
+            'ctx': {'min_length': 4},
+            'msg': 'String should have at least 4 characters',
+            'type': 'string_too_short',
+        }
+    ]