Always store the original field assignment on FieldInfo

Viicos · Viicos · commit dc7a9d20bee5 · 2025-06-13T10:45:04.000+02:00
Backport of: #11946
diff --git a/pydantic/_internal/_fields.py b/pydantic/_internal/_fields.py
@@ -235,12 +235,13 @@ def collect_model_fields(  # noqa: C901
             )
 
             field_info = FieldInfo_.from_annotated_attribute(ann_type, assigned_value, _source=AnnotationSource.CLASS)
+            # Store the original annotation and assignment value that should be used to rebuild the field info later.
+            # Note that the assignment is always stored as the annotation might contain a type var that is later
+            #  parameterized with an unknown forward reference (and we'll need it to rebuild the field info):
+            field_info._original_assignment = original_assignment
             if not evaluated:
                 field_info._complete = False
-                # Store the original annotation and assignment value that should be used to rebuild
-                # the field info later:
                 field_info._original_annotation = ann_type
-                field_info._original_assignment = original_assignment
             elif 'final' in field_info._qualifiers and not field_info.is_required():
                 warnings.warn(
                     f'Annotation {ann_name!r} is marked as final and has a default value. Pydantic treats {ann_name!r} as a '
diff --git a/tests/test_forward_ref.py b/tests/test_forward_ref.py
@@ -7,7 +7,7 @@
 
 import pytest
 
-from pydantic import BaseModel, PydanticUserError, TypeAdapter, ValidationError
+from pydantic import BaseModel, Field, PydanticUserError, TypeAdapter, ValidationError
 
 
 def test_postponed_annotations(create_module):
@@ -1239,11 +1239,11 @@ class SubChild(Child):
     ),
 )
 def test_forward_ref_in_class_parameter() -> None:
-    """https://github.com/pydantic/pydantic/issues/11854"""
+    """https://github.com/pydantic/pydantic/issues/11854, https://github.com/pydantic/pydantic/issues/11920"""
     T = TypeVar('T')
 
     class Model(BaseModel, Generic[T]):
-        f: T
+        f: T = Field(json_schema_extra={'extra': 'value'})
 
     M = Model[list['Undefined']]
 
@@ -1253,6 +1253,7 @@ class Model(BaseModel, Generic[T]):
 
     assert M.__pydantic_fields_complete__
     assert M.model_fields['f'].annotation == list[int]
+    assert M.model_fields['f'].json_schema_extra == {'extra': 'value'}
 
 
 def test_uses_the_local_namespace_when_generating_schema():
