Fix schema-building bug with TypeAliasType for types with refs

pydantic/_internal/_core_utils.py

@@ -228,6 +228,14 @@ def _handle_ser_schemas(self, ser_schema: core_schema.SerSchema, f: Walk) -> cor
     def handle_definitions_schema(self, schema: core_schema.DefinitionsSchema, f: Walk) -> core_schema.CoreSchema:
         new_definitions: list[core_schema.CoreSchema] = []
         for definition in schema['definitions']:
+            if 'schema_ref' and 'ref' in definition:
+                # This indicates a purposely indirect reference
+                # We want to keep such references around for implications related to JSON schema, etc.:
+                new_definitions.append(definition)
+                # However, we still need to walk the referenced definition:
+                self.walk(definition, f)
+                continue
+
             updated_definition = self.walk(definition, f)
             if 'ref' in updated_definition:
                 # If the updated definition schema doesn't have a 'ref', it shouldn't go in the definitions

tests/test_type_alias_type.py

@@ -4,7 +4,7 @@
 
 import pytest
 from annotated_types import MaxLen
-from typing_extensions import Annotated, TypeAliasType
+from typing_extensions import Annotated, Literal, TypeAliasType
 
 from pydantic import BaseModel, Field, ValidationError
 from pydantic.type_adapter import TypeAdapter
@@ -366,3 +366,25 @@ class MyOuterModel(BaseModel):
 
     data = {'inner': {'x': 'hello'}, 'y': 1}
     assert MyOuterModel.model_validate(data).model_dump() == data
+
+
+def test_type_alias_to_type_with_ref():
+    class Div(BaseModel):
+        type: Literal['Div'] = 'Div'
+        components: List['AnyComponent']
+
+    AnyComponent = TypeAliasType('AnyComponent', Div)
+
+    adapter = TypeAdapter(AnyComponent)
+    adapter.validate_python({'type': 'Div', 'components': [{'type': 'Div', 'components': []}]})
+    with pytest.raises(ValidationError) as exc_info:
+        adapter.validate_python({'type': 'Div', 'components': [{'type': 'NotDiv', 'components': []}]})
+    assert exc_info.value.errors(include_url=False) == [
+        {
+            'ctx': {'expected': "'Div'"},
+            'input': 'NotDiv',
+            'loc': ('components', 0, 'type'),
+            'msg': "Input should be 'Div'",
+            'type': 'literal_error',
+        }
+    ]