Skip default_factory wrapping for non-callable type aliases (#3012)

* fix: skip default_factory wrapping for non-callable type aliases (#3009)

When --use-type-alias + --use-annotated + --enum-field-as-literal all are
combined, the generator produced `default_factory=lambda: Mode('default')`
where Mode is a PEP 695 type alias (not callable). Add a TypeAliasBase
guard in __wrap_root_model_default_values to skip wrapping for type aliases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: add black 22 skipif and ruff format for type alias test

Skip the enum_literal_type_alias_default test on black < 23 since
PEP 695 `type` statement syntax is unsupported. Reformat long
conditional in parser/base.py to satisfy ruff line-length.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* test: simplify docstring for type alias default test

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Koudai Aono <koxudaxi@gmail.com>

Author: 3 people

src/datamodel_code_generator/parser/base.py

@@ -2158,7 +2158,11 @@ def __wrap_root_model_default_values(
                 continue
             if isinstance(model_field.default, list):
                 continue
-            if data_type.reference and isinstance(data_type.reference.source, self.data_model_root_type):
+            if (
+                data_type.reference
+                and isinstance(data_type.reference.source, self.data_model_root_type)
+                and not isinstance(data_type.reference.source, TypeAliasBase)
+            ):
                 type_name = data_type.alias or data_type.reference.short_name
                 model_field.default = WrappedDefault(
                     value=model_field.default,

tests/data/expected/main/jsonschema/enum_literal_type_alias_default.py

@@ -0,0 +1,15 @@
+# generated by datamodel-codegen:
+#   filename:  enum_literal_type_alias_default.json
+#   timestamp: 2019-07-26T00:00:00+00:00
+
+from __future__ import annotations
+
+from typing import Literal
+
+from pydantic import BaseModel
+
+type Mode = Literal['default', 'plan']
+
+
+class Model(BaseModel):
+    mode: Mode | None = 'default'

tests/data/jsonschema/enum_literal_type_alias_default.json

@@ -0,0 +1,16 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "type": "object",
+  "definitions": {
+    "Mode": {
+      "type": "string",
+      "enum": ["default", "plan"]
+    }
+  },
+  "properties": {
+    "mode": {
+      "$ref": "#/definitions/Mode",
+      "default": "default"
+    }
+  }
+}

tests/main/jsonschema/test_main_jsonschema.py

@@ -5741,6 +5741,31 @@ def test_main_jsonschema_type_alias_with_field_description_py312(output_file: Pa
     )
 
 
+@pytest.mark.skipif(
+    int(black.__version__.split(".")[0]) < 23,
+    reason="Installed black doesn't support the new 'type' statement",
+)
+def test_main_jsonschema_enum_literal_type_alias_default(output_file: Path) -> None:
+    """Don't wrap type alias defaults in default_factory (TypeAliasType is not callable)."""
+    run_main_and_assert(
+        input_path=JSON_SCHEMA_DATA_PATH / "enum_literal_type_alias_default.json",
+        output_path=output_file,
+        input_file_type=None,
+        assert_func=assert_file_content,
+        expected_file="enum_literal_type_alias_default.py",
+        extra_args=[
+            "--use-type-alias",
+            "--use-annotated",
+            "--enum-field-as-literal",
+            "all",
+            "--target-python-version",
+            "3.12",
+            "--output-model-type",
+            "pydantic_v2.BaseModel",
+        ],
+    )
+
+
 @pytest.mark.cli_doc(
     options=["--type-mappings"],
     option_description="""Override default type mappings for schema formats.