Describe the bug

Version

• datamodel-code-generator: 0.54.0
• Python: 3.12.12

Summary

When all of these options are used together:

• --use-type-alias
• --use-annotated
• --enum-field-as-literal all

a defaulted $ref to an enum-like schema can generate code that calls a Python 3.12 type alias as if it were a constructor.

That produces invalid generated code like:

type Mode = Literal["default", "plan"]

class Model(BaseModel):
    mode: Annotated[Mode | None, Field(default_factory=lambda: Mode("default"))]
                                                             # ^ Object of type "TypeAliasType" is not callable

To Reproduce

Example schema:

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

Used commandline:

$ datamodel-codegen \
  --input repro.json \
  --input-file-type jsonschema \
  --output out.py \
  --output-model-type pydantic_v2.BaseModel \
  --target-python-version 3.12 \
  --enum-field-as-literal all \
  --use-type-alias \
  --use-annotated

Expected behavior
The generated default should not call a type alias.

Perhaps just this?

mode: Annotated[Mode | None, Field(default_factory=lambda: "default")]

Version:

• OS: [e.g. iOS]: macOS
• Python version: 3.12.12
• datamodel-code-generator version: [e.g. 22] 0.54.0

Additional context
This seems specific to the interaction of these flags:

• Without --use-type-alias, generation uses a wrapper model and works.
• Without --use-annotated, generation emits = "default" and works.
• Without --enum-field-as-literal all, generation uses an enum class and works.