Describe the bug
When using --set-default-enum-member, an IntEnum field default value 0 is not converted to the corresponding enum member (e.g. Status.integer_0). The generated model keeps the numeric default (0) instead of Status.integer_0.

To Reproduce

Example schema:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "type": "object",
  "properties": {
    "status": {
      "$ref": "#/$defs/Status",
      "default": 0
    }
  },
  "$defs": {
    "Status": {
      "type": "integer",
      "enum": [0, 1]
    }
  }
}

Used commandline:

$ datamodel-codegen --input test.json --set-default-enum-member

Output:

from __future__ import annotations

from enum import IntEnum

from pydantic import BaseModel


class Status(IntEnum):
    integer_0 = 0
    integer_1 = 1


class Model(BaseModel):
    status: Status | None = 0

Expected behavior
The default value should be converted to the corresponding enum member when --set-default-enum-member is enabled.

class Model(BaseModel):
    status: Status | None = Status.integer_0

Version:

• OS: macOS
• Python version: 3.13.11
• datamodel-code-generator version: 0.53.1

Additional context
Confirmed locally: the issue is fixed for this case by applying the following changes.

In

- if not model_field.default:
+ if model_field.default is None:

In

- field_default = str(field.default or "").strip("'\"")
+ field_default = str("" if field.default is None else field.default).strip("'\"")