Field order is wrong when non-required property is listed before required in schema

[k-jell-encentive]

Describe the bug
If a non-required property in the schema is listed before any required property, the field order is wrong when using pydantic dataclasses where fields where a field with default value can't appear before fields without. It seems like the sorting doesn't work correctly.

To Reproduce
Example schema:

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "title": "UserProfile",
  "type": "object",
  "required": ["name", "id", "email"],
  "properties": {
    "age": {
      "type": "integer",
      "minimum": 0
    },
    "id": {
      "type": "string",
      "description": "Unique identifier for the user"
    },
    "name": {
      "type": "string",
      "minLength": 1
    },
    "email": {
      "type": "string",
      "format": "email"
    },
    "isActive": {
      "type": "boolean",
      "default": true
    },
    "role": {
      "type": "string",
      "enum": ["admin", "editor", "viewer"]
    },
    "tags": {
      "type": "array",
      "items": {
        "type": "string"
      }
    },
    "address": {
      "type": "object",
      "required": ["city"],
      "properties": {
        "street": {
          "type": "string"
        },
        "city": {
          "type": "string"
        },
        "postalCode": {
          "type": "string",
          "pattern": "^[0-9]{5}$"
        }
      }
    }
  },
  "additionalProperties": false
}

Used commandline:

$ datamodel-codegen   --input ./test_schema.json   --input-file-type jsonschema   --output ./model.py   --snake-case-field --output-model-type pydantic_v2.dataclass --formatters ruff-format ruff-check isort --no-use-type-checking-imports --use-annotated --use-union-operator --use-standard-collections --use-default

Expected behavior
I get this:

@dataclass(config=ConfigDict(extra="forbid"))
class UserProfile:
    email: EmailStr
    age: Annotated[int | None, Field(ge=0)] = None
    id: Annotated[str, Field(description="Unique identifier for the user")]
    name: Annotated[str, Field(min_length=1)]
    is_active: Annotated[bool | None, Field(alias="isActive")] = True
    role: Role | None = None
    tags: list[str] | None = None
    address: Address | None = None

but I would expect this:

@dataclass(config=ConfigDict(extra="forbid"))
class UserProfile:
    email: EmailStr
    id: Annotated[str, Field(description="Unique identifier for the user")]
    name: Annotated[str, Field(min_length=1)]
    is_active: Annotated[bool | None, Field(alias="isActive")] = True
    age: Annotated[int | None, Field(ge=0)] = None
    role: Role | None = None
    tags: list[str] | None = None
    address: Address | None = None

Version:

• OS: linux
• Python version: tested with 3.11 and 3.13
• datamodel-code-generator version: 0.55.0
  Additional context
  Add any other context about the problem here.

[k-jell-encentive]

I think the problem might be here:

datamodel-code-generator/src/datamodel_code_generator/model/dataclass.py

Lines 39 to 43 in 5bd8eab

	def has_field_assignment(field: DataModelFieldBase) -> bool:
	"""Check if a dataclass field has a default value or field() assignment."""
	return bool(field.field) or not (
	field.required or (field.represented_default == "None" and field.strip_default_none)
	)

because bool(field.field) is always true when a field has metadata even though it doesn't have a default value. If I just change it to:

def has_field_assignment(field: DataModelFieldBase) -> bool:
    """Check if a dataclass field has a default value or field() assignment."""
    return not (
        field.required or (field.represented_default == "None" and field.strip_default_none)
    )

sorting is correct for me. Not sure about any other implications this might have though.