feat: Add --ignore-enum-constraints option (#2694)

* feat: Add --ignore-enum-constraints option to bypass enum generation

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* feat: Add test for --ignore-enum-constraints option and generated output

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

* docs: update CLI reference documentation

🤖 Generated by GitHub Actions

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: koxudaxi

docs/cli-reference/index.md

@@ -9,7 +9,7 @@ This documentation is auto-generated from test cases.
 | Category | Options | Description |
 |----------|---------|-------------|
 | 📁 [Base Options](base-options.md) | 5 | Input/output configuration |
-| 🔧 [Typing Customization](typing-customization.md) | 16 | Type annotation and import behavior |
+| 🔧 [Typing Customization](typing-customization.md) | 17 | Type annotation and import behavior |
 | 🏷️ [Field Customization](field-customization.md) | 20 | Field naming and docstring behavior |
 | 🏗️ [Model Customization](model-customization.md) | 26 | Model generation behavior |
 | 🎨 [Template Customization](template-customization.md) | 16 | Output formatting and custom rendering |
@@ -92,6 +92,7 @@ This documentation is auto-generated from test cases.
 
 ### I {#i}
 
+- [`--ignore-enum-constraints`](typing-customization.md#ignore-enum-constraints)
 - [`--ignore-pyproject`](general-options.md#ignore-pyproject)
 - [`--include-path-parameters`](openapi-only-options.md#include-path-parameters)
 - [`--input`](base-options.md#input)

docs/cli-reference/quick-reference.md

@@ -29,6 +29,7 @@ datamodel-codegen [OPTIONS]
 | [`--allof-merge-mode`](typing-customization.md#allof-merge-mode) | Merge constraints from root model references in allOf schemas. |
 | [`--disable-future-imports`](typing-customization.md#disable-future-imports) | Prevent automatic addition of __future__ imports in generated code. |
 | [`--enum-field-as-literal`](typing-customization.md#enum-field-as-literal) | Convert all enum fields to Literal types instead of Enum classes. |
+| [`--ignore-enum-constraints`](typing-customization.md#ignore-enum-constraints) | Ignore enum constraints and use base string type instead of Enum classes. |
 | [`--no-use-specialized-enum`](typing-customization.md#no-use-specialized-enum) | Disable specialized Enum classes for Python 3.11+ code generation. |
 | [`--output-datetime-class`](typing-customization.md#output-datetime-class) | Specify datetime class type for date-time schema fields. |
 | [`--strict-types`](typing-customization.md#strict-types) | Enable strict type validation for specified Python types. |
@@ -210,6 +211,7 @@ All options sorted alphabetically:
 - [`--http-headers`](general-options.md#http-headers) - Fetch schema from URL with custom HTTP headers.
 - [`--http-ignore-tls`](general-options.md#http-ignore-tls) - Disable TLS certificate verification for HTTPS requests.
 - [`--http-query-parameters`](general-options.md#http-query-parameters) - Add query parameters to HTTP requests for remote schemas.
+- [`--ignore-enum-constraints`](typing-customization.md#ignore-enum-constraints) - Ignore enum constraints and use base string type instead of ...
 - [`--ignore-pyproject`](general-options.md#ignore-pyproject) - Ignore pyproject.toml configuration file.
 - [`--include-path-parameters`](openapi-only-options.md#include-path-parameters) - Include OpenAPI path parameters in generated parameter model...
 - [`--input`](base-options.md#input) - Specify the input schema file path.

docs/cli-reference/typing-customization.md

@@ -7,6 +7,7 @@
 | [`--allof-merge-mode`](#allof-merge-mode) | Merge constraints from root model references in allOf schema... |
 | [`--disable-future-imports`](#disable-future-imports) | Prevent automatic addition of __future__ imports in generate... |
 | [`--enum-field-as-literal`](#enum-field-as-literal) | Convert all enum fields to Literal types instead of Enum cla... |
+| [`--ignore-enum-constraints`](#ignore-enum-constraints) | Ignore enum constraints and use base string type instead of ... |
 | [`--no-use-specialized-enum`](#no-use-specialized-enum) | Disable specialized Enum classes for Python 3.11+ code gener... |
 | [`--output-datetime-class`](#output-datetime-class) | Specify datetime class type for date-time schema fields. |
 | [`--strict-types`](#strict-types) | Enable strict type validation for specified Python types. |
@@ -1191,6 +1192,135 @@ of Enum classes for all enumerations.
 
 ---
 
+## `--ignore-enum-constraints` {#ignore-enum-constraints}
+
+Ignore enum constraints and use base string type instead of Enum classes.
+
+The `--ignore-enum-constraints` flag ignores enum constraints and uses
+the base type (str) instead of generating Enum classes. This is useful
+when you need flexibility in the values a field can accept beyond the
+defined enum members.
+
+!!! tip "Usage"
+
+    ```bash
+    datamodel-codegen --input schema.json --ignore-enum-constraints # (1)!
+    ```
+
+    1. :material-arrow-left: `--ignore-enum-constraints` - the option documented here
+
+??? example "Examples"
+
+    **Input Schema:**
+
+    ```graphql
+    "Employee shift status"
+    enum EmployeeShiftStatus {
+      "not on shift"
+      NOT_ON_SHIFT
+      "on shift"
+      ON_SHIFT
+    }
+    
+    enum Color {
+      RED
+      GREEN
+      BLUE
+    }
+    
+    enum EnumWithOneField {
+        FIELD
+    }
+    ```
+
+    **Output:**
+
+    === "With Option"
+
+        ```python
+        # generated by datamodel-codegen:
+        #   filename:  enums.graphql
+        #   timestamp: 2019-07-26T00:00:00+00:00
+        
+        from __future__ import annotations
+        
+        from pydantic import BaseModel
+        from typing_extensions import TypeAlias
+        
+        Boolean: TypeAlias = bool
+        """
+        The `Boolean` scalar type represents `true` or `false`.
+        """
+        
+        
+        String: TypeAlias = str
+        """
+        The `String` scalar type represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text.
+        """
+        
+        
+        class Color(BaseModel):
+            __root__: str
+        
+        
+        class EmployeeShiftStatus(BaseModel):
+            """
+            Employee shift status
+            """
+        
+            __root__: str
+        
+        
+        class EnumWithOneField(BaseModel):
+            __root__: str
+        ```
+
+    === "Without Option"
+
+        ```python
+        # generated by datamodel-codegen:
+        #   filename:  enums.graphql
+        #   timestamp: 2019-07-26T00:00:00+00:00
+        
+        from __future__ import annotations
+        
+        from enum import Enum
+        
+        from typing_extensions import TypeAlias
+        
+        Boolean: TypeAlias = bool
+        """
+        The `Boolean` scalar type represents `true` or `false`.
+        """
+        
+        
+        String: TypeAlias = str
+        """
+        The `String` scalar type represents textual data, represented as UTF-8 character sequences. The String type is most often used by GraphQL to represent free-form human-readable text.
+        """
+        
+        
+        class Color(Enum):
+            BLUE = 'BLUE'
+            GREEN = 'GREEN'
+            RED = 'RED'
+        
+        
+        class EmployeeShiftStatus(Enum):
+            """
+            Employee shift status
+            """
+        
+            NOT_ON_SHIFT = 'NOT_ON_SHIFT'
+            ON_SHIFT = 'ON_SHIFT'
+        
+        
+        class EnumWithOneField(Enum):
+            FIELD = 'FIELD'
+        ```
+
+---
+
 ## `--no-use-specialized-enum` {#no-use-specialized-enum}
 
 Disable specialized Enum classes for Python 3.11+ code generation.

src/datamodel_code_generator/__init__.py

@@ -417,6 +417,7 @@ def generate(  # noqa: PLR0912, PLR0913, PLR0914, PLR0915
     shared_module_name: str = DEFAULT_SHARED_MODULE_NAME,
     encoding: str = "utf-8",
     enum_field_as_literal: LiteralType | None = None,
+    ignore_enum_constraints: bool = False,
     use_one_literal_as_default: bool = False,
     use_enum_values_in_discriminator: bool = False,
     set_default_enum_member: bool = False,
@@ -663,6 +664,7 @@ def get_header_and_first_line(csv_file: IO[str]) -> dict[str, Any]:
         enum_field_as_literal=enum_field_as_literal
         if enum_field_as_literal is not None
         else (LiteralType.All if output_model_type == DataModelType.TypingTypedDict else None),
+        ignore_enum_constraints=ignore_enum_constraints,
         use_one_literal_as_default=use_one_literal_as_default,
         use_enum_values_in_discriminator=use_enum_values_in_discriminator,
         set_default_enum_member=True

src/datamodel_code_generator/__main__.py

@@ -405,6 +405,7 @@ def validate_all_exports_collision_strategy(cls, values: dict[str, Any]) -> dict
     shared_module_name: str = DEFAULT_SHARED_MODULE_NAME
     encoding: str = DEFAULT_ENCODING
     enum_field_as_literal: Optional[LiteralType] = None  # noqa: UP045
+    ignore_enum_constraints: bool = False
     use_one_literal_as_default: bool = False
     use_enum_values_in_discriminator: bool = False
     set_default_enum_member: bool = False
@@ -708,6 +709,7 @@ def run_generate_from_config(  # noqa: PLR0913, PLR0917
         shared_module_name=config.shared_module_name,
         encoding=config.encoding,
         enum_field_as_literal=config.enum_field_as_literal,
+        ignore_enum_constraints=config.ignore_enum_constraints,
         use_one_literal_as_default=config.use_one_literal_as_default,
         use_enum_values_in_discriminator=config.use_enum_values_in_discriminator,
         set_default_enum_member=config.set_default_enum_member,

src/datamodel_code_generator/arguments.py

@@ -348,6 +348,12 @@ def start_section(self, heading: str | None) -> None:
     choices=[lt.value for lt in LiteralType],
     default=None,
 )
+typing_options.add_argument(
+    "--ignore-enum-constraints",
+    help="Ignore enum constraints and use the base type (e.g., str, int) instead of generating Enum classes",
+    action="store_true",
+    default=None,
+)
 typing_options.add_argument(
     "--field-constraints",
     help="Use field constraints and not con* annotations",

src/datamodel_code_generator/cli_options.py

@@ -142,6 +142,7 @@ class CLIOptionMeta:
     "--use-type-alias": CLIOptionMeta(name="--use-type-alias", category=OptionCategory.TYPING),
     "--strict-types": CLIOptionMeta(name="--strict-types", category=OptionCategory.TYPING),
     "--enum-field-as-literal": CLIOptionMeta(name="--enum-field-as-literal", category=OptionCategory.TYPING),
+    "--ignore-enum-constraints": CLIOptionMeta(name="--ignore-enum-constraints", category=OptionCategory.TYPING),
     "--disable-future-imports": CLIOptionMeta(name="--disable-future-imports", category=OptionCategory.TYPING),
     "--use-pendulum": CLIOptionMeta(name="--use-pendulum", category=OptionCategory.TYPING),
     "--output-datetime-class": CLIOptionMeta(name="--output-datetime-class", category=OptionCategory.TYPING),

src/datamodel_code_generator/parser/base.py

@@ -683,6 +683,7 @@ def __init__(  # noqa: PLR0913, PLR0915
         shared_module_name: str = DEFAULT_SHARED_MODULE_NAME,
         encoding: str = "utf-8",
         enum_field_as_literal: LiteralType | None = None,
+        ignore_enum_constraints: bool = False,
         set_default_enum_member: bool = False,
         use_subclass_enum: bool = False,
         use_specialized_enum: bool = True,
@@ -783,6 +784,7 @@ def __init__(  # noqa: PLR0913, PLR0915
         self.shared_module_name: str = shared_module_name
         self.encoding: str = encoding
         self.enum_field_as_literal: LiteralType | None = enum_field_as_literal
+        self.ignore_enum_constraints: bool = ignore_enum_constraints
         self.set_default_enum_member: bool = set_default_enum_member
         self.use_subclass_enum: bool = use_subclass_enum
         self.use_specialized_enum: bool = use_specialized_enum

src/datamodel_code_generator/parser/graphql.py

@@ -134,6 +134,7 @@ def __init__(  # noqa: PLR0913
         shared_module_name: str = DEFAULT_SHARED_MODULE_NAME,
         encoding: str = "utf-8",
         enum_field_as_literal: LiteralType | None = None,
+        ignore_enum_constraints: bool = False,
         set_default_enum_member: bool = False,
         use_subclass_enum: bool = False,
         use_specialized_enum: bool = True,
@@ -227,6 +228,7 @@ def __init__(  # noqa: PLR0913
             shared_module_name=shared_module_name,
             encoding=encoding,
             enum_field_as_literal=enum_field_as_literal,
+            ignore_enum_constraints=ignore_enum_constraints,
             use_one_literal_as_default=use_one_literal_as_default,
             use_enum_values_in_discriminator=use_enum_values_in_discriminator,
             set_default_enum_member=set_default_enum_member,
@@ -414,10 +416,32 @@ def should_parse_enum_as_literal(self, obj: graphql.GraphQLEnumType) -> bool:
 
     def parse_enum(self, enum_object: graphql.GraphQLEnumType) -> None:
         """Parse a GraphQL enum type and add it to results."""
+        if self.ignore_enum_constraints:
+            return self.parse_enum_as_str_type(enum_object)
         if self.should_parse_enum_as_literal(enum_object):
             return self.parse_enum_as_literal(enum_object)
         return self.parse_enum_as_enum_class(enum_object)
 
+    def parse_enum_as_str_type(self, enum_object: graphql.GraphQLEnumType) -> None:
+        """Parse enum as a str type alias when ignoring enum constraints."""
+        data_type = self.data_type_manager.get_data_type(Types.string)
+        data_model_type = self._create_data_model(
+            model_type=self.data_model_root_type,
+            reference=self.references[enum_object.name],
+            fields=[
+                self.data_model_field_type(
+                    required=True,
+                    data_type=data_type,
+                )
+            ],
+            custom_base_class=self.base_class,
+            custom_template_dir=self.custom_template_dir,
+            extra_template_data=self.extra_template_data,
+            path=self.current_source_path,
+            description=enum_object.description,
+        )
+        self.results.append(data_model_type)
+
     def parse_enum_as_literal(self, enum_object: graphql.GraphQLEnumType) -> None:
         """Parse enum values as a Literal type."""
         data_type = self.data_type(literals=list(enum_object.values.keys()))

src/datamodel_code_generator/parser/jsonschema.py

@@ -544,6 +544,7 @@ def __init__(  # noqa: PLR0913
         shared_module_name: str = DEFAULT_SHARED_MODULE_NAME,
         encoding: str = "utf-8",
         enum_field_as_literal: LiteralType | None = None,
+        ignore_enum_constraints: bool = False,
         use_one_literal_as_default: bool = False,
         use_enum_values_in_discriminator: bool = False,
         set_default_enum_member: bool = False,
@@ -638,6 +639,7 @@ def __init__(  # noqa: PLR0913
             shared_module_name=shared_module_name,
             encoding=encoding,
             enum_field_as_literal=enum_field_as_literal,
+            ignore_enum_constraints=ignore_enum_constraints,
             use_one_literal_as_default=use_one_literal_as_default,
             use_enum_values_in_discriminator=use_enum_values_in_discriminator,
             set_default_enum_member=set_default_enum_member,
@@ -852,7 +854,15 @@ def _create_synthetic_enum_obj(
     def is_constraints_field(self, obj: JsonSchemaObject) -> bool:
         """Check if a field should include constraints."""
         return obj.is_array or (
-            self.field_constraints and not (obj.ref or obj.anyOf or obj.oneOf or obj.allOf or obj.is_object or obj.enum)
+            self.field_constraints
+            and not (
+                obj.ref
+                or obj.anyOf
+                or obj.oneOf
+                or obj.allOf
+                or obj.is_object
+                or (obj.enum and not self.ignore_enum_constraints)
+            )
         )
 
     def _resolve_field_flag(self, obj: JsonSchemaObject, flag: Literal["readOnly", "writeOnly"]) -> bool:
@@ -1500,7 +1510,7 @@ def _schema_signature(self, prop_schema: JsonSchemaObject | bool) -> str | bool:
             return prop_schema
         return json.dumps(prop_schema.dict(exclude_unset=True, by_alias=True), sort_keys=True, default=repr)
 
-    def _is_root_model_schema(self, obj: JsonSchemaObject) -> bool:  # noqa: PLR6301
+    def _is_root_model_schema(self, obj: JsonSchemaObject) -> bool:
         """Check if schema represents a root model (primitive type with constraints).
 
         Based on parse_raw_obj() else branch conditions. Returns True when
@@ -1516,7 +1526,7 @@ def _is_root_model_schema(self, obj: JsonSchemaObject) -> bool:  # noqa: PLR6301
             return False
         if obj.type == "object":
             return False
-        return not obj.enum
+        return not obj.enum or self.ignore_enum_constraints
 
     def _handle_allof_root_model_with_constraints(  # noqa: PLR0911, PLR0912
         self,
@@ -2328,7 +2338,7 @@ def parse_item(  # noqa: PLR0911, PLR0912
             return self.data_type_manager.get_data_type(
                 Types.object,
             )
-        if item.enum:
+        if item.enum and not self.ignore_enum_constraints:
             if self.should_parse_enum_as_literal(item):
                 return self.parse_enum_as_literal(item)
             return self.parse_enum(name, item, get_special_path("enum", path), singular_name=singular_name)
@@ -2401,7 +2411,7 @@ def parse_array_fields(
             data_types.append(self.parse_all_of(name, obj, get_special_path("allOf", path)))
         elif obj.is_object:
             data_types.append(self.parse_object(name, obj, get_special_path("object", path)))
-        if obj.enum:
+        if obj.enum and not self.ignore_enum_constraints:
             data_types.append(self.parse_enum(name, obj, get_special_path("enum", path)))
         return self.data_model_field_type(
             data_type=self.data_type(data_types=data_types),
@@ -2510,7 +2520,7 @@ def parse_root_type(  # noqa: PLR0912
                     data_type = data_types[0]
         elif obj.patternProperties:
             data_type = self.parse_pattern_properties(name, obj.patternProperties, path)
-        elif obj.enum:
+        elif obj.enum and not self.ignore_enum_constraints:
             if self.should_parse_enum_as_literal(obj):
                 data_type = self.parse_enum_as_literal(obj)
             else:  # pragma: no cover
@@ -3000,7 +3010,7 @@ def parse_obj(  # noqa: PLR0912
             self.parse_root_type(name, obj, path)
         elif obj.type == "object":
             self.parse_object(name, obj, path)
-        elif obj.enum and not self.should_parse_enum_as_literal(obj):
+        elif obj.enum and not self.ignore_enum_constraints and not self.should_parse_enum_as_literal(obj):
             self.parse_enum(name, obj, path)
         else:
             self.parse_root_type(name, obj, path)