Add --graphql-no-typename option to exclude typename field (#2899)

* Add --graphql-no-typename option to exclude typename field

* docs: update CLI reference documentation and prompt data

🤖 Generated by GitHub Actions

---------

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

Author: koxudaxi

docs/cli-reference/graphql-only-options.md

@@ -0,0 +1,92 @@
+# 📋 GraphQL-only Options
+
+## 📋 Options
+
+| Option | Description |
+|--------|-------------|
+| [`--graphql-no-typename`](#graphql-no-typename) | Exclude __typename field from generated GraphQL models. |
+
+---
+
+## `--graphql-no-typename` {#graphql-no-typename}
+
+Exclude __typename field from generated GraphQL models.
+
+The `--graphql-no-typename` flag prevents the generator from adding the
+`typename__` field (aliased to `__typename`) to generated models. This is
+useful when using generated models for GraphQL mutations, as servers typically
+don't expect this field in input data.
+
+!!! tip "Usage"
+
+    ```bash
+    datamodel-codegen --input schema.json --graphql-no-typename # (1)!
+    ```
+
+    1. :material-arrow-left: `--graphql-no-typename` - the option documented here
+
+??? example "Examples"
+
+    **Input Schema:**
+
+    ```graphql
+    type Book {
+      id: ID!
+      title: String
+    }
+    
+    interface Node {
+      id: ID!
+    }
+    
+    input BookInput {
+      title: String!
+    }
+    ```
+
+    **Output:**
+
+    ```python
+    # generated by datamodel-codegen:
+    #   filename:  no-typename.graphql
+    #   timestamp: 2019-07-26T00:00:00+00:00
+    
+    from __future__ import annotations
+    
+    from typing import TypeAlias
+    
+    from pydantic import BaseModel
+    
+    Boolean: TypeAlias = bool
+    """
+    The `Boolean` scalar type represents `true` or `false`.
+    """
+    
+    
+    ID: TypeAlias = str
+    """
+    The `ID` scalar type represents a unique identifier, often used to refetch an object or as key for a cache. The ID type appears in a JSON response as a String; however, it is not intended to be human-readable. When expected as an input type, any string (such as `"4"`) or integer (such as `4`) input value will be accepted as an ID.
+    """
+    
+    
+    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 Node(BaseModel):
+        id: ID
+    
+    
+    class Book(BaseModel):
+        id: ID
+        title: String | None = None
+    
+    
+    class BookInput(BaseModel):
+        title: String
+    ```
+
+---
+

docs/cli-reference/index.md

@@ -14,6 +14,7 @@ This documentation is auto-generated from test cases.
 | 🏗️ [Model Customization](model-customization.md) | 39 | Model generation behavior |
 | 🎨 [Template Customization](template-customization.md) | 18 | Output formatting and custom rendering |
 | 📘 [OpenAPI-only Options](openapi-only-options.md) | 7 | OpenAPI-specific features |
+| 📋 [GraphQL-only Options](graphql-only-options.md) | 1 |  |
 | ⚙️ [General Options](general-options.md) | 15 | Utilities and meta options |
 | 📝 [Utility Options](utility-options.md) | 6 | Help, version, debug options |
 
@@ -94,6 +95,7 @@ This documentation is auto-generated from test cases.
 - [`--generate-cli-command`](general-options.md#generate-cli-command)
 - [`--generate-prompt`](utility-options.md#generate-prompt)
 - [`--generate-pyproject-config`](general-options.md#generate-pyproject-config)
+- [`--graphql-no-typename`](graphql-only-options.md#graphql-no-typename)
 
 ### H {#h}
 

docs/cli-reference/quick-reference.md

@@ -162,6 +162,12 @@ datamodel-codegen [OPTIONS]
 | [`--use-status-code-in-response-name`](openapi-only-options.md#use-status-code-in-response-name) | Include HTTP status code in response model names. |
 | [`--validation`](openapi-only-options.md#validation) | Enable validation constraints (deprecated, use --field-constraints). |
 
+### 📋 GraphQL-only Options
+
+| Option | Description |
+|--------|-------------|
+| [`--graphql-no-typename`](graphql-only-options.md#graphql-no-typename) | Exclude __typename field from generated GraphQL models. |
+
 ### ⚙️ General Options
 
 | Option | Description |
@@ -251,6 +257,7 @@ All options sorted alphabetically:
 - [`--generate-cli-command`](general-options.md#generate-cli-command) - Generate CLI command from pyproject.toml configuration.
 - [`--generate-prompt`](utility-options.md#generate-prompt) - Generate a prompt for consulting LLMs about CLI options
 - [`--generate-pyproject-config`](general-options.md#generate-pyproject-config) - Generate pyproject.toml configuration from CLI arguments.
+- [`--graphql-no-typename`](graphql-only-options.md#graphql-no-typename) - Exclude __typename field from generated GraphQL models.
 - [`--help`](utility-options.md#help) - Show help message and exit
 - [`--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.

docs/graphql.md

@@ -207,6 +207,39 @@ class A(BaseModel):
 
 ---
 
+## 🚫 Excluding __typename Field
+
+When using generated models for GraphQL mutations, the `__typename` field may cause issues
+as GraphQL servers typically don't expect this field in input data.
+
+Use the `--graphql-no-typename` option to exclude this field:
+
+```bash
+datamodel-codegen --input schema.graphql --input-file-type graphql --output model.py --graphql-no-typename
+```
+
+**Before (default):**
+```python
+class Book(BaseModel):
+    id: ID
+    title: String | None = None
+    typename__: Literal['Book'] | None = Field('Book', alias='__typename')
+```
+
+**After (with --graphql-no-typename):**
+```python
+class Book(BaseModel):
+    id: ID
+    title: String | None = None
+```
+
+!!! warning "Union Type Discrimination"
+    If your schema uses GraphQL union types and you rely on `__typename` for type
+    discrimination during deserialization, excluding this field may break that functionality.
+    Consider using this option only for input types or schemas without unions.
+
+---
+
 ## 📖 See Also
 
 - 🖥️ [CLI Reference](cli-reference/index.md) - Complete CLI options reference

src/datamodel_code_generator/__main__.py

@@ -551,6 +551,7 @@ def validate_class_name_affix_scope(cls, v: str | ClassNameAffixScope | None) ->
     openapi_scopes: Optional[list[OpenAPIScope]] = [OpenAPIScope.Schemas]  # noqa: UP045
     include_path_parameters: bool = False
     openapi_include_paths: Optional[list[str]] = None  # noqa: UP045
+    graphql_no_typename: bool = False
     wrap_string_literal: Optional[bool] = None  # noqa: UP045
     use_title_as_name: bool = False
     use_operation_id_as_name: bool = False
@@ -929,6 +930,7 @@ def run_generate_from_config(  # noqa: PLR0913, PLR0917
         openapi_scopes=config.openapi_scopes,
         include_path_parameters=config.include_path_parameters,
         openapi_include_paths=config.openapi_include_paths,
+        graphql_no_typename=config.graphql_no_typename,
         wrap_string_literal=config.wrap_string_literal,
         use_title_as_name=config.use_title_as_name,
         use_operation_id_as_name=config.use_operation_id_as_name,
@@ -1000,6 +1002,9 @@ def run_generate_from_config(  # noqa: PLR0913, PLR0917
 
 def main(args: Sequence[str] | None = None) -> Exit:  # noqa: PLR0911, PLR0912, PLR0914, PLR0915
     """Execute datamodel code generation from command-line arguments."""
+    vars(namespace).clear()
+    namespace.no_color = False
+
     if "_ARGCOMPLETE" in os.environ:  # pragma: no cover
         import argcomplete  # noqa: PLC0415
 

src/datamodel_code_generator/_types/generate_config_dict.py

@@ -104,6 +104,7 @@ class GenerateConfigDict(TypedDict):
     include_path_parameters: NotRequired[bool]
     openapi_include_paths: NotRequired[list[str] | None]
     graphql_scopes: NotRequired[list[GraphQLScope] | None]
+    graphql_no_typename: NotRequired[bool]
     wrap_string_literal: NotRequired[bool | None]
     use_title_as_name: NotRequired[bool]
     use_operation_id_as_name: NotRequired[bool]

src/datamodel_code_generator/_types/parser_config_dicts.py

@@ -152,6 +152,7 @@ class ParserConfigDict(TypedDict):
 class GraphQLParserConfigDict(ParserConfigDict):
     data_model_scalar_type: NotRequired[type[DataModel]]
     data_model_union_type: NotRequired[type[DataModel]]
+    graphql_no_typename: NotRequired[bool]
 
 
 class JSONSchemaParserConfigDict(ParserConfigDict):

src/datamodel_code_generator/arguments.py

@@ -103,6 +103,7 @@ def start_section(self, heading: str | None) -> None:
 extra_fields_model_options = model_options.add_mutually_exclusive_group()
 template_options = arg_parser.add_argument_group("Template customization")
 openapi_options = arg_parser.add_argument_group("OpenAPI-only options")
+graphql_options = arg_parser.add_argument_group("GraphQL-only options")
 general_options = arg_parser.add_argument_group("General options")
 
 # ======================================================================================
@@ -958,6 +959,17 @@ def start_section(self, heading: str | None) -> None:
     default=None,
 )
 
+# ======================================================================================
+# Options specific to GraphQL input schemas
+# ======================================================================================
+graphql_options.add_argument(
+    "--graphql-no-typename",
+    help="Exclude __typename field from generated GraphQL models. "
+    "Useful when using generated models for GraphQL mutations.",
+    action="store_true",
+    default=None,
+)
+
 # ======================================================================================
 # General options
 # ======================================================================================

src/datamodel_code_generator/cli_options.py

@@ -24,6 +24,7 @@ class OptionCategory(str, Enum):
     MODEL = "Model Customization"
     TEMPLATE = "Template Customization"
     OPENAPI = "OpenAPI-only Options"
+    GRAPHQL = "GraphQL-only Options"
     GENERAL = "General Options"
 
 
@@ -244,6 +245,10 @@ class CLIOptionMeta:
         deprecated_message="Use --field-constraints instead",
     ),
     # ==========================================================================
+    # GraphQL-only Options
+    # ==========================================================================
+    "--graphql-no-typename": CLIOptionMeta(name="--graphql-no-typename", category=OptionCategory.GRAPHQL),
+    # ==========================================================================
     # General Options
     # ==========================================================================
     "--check": CLIOptionMeta(name="--check", category=OptionCategory.GENERAL),

src/datamodel_code_generator/config.py

@@ -141,6 +141,7 @@ class Config:
     include_path_parameters: bool = False
     openapi_include_paths: list[str] | None = None
     graphql_scopes: list[GraphQLScope] | None = None
+    graphql_no_typename: bool = False
     wrap_string_literal: bool | None = None
     use_title_as_name: bool = False
     use_operation_id_as_name: bool = False
@@ -336,6 +337,7 @@ class GraphQLParserConfig(ParserConfig):
 
     data_model_scalar_type: type[DataModel] = DataTypeScalar
     data_model_union_type: type[DataModel] = DataTypeUnion
+    graphql_no_typename: bool = False
 
 
 class JSONSchemaParserConfig(ParserConfig):