koxudaxi/datamodel-code-generator 0.52.0 on GitHub

Breaking Changes

Code Generation Changes

Union fields with titles now wrapped in named models when --use-title-as-name is enabled - Previously, union-typed fields with a title were generated as inline union types (e.g., TypeA | TypeB | TypeC | None). Now they generate a separate wrapper model using the title name, and the field references this wrapper type (e.g., ProcessingStatusUnionTitle | None). This affects code that directly accesses union field values, as they now need to access the .root attribute (Pydantic v2) or .__root__ (Pydantic v1) of the wrapper model. (#2889)
Before:

class ProcessingTaskTitle(BaseModel):
    processing_status_union: (
        ProcessingStatusDetail | ExtendedProcessingTask | ProcessingStatusTitle | None
    ) = Field('COMPLETED', title='Processing Status Union Title')

After:

class ProcessingStatusUnionTitle(BaseModel):
    __root__: (
        ProcessingStatusDetail | ExtendedProcessingTask | ProcessingStatusTitle
    ) = Field(..., title='Processing Status Union Title')
class ProcessingTaskTitle(BaseModel):
    processing_status_union: ProcessingStatusUnionTitle | None = Field(
        default_factory=lambda: ProcessingStatusUnionTitle.parse_obj('COMPLETED'),
        title='Processing Status Union Title',
    )

Inline types with titles now generate named type aliases when --use-title-as-name is enabled - Arrays, dicts, enums-as-literals, and oneOf/anyOf unions that have a title in the schema now generate named type aliases or RootModel classes instead of being inlined. This improves readability but changes the generated type structure. For TypedDict output, generates type MyArrayName = list[str]. For Pydantic output, generates class MyArrayName(RootModel[list[str]]). (#2889)
Default value handling changed for wrapped union fields - Fields that previously had simple default values now use default_factory with a lambda that calls parse_obj() (Pydantic v1) or model_validate() (Pydantic v2) to construct the wrapper model. Code that introspects field defaults will see a factory function instead of a direct value. (#2889)
Different output for $ref with nullable: true - When a JSON Schema property has a $ref combined with only nullable: true (and optionally metadata like title/description), the generator now uses the referenced type directly with Optional annotation instead of creating a new merged model. For example, a schema with multiple properties referencing User with nullable: true will now generate user_a: User | None instead of creating separate UserA, UserB model classes. This is a bug fix that reduces redundant model generation, but existing code that depends on the previously generated class names will break. (#2890)
Before:
```
class UserA(BaseModel):
    name: str
class UserB(BaseModel):
    name: str
class Model(BaseModel):
    user_a: UserA | None = None
    user_b: UserB | None = None
```
After:
```
class User(BaseModel):
    name: str
class Model(BaseModel):
    user_a: User | None = None
    user_b: User | None = None
```
Type alias generation expanded for --use-title-as-name - When using --use-title-as-name, the generator now creates type aliases for additional cases: nested array items with titles, additionalProperties values with titles, oneOf/anyOf branches with titles, patternProperties, propertyNames, and primitive types with titles. Previously these were inlined; now they generate named type aliases. This is a bug fix per #2887, but changes generated output for schemas with titles on nested elements. (#2891)
Title no longer inherited in combined schemas - In anyOf/oneOf/allOf schemas, the parent schema's title is now excluded when merging with child schemas. This prevents unintended title inheritance that could affect model naming when --use-title-as-name is enabled. (#2891)
allOf with single $ref no longer creates wrapper class - When a schema property uses allOf with only a single $ref and no additional properties, the generator now directly references the target type instead of creating an unnecessary wrapper class. This may affect code that depends on the previously generated wrapper class names or structure. For example, a property defined as allOf: [$ref: '#/components/schemas/ACHClass'] will now generate ach_class: ACHClass | None instead of creating an intermediate wrapper type. (#2902)

What's Changed

Add ULID and Email format documentation by @koxudaxi in #2886
Add --class-name-prefix, --class-name-suffix, and --class-name-affix-scope options by @koxudaxi in #2885
Use class-name-suffix for parser config TypedDicts by @koxudaxi in #2888
Create type aliases for inline types with title when use-title-as-name is enabled by @koxudaxi in #2889
Fix duplicate model generation for $ref with nullable by @koxudaxi in #2890
Create type aliases for nested elements with titles when use-title-as-name is enabled by @koxudaxi in #2891
Clarify --aliases help text to explain schema field becomes Pydantic alias by @koxudaxi in #2892
Document external library import use case for --type-overrides by @koxudaxi in #2893
Add documentation for reducing duplicate field types by @koxudaxi in #2896
Add FutureWarning for upcoming ruff default formatters by @koxudaxi in #2895
Add --openapi-include-paths option for path-based model filtering by @koxudaxi in #2894
Add --graphql-no-typename option to exclude typename field by @koxudaxi in #2899
Add --default-values CLI option for overriding field defaults by @koxudaxi in #2897
Fix allOf with single ref creating unnecessary wrapper class by @koxudaxi in #2902
Fix --reuse-model --collapse-reuse-models to deduplicate identical inline definitions by @koxudaxi in #2903
Add --use-serialization-alias option for Pydantic v2 by @koxudaxi in #2905
Fix Pydantic v2 discriminated unions in array fields by @koxudaxi in #2907

Full Changelog: 0.51.0...0.52.0