github koxudaxi/datamodel-code-generator 0.56.0
on GitHub

8 hours ago

Breaking Changes

Code Generation Changes

  • Generated default field syntax changed - Fields with structured defaults (dicts, lists, model references) now use Field(default_value, validate_default=True) instead of default_factory=lambda: TypeAdapter(...).validate_python(...) or default_factory=lambda: Model.model_validate(...). This produces simpler, more readable code but changes the generated output format. (#3050)
  • TypeAdapter import removed from generated code - Generated models no longer import TypeAdapter from pydantic since validate_default=True handles validation natively. (#3050)
  • Default value handling for model-referencing fields rewritten - Fields with defaults referencing Pydantic models (BaseModel, RootModel, type aliases) now generate Field(<raw_value>, validate_default=True) instead of default_factory=lambda: Model.model_validate(...), default_factory=lambda: TypeAdapter(...).validate_python(...), or default_factory=lambda: Model(...). Empty collection defaults changed from default_factory=list/default_factory=dict to Field([], validate_default=True)/Field({}, validate_default=True). The generated code is semantically equivalent under Pydantic v2 but textually different, which will break snapshot tests or tooling that matches exact output. pydantic.TypeAdapter is no longer imported in generated code. (#3070)
  • Default values for model-referencing fields now use validate_default=True instead of default_factory lambdas - Fields with structured defaults (dicts, lists, or scalars referencing Pydantic models/RootModels) previously generated default_factory=lambda: ModelName.model_validate(value) or default_factory=lambda: ModelName(value). They now generate Field(value, validate_default=True), producing simpler but different output. Empty collection defaults changed from default_factory=list/default_factory=dict to Field([], validate_default=True)/Field({}, validate_default=True). Users who regenerate code will see different output. (#3071)
    Before: 
    count: CountType | None = Field(default_factory=lambda: CountType(10))
items: dict[str, Item] | None = Field(default_factory=dict, title='Items')
    After: 
    count: CountType | None = Field(10, validate_default=True)
items: dict[str, Item] | None = Field({}, title='Items', validate_default=True)
  • Default values for fields referencing models now use validate_default=True instead of default_factory=lambda: - Fields with structured defaults (dicts/lists) that reference Pydantic models previously generated default_factory=lambda: Model.model_validate(...) or default_factory=lambda: TypeAdapter(Type).validate_python(...) patterns. They now generate the raw default value directly with validate_default=True (e.g., Field({'key': 'val'}, validate_default=True) instead of Field(default_factory=lambda: Model.model_validate({'key': 'val'}))). This changes the generated code output and may affect users who depend on the exact generated code structure, pin generated output in tests, or use custom post-processing. The runtime behavior should be equivalent for Pydantic v2 users. (#3072)
  • TypeAdapter import removed from generated code - Generated code no longer imports pydantic.TypeAdapter for default value handling. Code that previously used TypeAdapter(...).validate_python(...) in default factories now uses inline defaults with validate_default=True. (#3072)
  • Integer and boolean discriminator values now supported in generated Literal types - Discriminator fields previously only generated string literal values. They now support int and bool discriminator values (e.g., Literal[1] instead of Literal['1']), which changes generated code for schemas using integer discriminator mappings. (#3072)

API/CLI Changes

  • ValidatedDefault and WrappedDefault classes removed - These internal classes were exported from datamodel_code_generator.model.base and have been removed. Code importing these types will break: 
    # Before (broken)
from datamodel_code_generator.model.base import ValidatedDefault, WrappedDefault
    (#3050)
  • SUPPORTS_WRAPPED_DEFAULT and SUPPORTS_VALIDATED_DEFAULT class variables removed - These flags were removed from the DataModel base class. Custom model classes that override these variables will see attribute errors. (#3050)
  • Internal types ValidatedDefault and WrappedDefault removed - The datamodel_code_generator.model._types module was deleted and ValidatedDefault/WrappedDefault are no longer exported from datamodel_code_generator.model.base. Code that imports or subclasses these types will break. The SUPPORTS_WRAPPED_DEFAULT and SUPPORTS_VALIDATED_DEFAULT class variables were removed from DataModel and its subclasses; custom model classes referencing these attributes will need updating. (#3070)
  • Removed WrappedDefault, ValidatedDefault classes and SUPPORTS_WRAPPED_DEFAULT, SUPPORTS_VALIDATED_DEFAULT class variables - The WrappedDefault and ValidatedDefault classes from datamodel_code_generator.model._types (re-exported via datamodel_code_generator.model.base) have been deleted. The DataModel class variables SUPPORTS_WRAPPED_DEFAULT and SUPPORTS_VALIDATED_DEFAULT have also been removed. Code that imports or references these will break. (#3071)
  • New --allow-remote-refs / --no-allow-remote-refs CLI option and allow_remote_refs config field - Remote $ref fetching over HTTP/HTTPS now emits a deprecation warning by default. Pass --allow-remote-refs to suppress the warning, or --no-allow-remote-refs to block remote fetching entirely. In a future version, remote fetching will be disabled by default. Users relying on remote $ref resolution should add --allow-remote-refs to their invocations to avoid the deprecation warning and prepare for the future default change. (#3072)
  • New SchemaFetchError exception for HTTP fetch failures - Remote schema fetching now raises SchemaFetchError (instead of propagating raw httpx exceptions) on HTTP errors, non-2xx status codes, or unexpected HTML responses. Users catching specific httpx exceptions from remote ref resolution will need to catch SchemaFetchError instead. (#3072)

Error Handling Changes

  • Missing local $ref now raises Error instead of FileNotFoundError - Previously, when a $ref pointed to a non-existent local file, a raw FileNotFoundError propagated to callers. Now it raises datamodel_code_generator.Error with the message "$ref file not found: <path>". Programmatic users catching FileNotFoundError specifically will need to catch Error instead (#3051)
  • HTTP fetch failures now raise SchemaFetchError instead of propagating raw exceptions - HTTP errors (4xx/5xx status codes), unexpected HTML responses, and transport errors (DNS, timeout, connection) that previously resulted in downstream YAML/JSON parse errors or raw httpx exceptions now raise SchemaFetchError (a subclass of Error) before parsing is attempted. Users catching specific parse errors or httpx exceptions for these scenarios will need to update their error handling (#3051)
  • HTTP fetch errors now raise SchemaFetchError instead of raw httpx exceptions - The get_body() function in http.py now catches HTTP errors and raises SchemaFetchError (a new Error subclass) for HTTP status >= 400, network failures, and unexpected HTML responses. Code that caught raw httpx exceptions from remote schema fetching will need to catch SchemaFetchError instead. (#3071)
  • Remote $ref fetching now emits FutureWarning without --allow-remote-refs - Fetching remote HTTP/HTTPS $ref references without explicitly passing --allow-remote-refs now emits a FutureWarning deprecation warning. In a future version, remote fetching will be disabled by default. Users relying on implicit remote ref fetching should add --allow-remote-refs to suppress the warning. (#3071)
  • HTTP fetch errors now raise SchemaFetchError with validation of response content type - Previously, fetching a remote $ref that returned an HTML error page would silently pass the HTML through as schema content. Now it raises SchemaFetchError if the response has text/html content type or a 4xx/5xx status code. This may cause previously-silent failures to become loud errors. (#3072)

Default Behavior Changes

  • Implicit remote $ref fetching now emits FutureWarning - When a $ref resolves to an HTTP(S) URL and --allow-remote-refs is not explicitly passed, the tool still fetches the remote reference but emits a FutureWarning. This may cause failures in environments running with -W error (warnings as errors) or strict warning filters. Pass --allow-remote-refs explicitly to suppress the warning (#3051)
  • Remote $ref fetching now emits a FutureWarning - When the parser encounters an HTTP/HTTPS $ref without --allow-remote-refs being explicitly set, a FutureWarning is emitted warning that remote fetching will be disabled by default in a future version. Pass --allow-remote-refs to silence the warning, or --no-allow-remote-refs to block remote fetching immediately. (#3070)

Custom Template Update Required

  • Type alias templates updated with fields guard - All six type alias templates (TypeAliasAnnotation.jinja2, TypeAliasType.jinja2, TypeStatement.jinja2, UnionTypeAliasAnnotation.jinja2, UnionTypeAliasType.jinja2, UnionTypeStatement.jinja2) now wrap the main body in {% if fields %}...{% else %} blocks that fall back to {{ base_class }} when no fields are present. Users with custom copies of these templates must add the same guard or handle the empty-fields case. (#3070)
  • Type alias Jinja2 templates now require fields guard and base_class fallback - The built-in templates TypeAliasAnnotation.jinja2, TypeAliasType.jinja2, TypeStatement.jinja2, and their Union variants now wrap field access in {%- if fields %}...{%- else %} blocks with a base_class fallback for empty field lists. Users with custom templates derived from the old versions will need to add similar guards. (#3071)
  • Type alias templates (TypeAliasAnnotation.jinja2, TypeAliasType.jinja2, TypeStatement.jinja2, and their Union variants) now handle an empty fields list with a fallback to base_class - If you have custom copies of these templates, they need to be updated to include the new {%- if fields %}...{%- else %}...{%- endif %} branching logic. Without this update, custom templates may error when fields is empty. (#3072)

What's Changed

  • Use validate_default=True for structured union defaults by @butvinm in #3050
  • Switch download badge from pepy.tech to pypistats.org by @koxudaxi in #3052
  • Update projects list with notable AI/LLM ecosystem projects by @koxudaxi in #3053
  • Add ryaml as optional YAML backend for faster parsing by @koxudaxi in #3055
  • Update release draft model and preserve breaking changes by @koxudaxi in #3057
  • Add --allow-remote-refs to disable HTTP fetching of $ref by default by @butvinm in #3051
  • Fix type alias template crash with reuse_model on empty fields by @butvinm in #3060
  • Fix non-string OpenAPI discriminator literals by @koxudaxi in #3070
  • Support JSON files for mapping options by @koxudaxi in #3071
  • Refresh project usage list by @koxudaxi in #3072

Full Changelog: 0.55.0...0.56.0

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