fix: enforce minProperties on generated models#55
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damaz91 merged 5 commits intoJul 17, 2026
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…otocol#49) datamodel-code-generator drops minProperties on object schemas with declared properties, so Description() validated with zero fields in violation of description.json's minProperties: 1. (minProperties on free-form object properties is unaffected — the generator already maps those to Field(min_length=...) on the dict field.) A new post-generation step (postprocess_models.py, wired into generate_models.sh before formatting) scans the preprocessed schemas for root-level minProperties constraints and injects a model_validator(mode="after") into each matching generated class. JSON Schema counts the keys present on the object, so the validator counts provided fields (model_fields_set) unioned with extra keys (model_extra): an explicit null is a present key, and unknown keys on extra="allow" models count too. The step is idempotent, data-driven from the schemas (future minProperties additions are picked up on regeneration), and fails generation loudly if a constraint can't be mapped to a generated class. The committed Description model is regenerated with the validator. Tests cover the injector (dependency-free) and the enforced semantics on Description; the workflow now installs the package so those semantic tests run in CI.
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Jul 17, 2026
Deletes tests/test_min_properties.py and merges its test cases into tests/test_codegen_pipeline.py (renamed from test_preprocess_schemas.py to better reflect its expanded scope of testing both pre- and post-processing).
Replaces print statements with sys.stdout.write/sys.stderr.write (T201), splits long lines (E501), and adds docstring to main (D103) to comply with project lint configuration.
Replaces propert{y_ies} template variable with properties_noun to avoid codespell false positive on propert. Regenerated models to apply template change.
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Fixes #49:
datamodel-code-generatordropsminPropertieson object schemas with declared properties, soDescription()validates with zero fields in violation ofdescription.json'sminProperties: 1. (The free-form-object case is unaffected — the generator already maps that toField(min_length=...)on the dict field, e.g.AvailablePaymentInstrument.constraints.)Implements the post-processing option proposed in the issue: a new
postprocess_models.pystep (wired intogenerate_models.shbetween generation and formatting) scans the preprocessed schemas for root-levelminPropertiesconstraints and injects amodel_validator(mode="after")into each matching generated class.Counting semantics follow JSON Schema (keys present on the object), verified empirically against pydantic: provided fields (
model_fields_set) unioned with extra keys (model_extra) — an explicitnullis a present key, and unknown keys onextra="allow"models count too; the union avoids double-counting since pydantic includes extras inmodel_fields_set.Properties of the step:
minPropertiesadditions to any schema are picked up on regeneration, no code change needed (currentlydescription.jsonis the only root-level case onucpmain; there are no nested property-carrying cases).Descriptionmodel is regenerated with the validator.Validation
tests/test_min_properties.py: dependency-free injector tests (insertion, idempotency, schema scan, multi-class modules) + semantic tests on the realDescriptionmodel (empty rejected; single field, explicit-null key, and extra-only key accepted). Fullunittest discover: 23/23 green.pip install -e .so the semantic tests execute in CI rather than skipping.ruff format+ruff checkclean.