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fix: support Zod-generated schemas with $schema property #6281

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fix: support Zod-generated schemas with $schema property #6281

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mcollina
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@mcollina mcollina commented Aug 8, 2025

Summary

  • Fixes Add Support for Zod Exported JSON Schema #6279 by adding support for JSON schemas containing the $schema meta-property
  • Allows Zod's toJSONSchema() output to work seamlessly with Fastify's validation system
  • Strips the $schema property from schemas before validation to prevent "no schema with key or ref" errors

Implementation Details

  • Added stripSchemaKeyword() helper function that safely removes $schema while preserving all other schema properties
  • Applied the fix to all validation paths: headers, body, querystring, and params schemas
  • Handles both simple schemas and content-type-specific schemas
  • No breaking changes - existing functionality is preserved

Test Coverage

  • Added comprehensive test covering all schema types (headers, body, querystring, params) with $schema property
  • Tests both valid and invalid request scenarios to ensure validation still works correctly
  • All existing tests continue to pass

Related Issues

Closes #6279

@mcollina
fix: support Zod-generated schemas with $schema property
a14dc29 
Fixes #6279 by stripping the $schema meta-property from schemas before
validation. This allows Zod's toJSONSchema() output to work seamlessly
with Fastify's validation system without throwing "no schema with key
or ref" errors.

The fix preserves all schema validation functionality while safely
ignoring the JSON Schema meta-schema declaration.
@mcollina mcollina requested a review from climba03003 August 8, 2025 16:20
@climba03003
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It doesn't like a good idea to remove the $schema property.
It tells the validator whether it can support the schema and most recent schema is not backward compatible.

If the defined schema is draft-04, he or she should use the ajv@6 instead.
https://ajv.js.org/guide/schema-language.html#draft-04

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@climba03003 climba03003 Awaiting requested review from climba03003

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Add Support for Zod Exported JSON Schema
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@mcollina @climba03003