feat(json-schema): Add discriminator support and oneOf/anyOf union option

[mike-taylor99]

Summary

Adds support for discriminator properties in JSON Schema emitter with an opt-in oneOf/anyOf union generation option.

Changes

• Automatically injects discriminator property into base models with @discriminator decorator
• Marks discriminator property as required in generated schemas
• Adds new polymorphic-models-strategy emitter option to generate oneOf or anyOf schemas for closed discriminated unions
• Includes discriminator.mapping for improved validation

Testing

• Added 11 comprehensive tests covering:
  • Basic discriminator property injection
  • Required field marking
  • OneOf union generation with mapping
  • Edge cases and validation

Documentation

All tests passing. Changeset included for release notes.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/microsoft/typespec/@typespec/json-schema@9038

commit: 1dc719a

[github-actions]

All changed packages have been documented.

• ✅ @typespec/json-schema

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@typespec/json-schema - feature ✏️

Add discriminator support and polymorphic models strategy option,> ,> - Automatically injects discriminator property into base models with @discriminator decorator,> - Marks discriminator property as required in generated schemas,> - New polymorphic-models-strategy emitter option with three strategies:,> - ignore: Emit as regular object schema (default),> - oneOf: Emit oneOf schema for closed discriminated unions,> - anyOf: Emit anyOf schema for open discriminated unions,> - Includes discriminator.mapping in oneOf/anyOf schemas for improved validation

[timotheeguerin]

/azp run typespec - pr tools

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Azure Pipelines successfully started running 1 pipeline(s).

[timotheeguerin]

just nit on the test name

[timotheeguerin]

/azp run typespec - pr tools

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[azure-sdk]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

[timotheeguerin]

/azp run typespec - pr tools

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).