Incorrect Type Generation for Discriminator Mappings: Common Schema Discriminator Values Not Fully Propagated

[Omarov3000]

Description

When using a discriminator where multiple mapping keys (e.g., "approval_policy" and "entity") point to the same common schema, the generated TypeScript types incorrectly narrow the allowed discriminator values to only one representative (in this case, "approval_policy").

Reproducible example or configuration

npx @hey-api/openapi-ts \
  -i https://pub-32c654c6a381482f95842971390c1d2f.r2.dev/gh-issues/discriminator-bug.yaml \
  -o src \
  -c @hey-api/client-fetch

generated:

export type RootSchemaInput = ({
    object_type?: 'approval_policy';
} & CommonSchemaInput) | ({
    object_type?: 'payable';
} & PayableSchemaInput);

export type CommonSchemaInput = {
    object_type?: 'approval_policy' | 'entity';
};

export type PayableSchemaInput = {
    object_type?: 'payable';
};

expected

export type RootSchemaInput = ({
    object_type: 'approval_policy' | 'entity';
} & CommonSchemaInput) | ({
    object_type: 'payable';
} & PayableSchemaInput);

export type CommonSchemaInput = {
    object_type: 'approval_policy' | 'entity';
};

export type PayableSchemaInput = {
    object_type: 'payable';
};

OpenAPI specification (optional)

openapi: "3.0.3"
info:
  title: Minimal Discriminator Example
  version: "1.0"
paths: {}
components:
  schemas:
    RootSchemaInput:
      oneOf:
        - $ref: "#/components/schemas/CommonSchemaInput"
        - $ref: "#/components/schemas/PayableSchemaInput"
      discriminator:
        propertyName: object_type
        mapping:
          approval_policy: "#/components/schemas/CommonSchemaInput"
          entity: "#/components/schemas/CommonSchemaInput"
          payable: "#/components/schemas/PayableSchemaInput"
    CommonSchemaInput:
      type: object
      properties:
        object_type:
          type: string
          enum:
            - approval_policy
            - entity
    PayableSchemaInput:
      type: object
      properties:
        object_type:
          type: string
          enum:
            - payable

System information (optional)

"@hey-api/openapi-ts": "^0.65.0"

[Omarov3000]

Note: the same issue happens for both: input and output

[Omarov3000]

Probably duplicate of #1805 but with a bit easier reproduction

[mrlubos]

Yep! Thanks for flagging