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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Merging schema's with undefined properties doesn't work","articleBody":"oapi-codegen isn't able to merge schema's which have incompatible properties, even if the properties aren't defined (!).\r\n\r\n\r\nIf a property needs to be overwritten, or should be defined at a later moment depending on context, it's common to use `allOf` + `readOnly: true`. Example:\r\n\r\n```yaml\r\nallOf:\r\n - $ref '#/components/myField'\r\nreadOnly: true\r\n```\r\n\r\n\r\n## Reproduce\r\n\r\nIn this example, I defined `identityId`, which is shared across payloads, but should /sometimes/ be set to readOnly. \r\n\r\n### `config.yaml`\r\n```yaml\r\npackage: identities\r\ngenerate:\r\n  client: true\r\n  echo-server: true\r\n  strict-server: true\r\n  embedded-spec: false\r\n  models: true\r\noutput: ./identities/identities.gen.go\r\n```\r\n\r\n### `identities.yaml`\r\n```\r\nopenapi: 3.0.0\r\ninfo:\r\n  title: test\r\n  version: 0.0.0\r\npaths:\r\n  /identities/{identityId}:\r\n    get:\r\n      operationId: getIdentity\r\n      parameters:\r\n        - $ref: '#/components/parameters/PathIdentityId'\r\n      responses:\r\n        '200':\r\n          description: get identity\r\n          content:\r\n            application/json:\r\n              schema:\r\n                $ref: '#/components/schemas/Identity'\r\n    post:\r\n      operationId: updateIdentity\r\n      requestBody:\r\n        required: true\r\n        content:\r\n          application/json:\r\n            schema:\r\n              allOf:\r\n                - $ref: '#/components/schemas/Identity'\r\n                - type: object\r\n                  properties:\r\n                    identity_id: # setting identityId to readOnly, so it can't be changed/upserted.\r\n                      readOnly: true\r\n      parameters:\r\n        - $ref: '#/components/parameters/PathIdentityId'\r\n      responses:\r\n        '200':\r\n          description: get identity\r\n          content:\r\n            application/json:\r\n              schema:\r\n                $ref: '#/components/schemas/Identity'\r\ncomponents:\r\n  parameters:\r\n    PathIdentityId:\r\n      in: path\r\n      name: identityId\r\n      schema:\r\n        $ref: '#/components/schemas/IdentityId'\r\n      required: true\r\n  schemas:\r\n    IdentityId:\r\n      description: unique id of an identity\r\n      type: string\r\n      pattern: ^[ 0-9a-zA-Z- ]+$\r\n      minLength: 1\r\n      maxLength: 64\r\n      example: 89e0ec57-4a7c-41a0-9433-970ba7709733\r\n    Identity:\r\n      type: object\r\n      required:\r\n        - identity_id\r\n        - name\r\n      properties:\r\n        identity_id:\r\n          $ref: '#/components/schemas/IdentityId'\r\n        name:\r\n          type: string\r\n```\r\n\r\n### cmd\r\n\r\n\r\n`go run github.com/oapi-codegen/oapi-codegen/v2/cmd/oapi-codegen@v2.4.1 --config=./config/rest-gen/identities.yml ./internal/rest/identities/identities.yaml`\r\n\r\nthrows the following error:\r\n\r\n```\r\nerror generating code: error generating type definitions: error generating Go types for component schemas: error converting Schema User to Go type: error generating Go schema for property 'identity_id': error merging schemas: error merging schemas for AllOf: merging two schemas with different ReadOnly\r\nexit status 1\r\n```\r\n\r\n\r\nLooking at the code, it seems that the reader is defaulting to `false`, and has no way to differentiate later if the property was _set_ to `false`, or defaulted to `false`.\r\nhttps://github.com/oapi-codegen/oapi-codegen/blob/main/pkg/codegen/merge_schemas.go#L176-L178","author":{"url":"https://github.com/thumbnail","@type":"Person","name":"thumbnail"},"datePublished":"2025-01-15T08:02:32Z","url":"https://github.com/oapi-codegen/oapi-codegen/issues/1883"}