Supporting different content-type responses

[WoH]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the feature has not already been requested

🚀 Feature Proposal

This plugin does not support response validation in combination with different content types.

Motivation

While not supported by this plugin, both fastify and swagger support it already:

• Add support for different content-type response fastify#3902
• schema response per content type help#621
• feat: Supporting different content-type responses fastify#4264
• feat: rendering the syntax of different content types responses fastify-swagger#665

Example

The following setup is supported by @fastify/swagger(-ui), but does not work when used with the fastify response validation plugin:

    {
      schema: {
        body: Polygon,
        response: {
          200: {
            description: "Success",
            content: {
              "application/geo+json": {
                schema: FeatureCollection,
              },
            },
          },
      },
  }

Results are errors, but at the end of the day, it just does not seem to be intended.

ERROR (110): strict mode: unknown keyword: "application/geo+json"
    err: {
      "type": "Error",
      "message": "strict mode: unknown keyword: \"application/geo+json\"",
      "stack":
          Error: strict mode: unknown keyword: "application/geo+json"
              at checkStrictMode (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/util.js:174:15)
              at checkUnknownRules (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/util.js:32:13)
              at alwaysValidSchema (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/util.js:19:5)
              at <anonymous> (/node_modules/@fastify/response-validation/node_modules/ajv/dist/vocabularies/applicator/properties.js:23:63)
              at Array.filter (<anonymous>)
              at Object.code (/node_modules/@fastify/response-validation/node_modules/ajv/dist/vocabularies/applicator/properties.js:23:37)
              at keywordCode (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/validate/index.js:454:13)
              at <anonymous> (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/validate/index.js:222:17)
              at CodeGen.code (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/codegen/index.js:439:13)
              at CodeGen.block (/node_modules/@fastify/response-validation/node_modules/ajv/dist/compile/codegen/index.js:568:18)
    }

ERROR (62): schema is invalid: data/properties/description must be object,boolean
    err: {
      "type": "Error",
      "message": "schema is invalid: data/properties/description must be object,boolean",
      "stack":
          Error: schema is invalid: data/properties/description must be object,boolean
              at Ajv.validateSchema (/node_modules/@fastify/response-validation/node_modules/ajv/dist/core.js:266:23)
              at Ajv._addSchema /node_modules/@fastify/response-validation/node_modules/ajv/dist/core.js:460:18)
              at Ajv.compile (/node_modules/@fastify/response-validation/node_modules/ajv/dist/core.js:158:26)
              at buildHook /node_modules/@fastify/response-validation/index.js:46:37)
              at Object.onRoute (/node_modules/@fastify/response-validation/index.js:38:34)
              at Object.addNewRoute (/node_modules/fastify/lib/route.js:243:16)
              at Object.route (/node_modules/fastify/lib/route.js:217:19)
              at Object.prepareRoute (/node_modules/fastify/lib/route.js:150:18)
              at Object._post (/node_modules/fastify/fastify.js:258:34)
              [...]

[mcollina]

Thanks for reporting! Would you like to send a Pull Request to address this issue? Remember to add unit tests.