Add output response parser

[jlalmes]

🚧 Work in progress

Added output validation to router queries & mutations

I have a goal to try and auto-generate OpenAPI docs for a TRPC router (cc. #755). The feature in this PR will enable us to generate JSON schemas for request and response payloads. This output parser is opt-in only and should not introduce any breaking changes.

API

const appRouter = new trpc.router<Context>()
  .query({
    input: z.string(),
    output: z.object({
      input: z.string(),
    }),
    resolve: ({ input }) => {
      return { input };
    }
  });

• Added a new optional output property.
• When output is provided, the resolve function will expect a return type inferred from the output parser.
• The response data will be validated against the output parser, unless NODE_ENV is production.
• If the response data fails validation a TRPCError INTERNAL_SERVER_ERROR error will be thrown.

Todo

• Get some feedback (cc. @KATT)
• Write some comprehensive output parser tests.
• Update documentation.

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[KATT]

Not able to look it through until tomorrow at the earliest but it is great! I would love for optional output validation

[KATT]

I think if there is an output validation, it should always run, we can add the optionality in prod as a feature later!

I would use this myself to guarantee that I don't leak anything sensitive.

[KATT]

Also setup github sponsors so I can send you 💷💷!

[sachinraja]

I have a goal to try and auto-generate OpenAPI docs for a TRPC router

Let me know if there's any way I can help! I have some experience in this area with zod-to-ts and tRPC Playground.

[KATT]

This all looks really sound to me. GOOD JOB!! 🙏 🙏

Some suggestions:

• Make the output parser stuff into its own test file
• Don't allow bad outputs regardless of the environment
• Some smaller comments inline

[KATT]

You might've accidentally removed the #1182 feature BTW ☺

[jlalmes]

#1182

Rolled it back - will make sure that any transforms in the output zod schemas are also handled!

[KATT]

#1182

Rolled it back - will make sure that any transforms in the output zod schemas are also handled!

Seems like an edge case to have transformers in the output but why not!

[KATT]

Will merge this tomorrow and do a release.

I removed the TRPC_SKIP_OUTPUT_VALIDATION because I don't want magic runtime variables - this should either be explicitly implemented per procedure or on the app router similarily to transformers/error formatters.

Stale

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