feat: add a type inferRouterFunctions<AppRouter>

[ghdoergeloh]

Describe the feature you'd like to request

It would be nice to have the type of a procedure function. So not only the input or the output, but the function that is called by it. I needed it to create typesafe mock functions.

Describe the solution you'd like to see

I copied the GetInferenceHelpers and changed it a bit.

export type GetInferenceHelpers<
  TRoot extends AnyClientTypes,
  TRecord extends RouterRecord,
> = {
  [TKey in keyof TRecord]: TRecord[TKey] extends infer $Value
    ? $Value extends RouterRecord
      ? GetInferenceHelpers<TRoot, $Value>
      : $Value extends AnyProcedure
        ? (
            input: inferProcedureInput<$Value>,
          ) => inferTransformedProcedureOutput<TRoot, $Value>
        : never
    : never;
};

export type inferRouterFunctions<TRouter extends AnyRouter> =
  GetInferenceHelpers<
    TRouter["_def"]["_config"]["$types"],
    TRouter["_def"]["record"]
  >;

Now I can use it for my AppRouter

export type RouterFunctions = inferRouterFunctions<AppRouter>;

And finally create some mocks:

const accountList = vi.fn<RouterFunctions["account"]["list"]>(() => ({
  items: [],
  total: 0,
}));

which I can use for trpc-msw:

server.use(trpcMsw.account.list.query(accountList));

Describe alternate solutions

My workaround was to add this code into my own project.
But then I have these Imports from @trpc/server/src/unstable-core-do-not-import which is not the best practice.
So It would be nice, if you could just add the type.

Additional information

No response

👨‍👧‍👦 Contributing

• 🙋‍♂️ Yes, I'd be down to file a PR implementing this feature!

Funding

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[juliusmarminge]

Is it too much to get both inputs and outputs? Like sure this could be some syntactic sugar but isn't this already "good enough"?

const accountList = vi.fn<
  (input: RouterInputs["account"]["list"]) => Promise<RouterOutputs["account"]["list"]>
>(() => Promise.resolve({ items: [], total: 0 }));

[ghdoergeloh]

There would be more type than actual code, which makes it a bit confusing. It quickly becomes a lot of types if you need to mock multiple routes. So I thought a extra type would be nice. If you add this to the original code it would be just about 6 extra lines, saving a lot of extra lines in the test files.

Therefore I would say, it is worth the tiny patch.