Nivoa•5mo ago

When a procedure returns an instance of a class, the superjson isApplicable doesnt detect it

When a procedure returns an instance of a class, the superjson isApplicable doesnt detect it as that class, but when you return it inside an object or array, it does.

// ❌
class Test {
        a: string;
        constructor() {
          this.a = "a";
        }
        serialize() {
          return "a"
        }
        deserialize() {
          return "b"
        }
      }
test: publicProcedure
    .query(async ({ input, ctx }) => {
      return new Test()
    }),

// ❌
class Test {
        a: string;
        constructor() {
          this.a = "a";
        }
        serialize() {
          return "a"
        }
        deserialize() {
          return "b"
        }
      }
test: publicProcedure
    .query(async ({ input, ctx }) => {
      return new Test()
    }),

// ✅
test: publicProcedure
    .query(async ({ input, ctx }) => {
      return { test: new Test() }
    }),

// ✅
test: publicProcedure
    .query(async ({ input, ctx }) => {
      return { test: new Test() }
    }),

then in superjson:

superjson.registerCustom(
  {
    deserialize: (test) => {
      return null;
    },
    serialize: (test) => {
      return null;
    },
    isApplicable: (val: unknown) => {
      return val instanceof Test
    },
  },
  "Test",
);

superjson.registerCustom(
  {
    deserialize: (test) => {
      return null;
    },
    serialize: (test) => {
      return null;
    },
    isApplicable: (val: unknown) => {
      return val instanceof Test
    },
  },
  "Test",
);

what happens is that val is never an actual instanceof Test, it is an object with the properties of Test, but not the instance itself. But when I return it as the 2nd procedure, val.test instanceof Test evals to true. is this a bug?

4 Replies

Alex / KATT 🐱•5mo ago

If it's a bug it's likely a bug in superjson Or maybe this is in trpc, idk I've never serialized classes

Alex / KATT 🐱•5mo ago

You should be able to create a failing test pretty easily in https://github.com/trpc/trpc/blob/next/packages/tests/server/transformer.test.ts

GitHub

trpc/packages/tests/server/transformer.test.ts at next · trpc/trpc

🧙‍♀️ Move Fast and Break Nothing. End-to-end typesafe APIs made easy. - trpc/trpc

Alex / KATT 🐱•5mo ago

Run local vitest with pnpm test-watch transformer

Nivoa•5mo ago

ty, ill try It seems a bug in unstable_httpBatchStreamLink because with httpBatchLink it works as expected i'll investigate more