coerce and transform not having proper types in output

[teaishealthy]

Typescript reports an error when using z.coerce or .transform in output.

Additionally generating an OpenAPI spec fails at runtime when using z.coere.bigint in input

Minimal reproducible example

import { defaultEndpointsFactory, z } from "express-zod-api";

const testEndpoint = defaultEndpointsFactory.build({
  method: "get",
  input: z.object({}),
  output: z.object({
    name: z.coerce.string(),
    id: z.coerce.bigint().
  }),
  handler: async () => {
    return { name: 1, id: "1" };  // <-  Type 'number' is not assignable to type 'string'
  },
});

Edit: Reading a bit through issues and discussions the behavior for output transforms seems intended?
Anyhow generating a OpenAPI spec still fails with z.coerce.bigint in input.

[RobinTail]

Well-well-well...
You're assigning a number to the property having schema z.coerce.string().
Typescript validates the handler's returns using z.input< typeof z.coerce.string() >, and it seems to be just string, so you're getting an error.
I'd say, that this is more likely the zod's issue of the way the schemas with coercion being inferred.

But I'll check it more precisely tomorrow.
Thank you for letting me know, @teaishealthy

[teaishealthy]

I think it's not about bigint, it's about your name property, which is string, but you're assigning a number to it,

I don't think my provided example was directly related to the schema issue, I just found it while tinkering around. I can try to provide an example later this day.

[RobinTail]

I don't think my provided example was directly related to the schema issue, I just found it while tinkering around. I can try to provide an example later this day.

I checked the example in details — it's fine and it really reveals the confusion with the new coercion feature in Zod.
The problem is that coerce feature is not reflected on the type level, it only works in runtime.

I posted a more generic issue in Zod repo with a question to Colin. Maybe they would explain should it be fixed or it's somehow intentional.

colinhacks/zod#1760

Anyway, thank you @teaishealthy

[RobinTail]

The issue confirmed as a bug of zod, @teaishealthy
colinhacks/zod#1760 (comment)

[RobinTail]

I made a PR that should fix the issue in zod, but I'm still waiting for its approval.
colinhacks/zod#1793

[RobinTail]

Bad news, @teaishealthy .
The author of zod confirmed the bug, but does not want to fix it (now), since according to the author's vision it requires a complete refactoring of zod to be less messy.
¯\_(ツ)_/¯
Not sure yet what I can do about it...

[teaishealthy]

That's really unfortunate 😕 although I should be able to get along without .coere for the time being

Anyway thank you for your efforts on this issue 👍

[RobinTail]

Regarding z.coerce.bigint() — this is also third party bug:
colinhacks/zod#1911