Generating a schema from a type with a nullable object causes an error. (v3.7.0)

[yumemi-tokumoto]

Bug description

Error occurs and schema generation fails.
Generating a schema from a type with a nullable object causes an error. (v3.7.0)

Input

export type User = {
  name: string
}

export type Article = {
  user: User | null
}

Expected output

export const userSchema = z.object({
  name: z.string(),
})

export const articleSchema = z.object({
  user: userSchema.nullable(),
})

Actual output

✖ Validating generated types
 ›   Error: 'Article' is not compatible with 'articleSchema':
 ›   Argument of type 'Article' is not assignable to parameter of type '{ user: { name: string; } | null; }'.
 ›     Types of property 'user' are incompatible.
 ›       Type 'User | null | undefined' is not assignable to type '{ name: string; } | null'.
 ›         Type 'undefined' is not assignable to type '{ name: string; } | null'.

Versions

• Typescript: v5.3.3
• Zod: v3.22.4

[schiller-manuel]

did this work with previous versions of ts-to-zod?

[yumemi-tokumoto]

When I was using version 3.6.1, I was able to generate it without error.

[schiller-manuel]

@tvillaren can you have a look please? seems like your latest changes introduced a regression.

[adamwdennis]

I am also getting this error.

[tvillaren]

@tvillaren can you have a look please? seems like your latest changes introduced a regression.

I'll have a look.
You can assign the ticket to me 😄 (I don't have any rights on the project)

[schiller-manuel]

This can be reproduced by running

$ yarn gen:example

output:

yarn run v1.22.19
warning ../../package.json: No license field
$ ./bin/run --config example
- Validating generated types
✖ Validating generated types
 ›   Error: 'SkillsSpeedEnemy' is not compatible with 'skillsSpeedEnemySchema':
 ›   Argument of type 'SkillsSpeedEnemy' is not assignable to parameter of type
 ›    '{ power: EnemyPower.Speed; }'.
 ›     Types of property 'power' are incompatible.
 ›       Type 'EnemyPower.Speed | undefined' is not assignable to type 
 ›   'EnemyPower.Speed'.
 ›         Type 'undefined' is not assignable to type 'EnemyPower.Speed'.
 ›   'Superman' is not compatible with 'supermanSchema':
 ›   Argument of type 'Superman' is not assignable to parameter of type '{ 
 ›   name: "superman" | "clark kent" | "kal-l"; enemies: Record<string, any>; 
 ›   age: number; powers: ["fly", "laser", "invincible"]; underKryptonite?: 
 ›   boolean | undefined; }'.
 ›     Types of property 'enemies' are incompatible.
 ›       Type 'Record<string, Enemy> | undefined' is not assignable to type 
 ›   'Record<string, any>'.
 ›         Type 'undefined' is not assignable to type 'Record<string, any>'.
 ›   'Exported' is not compatible with 'exportedSchema':
 ›   Argument of type 'Exported' is not assignable to parameter of type '{ a: {
 ›    name: string; }; b: string; }'.
 ›     Types of property 'a' are incompatible.
 ›       Type 'NonExported | undefined' is not assignable to type '{ name: 
 ›   string; }'.
 ›         Type 'undefined' is not assignable to type '{ name: string; }'.
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

I see 3 separate issues:

1. most obvious: why didn't our tests find this?
2. | undefined is somehow added to referenced types in the validation
3. if a type is imported from a separate file, it correctly generates the type but during validation this separate file is not imported; see Record<string, any> above which should be Record<string, Enemy>;

@tvillaren do you typically use --skipValidation?

[tvillaren]

Yes, the use case is specific to TypeReference being set as optional by fixOptionalAny during the validation step.

This was introduced for any keyword due a known issue with ts-to-zod (see #140) but I updated this method to handle external imports (which are inferred as any as well in our validation step).

Pushed a failing test to reproduce: main...tvillaren:ts-to-zod:fix-issue-203
The issue is that we now mark all TypeReference as optional while we should do so only for imported ones...

We were missing test to cover use cases before my addition of import handling so it didn't catch it.

[mpiltz]

We have run in to this same issues when we are generating TS Type Definitions from OpenAPI Schemas and then genarate zod-schemas from the generated TS types and interfaces.

TL;DR; zod-schema generation fails with same error from this:

export type MyField = string
export interface MyObject {
 myField: MyField
}

[johnnyp-gg]

Im having the same issue with:

Input

export type User = {
  username: string | undefined
}

Expected output

export const userSchema = z.object({
  name: z.string().optional(),
})

on version 3.8.3 could it need the same fix?

[tvillaren]

@johnnyp-gg: actually

export type User = {
  username: string | undefined
}

generates (with --skipValidation flag)

// Generated by ts-to-zod
import { z } from "zod";

export const userSchema = z.object({
  username: z.union([z.string(), z.undefined()]),
});

which is the expected schema.
Indeed, it's not the same to check for an optional field and for a mandatory one which may take the undefined value.
The validation error you're getting comes from a known bug in Zod inference (colinhacks/zod#2464)