Typescript Error On Optional And Nullable Fields With exactOptionalPropertyTypes

[AdrianAndersen]

Package version

4.3.0

Describe the bug

Hello,

I just upgraded to 4.3.0, and migrated to vine.create(...). I am currently facing an issue where every optional or nullable field produces the following TS error:

TS2375: Type OptionalModifier<VineString> is not assignable to type SchemaTypes with 'exactOptionalPropertyTypes: true'.

Currently, I just have to disable this rule, but I would love for VineJS to work with this enabled by default.

Let me know if I am missing something, or if you need more details.

Reproduction repo

No response

[thetutlage]

Can you share some code that we could use to reproduce the issue?

[AdrianAndersen]

Sorry for the late response here. Just add "exactOptionalPropertyTypes": true, to any AdonisJS project, for instance the api/ in starter-kits

{
  "extends": "@adonisjs/tsconfig/tsconfig.app.json",
  "compilerOptions": {
    "exactOptionalPropertyTypes": true, // this produces TS errors for all VineJS validators
    "rootDir": "./",
    "jsx": "react",
    "outDir": "./build"
  }
}

Let me know if you need further details.

[TomBeckett]

Ran into this too and dug into where it's coming from — sharing in case it helps move things along 🙂

It looks like a mismatch inside Vine's own types when exactOptionalPropertyTypes is on:

• ConstructableSchema has allowNull?: boolean (in src/types.ts). With exactOptionalPropertyTypes, that optional ?: boolean means "either absent or a boolean" — notably not present-and-undefined.
• But the schema base getters return get allowNull(): boolean | undefined (src/schema/base/main.ts and literal.ts).

So a modifier's allowNull: boolean | undefined isn't assignable back to allowNull?: boolean, which trips the extends SchemaTypes constraint every schema has to satisfy. That's the source of the OptionalModifier<...> is not assignable to SchemaTypes errors on any optional/nullable field — and because the constraint quietly fails, Infer<typeof schema> also degrades to { [x: string]: any }, which silently un-types validated output.

The fix looks like a one-liner either way:

• narrow the getters to get allowNull(): boolean, or
• widen the interface to allowNull?: boolean | undefined.

Repro is just vine.object({ x: vine.string().optional() }) with exactOptionalPropertyTypes: true (saw it on 4.3.0–4.4.0).

Happy to put up a PR if you've got a preference on which side to fix — thanks for all the work on Vine!