Projection types not working in practice with zod or as parameters

[zackdotcomputer]

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Bug report

Running code as shown in the docs against my own schema is throwing a type error:

export type SchemaConfig = {
  schemaTypes: SanityTypes.AllSanitySchemaTypes;
  referenceSymbol: typeof SanityTypes.internalGroqTypeReferenceTo;
  parameters?: Record<string, unknown>;
};

const q = createGroqBuilder<SchemaConfig>();

q.star.filterByType("banner").project({
  title: q.string()
});

For reference, the Banner type inside of SanityTypes looks like:

export type Banner = {
  _id: string;
  _type: "banner";
  _createdAt: string;
  _updatedAt: string;
  _rev: string;
  title?: string;
}

That code has a build error at the .project call stating:

Argument of type '[]' is not assignable to parameter of type '["⛔️ Error: this projection has type mismatches: ⛔️"] | ["Error in \"title\": ⛔️ Parser expects a different input type ⛔️"]'.
  Type '[]' is not assignable to type '["Error in \"title\": ⛔️ Parser expects a different input type ⛔️"]'.
    Source has 0 element(s) but target requires 1.ts(2345)

If I replace the call with the shorthand form, then it compiles:

q.star.filterByType("banner").project({
  title: true
});

I think this is a result from the complexity of the ProjectionMap type being larger than the TS compiler can handle in practice. I've also been running into issues attempting to make a service function that takes in a GroqBuilder and projection, and would then call builder.filter(/* some common filters across my CMS */).project(projection) - it doesn't seem possible to define a parameter type for projection which will actually work as an argument to .project. Even directly copy-pasting it from the internal function declaration, I get type mismatch errors.

[nstam-stytch]

I believe I have the same issue, but let me know if I should file a different issue! I attempted to set up a simple query following the docs, which should just validate that a given slug exists:

const slugQuery = q
  .parameters<{ slug: string }>()
  .star.filterByType('page')
  .filterBy('slug.current == $slug')
  .slice(0)
  .project({
    route: q.slug('slug'),
  })
  .nullable();

In my exported Sanity types I have

export type Slug = {
  _type: 'slug';
  current?: string;
  source?: string;
};

export type Page = {
  { ... }
  slug?: Slug;
}

I get the type error Argument of type 'string' is not assignable to parameter of type 'never'. on the slug filter:

If I just use filter, so

const slugQuery = q
  .parameters<{ slug: string }>()
  .star.filter('_type === "page" && slug.current === $slug')
  .slice(0)
  .project({
    route: q.slug('slug'),
  })
  .nullable();

The typecheck passes, but the result of slugQuery is incorrect. InferResultType<typeof slugQuery> results in

type Slug = {
    route: never;
}[] | {
    route: never;
} | null