multiSearch function does not resolve the right type after passing a FederatedMultiSearchParams type in parameter

[ldelhommeau]

Description
I just updated the Meilisearch Javascript SDK to 0.45 to use the new multiSearch function with the mergeFacets attribute.
I have strongly typed my parameter to be of type FederatedMultiSearchParams as written in the SDK definition:

meilisearch-js/src/meilisearch.ts

Lines 217 to 232 in 74aa48c

	multiSearch<T extends Record<string, unknown> = Record<string, any>>(
	queries: MultiSearchParams,
	config?: Partial<Request>,
	): Promise<MultiSearchResponse<T>>;
	multiSearch<T extends Record<string, unknown> = Record<string, any>>(
	queries: FederatedMultiSearchParams,
	config?: Partial<Request>,
	): Promise<SearchResponse<T>>;
	async multiSearch<T extends Record<string, unknown> = Record<string, any>>(
	queries: MultiSearchParams | FederatedMultiSearchParams,
	config?: Partial<Request>,
	): Promise<MultiSearchResponse<T> | SearchResponse<T>> {
	const url = `multi-search`;
	return await this.httpRequest.post(url, queries, undefined, config);
	}

But the return type of the function is always of type MultiSearchResponse<Record<string, any>> were I was expecting Promise<SearchResponse<T>>.

Important note: I tried using this hack to check what was the returned object's type at runtime:
const searchResults = (await this.meilisearchClient().multiSearch(multiSearchArgs)) as unknown as SearchResponse;

And the object is of type SearchResponse with the correct properties at the root level of the object (estimatedTotalHits and facetDistribution):

Expected behavior
When calling the multiSearch function with the parameter queries of type FederatedMultiSearchParams I expect to have a response of type SearchResponse.

Current behavior
The TS resolution shows that the return type is MultiSearchResponse.

Screenshots or Logs

Environment (please complete the following information):

• OS: MacOS Sonoma Apple M1 Pro
• Meilisearch version: Meilisearch v1.11.3 (from docker image getmeili/meilisearch:v1.11)
• meilisearch-js version: v0.45 (from my package.json "meilisearch": "^0.45.0",)
• Browser: No brower, the process is run via a Strapi backend v4.15.5 (nodejs)

[Barabasbalazs]

It seems the TS typechecker is not able to infer the return type properly just by the type of the searchparameters. I think creating conditional type could solve this issue.
Something like this:

export type MultiSearchResponseOrSearchResponse<
  T1 extends FederatedMultiSearchParams | MultiSearchParams,
  T2 extends Record<string, unknown> = Record<string, any>,
> = T1 extends FederatedMultiSearchParams
  ? SearchResponse<T2>
  : MultiSearchResponse<T2>;

@flevi29 what do you think?

[Barabasbalazs]

I think this: #1776 should fix it

[flevi29]

Reopened for the following reason: #1689 (comment)
We want to be able to provide the type of hits via generics, but at the same time we also want to infer the return type based on another generic, which dictates the type of the parameters. If we provide one generic, the others won't be inferred. If we don't provide generics, it's kind of rough to specify the desired shape of hits. What's the solution here, I'm not sure yet.

[flevi29]

It seems that if you don't pass the arguments directly into the function as they are, TS doesn't even try to infer from it, which feels like a bug to me. There's no nice solution here, the result will have to be casted, which honestly is pretty much what you'd be doing with generics either way, and not a lot more verbose.