Why does the params definition change and why did it stop supporting undefined?

[KonradLinkowski]

In 0.39.2 the definition of get looked like that:

get: <RequestBodyType_2 extends DefaultRequestBody = DefaultRequestBody, Params_2 extends PathParams = PathParams, ResponseBody_2 extends DefaultRequestBody = DefaultRequestBody>(path: Path, resolver: ResponseResolver<RestRequest<never, Params_2>, RestContext, ResponseBody_2>) => RestHandler<import("./handlers/RequestHandler").MockedRequest<DefaultRequestBody>>;

params:

Params_2 extends PathParams = PathParams

PathParams:

export declare type PathParams = Record<string, string | ReadonlyArray<string>>;

In 1.0.0 the definition of get looks like that:

get: <RequestBodyType_2 extends DefaultBodyType = DefaultBodyType, Params_2 extends PathParams<keyof Params_2> = PathParams<string>, ResponseBody_2 extends DefaultBodyType = DefaultBodyType>(path: Path, resolver: ResponseResolver<RestRequest<never, Params_2>, RestContext, ResponseBody_2>) => RestHandler<MockedRequest<DefaultBodyType>>;

params:

Params_2 extends PathParams<keyof Params_2> = PathParams<string>

PathParams

type PathParams<KeyType extends keyof any = string> = {
    [ParamName in KeyType]: string | ReadonlyArray<string>;

Now params cannot be marked as potentially undefined, because it throws a typescript error:

type UpdateParams = {
   sort: string | undefined;
}
Type 'UpdateParams' does not satisfy the constraint 'PathParams<"sort">'.
 Types of property 'sort' are incompatible.
   Type 'string | undefined' is not assignable to type 'string | readonly string[]'.
     Type 'undefined' is not assignable to type 'string | readonly string[]'.

But it worked fine before.

Why do query params have to be defined now?

[kettanaito]

Hey, @KonradLinkowski. Thanks for reporting this.

Could you please confirm this is still an issue for you on the latest version of MSW? npm i msw@latest. We've introduced quite a number of bug fixes since you reported this issue, there's a chance this has been fixed. Thanks.

[sgoridotla1]

@kettanaito, I am still facing the same issue.

{
  "msw": "^2.0.11",
  "typescript": "^4.9.3"
}

[kettanaito]

Thanks! Looks like a bug to me. Path parameters should extend undefined since there's no guarantee they will be defined on runtime:

msw/src/core/utils/matching/matchRequestUrl.ts

Lines 6 to 8 in ea28bd9

	export type PathParams<KeyType extends keyof any = string> = {
	[ParamName in KeyType]: string | ReadonlyArray<string>
	}

@sgoridotla1, would you be interested in opening a pull request to fix this?