Type mismatch for RequestHeaderMatcher

[davidlj95]

What is the expected behavior?
Definition of types for RequestHeaderMatcher is as this:

  type RequestHeaderMatcher =
    | string
    | RegExp
    | { (fieldValue: string): boolean }

Specifically, for the last one { (fieldValue: string): boolean }, seems when debugging that it's not the proper type.

What is the actual behavior?
When using matchHeader(name: string, value: RequestHeaderMatcher): this, and using a function in there as RequestHeaderMatcher, the fieldValue is not a string, but a string[]

If only one header is set for that name, we just receive 1 item in the array.

Possible solution
Update types for RequestHeaderMatcher, so that the fieldValue is actually a string[] as checked whilst debugging.

  type RequestHeaderMatcher =
    | string
    | RegExp
    | { (fieldValue: string[]): boolean }

However, unsure if rest of references to it (found 3 more) behave the same.

How to reproduce the issue
In a project with Typescript, use matchHeader to intercept a request, and use a function as RequestHeaderMatcher. You'll receive a string[] instead of a string as types say.

Runkit: Example link

Having problem producing a test case? Try and ask the community for help. If the test case cannot be reproduced, the Nock community might not be able to help you.

Does the bug have a test case?
Nope! Not sure how to add something in https://github.com/nock/nock/blob/v13.1.4/types/tests.ts ! Though can try if have some time

Versions

Software	Version(s)
Nock	Detected on 13.1.4
Node	Any
TypeScript	Any

[gr2m]

We would appreciate a pull request!