Unable to infer an interface for `DataMatcher` definition

What is the expected behavior?

The following example should compile:

import * as nock from 'nock';

interface Body {
  param: number;
}

const body: Body = {
  param: 1,
};

const scope = nock('http://example.test')
  .post('/users', body)
  .reply(200);

What is the actual behavior? Typescript does not allow this, because it can not infer an interface as a dictionary. ({ [k: string]: ... }) if it is not explicitly intended as one. More on this issue here https://github.com/microsoft/TypeScript/issues/15300 and here.

The following error is thrown upon compilation:

Argument of type 'Body' is not assignable to parameter of type 'string | RegExp | Buffer | DataMatcher | ((body: any) => boolean) | undefined'.
  Type 'Body' is not assignable to type 'DataMatcher'.
    Index signature is missing in type 'Body'.

Possible solution

How to reproduce the issue The latest typescript definitions are not yet released which are required for this to reproduce. The example above can be run instead.

Does the bug have a test case?

Versions

Software	Version(s)
Nock	master
Node	10

[mastermatt]

@jmtelljohann while that would make @JrSchild 's error go away, it would do so at the expense of actually enforcing correct types. Because you can’t actually provide anything you want as values to an object as a body matcher. For instance .post('/', { foo: Buffer.from('bar') }) wouldn’t work, but that type change would appear to allow it.

At this point, I still stand by my suggestion that we should include correct types (as best as TS allows) and if users know for a fact that they’re interfaces are correct then they can cast to any manually.

[mastermatt]

@ctotheameron I agree, the issue is that a root array is currently missing as valid. However, for housekeeping, this is related/an extension of #1703 and is not the same issue @JrSchild is having.

I’d like to spend some time on this fix doing some testing around passing scalars as the body to see if any value that JSON.parse can handle should be considered legit. I just haven’t had the time the last couple of days.