description field for Custom Matcher should be optional

[blzsaa]

The custom matcher part in read me would throw a compile error if used.

• According to readme we can create a custom matcher with the following code:

import { MatcherCreator, Matcher } from 'jest-mock-extended';

// expectedValue is optional
export const myMatcher: MatcherCreator<MyType> = (expectedValue) => new Matcher((actualValue) => {
    return (expectedValue === actualValue && actualValue.isSpecial);
});

• while currently cunstuctor of Matcher requires string description field as well:
  • constructor(readonly asymmetricMatch: MatcherFn, private readonly description: string)

[marchaos]

Hmm, when the matcher fails, surely the error is indecipherable without a description though?

[blzsaa]

I am not sure if I understand the question correctly but according to my understanding:

• matchers are only used by calledWith which defines behavior and not asserts them, therefore the matchers cannot really fail.
• if no matcher found the mock will return the default behavior a.k.a undefined and not some kind of message with the description of that matcher.

E.g. the following code on both the current master branch and on my PR will print out the default jest failure message for toEqual without mentioning anything about description of the matcher.

const stringMatcher = new Matcher((actualValue) => {
    return (actualValue === "value");
}, "description");
const provider = mock<PartyProvider>();
provider.getSongs.calledWith(stringMatcher).mockReturnValue(['Dance the night away', 'Stayin Alive']);
expect(provider.getSongs('disco party')).toEqual(['Dance the night away', 'Stayin Alive']);

will print out:

Error: expect(received).toEqual(expected) // deep equality

Expected: ["Dance the night away", "Stayin Alive"]
Received: undefined

p.s.
I hope I did not misunderstand the question or the production code.