[toMatchObject] Check different Error objects (#3864)

[nathanforce]

Summary

Fixes #3859. Similar to PR #3864 but fixes the issue further up the chain.

Test Plan

yarn jest after adding to matchers-test.js

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[thymikee]

Makes sense, thanks for your contribution! Let's wait for CI to pass.

[codecov-io]

Codecov Report

Merging #3866 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3866      +/-   ##
==========================================
+ Coverage   57.63%   57.65%   +0.01%     
==========================================
  Files         194      194              
  Lines        6782     6782              
  Branches        6        6              
==========================================
+ Hits         3909     3910       +1     
+ Misses       2870     2869       -1     
  Partials        3        3

Impacted Files	Coverage Δ
packages/jest-matchers/src/jasmine-utils.js	79.81% <100%> (+0.91%)	⬆️

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[thymikee]

@thymikee toMatchObject should compare Error objects too? Or it should just fail without comparing when we encounter Error objects?

@anilreddykatta let's discuss it here. I'm good with Errors being compared by message.

[cpojer]

Please rebase.

[cpojer]

@nathanforce can you rebase this PR so I can merge it? :)

[jseminck]

I also investigated this issue and my fix was slightly different. I updated the subsetEquality matcher so that the bug with the customMatchers got fixed.

This way we don't have to rely on the ordering of the code of Error objects vs customMatchers checking.

It turns out that running every() on an empty array produces true:

const test = [].every(key => key === 1);
console.log(test)
VM178:1 true

And an error is an object with an empty array for Object.keys():

const error = new Error('a');
console.log(Object.keys(error))
VM272:1 []

Therefore I updated the code for this matcher:

const isObjectWithKeys = a =>
  a !== null &&
  typeof a === 'object' &&
  Object.keys(a).length && // <------ new code 
  !(a instanceof Array) &&
  !(a instanceof Date);
const subsetEquality = (object, subset) => {
  if (!isObjectWithKeys(object) || !isObjectWithKeys(subset)) {
    return undefined;
  }

  return Object.keys(subset).every(
    key =>
      hasOwnProperty(object, key) &&
      equals(object[key], subset[key], [iterableEquality, subsetEquality]),
  );
};

Additionally, it seems like this code could be moved to the ./utils.js file, were also iterableEquality lives.

WDYT?

[nathanforce]

@jseminck I see your point. Do you have those changes already made?

[jseminck]

I have them in a local branch. But maybe it can be a separate PR after this is merged (just as a part of some code cleanup)?

[nathanforce]

@jseminck I am closing this in favor of your changes. Could you open a PR against the issue?

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