expect: Avoid incorrect difference for subset when toMatchObject fails

[pedrottimark]

Summary

Fixes #8947

When the getObjectSubset function copies the relevant subset of object properties recursively, it creates ordinary Object instances. If expected and received values are a subclass or typed array, then the type change of the received subset becomes an incorrect change in the difference when toMatchObject fails.

If corresponding values:

• are subset match, then return the expected value instead of a copy of the received value
• are not subset match, then incorrect type difference is still possible

Although the function returns an unnecessary copy for arrays, I left it as is, because the map method returns the same array class as the subset

Background information:

• toMatchObject does not require same type: like toEqual and unlike toStrictEqual
• Array.isArray returns false for typed arrays

Test plan

Separate tests for deep equality versus referential identity of returned subset

Add 3 new tests which failed before the code change

See also pictures in following comments: baseline is at left and improved is at right

[pedrottimark]

Here is minimal reproduction of reported problem for Uint8Array object type

both expected and received are Uint8Array with equal properties:

only expected is UintArray8 and received is Object with equal properties:

only received is UintArray8 and expected is Object with equal properties was correct:

The example above was correct, but now avoids unnecessary copy of matching subset

P.S. change counts would be nice in these side-by-side comparisons, heh?

[pedrottimark]

Here is another minimal reproduction for object subclass

only expected is SubObject and received is Object with equal properties:

only received is SubObject and expected is Object with equal properties:

The example above was correct, but now avoids unnecessary copy of matching subset

[pedrottimark]

Here is demonstration that the difference is correct for array subclass, because even if a copy in unnecessary, the map method returns the correct subclass of the subset

only expected is SubArray and received is Array with equal properties

only received is SubArray and expected is Array with equal properties

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@fa0eb6d). Click here to learn what that means.
The diff coverage is 100%.

@@           Coverage Diff            @@
##             master   #9005   +/-   ##
========================================
  Coverage          ?   63.9%           
========================================
  Files             ?     277           
  Lines             ?   11654           
  Branches          ?    2860           
========================================
  Hits              ?    7448           
  Misses            ?    3576           
  Partials          ?     630

Impacted Files	Coverage Δ
packages/expect/src/utils.ts	94.93% <100%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update fa0eb6d...7414ae4. Read the comment docs.

[jeysal]

Test names could be a bit clearer IMO, other than that LGTM! :)
(sorry for the review delay)

[pedrottimark]

@jeysal Your critique is worth waiting for, my friend.

[pedrottimark]

I will merge changes from master to see if #9030 solves test-node-12 failure

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
Please note this issue tracker is not a help forum. We recommend using StackOverflow or our discord channel for questions.