pretty-format: Support HTMLCollection and NodeList in DOMCollection plugin

[pedrottimark]

Summary

Fixes #7121

Problem: When pretty-format serializes a jsdom object instance for which no plugin matches, it takes a “stupid amount of time” on the property with key Symbol(impl) and then fails.

Solution: Support HTML collection classes to write assertions for received values:

• element properties childNodes, children, elements, options
• getElementsByTagName and so on
• querySelectorAll

Also added support for config.min option to omit class name.

Be aware that class names can be moving targets even in browsers:

• form.elements returned HTMLFormControlsCollection
• fieldset.elements returned HTMLCollection

despite the claim at Mozilla Developer Network

The HTMLFormControlsCollection interface represents a collection of HTML form control elements. It represents the lists returned by the HTMLFormElement interface's elements property and the HTMLFieldSetElement interface's elements property.

So there is some risk for test writers that snapshots might need to be updated at major version upgrades of jsdom package.

Test plan

• added 8 tests for collection classes
• added 1 test for config.min option
• added 1 test for config.maxDepth option

[codecov-io]

Codecov Report

Merging #7125 into master will not change coverage.
The diff coverage is 88.88%.

@@          Coverage Diff           @@
##           master   #7125   +/-   ##
======================================
  Coverage    66.6%   66.6%           
======================================
  Files         253     253           
  Lines       10629   10629           
  Branches        3       4    +1     
======================================
  Hits         7079    7079           
  Misses       3549    3549           
  Partials        1       1

Impacted Files	Coverage Δ
...ckages/pretty-format/src/plugins/dom_collection.js	93.33% <88.88%> (ø)	⬆️

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[SimenB]

jsdom 12 is released, and while we won't upgrade for some time, maybe we can normalize the name to HTMLFormControlsCollection?

[pedrottimark]

Verified outside Jest that form.elements still HTMLCollection class in jsdom@12.2.0 so added the test. Wrote a comment so that we will know to update the criterion if it ever changes.

[SimenB]

Array.from?

[pedrottimark]

Yes, I will leave the compiling to Babel :)

[pedrottimark]

Documenting decision to serialize in list item format:

• con: comma after item of markup looks awkward
• pro: minimize change to snapshot if class names change in future jsdom versions
• pro: minimize change to snapshot if received value changes to or from Array.from idiom

[github-actions]

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