fix: missing actions (#10327)

[crenshaw-dev]

Fixes #10327

The rxJS merge operator works by spitting out whatever its operands produce, in whatever order its operands produce it.

merge(from([items]), from(resourceActions), from(execAction))

So from([items]) is always going to produce its value first - it's already been evaluated.

After that, it's a race between from(resourceActions) and from(execAction). In both cases, the Promise concatenates additional action menu items with the already-populated items. resourceActions pays no mind to the output of execAction, and execAction pays no mind to resourceActions. So whichever finishes last wins, and overwrites the output of the other.

Instead of concatenating outputs in Promises, we should have each menu-item-populater (hard-coded, actions, and exec) produce the menu item it's responsible for, and combine those outputs using rxJS.

So, going line-by-line:

    // whatever return an array of whatever each of the operands most recently produced
    return combineLatest(
        // immediately produce the hard-coded menu items
        from([items]),
        // immediately produce an empty list, and then produce whatever the resourceActions Promise returns
        concat([[] as MenuItem[]], resourceActions),
        // immediately produce an empty list, and then produce whatever the execAction Promise returns
        concat([[] as MenuItem[]], execAction)
    // whatever arrays of menu items have been produced, concatenate the arrays into a single array
    ).pipe(map(res => ([] as MenuItem[]).concat(...res)));

By immediately producing [] for the two network-bound Promises, we allow the list to be eagerly populated in the case of a slow network. In this video, I've throttled the response for the "actions" request to show how the UI will behave.

Screen.Recording.2022-08-16.at.5.54.11.PM.mov

Ideally, there would be some loading indicator. For now, this PR will solve the problem of the partially-populated dropdown.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.16%. Comparing base (377ae07) to head (574f2a6).
Report is 2628 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #10359   +/-   ##
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  Coverage   46.16%   46.16%           
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  Files         228      228           
  Lines       28004    28004           
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  Hits        12927    12927           
  Misses      13324    13324           
  Partials     1753     1753           

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[alexmt]

Reviewed and tested locally. Looks great!

[crenshaw-dev]

Cherry-picked onto release-2.4 for 2.4.10.