SimpleTableManual sort on empty values incorrect on Firefox

[wimbarelds]

Describe the bug
SimpleTableManual's sorting is reversed in Firefox when orderedBy is empty, or a non-existing column.

As a result, in 'editable' mode, where orderedBy is always an empty string, sorting is always reversed (in Firefox).

The rows being reversed also causes row-actions (such as Delete or Edit) to be applied to the incorrect row (because these send the client-index to the server, while the server's rows aren't reversed.

The cause of this issue:

Chrome and Firefox use a different underlying sorting algorithm. As an example, this snippet:

[1, 2].sort((a, b) => -1)

returns [2, 1] in Chrome, but [1, 2] in Firefox.

SimpleTableManual uses the following comparator function:

function descendingComparator<T>(a: T, b: T, orderedBy: keyof T) {
  if (!b[orderedBy] || b[orderedBy] < a[orderedBy]) {
    return -1;
  }
  if (!a[orderedBy] || b[orderedBy] > a[orderedBy]) {
    return 1;
  }
  return 0;
}

When a[orderedBy] and b[orderedBy] are both falsy (false, 0, null, undefined or ""), this function will return -1, which causes the firefox results to come out in reversed order.

A fixed version of this function would be

function descendingComparator<T>(a: T, b: T, orderedBy: keyof T) {
  if (!orderedBy || !a[orderedBy] && !b[orderedBy]) {
    return 0;
  }
  if (!b[orderedBy] || b[orderedBy] < a[orderedBy]) {
    return -1;
  }
  if (!a[orderedBy] || b[orderedBy] > a[orderedBy]) {
    return 1;
  }
  return 0;
}

To Reproduce
Steps to reproduce the behavior:

1. Compare the row-order of an editable SimpleTableManual in Chrome and Firefox
2. See difference
3. Try edit the first of multiple rows in Firefox
4. See that you're editing the last row instead

Expected behavior

1. The same order in Chrome and Firefox
2. The correct item being edited

Desktop:

• OS: MacOS
• Browser Firefox

[tumms2021389]

Thanks @wimbarelds for identifying and providing solution for the issue.

Our team is working on fixing this issue as part of 24.2.10 release.

[nhe050]

Thanks @tumms2021389. Could you please also make the fix available in 24.1.x? Asking since we're not able to upgrade to 24.2.x before our go-live.
(working in same project as @wimbarelds)