feat(testing/asserts): return error from assertRejects and assertThrows

[mrkldshv]

Makes assertRejects and assertThrows return caught error.

• Deprecate error callback from assertRejects and assertThrows signatures
• Allow throwing non-error values

Closes #1362, #2220.

[CLAassistant]

All committers have signed the CLA.

[KyleJune]

I'm not on the core team, just another contributor. Giving my feedback because I worked in this area before and think the change in call signature issue is a good opportunity to also fix another issue related to assertThrows and assertRejects.

[mrkldshv]

I've changed it to required, because none of the signatures of assertThrows function matches the way this function is called. I'm open to refactoring it to keep it optional though. It can be something like:

if (ErrorClass) {
    assertThrows(
    () => {
      slidingWindows(...input);
    },
    ErrorClass,
    msgIncludes,
    msg,
  );
} else {
  assertThrows(
    () => {
      slidingWindows(...input);
    },
    msg,
  );
}

[mrkldshv]

Was thinking to remove this bit about error callback from the documentation not to encourage developers to use it, because we're deprecating this parameter. What do you think?

[kt3k]

@mrkldshv LGTM. Nice work!

[kt3k]

Note: This is going to be a breaking change in 2 points.

• Now errorCallback signature is deprecated. The usages are need to be migrated to the pattern of returning error and asserting on it. This doesn't break code immediately, but the users see the deprecation warnings in IDE.
• Now ErrorClass parameter is non optional. This can break the type checking if a user uses undefined for it. The users need to pass something there