[BUGFIX release] Fix array QP serialization

[lan0]

A twiddle reproducing the issue: https://ember-twiddle.com/c0f6b0efd71731ecb7e474ddedc7a7a4 - after a click on set array and then on refresh the array QP becomes a string.

"[1]" gets stringified in the second call to serializeQueryParam, resulting in the serialized param being ""[1]"" instead of "[1]".

This fixes #13591 and is similar to #13816.

[nathanhammond]

@lan0 I believe that both this approach and the original behavior are wrong. Per our adoption of route-recognizer and the way it handles arrays the result should be:

QS.stringify({
  array: [ 1 ]
});
// => ?array[] = 1

[nathanhammond]

So these are the lines which implement the behavior:
https://github.com/emberjs/ember.js/blob/master/packages/ember-routing/lib/system/route.js#L421-L464

This is a completely custom (and broken) QP serialization strategy which doesn't match our approach for route-recognizer. The behavior for non-string and non-numeric values should be considered broken since who knows when and therefore should not be relied upon.

[nathanhammond]

Last note: this should be compared to route-recognizer's current QP implementation:

• https://github.com/tildeio/route-recognizer/blob/master/lib/route-recognizer.js#L455-L483
• https://github.com/tildeio/route-recognizer/blob/master/lib/route-recognizer.js#L423-L453

The real bug here is actually that these are inconsistent. As a result we should not merge this PR (which will create yet another new failure mode) and instead solve it at the more-fundamental level.

Blog post coming on query strings this week.

[homu]

☔ The latest upstream changes (presumably #14415) made this pull request unmergeable. Please resolve the merge conflicts.

[lan0]

Agreed that the array serialization should be ?array[]=, but it worked for us so we rolled with it long ago.

Closing this since we fixed it in our app by overwriting serializeQueryParam in routes where there are array QP:

  serializeQueryParam(value, urlKey, defaultValueType) {
    if (defaultValueType === 'array' && Array.isArray(value)) {
      return JSON.stringify(value);
    }
    return `${value}`;
  },