Dart2's ResizeObserverEntry being broken by minifier

[janvladimirmostert]

I've logged a bug for ResizeObserver that was breaking when building with release mode (https://github.com/dart-lang/sdk/issues/40961), that is working now in 2.8 dev-13, but ResizeObserverEntry is still breaking.

import "dart:html";
import "dart:js";

void main() {
  final DivElement div1 = querySelector("div.div1");
  final DivElement div2 = querySelector("div.div2");

  final void Function(List blah1, ResizeObserver blah2) callback = (blah1, _) {
    print("inside divResizeObserverCallback");
    blah1.forEach((entry) {
      context["console"].callMethod("log", [entry]);
      div2.style.height = "${entry.target.clientHeight}px";
    });
  };
  final ResizeObserver divResizeObserver = ResizeObserver(callback);
  divResizeObserver.observe(div1);
}

the console.log outputs that entry is of type DartObject which contains ResizeObserverEntry, casting entry to that however fails with a cast error and trying to access target from entry.target fails with:

Uncaught TypeError: J.d8(...).gv is not a function
    at Object.dD (bug_resize_observer.dart.js:1114)
    at c7.$1 (bug_resize_observer.dart.js:1995)
    at r.u (bug_resize_observer.dart.js:1419)
    at Object.dB (bug_resize_observer.dart.js:1109)
    at c8.$2 (bug_resize_observer.dart.js:1986)
    at eW (bug_resize_observer.dart.js:227)
    at ResizeObserver.<anonymous> (bug_resize_observer.dart.js:232)
dD @ bug_resize_observer.dart.js:1114
$1 @ bug_resize_observer.dart.js:1995
u @ bug_resize_observer.dart.js:1419
dB @ bug_resize_observer.dart.js:1109
$2 @ bug_resize_observer.dart.js:1986
eW @ bug_resize_observer.dart.js:227
(anonymous) @ bug_resize_observer.dart.js:232

Casting:

      div2.style.height = "${(entry as ResizeObserverEntry).target.clientHeight}px";

Uncaught CastError: Instance of 'ResizeObserverEntry': type 'minified:aC' is not a subtype of type 'minified:f7'

[vakenbolt]

I can confirm that this still broken:

Dart Version: 2.16.2

main.dart.js:384 Uncaught TypeError: Instance of 'ResizeObserverEntry': type 'minified:db' is not a subtype of type 'minified:SH'
    at Object.c (main.dart.js:384:3)
    at Object.L7 (main.dart.js:953:17)
    at cx.Qy [as a] (main.dart.js:948:3)
    at cx.QE (main.dart.js:920:10)
    at vL.$2 (main.dart.js:20958:34)
    at RG (main.dart.js:465:17)
    at ResizeObserver.<anonymous> (main.dart.js:472:51)

Steps to reproduce:

var resizeObserver = ResizeObserver(((entries, observer) {
  for (ResizeObserverEntry entry in entries) {
    print(entry);
  }
}

NOTE: The code above works fine when you are running it locally with pub serve however it breaks when the code is minified as mentioned by the OP.

If you try to work around the issue without adding a type:

var resizeObserver = ResizeObserver(((entries, observer) {
  for (var entry in entries) {
    print(entry);
  }
}

Still produces an error when minified:

main.dart.js:20990 Uncaught TypeError: r.gql is not a function
    at vO.$2 (main.dart.js:20990:3)
    at RK (main.dart.js:465:17)
    at ResizeObserver.<anonymous> (main.dart.js:472:51)