From d6ebdd2c7ede4d2064df8709ce90b1db464fd300 Mon Sep 17 00:00:00 2001
From: Joshua Litt <joshualitt@google.com>
Date: Fri, 9 Sep 2022 22:54:51 +0000
Subject: [PATCH] [web] Upstream some fixes for dart2wasm.

---
 lib/web_ui/lib/initialization.dart                  |  5 +----
 lib/web_ui/lib/src/engine/dom.dart                  | 11 +++++++++--
 lib/web_ui/lib/src/engine/js_interop/js_loader.dart |  8 +++++++-
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/lib/web_ui/lib/initialization.dart b/lib/web_ui/lib/initialization.dart
index e19f24103cdf4..c28a3056e3515 100644
--- a/lib/web_ui/lib/initialization.dart
+++ b/lib/web_ui/lib/initialization.dart
@@ -81,11 +81,8 @@ Future<void> webOnlyWarmupEngine({
 
   // Should the app "autoStart"?
   bool autoStart = true;
-  try {
+  if (engine.flutter != null && engine.loader != null) {
     autoStart = engine.didCreateEngineInitializer == null;
-  } catch (e) {
-    // Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'loader')
-    autoStart = true;
   }
   if (autoStart) {
     // The user does not want control of the app, bootstrap immediately.
diff --git a/lib/web_ui/lib/src/engine/dom.dart b/lib/web_ui/lib/src/engine/dom.dart
index 3c6bac0aa0b31..b1a02a82d29df 100644
--- a/lib/web_ui/lib/src/engine/dom.dart
+++ b/lib/web_ui/lib/src/engine/dom.dart
@@ -1276,8 +1276,7 @@ class DomStyleSheet {}
 class DomCSSStyleSheet extends DomStyleSheet {}
 
 extension DomCSSStyleSheetExtension on DomCSSStyleSheet {
-  List<DomCSSRule> get cssRules =>
-      js_util.getProperty<List<Object?>>(this, 'cssRules').cast<DomCSSRule>();
+  external DomCSSRuleList get cssRules;
   int insertRule(String rule, [int? index]) => js_util
       .callMethod(this, 'insertRule', <Object>[rule, if (index != null) index]);
 }
@@ -1381,6 +1380,14 @@ extension DomMessageChannelExtension on DomMessageChannel {
   external DomMessagePort get port2;
 }
 
+@JS()
+@staticInterop
+class DomCSSRuleList {}
+
+extension DomCSSRuleListExtension on DomCSSRuleList {
+  external int get length;
+}
+
 DomMessageChannel createDomMessageChannel() =>
     domCallConstructorString('MessageChannel', <Object>[])!
         as DomMessageChannel;
diff --git a/lib/web_ui/lib/src/engine/js_interop/js_loader.dart b/lib/web_ui/lib/src/engine/js_interop/js_loader.dart
index 9b75840840f42..655e69d837a20 100644
--- a/lib/web_ui/lib/src/engine/js_interop/js_loader.dart
+++ b/lib/web_ui/lib/src/engine/js_interop/js_loader.dart
@@ -14,7 +14,13 @@ import 'js_promise.dart';
 /// programmer can control the initialization sequence.
 typedef DidCreateEngineInitializerFn = void Function(FlutterEngineInitializer);
 
-// A JS-interop representation of `_flutter?.loader?.didCreateEngineInitializer?`:
+// Both `flutter`, `loader`(_flutter.loader), must be checked for null before
+// `didCreateEngineInitializer` can be safely accessed.
+@JS('_flutter')
+external Object? get flutter;
+
+@JS('_flutter.loader')
+external Object? get loader;
 
 @JS('_flutter.loader.didCreateEngineInitializer')
 external DidCreateEngineInitializerFn? get didCreateEngineInitializer;