(Do not merge!) Poked around wakelock_plus (web)

wakelock_plus/lib/src/wakelock_plus_web_plugin.dart

@@ -1,7 +1,7 @@
 import 'dart:async';
 
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
-import 'package:js/js.dart';
+import 'package:js/js_util.dart';
 import 'package:wakelock_plus_platform_interface/wakelock_plus_platform_interface.dart';
 import 'package:wakelock_plus/src/web_impl/import_js_library.dart';
 import 'package:wakelock_plus/src/web_impl/js_wakelock.dart'
@@ -11,39 +11,36 @@ import 'package:wakelock_plus/src/web_impl/js_wakelock.dart'
 ///
 /// This class implements the `wakelock_plus` plugin functionality for web.
 class WakelockPlusWebPlugin extends WakelockPlusPlatformInterface {
+  /// Builds an instance of the plugin, and imports the JS implementation.
+  WakelockPlusWebPlugin() {
+    _jsLoaded = importJsLibrary(
+        url: 'packages/wakelock_plus/assets/no_sleep.js', flutterPluginName: 'wakelock_plus');
+  }
+
+  // The future that signals when the JS is loaded.
+  // This needs to be `await`ed before accessing any methods of the
+  // JS-interop layer.
+  Future<void>? _jsLoaded;
+
   /// Registers [WakelockPlusWebPlugin] as the default instance of the
   /// [WakelockPlatformInterface].
   static void registerWith(Registrar registrar) {
-    // Import a version of `NoSleep.js` that was adjusted for the wakelock
-    // plugin.
-    importJsLibrary(
-        url: 'assets/no_sleep.js', flutterPluginName: 'wakelock_plus');
-
     WakelockPlusPlatformInterface.instance = WakelockPlusWebPlugin();
   }
 
   @override
   Future<void> toggle({required bool enable}) async {
+    // Await _jsLoaded before accessing wakelock_plus_web
+    await _jsLoaded!;
+
     wakelock_plus_web.toggle(enable);
   }
 
   @override
   Future<bool> get enabled async {
-    final completer = Completer<bool>();
-
-    wakelock_plus_web.enabled().then(
-      // onResolve
-      allowInterop((value) {
-        assert(value is bool);
-
-        completer.complete(value);
-      }),
-      // onReject
-      allowInterop((error) {
-        completer.completeError(error);
-      }),
-    );
-
-    return completer.future;
+    await _jsLoaded!;
+
+    // Can be simplified a lot
+    return promiseToFuture(wakelock_plus_web.enabled());
   }
 }

wakelock_plus/lib/src/web_impl/import_js_library.dart

@@ -1,29 +1,35 @@
 import 'dart:html' as html;
+import 'dart:ui_web' as ui_web;
 
 /// This is an implementation of the `import_js_library` plugin that is used
 /// until that plugin is migrated to null safety.
 /// See https://github.com/florent37/flutter_web_import_js_library/pull/6#issuecomment-735349208.
 
 /// Imports a JS script file from the given [url] given the relative
 /// [flutterPluginName].
-void importJsLibrary({required String url, String? flutterPluginName}) {
+///
+/// Returns a Future that resolves when the library is loaded.
+Future<void> importJsLibrary({required String url, String? flutterPluginName}) {
   if (flutterPluginName == null) {
-    _importJSLibraries([url]);
-  } else {
-    _importJSLibraries([_libraryUrl(url, flutterPluginName)]);
+    return _importJSLibraries([url]);
   }
+  return _importJSLibraries([_libraryUrl(url, flutterPluginName)]);
 }
 
 String _libraryUrl(String url, String pluginName) {
-  if (url.startsWith('./')) {
-    url = url.replaceFirst('./', '');
-    return './assets/packages/$pluginName/$url';
-  }
-  if (url.startsWith('assets/')) {
-    return './assets/packages/$pluginName/$url';
-  } else {
-    return url;
-  }
+  return ui_web.assetManager.getAssetUrl(url);
+  //
+  //   TODO: Fix this properly!
+  //
+  // if (url.startsWith('./')) {
+  //   url = url.replaceFirst('./', '');
+  //   return './assets/packages/$pluginName/$url';
+  // }
+  // if (url.startsWith('assets/')) {
+  //   return './assets/packages/$pluginName/$url';
+  // } else {
+  //   return url;
+  // }
 }
 
 html.ScriptElement _createScriptTag(String library) {
@@ -46,6 +52,14 @@ Future<void> _importJSLibraries(List<String> libraries) {
       final scriptTag = _createScriptTag(library);
       head!.children.add(scriptTag);
       loading.add(scriptTag.onLoad.first);
+      // Recommended: add an onError listener to know that something
+      // went wrong here, rather than swallowing the problem.
+      scriptTag.onError.listen((html.Event e) {
+        final String src = (e.target as html.ScriptElement).src;
+        loading.add(Future.error(
+          Exception('Error loading: $src')
+        ));
+      });
     }
   }
 

wakelock_plus/pubspec.yaml

@@ -99,4 +99,5 @@ flutter:
   # https://flutter.dev/custom-fonts/#from-packages
 
   assets:
-    - assets/no_sleep.js
+    - lib/assets/no_sleep.js
+    - packages/wakelock_plus/assets/no_sleep.js

wakelock_plus/test/wakelock_plus_web_plugin_test.dart

@@ -6,6 +6,14 @@ import 'package:wakelock_plus/src/wakelock_plus_web_plugin.dart';
 import 'package:wakelock_plus/wakelock_plus.dart';
 import 'package:wakelock_plus_platform_interface/wakelock_plus_platform_interface.dart';
 
+// This test could be run with: 
+//   flutter run test --platform chrome
+// But there's something weird about the JS not loading.
+//
+// The test can be manually run with:
+//   flutter run -d chrome test/wakelock_plus_web_plugin_test.dart
+// or:
+//   with -d web-server to run it in other browsers.
 void main() {
   group('$WakelockPlusWebPlugin', () {
     setUpAll(() async {
@@ -28,6 +36,7 @@ void main() {
     });
 
     test('disable', () async {
+      await WakelockPlus.enable();
       await WakelockPlus.disable();
       expect(WakelockPlus.enabled, completion(isFalse));
     });
@@ -36,6 +45,10 @@ void main() {
       await WakelockPlus.toggle(enable: true);
       expect(WakelockPlus.enabled, completion(isTrue));
 
+      // toggle(false) fails after toggle(true).
+      // (This seems like a no_sleep.js issue.)
+      // You can see this same failure by calling `WakelockPlus.enable()`
+      // right before `disable()` in the test above.
       await WakelockPlus.toggle(enable: false);
       expect(WakelockPlus.enabled, completion(isFalse));
     });