Rewrite license code to avoid async* (#95130)

packages/flutter/lib/src/foundation/licenses.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:async';
+
 import 'package:meta/meta.dart' show visibleForTesting;
 
 /// Signature for callbacks passed to [LicenseRegistry.addLicense].
@@ -70,8 +72,8 @@ enum _LicenseEntryWithLineBreaksParserState {
 ///
 /// ```dart
 /// void initMyLibrary() {
-///   LicenseRegistry.addLicense(() async* {
-///     yield const LicenseEntryWithLineBreaks(<String>['my_library'], '''
+///   LicenseRegistry.addLicense(() => Stream<LicenseEntry>.value(
+///     const LicenseEntryWithLineBreaks(<String>['my_library'], '''
 /// Copyright 2016 The Sample Authors. All rights reserved.
 ///
 /// Redistribution and use in source and binary forms, with or without
@@ -98,8 +100,9 @@ enum _LicenseEntryWithLineBreaksParserState {
 /// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 /// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 /// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-/// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.''');
-///   });
+/// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.''',
+///     ),
+///   ));
 /// }
 /// ```
 /// {@end-tool}
@@ -309,14 +312,19 @@ class LicenseRegistry {
   /// Returns the licenses that have been registered.
   ///
   /// Generating the list of licenses is expensive.
-  // TODO(dnfield): Refactor the license logic.
-  // https://github.com/flutter/flutter/issues/95043
-  // flutter_ignore: no_sync_async_star
-  static Stream<LicenseEntry> get licenses async* {
+  static Stream<LicenseEntry> get licenses {
     if (_collectors == null)
-      return;
+      return const Stream<LicenseEntry>.empty();
+
+    late final StreamController<LicenseEntry> controller;
+    controller = StreamController<LicenseEntry>(
+      onListen: () async {
         for (final LicenseEntryCollector collector in _collectors!)
-      yield* collector();
+          await controller.addStream(collector());
+        await controller.close();
+      },
+    );
+    return controller.stream;
   }
 
   /// Resets the internal state of [LicenseRegistry]. Intended for use in

packages/flutter/lib/src/services/binding.dart

@@ -6,6 +6,7 @@
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
+import 'dart:typed_data';
 import 'dart:ui' as ui;
 
 import 'package:flutter/foundation.dart';
@@ -144,45 +145,29 @@ mixin ServicesBinding on BindingBase, SchedulerBinding {
     LicenseRegistry.addLicense(_addLicenses);
   }
 
-  // TODO(dnfield): Refactor the license logic.
-  // https://github.com/flutter/flutter/issues/95043
-  // flutter_ignore: no_sync_async_star
-  Stream<LicenseEntry> _addLicenses() async* {
-    // Using _something_ here to break
-    // this into two parts is important because isolates take a while to copy
-    // data at the moment, and if we receive the data in the same event loop
-    // iteration as we send the data to the next isolate, we are definitely
-    // going to miss frames. Another solution would be to have the work all
-    // happen in one isolate, and we may go there eventually, but first we are
-    // going to see if isolate communication can be made cheaper.
-    // See: https://github.com/dart-lang/sdk/issues/31959
-    //      https://github.com/dart-lang/sdk/issues/31960
-    // TODO(ianh): Remove this complexity once these bugs are fixed.
-    final Completer<String> rawLicenses = Completer<String>();
-    scheduleTask(() async {
-      rawLicenses.complete(
-        kIsWeb
+  Stream<LicenseEntry> _addLicenses() {
+    late final StreamController<LicenseEntry> controller;
+    controller = StreamController<LicenseEntry>(
+      onListen: () async {
+        late final String rawLicenses;
+        if (kIsWeb) {
           // NOTICES for web isn't compressed since we don't have access to
           // dart:io on the client side and it's already compressed between
           // the server and client.
-            ? rootBundle.loadString('NOTICES', cache: false)
-            : () async {
+          rawLicenses = await rootBundle.loadString('NOTICES', cache: false);
+        } else {
           // The compressed version doesn't have a more common .gz extension
           // because gradle for Android non-transparently manipulates .gz files.
           final ByteData licenseBytes = await rootBundle.load('NOTICES.Z');
-              List<int> bytes = licenseBytes.buffer.asUint8List();
-              bytes = gzip.decode(bytes);
-              return utf8.decode(bytes);
-            }(),
+          final List<int> unzippedBytes = await compute<List<int>, List<int>>(gzip.decode, licenseBytes.buffer.asUint8List(), debugLabel: 'decompressLicenses');
+          rawLicenses = await compute<List<int>, String>(utf8.decode, unzippedBytes, debugLabel: 'utf8DecodeLicenses');
+        }
+        final List<LicenseEntry> licenses = await compute<String, List<LicenseEntry>>(_parseLicenses, rawLicenses, debugLabel: 'parseLicenses');
+        licenses.forEach(controller.add);
+        await controller.close();
+      },
     );
-    }, Priority.animation);
-    await rawLicenses.future;
-    final Completer<List<LicenseEntry>> parsedLicenses = Completer<List<LicenseEntry>>();
-    scheduleTask(() async {
-      parsedLicenses.complete(compute<String, List<LicenseEntry>>(_parseLicenses, await rawLicenses.future, debugLabel: 'parseLicenses'));
-    }, Priority.animation);
-    await parsedLicenses.future;
-    yield* Stream<LicenseEntry>.fromIterable(await parsedLicenses.future);
+    return controller.stream;
   }
 
   // This is run in another isolate created by _addLicenses above.