From ec02d37ef264fb6aa27a5d94e0ea10771656d3b4 Mon Sep 17 00:00:00 2001
From: Mouad Debbar <mdebbar@google.com>
Date: Wed, 7 Apr 2021 09:40:51 -0700
Subject: [PATCH 1/4] [web] Start splitting the engine into smaller libs

---
 lib/web_ui/lib/src/engine.dart                |  81 ++++++---
 lib/web_ui/lib/src/engine/alarm_clock.dart    |   4 +-
 .../lib/src/engine/browser_detection.dart     |   4 +-
 lib/web_ui/lib/src/engine/mouse_cursor.dart   |   2 +-
 .../lib/src/engine/navigation/history.dart    |   9 +-
 .../engine/navigation/js_url_strategy.dart    |   8 +-
 .../src/engine/navigation/url_strategy.dart   |   7 +-
 lib/web_ui/lib/src/engine/plugins.dart        |   4 +-
 .../lib/src/engine/pointer_binding.dart       |  11 +-
 .../lib/src/engine/pointer_converter.dart     |   2 +-
 .../lib/src/engine/services/buffers.dart      |   3 +-
 .../src/engine/services/message_codec.dart    |   4 +-
 .../src/engine/services/message_codecs.dart   |   6 +-
 .../src/engine/services/serialization.dart    |   4 +-
 lib/web_ui/lib/src/engine/shadow.dart         |   6 +-
 lib/web_ui/lib/src/engine/test_embedding.dart |   7 +-
 lib/web_ui/lib/src/engine/ulps.dart           |   3 +-
 lib/web_ui/lib/src/engine/validators.dart     |   4 +-
 lib/web_ui/lib/src/engine/vector_math.dart    |   5 +-
 .../lib/src/engine/web_experiments.dart       |   4 +-
 lib/web_ui/test/alarm_clock_test.dart         |   2 +-
 lib/web_ui/test/browser_detect_test.dart      |   2 +-
 lib/web_ui/test/engine/history_test.dart      |   8 +-
 .../test/engine/pointer_binding_test.dart     |   4 +-
 lib/web_ui/test/engine/ulps_test.dart         |   2 +-
 .../test/engine/web_experiments_test.dart     |   2 +-
 web_sdk/sdk_rewriter.dart                     | 159 +++++++++++++-----
 27 files changed, 274 insertions(+), 83 deletions(-)

diff --git a/lib/web_ui/lib/src/engine.dart b/lib/web_ui/lib/src/engine.dart
index 9e2537f8a7097..87a56cb6643ed 100644
--- a/lib/web_ui/lib/src/engine.dart
+++ b/lib/web_ui/lib/src/engine.dart
@@ -8,6 +8,8 @@ library engine;
 
 import 'dart:async';
 import 'dart:collection'
+    // Some of these names are used in services/buffers.dart for example.
+    // ignore: unused_shown_name
     show ListBase, IterableBase, DoubleLinkedQueue, DoubleLinkedQueueEntry;
 import 'dart:convert' hide Codec;
 import 'dart:developer' as developer;
@@ -22,10 +24,68 @@ import 'package:meta/meta.dart';
 
 import '../ui.dart' as ui;
 
-part 'engine/alarm_clock.dart';
+import 'engine/alarm_clock.dart';
+export 'engine/alarm_clock.dart';
+
+import 'engine/browser_detection.dart';
+export 'engine/browser_detection.dart';
+
+import 'engine/mouse_cursor.dart';
+export 'engine/mouse_cursor.dart';
+
+import 'engine/navigation/history.dart';
+export 'engine/navigation/history.dart';
+
+import 'engine/navigation/js_url_strategy.dart';
+export 'engine/navigation/js_url_strategy.dart';
+
+import 'engine/navigation/url_strategy.dart';
+export 'engine/navigation/url_strategy.dart';
+
+import 'engine/plugins.dart';
+export 'engine/plugins.dart';
+
+import 'engine/pointer_binding.dart';
+export 'engine/pointer_binding.dart';
+
+// This import is intentionally commented out because the analyzer says it's unused.
+// import 'engine/pointer_converter.dart';
+export 'engine/pointer_converter.dart';
+
+// This import is intentionally commented out because the analyzer says it's unused.
+// import 'engine/services/buffers.dart';
+export 'engine/services/buffers.dart';
+
+import 'engine/services/message_codec.dart';
+export 'engine/services/message_codec.dart';
+
+import 'engine/services/message_codecs.dart';
+export 'engine/services/message_codecs.dart';
+
+// This import is intentionally commented out because the analyzer says it's unused.
+// import 'engine/services/serialization.dart';
+export 'engine/services/serialization.dart';
+
+import 'engine/shadow.dart';
+export 'engine/shadow.dart';
+
+import 'engine/test_embedding.dart';
+export 'engine/test_embedding.dart';
+
+import 'engine/ulps.dart';
+export 'engine/ulps.dart';
+
+import 'engine/validators.dart';
+export 'engine/validators.dart';
+
+import 'engine/vector_math.dart';
+export 'engine/vector_math.dart';
+
+import 'engine/web_experiments.dart';
+export 'engine/web_experiments.dart';
+
 part 'engine/assets.dart';
 part 'engine/bitmap_canvas.dart';
-part 'engine/browser_detection.dart';
 part 'engine/canvaskit/canvas.dart';
 part 'engine/canvaskit/canvaskit_canvas.dart';
 part 'engine/canvaskit/canvaskit_api.dart';
@@ -64,9 +124,6 @@ part 'engine/dom_canvas.dart';
 part 'engine/dom_renderer.dart';
 part 'engine/engine_canvas.dart';
 part 'engine/frame_reference.dart';
-part 'engine/navigation/history.dart';
-part 'engine/navigation/js_url_strategy.dart';
-part 'engine/navigation/url_strategy.dart';
 part 'engine/html/backdrop_filter.dart';
 part 'engine/html/canvas.dart';
 part 'engine/html/clip.dart';
@@ -102,14 +159,10 @@ part 'engine/html_image_codec.dart';
 part 'engine/keyboard_binding.dart';
 part 'engine/keyboard.dart';
 part 'engine/key_map.dart';
-part 'engine/mouse_cursor.dart';
 part 'engine/onscreen_logging.dart';
 part 'engine/picture.dart';
 part 'engine/platform_dispatcher.dart';
 part 'engine/platform_views.dart';
-part 'engine/plugins.dart';
-part 'engine/pointer_binding.dart';
-part 'engine/pointer_converter.dart';
 part 'engine/profiler.dart';
 part 'engine/rrect_renderer.dart';
 part 'engine/semantics/accessibility.dart';
@@ -123,12 +176,6 @@ part 'engine/semantics/semantics.dart';
 part 'engine/semantics/semantics_helper.dart';
 part 'engine/semantics/tappable.dart';
 part 'engine/semantics/text_field.dart';
-part 'engine/services/buffers.dart';
-part 'engine/services/message_codec.dart';
-part 'engine/services/message_codecs.dart';
-part 'engine/services/serialization.dart';
-part 'engine/shadow.dart';
-part 'engine/test_embedding.dart';
 part 'engine/text/font_collection.dart';
 part 'engine/text/layout_service.dart';
 part 'engine/text/line_break_properties.dart';
@@ -145,11 +192,7 @@ part 'engine/text_editing/autofill_hint.dart';
 part 'engine/text_editing/input_type.dart';
 part 'engine/text_editing/text_capitalization.dart';
 part 'engine/text_editing/text_editing.dart';
-part 'engine/ulps.dart';
 part 'engine/util.dart';
-part 'engine/validators.dart';
-part 'engine/vector_math.dart';
-part 'engine/web_experiments.dart';
 part 'engine/window.dart';
 
 // The mode the app is running in.
diff --git a/lib/web_ui/lib/src/engine/alarm_clock.dart b/lib/web_ui/lib/src/engine/alarm_clock.dart
index 1a9c384f2c898..0dc69462fd35f 100644
--- a/lib/web_ui/lib/src/engine/alarm_clock.dart
+++ b/lib/web_ui/lib/src/engine/alarm_clock.dart
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:async';
+
+import 'package:ui/ui.dart' as ui;
 
 /// A function that returns current system time.
 typedef TimestampFunction = DateTime Function();
diff --git a/lib/web_ui/lib/src/engine/browser_detection.dart b/lib/web_ui/lib/src/engine/browser_detection.dart
index 3bcf63640081f..5fc9728cd4332 100644
--- a/lib/web_ui/lib/src/engine/browser_detection.dart
+++ b/lib/web_ui/lib/src/engine/browser_detection.dart
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:html' as html;
+
+import 'package:meta/meta.dart';
 
 /// The HTML engine used by the current browser.
 enum BrowserEngine {
diff --git a/lib/web_ui/lib/src/engine/mouse_cursor.dart b/lib/web_ui/lib/src/engine/mouse_cursor.dart
index ad926e4a6c4bf..fad04d0e4f950 100644
--- a/lib/web_ui/lib/src/engine/mouse_cursor.dart
+++ b/lib/web_ui/lib/src/engine/mouse_cursor.dart
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'package:ui/src/engine.dart' show domRenderer, DomRenderer;
 
 /// Provides mouse cursor bindings, such as the `flutter/mousecursor` channel.
 class MouseCursor {
diff --git a/lib/web_ui/lib/src/engine/navigation/history.dart b/lib/web_ui/lib/src/engine/navigation/history.dart
index 3d5ea02569c0f..734bea3f78dec 100644
--- a/lib/web_ui/lib/src/engine/navigation/history.dart
+++ b/lib/web_ui/lib/src/engine/navigation/history.dart
@@ -3,7 +3,14 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:html' as html;
+
+import 'package:ui/src/engine.dart' show EnginePlatformDispatcher;
+import 'package:ui/ui.dart' as ui;
+
+import '../services/message_codec.dart';
+import '../services/message_codecs.dart';
+import 'url_strategy.dart';
 
 /// An abstract class that provides the API for [EngineWindow] to delegate its
 /// navigating events.
diff --git a/lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart b/lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart
index 1592d9451c974..41c7c90f759ab 100644
--- a/lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart
+++ b/lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart
@@ -3,7 +3,13 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+@JS()
+library js_url_strategy;
+
+import 'dart:html' as html;
+
+import 'package:js/js.dart';
+import 'package:ui/ui.dart' as ui;
 
 typedef _PathGetter = String Function();
 
diff --git a/lib/web_ui/lib/src/engine/navigation/url_strategy.dart b/lib/web_ui/lib/src/engine/navigation/url_strategy.dart
index 0cf1470050512..49ae240c4245e 100644
--- a/lib/web_ui/lib/src/engine/navigation/url_strategy.dart
+++ b/lib/web_ui/lib/src/engine/navigation/url_strategy.dart
@@ -3,7 +3,12 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:async';
+import 'dart:html' as html;
+
+import 'package:ui/ui.dart' as ui;
+
+import 'js_url_strategy.dart';
 
 /// Represents and reads route state from the browser's URL.
 ///
diff --git a/lib/web_ui/lib/src/engine/plugins.dart b/lib/web_ui/lib/src/engine/plugins.dart
index 1f7361be83347..5233fb1e8aff5 100644
--- a/lib/web_ui/lib/src/engine/plugins.dart
+++ b/lib/web_ui/lib/src/engine/plugins.dart
@@ -3,6 +3,8 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:typed_data';
+
+import 'package:ui/ui.dart' as ui;
 
 Future<void> Function(String, ByteData?, ui.PlatformMessageResponseCallback?)? pluginMessageCallHandler;
diff --git a/lib/web_ui/lib/src/engine/pointer_binding.dart b/lib/web_ui/lib/src/engine/pointer_binding.dart
index d2a44b87f7954..bf76e01b51750 100644
--- a/lib/web_ui/lib/src/engine/pointer_binding.dart
+++ b/lib/web_ui/lib/src/engine/pointer_binding.dart
@@ -3,7 +3,16 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:html' as html;
+import 'dart:js' as js;
+import 'dart:js_util' as js_util;
+import 'dart:math' as math;
+
+import 'package:meta/meta.dart';
+import 'package:ui/src/engine.dart';
+import 'package:ui/ui.dart' as ui;
+
+import 'pointer_converter.dart';
 
 /// Set this flag to true to see all the fired events in the console.
 const bool _debugLogPointerEvents = false;
diff --git a/lib/web_ui/lib/src/engine/pointer_converter.dart b/lib/web_ui/lib/src/engine/pointer_converter.dart
index c2370d8ea187e..0aaf464c20477 100644
--- a/lib/web_ui/lib/src/engine/pointer_converter.dart
+++ b/lib/web_ui/lib/src/engine/pointer_converter.dart
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'package:ui/ui.dart' as ui;
 
 const bool _debugLogPointerConverter = false;
 
diff --git a/lib/web_ui/lib/src/engine/services/buffers.dart b/lib/web_ui/lib/src/engine/services/buffers.dart
index 33455825f05af..e5708ab1decf8 100644
--- a/lib/web_ui/lib/src/engine/services/buffers.dart
+++ b/lib/web_ui/lib/src/engine/services/buffers.dart
@@ -3,7 +3,8 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:collection';
+import 'dart:typed_data';
 
 abstract class _TypedDataBuffer<E> extends ListBase<E> {
   static const int _initialLength = 8;
diff --git a/lib/web_ui/lib/src/engine/services/message_codec.dart b/lib/web_ui/lib/src/engine/services/message_codec.dart
index 1ae695210c8e4..032b16b74b893 100644
--- a/lib/web_ui/lib/src/engine/services/message_codec.dart
+++ b/lib/web_ui/lib/src/engine/services/message_codec.dart
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:typed_data';
+
+import 'package:meta/meta.dart';
 
 /// A message encoding/decoding mechanism.
 ///
diff --git a/lib/web_ui/lib/src/engine/services/message_codecs.dart b/lib/web_ui/lib/src/engine/services/message_codecs.dart
index 768a744fa2f3f..5dd32df395a8e 100644
--- a/lib/web_ui/lib/src/engine/services/message_codecs.dart
+++ b/lib/web_ui/lib/src/engine/services/message_codecs.dart
@@ -3,7 +3,11 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'message_codec.dart';
+import 'serialization.dart';
 
 /// [MessageCodec] with unencoded binary messages represented using [ByteData].
 ///
diff --git a/lib/web_ui/lib/src/engine/services/serialization.dart b/lib/web_ui/lib/src/engine/services/serialization.dart
index 2fc103a31c288..d27c4e7e909b1 100644
--- a/lib/web_ui/lib/src/engine/services/serialization.dart
+++ b/lib/web_ui/lib/src/engine/services/serialization.dart
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:typed_data';
+
+import 'buffers.dart';
 
 /// Write-only buffer for incrementally building a [ByteData] instance.
 ///
diff --git a/lib/web_ui/lib/src/engine/shadow.dart b/lib/web_ui/lib/src/engine/shadow.dart
index fb5dbec217701..4a2a2c659131e 100644
--- a/lib/web_ui/lib/src/engine/shadow.dart
+++ b/lib/web_ui/lib/src/engine/shadow.dart
@@ -3,7 +3,11 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:html' as html;
+import 'dart:math' as math;
+
+import 'package:meta/meta.dart';
+import 'package:ui/ui.dart' as ui;
 
 /// How far is the light source from the surface of the UI.
 ///
diff --git a/lib/web_ui/lib/src/engine/test_embedding.dart b/lib/web_ui/lib/src/engine/test_embedding.dart
index 17c582605b32e..d10db9e280d01 100644
--- a/lib/web_ui/lib/src/engine/test_embedding.dart
+++ b/lib/web_ui/lib/src/engine/test_embedding.dart
@@ -3,7 +3,12 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:async';
+import 'dart:html' as html;
+
+import 'package:ui/ui.dart' as ui;
+
+import 'navigation/url_strategy.dart';
 
 const bool _debugLogHistoryActions = false;
 
diff --git a/lib/web_ui/lib/src/engine/ulps.dart b/lib/web_ui/lib/src/engine/ulps.dart
index e65792d5db9bf..53b61bb517278 100644
--- a/lib/web_ui/lib/src/engine/ulps.dart
+++ b/lib/web_ui/lib/src/engine/ulps.dart
@@ -3,7 +3,8 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:math' as math;
+import 'dart:typed_data';
 
 // This is a small library to handle stability for floating point operations.
 //
diff --git a/lib/web_ui/lib/src/engine/validators.dart b/lib/web_ui/lib/src/engine/validators.dart
index d90acc59c4201..ecec9e8268572 100644
--- a/lib/web_ui/lib/src/engine/validators.dart
+++ b/lib/web_ui/lib/src/engine/validators.dart
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:typed_data';
+
+import 'package:ui/ui.dart' as ui;
 
 bool rectIsValid(ui.Rect rect) {
   assert(rect != null, 'Rect argument was null.'); // ignore: unnecessary_null_comparison
diff --git a/lib/web_ui/lib/src/engine/vector_math.dart b/lib/web_ui/lib/src/engine/vector_math.dart
index fe0b3cd5fd67d..4e9b9d7d1f544 100644
--- a/lib/web_ui/lib/src/engine/vector_math.dart
+++ b/lib/web_ui/lib/src/engine/vector_math.dart
@@ -3,7 +3,10 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:math' as math;
+import 'dart:typed_data';
+
+import 'package:ui/src/engine.dart' show assertionsEnabled;
 
 class Matrix4 {
   final Float32List _m4storage;
diff --git a/lib/web_ui/lib/src/engine/web_experiments.dart b/lib/web_ui/lib/src/engine/web_experiments.dart
index 058600987bf0f..96092439cb727 100644
--- a/lib/web_ui/lib/src/engine/web_experiments.dart
+++ b/lib/web_ui/lib/src/engine/web_experiments.dart
@@ -3,7 +3,9 @@
 // found in the LICENSE file.
 
 // @dart = 2.12
-part of engine;
+import 'dart:js' as js;
+
+import 'package:ui/src/engine.dart' show registerHotRestartListener;
 
 /// A bag of all experiment flags in the web engine.
 ///
diff --git a/lib/web_ui/test/alarm_clock_test.dart b/lib/web_ui/test/alarm_clock_test.dart
index b56d0dc27d798..f4e2676448fd3 100644
--- a/lib/web_ui/test/alarm_clock_test.dart
+++ b/lib/web_ui/test/alarm_clock_test.dart
@@ -8,7 +8,7 @@ import 'package:test/test.dart';
 import 'package:quiver/testing/async.dart';
 import 'package:quiver/time.dart';
 
-import 'package:ui/src/engine.dart';
+import 'package:ui/src/engine/alarm_clock.dart';
 
 void main() {
   internalBootstrapBrowserTest(() => testMain);
diff --git a/lib/web_ui/test/browser_detect_test.dart b/lib/web_ui/test/browser_detect_test.dart
index 501a764f251dd..d45159c20a072 100644
--- a/lib/web_ui/test/browser_detect_test.dart
+++ b/lib/web_ui/test/browser_detect_test.dart
@@ -5,7 +5,7 @@
 // @dart = 2.12
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
-import 'package:ui/src/engine.dart';
+import 'package:ui/src/engine/browser_detection.dart';
 
 void main() {
   internalBootstrapBrowserTest(() => testMain);
diff --git a/lib/web_ui/test/engine/history_test.dart b/lib/web_ui/test/engine/history_test.dart
index 920cce6e6cfd3..a4cc9514f1176 100644
--- a/lib/web_ui/test/engine/history_test.dart
+++ b/lib/web_ui/test/engine/history_test.dart
@@ -11,7 +11,13 @@ import 'dart:html' as html;
 
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
-import 'package:ui/src/engine.dart';
+import 'package:ui/src/engine.dart' show window;
+import 'package:ui/src/engine/browser_detection.dart';
+import 'package:ui/src/engine/navigation/history.dart';
+import 'package:ui/src/engine/navigation/url_strategy.dart';
+import 'package:ui/src/engine/services/message_codec.dart';
+import 'package:ui/src/engine/services/message_codecs.dart';
+import 'package:ui/src/engine/test_embedding.dart';
 
 import '../spy.dart';
 
diff --git a/lib/web_ui/test/engine/pointer_binding_test.dart b/lib/web_ui/test/engine/pointer_binding_test.dart
index 15a7eeee9ea7c..8b85d0bda615d 100644
--- a/lib/web_ui/test/engine/pointer_binding_test.dart
+++ b/lib/web_ui/test/engine/pointer_binding_test.dart
@@ -9,7 +9,9 @@ import 'dart:js_util' as js_util;
 import 'package:meta/meta.dart';
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
-import 'package:ui/src/engine.dart';
+import 'package:ui/src/engine.dart' show domRenderer, window;
+import 'package:ui/src/engine/browser_detection.dart';
+import 'package:ui/src/engine/pointer_binding.dart';
 import 'package:ui/ui.dart' as ui;
 
 const int _kNoButtonChange = -1;
diff --git a/lib/web_ui/test/engine/ulps_test.dart b/lib/web_ui/test/engine/ulps_test.dart
index d0a26c45faad7..42ea75c38778b 100644
--- a/lib/web_ui/test/engine/ulps_test.dart
+++ b/lib/web_ui/test/engine/ulps_test.dart
@@ -5,7 +5,7 @@
 import 'dart:typed_data';
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
-import 'package:ui/src/engine.dart';
+import 'package:ui/src/engine/ulps.dart';
 
 void main() {
   internalBootstrapBrowserTest(() => testMain);
diff --git a/lib/web_ui/test/engine/web_experiments_test.dart b/lib/web_ui/test/engine/web_experiments_test.dart
index c38de84767e7e..18a665b2249f8 100644
--- a/lib/web_ui/test/engine/web_experiments_test.dart
+++ b/lib/web_ui/test/engine/web_experiments_test.dart
@@ -8,7 +8,7 @@ import 'dart:js_util' as js_util;
 
 import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
-import 'package:ui/src/engine.dart';
+import 'package:ui/src/engine/web_experiments.dart';
 
 const bool _defaultUseCanvasText = true;
 const bool _defaultUseCanvasRichText = true;
diff --git a/web_sdk/sdk_rewriter.dart b/web_sdk/sdk_rewriter.dart
index 78122e9a3fe49..c0d894188fdcd 100644
--- a/web_sdk/sdk_rewriter.dart
+++ b/web_sdk/sdk_rewriter.dart
@@ -17,78 +17,159 @@ final ArgParser argParser = ArgParser()
   ..addMultiOption('input')
   ..addOption('stamp');
 
-const List<List<String>> uiPatterns = <List<String>>[
-  <String>['library ui;', 'library dart.ui;'],
-  <String>['part of ui;', 'part of dart.ui;'],
-  <String>[
-    r'''
+final List<Replacer> uiPatterns = <Replacer>[
+  AllReplacer('library ui;', 'library dart.ui;'),
+  AllReplacer('part of ui;', 'part of dart.ui;'),
+  AllReplacer(r'''
 import 'src/engine.dart' as engine;
-''',
-    r'''
+''', r'''
 import 'dart:_engine' as engine;
-'''
-  ],
-  <String>[
+'''),
+  AllReplacer(
     r'''
 export 'src/engine.dart'
 ''',
     r'''
 export 'dart:_engine'
 ''',
-  ],
+  ),
 ];
 
-const List<List<String>> enginePatterns = <List<String>>[
-  <String>['library engine;', 'library dart._engine;'],
-  <String>['part of engine;', 'part of dart._engine;'],
-  <String>[
-    r'''
+final List<Replacer> engineLibraryPatterns = <Replacer>[
+  AllReplacer('library engine;', 'library dart._engine;'),
+  AllReplacer(r'''
 import '../ui.dart' as ui;
-''',
-    r'''
+''', r'''
+import 'dart:ui' as ui;
+'''),
+  AllReplacer(r'''
+import 'package:ui/ui.dart' as ui;
+''', r'''
 import 'dart:ui' as ui;
-'''
-  ],
-  <String>[
+'''),
+  // Remove imports of engine part files.
+  AllReplacer(RegExp(r"import 'engine/.*';"), ''),
+  // Replace exports of engine files with "part" directives.
+  MappedReplacer(RegExp(r'''
+export 'engine/(.*)';
+'''), (Match match) => '''
+part 'engine/${match.group(1)}';
+'''),
+  AllReplacer(
     'import \'package:js/js.dart\'',
     'import \'dart:_js_annotations\'',
-  ],
+  ),
 ];
 
-const List<List<String>> sharedPatterns = <List<String>>[
-  <String>["import 'package:meta/meta.dart';", ''],
-  <String>['@required', ''],
-  <String>['@protected', ''],
-  <String>['@mustCallSuper', ''],
-  <String>['@immutable', ''],
-  <String>['@visibleForTesting', '']
+final List<Replacer> enginePartsPatterns = <Replacer>[
+  AllReplacer('part of engine;', 'part of dart._engine;'),
+  // Remove library-level JS annotations.
+  AllReplacer(RegExp(r'\n@JS(.*)\nlibrary .+;'), ''),
+  // Remove library directives.
+  AllReplacer(RegExp(r'\nlibrary .+;'), ''),
+  // Remove imports/exports from all engine parts.
+  AllReplacer(RegExp(r'import .*'), ''),
+  AllReplacer(RegExp(r'export .*'), ''),
+];
+
+final List<Replacer> sharedPatterns = <Replacer>[
+  AllReplacer("import 'package:meta/meta.dart';", ''),
+  AllReplacer('@required', ''),
+  AllReplacer('@protected', ''),
+  AllReplacer('@mustCallSuper', ''),
+  AllReplacer('@immutable', ''),
+  AllReplacer('@visibleForTesting', ''),
 ];
 
 // Rewrites the "package"-style web ui library into a dart:ui implementation.
 // So far this only requires a replace of the library declarations.
 void main(List<String> arguments) {
   final ArgResults results = argParser.parse(arguments);
-  final Directory directory = Directory(results['output-dir']);
-  final String inputDirectoryPath = results['input-dir'];
-  for (String inputFilePath in results['input']) {
+  final Directory directory = Directory(results['output-dir'] as String);
+  final String inputDirectoryPath = results['input-dir'] as String;
+  for (final String inputFilePath in results['input'] as Iterable<String>) {
     final File inputFile = File(inputFilePath);
     final File outputFile = File(path.join(
         directory.path, inputFile.path.substring(inputDirectoryPath.length)))
       ..createSync(recursive: true);
     String source = inputFile.readAsStringSync();
-    final List<List<String>> replacementPatterns = <List<String>>[];
+    final List<Replacer> replacementPatterns = <Replacer>[];
     replacementPatterns.addAll(sharedPatterns);
-    if (results['ui']) {
+    if (results['ui'] as bool) {
       replacementPatterns.addAll(uiPatterns);
-    } else if (results['engine']) {
-      replacementPatterns.addAll(enginePatterns);
+    } else if (results['engine'] as bool) {
+      if (inputFilePath.endsWith('lib/src/engine.dart')) {
+        replacementPatterns.addAll(engineLibraryPatterns);
+      } else {
+        source = _preprocessEnginePartFile(source);
+        replacementPatterns.addAll(enginePartsPatterns);
+      }
     }
-    for (List<String> patterns in replacementPatterns) {
-      source = source.replaceAll(patterns.first, patterns.last);
+    for (final Replacer replacer in replacementPatterns) {
+      source = replacer.perform(source);
     }
     outputFile.writeAsStringSync(source);
     if (results['stamp'] != null) {
-      File(results['stamp']).writeAsStringSync("stamp");
+      File(results['stamp'] as String).writeAsStringSync('stamp');
     }
   }
 }
+
+final RegExp _dartLangVersion = RegExp(r'\n// @dart = (.*)');
+
+String _preprocessEnginePartFile(String source) {
+  if (source.contains('\npart of engine;')) {
+    // The file hasn't been migrated yet.
+    // Do nothing.
+  } else if (_dartLangVersion.hasMatch(source)) {
+    // The file contains a dart language version. We should insert the part
+    // directive after it.
+    source = source.replaceFirstMapped(_dartLangVersion, (Match match) {
+      return '${match.group(0)}\npart of engine;';
+    });
+  } else {
+    // The file doesn't have a dart language version, so we just insert the part
+    // directive at the beginning.
+    source = 'part of engine;\n' + source;
+  }
+  return source;
+}
+
+/// Responsible for performing string replacements.
+abstract class Replacer {
+  /// Performs the replacement in the provided [text].
+  String perform(String text);
+}
+
+/// Replaces all occurrences of a pattern with a fixed string.
+class AllReplacer implements Replacer {
+  /// Creates a new tuple with the given [pattern] and [replacement] string.
+  AllReplacer(this._pattern, this._replacement);
+
+  /// The pattern to be replaced.
+  final Pattern _pattern;
+
+  /// The replacement string.
+  final String _replacement;
+
+  @override
+  String perform(String text) {
+    return text.replaceAll(_pattern, _replacement);
+  }
+}
+
+/// Uses a callback to replace each occurrence of a pattern.
+class MappedReplacer implements Replacer {
+  MappedReplacer(this._pattern, this._replace);
+
+  /// The pattern to be replaced.
+  final RegExp _pattern;
+
+  /// A callback to replace each occurrence of [_pattern].
+  final String Function(Match match) _replace;
+
+  @override
+  String perform(String text) {
+    return text.replaceAllMapped(_pattern, _replace);
+  }
+}

From 30e445560364b4658143ddf01b5bc018d57cb99b Mon Sep 17 00:00:00 2001
From: Mouad Debbar <mdebbar@google.com>
Date: Wed, 14 Apr 2021 09:58:15 -0700
Subject: [PATCH 2/4] add navigation.dart and services.dart

---
 lib/web_ui/lib/src/engine/navigation.dart | 8 ++++++++
 lib/web_ui/lib/src/engine/services.dart   | 9 +++++++++
 lib/web_ui/test/engine/history_test.dart  | 6 ++----
 3 files changed, 19 insertions(+), 4 deletions(-)
 create mode 100644 lib/web_ui/lib/src/engine/navigation.dart
 create mode 100644 lib/web_ui/lib/src/engine/services.dart

diff --git a/lib/web_ui/lib/src/engine/navigation.dart b/lib/web_ui/lib/src/engine/navigation.dart
new file mode 100644
index 0000000000000..cd9b9de1d2d4e
--- /dev/null
+++ b/lib/web_ui/lib/src/engine/navigation.dart
@@ -0,0 +1,8 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart = 2.12
+export 'navigation/history.dart';
+export 'navigation/js_url_strategy.dart';
+export 'navigation/url_strategy.dart';
\ No newline at end of file
diff --git a/lib/web_ui/lib/src/engine/services.dart b/lib/web_ui/lib/src/engine/services.dart
new file mode 100644
index 0000000000000..e15100973e2b1
--- /dev/null
+++ b/lib/web_ui/lib/src/engine/services.dart
@@ -0,0 +1,9 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart = 2.12
+export 'services/buffers.dart';
+export 'services/message_codec.dart';
+export 'services/message_codecs.dart';
+export 'services/serialization.dart';
\ No newline at end of file
diff --git a/lib/web_ui/test/engine/history_test.dart b/lib/web_ui/test/engine/history_test.dart
index a4cc9514f1176..5a54daefbbb09 100644
--- a/lib/web_ui/test/engine/history_test.dart
+++ b/lib/web_ui/test/engine/history_test.dart
@@ -13,10 +13,8 @@ import 'package:test/bootstrap/browser.dart';
 import 'package:test/test.dart';
 import 'package:ui/src/engine.dart' show window;
 import 'package:ui/src/engine/browser_detection.dart';
-import 'package:ui/src/engine/navigation/history.dart';
-import 'package:ui/src/engine/navigation/url_strategy.dart';
-import 'package:ui/src/engine/services/message_codec.dart';
-import 'package:ui/src/engine/services/message_codecs.dart';
+import 'package:ui/src/engine/navigation.dart';
+import 'package:ui/src/engine/services.dart';
 import 'package:ui/src/engine/test_embedding.dart';
 
 import '../spy.dart';

From 05fe551895ebdc1417350f99655b0895f62e97c0 Mon Sep 17 00:00:00 2001
From: Mouad Debbar <mdebbar@google.com>
Date: Wed, 14 Apr 2021 10:43:26 -0700
Subject: [PATCH 3/4] licenses + explanation of transformations

---
 ci/licenses_golden/licenses_flutter | 2 ++
 lib/web_ui/lib/src/engine.dart      | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/ci/licenses_golden/licenses_flutter b/ci/licenses_golden/licenses_flutter
index 093f8c362cfd8..0b331014078dd 100755
--- a/ci/licenses_golden/licenses_flutter
+++ b/ci/licenses_golden/licenses_flutter
@@ -514,6 +514,7 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/key_map.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/keyboard.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/keyboard_binding.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/mouse_cursor.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/history.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/navigation/url_strategy.dart
@@ -537,6 +538,7 @@ FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/semantics.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/semantics_helper.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/tappable.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/semantics/text_field.dart
+FILE: ../../../flutter/lib/web_ui/lib/src/engine/services.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/services/buffers.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/services/message_codec.dart
 FILE: ../../../flutter/lib/web_ui/lib/src/engine/services/message_codecs.dart
diff --git a/lib/web_ui/lib/src/engine.dart b/lib/web_ui/lib/src/engine.dart
index 87a56cb6643ed..699270fc1c4e0 100644
--- a/lib/web_ui/lib/src/engine.dart
+++ b/lib/web_ui/lib/src/engine.dart
@@ -6,6 +6,15 @@
 @JS()
 library engine;
 
+// This file is transformed during the build process in order to make it a
+// single library. Some notable transformations:
+//
+// 1. Imports of engine/* files are stripped out.
+// 2. Exports of engine/* files are replaced with a part directive.
+//
+// The code that performs the transformations lives in:
+// - https://github.com/flutter/engine/blob/master/web_sdk/sdk_rewriter.dart
+
 import 'dart:async';
 import 'dart:collection'
     // Some of these names are used in services/buffers.dart for example.

From 8e1abd0218e257ab60cf09076991b1b52dd4eb36 Mon Sep 17 00:00:00 2001
From: Mouad Debbar <mdebbar@google.com>
Date: Mon, 19 Apr 2021 12:15:49 -0700
Subject: [PATCH 4/4] remove the dart language check

---
 web_sdk/sdk_rewriter.dart | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/web_sdk/sdk_rewriter.dart b/web_sdk/sdk_rewriter.dart
index c0d894188fdcd..dfa63e2652d6d 100644
--- a/web_sdk/sdk_rewriter.dart
+++ b/web_sdk/sdk_rewriter.dart
@@ -115,21 +115,12 @@ void main(List<String> arguments) {
   }
 }
 
-final RegExp _dartLangVersion = RegExp(r'\n// @dart = (.*)');
-
 String _preprocessEnginePartFile(String source) {
   if (source.contains('\npart of engine;')) {
     // The file hasn't been migrated yet.
     // Do nothing.
-  } else if (_dartLangVersion.hasMatch(source)) {
-    // The file contains a dart language version. We should insert the part
-    // directive after it.
-    source = source.replaceFirstMapped(_dartLangVersion, (Match match) {
-      return '${match.group(0)}\npart of engine;';
-    });
   } else {
-    // The file doesn't have a dart language version, so we just insert the part
-    // directive at the beginning.
+    // Insert the part directive at the beginning of the file.
     source = 'part of engine;\n' + source;
   }
   return source;