Implement sass --embedded in pure JS mode

.github/workflows/test.yml

@@ -126,24 +126,40 @@ jobs:
         working-directory: sass-spec
 
   sass_spec_js_embedded:
-    name: 'JS API Tests | Embedded | Node ${{ matrix.node-version }} | ${{ matrix.os }}'
+    name: "JS API Tests | Embedded ${{ matrix.js && 'Pure JS' || 'Dart' }} | Node ${{ matrix.node-version }} | ${{ matrix.os }}"
     runs-on: ${{ matrix.os }}
     if: "github.event_name != 'pull_request' || !contains(github.event.pull_request.body, 'skip sass-embedded')"
 
     strategy:
       fail-fast: false
       matrix:
+        js: [true, false]
         os: [ubuntu-latest, windows-latest, macos-latest]
         node-version: ['lts/*']
         include:
           # Test older LTS versions
-          - os: ubuntu-latest
+          - js: true
+            os: ubuntu-latest
             dart_channel: stable
             node-version: lts/-1
-          - os: ubuntu-latest
+          - js: true
+            os: ubuntu-latest
             dart_channel: stable
             node-version: lts/-2
-          - os: ubuntu-latest
+          - js: true
+            os: ubuntu-latest
+            dart_channel: stable
+            node-version: lts/-3
+          - js: false
+            os: ubuntu-latest
+            dart_channel: stable
+            node-version: lts/-1
+          - js: false
+            os: ubuntu-latest
+            dart_channel: stable
+            node-version: lts/-2
+          - js: false
+            os: ubuntu-latest
             dart_channel: stable
             node-version: lts/-3
 
@@ -166,19 +182,13 @@ jobs:
       - name: Initialize embedded host
         run: |
           npm install
-          npm run init -- --compiler-path=.. --language-path=../build/language
+          npm run init -- --compiler-path=.. --language-path=../build/language --compiler-js=${{ matrix.js && 'true' || 'false' }}
           npm run compile
-          mv {`pwd`/,dist/}lib/src/vendor/dart-sass
         working-directory: embedded-host-node
 
       - name: Version info
-        run: |
-          path=embedded-host-node/dist/lib/src/vendor/dart-sass/sass
-          if [[ -f "$path.cmd" ]]; then "./$path.cmd" --version
-          elif [[ -f "$path.bat" ]]; then "./$path.bat" --version
-          elif [[ -f "$path.exe" ]]; then "./$path.exe" --version
-          else "./$path" --version
-          fi
+        run: node dist/bin/sass.js --version
+        working-directory: embedded-host-node
 
       - name: Run tests
         run: npm run js-api-spec -- --sassPackage ../embedded-host-node --sassSassRepo ../build/language

README.md

@@ -434,9 +434,7 @@ an API for users to invoke Sass and define custom functions and importers.
 * `sass --embedded --version` prints `versionResponse` with `id = 0` in JSON and
   exits.
 
-The `--embedded` command-line flag is not available when you install Dart Sass
-as an [npm package]. No other command-line flags are supported with
-`--embedded`.
+No other command-line flags are supported with `--embedded`.
 
 [npm package]: #from-npm
 

bin/sass.dart

@@ -18,8 +18,7 @@ import 'package:sass/src/io.dart';
 import 'package:sass/src/stylesheet_graph.dart';
 import 'package:sass/src/utils.dart';
 import 'package:sass/src/embedded/executable.dart'
-    // Never load the embedded protocol when compiling to JS.
-    if (dart.library.js) 'package:sass/src/embedded/unavailable.dart'
+    if (dart.library.js) 'package:sass/src/embedded/js/executable.dart'
     as embedded;
 
 Future<void> main(List<String> args) async {

lib/src/embedded/compilation_dispatcher.dart

@@ -3,17 +3,17 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:convert';
-import 'dart:io';
-import 'dart:isolate';
+import 'dart:io' if (dart.library.js) 'js/io.dart';
+import 'dart:isolate' if (dart.library.js) 'js/isolate.dart';
 import 'dart:typed_data';
 
-import 'package:native_synchronization/mailbox.dart';
 import 'package:path/path.dart' as p;
 import 'package:protobuf/protobuf.dart';
 import 'package:pub_semver/pub_semver.dart';
 import 'package:sass/sass.dart' as sass;
 import 'package:sass/src/importer/node_package.dart' as npi;
 
+import '../io.dart' show FileSystemException;
 import '../logger.dart';
 import '../value/function.dart';
 import '../value/mixin.dart';
@@ -23,6 +23,7 @@ import 'host_callable.dart';
 import 'importer/file.dart';
 import 'importer/host.dart';
 import 'logger.dart';
+import 'sync_receive_port.dart';
 import 'util/proto_extensions.dart';
 import 'utils.dart';
 
@@ -35,8 +36,8 @@ final _outboundRequestId = 0;
 /// A class that dispatches messages to and from the host for a single
 /// compilation.
 final class CompilationDispatcher {
-  /// The mailbox for receiving messages from the host.
-  final Mailbox _mailbox;
+  /// The synchronous receive port for receiving messages from the host.
+  final SyncReceivePort _receivePort;
 
   /// The send port for sending messages to the host.
   final SendPort _sendPort;
@@ -52,8 +53,8 @@ final class CompilationDispatcher {
   late Uint8List _compilationIdVarint;
 
   /// Creates a [CompilationDispatcher] that receives encoded protocol buffers
-  /// through [_mailbox] and sends them through [_sendPort].
-  CompilationDispatcher(this._mailbox, this._sendPort);
+  /// through [_receivePort] and sends them through [_sendPort].
+  CompilationDispatcher(this._receivePort, this._sendPort);
 
   /// Listens for incoming `CompileRequests` and runs their compilations.
   void listen() {
@@ -366,14 +367,14 @@ final class CompilationDispatcher {
     message.writeToCodedBufferWriter(protobufWriter);
 
     // Add one additional byte to the beginning to indicate whether or not the
-    // compilation has finished (1) or encountered a fatal error (2), so the
-    // [IsolateDispatcher] knows whether to treat this isolate as inactive or
-    // close out entirely.
+    // compilation has finished (1) or encountered a fatal error (exitCode), so
+    // the [IsolateDispatcher] knows whether to treat this isolate as inactive
+    // or close out entirely.
     var packet = Uint8List(
         1 + _compilationIdVarint.length + protobufWriter.lengthInBytes);
     packet[0] = switch (message.whichMessage()) {
       OutboundMessage_Message.compileResponse => 1,
-      OutboundMessage_Message.error => 2,
+      OutboundMessage_Message.error => exitCode,
       _ => 0
     };
     packet.setAll(1, _compilationIdVarint);
@@ -384,9 +385,9 @@ final class CompilationDispatcher {
   /// Receive a packet from the host.
   Uint8List _receive() {
     try {
-      return _mailbox.take();
+      return _receivePort.receive();
     } on StateError catch (_) {
-      // The [_mailbox] has been closed, exit the current isolate immediately
+      // The [SyncReceivePort] has been closed, exit the current isolate immediately
       // to avoid bubble the error up as [SassException] during [_sendRequest].
       Isolate.exit();
     }

lib/src/embedded/concurrency.dart

@@ -0,0 +1,10 @@
+// Copyright 2024 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'dart:ffi';
+
+/// More than MaxMutatorThreadCount isolates in the same isolate group
+/// can deadlock the Dart VM.
+/// See https://github.com/sass/dart-sass/pull/2019
+int get concurrencyLimit => sizeOf<IntPtr>() <= 4 ? 7 : 15;

lib/src/embedded/executable.dart

@@ -3,35 +3,19 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:io';
-import 'dart:convert';
 
 import 'package:stream_channel/stream_channel.dart';
 
 import 'isolate_dispatcher.dart';
+import 'options.dart';
 import 'util/length_delimited_transformer.dart';
 
 void main(List<String> args) {
-  switch (args) {
-    case ["--version", ...]:
-      var response = IsolateDispatcher.versionResponse();
-      response.id = 0;
-      stdout.writeln(
-          JsonEncoder.withIndent("  ").convert(response.toProto3Json()));
-      return;
-
-    case [_, ...]:
-      stderr.writeln(
-          "sass --embedded is not intended to be executed with additional "
-          "arguments.\n"
-          "See https://github.com/sass/dart-sass#embedded-dart-sass for "
-          "details.");
-      // USAGE error from https://bit.ly/2poTt90
-      exitCode = 64;
-      return;
+  if (parseOptions(args)) {
+    IsolateDispatcher(
+            StreamChannel.withGuarantees(stdin, stdout, allowSinkErrors: false)
+                .transform(lengthDelimited),
+            gracefulShutdown: false)
+        .listen();
   }
-
-  IsolateDispatcher(
-          StreamChannel.withGuarantees(stdin, stdout, allowSinkErrors: false)
-              .transform(lengthDelimited))
-      .listen();
 }

lib/src/embedded/isolate_dispatcher.dart

@@ -3,19 +3,17 @@
 // https://opensource.org/licenses/MIT.
 
 import 'dart:async';
-import 'dart:ffi';
-import 'dart:io';
-import 'dart:isolate';
+import 'dart:io' if (dart.library.js) 'js/io.dart';
 import 'dart:typed_data';
 
-import 'package:native_synchronization/mailbox.dart';
 import 'package:pool/pool.dart';
 import 'package:protobuf/protobuf.dart';
 import 'package:stream_channel/stream_channel.dart';
 
-import 'compilation_dispatcher.dart';
+import 'concurrency.dart' if (dart.library.js) 'js/concurrency.dart';
 import 'embedded_sass.pb.dart';
-import 'reusable_isolate.dart';
+import 'isolate_main.dart' if (dart.library.js) 'js/isolate_main.dart';
+import 'reusable_isolate.dart' if (dart.library.js) 'js/reusable_isolate.dart';
 import 'util/proto_extensions.dart';
 import 'utils.dart';
 
@@ -25,6 +23,10 @@ class IsolateDispatcher {
   /// The channel of encoded protocol buffers, connected to the host.
   final StreamChannel<Uint8List> _channel;
 
+  /// Whether to wait for all worker isolates to exit before exiting the main
+  /// isolate or not.
+  final bool _gracefulShutdown;
+
   /// All isolates that have been spawned to dispatch to.
   ///
   /// Only used for cleaning up the process when the underlying channel closes.
@@ -38,16 +40,13 @@ class IsolateDispatcher {
 
   /// A pool controlling how many isolates (and thus concurrent compilations)
   /// may be live at once.
-  ///
-  /// More than MaxMutatorThreadCount isolates in the same isolate group
-  /// can deadlock the Dart VM.
-  /// See https://github.com/sass/dart-sass/pull/2019
-  final _isolatePool = Pool(sizeOf<IntPtr>() <= 4 ? 7 : 15);
+  final _isolatePool = Pool(concurrencyLimit);
 
   /// Whether [_channel] has been closed or not.
   var _closed = false;
 
-  IsolateDispatcher(this._channel);
+  IsolateDispatcher(this._channel, {bool gracefulShutdown = true})
+      : _gracefulShutdown = gracefulShutdown;
 
   void listen() {
     _channel.stream.listen((packet) async {
@@ -96,8 +95,12 @@ class IsolateDispatcher {
     }, onError: (Object error, StackTrace stackTrace) {
       _handleError(error, stackTrace);
     }, onDone: () {
-      _closed = true;
-      _allIsolates.stream.listen((isolate) => isolate.kill());
+      if (_gracefulShutdown) {
+        _closed = true;
+        _allIsolates.stream.listen((isolate) => isolate.kill());
+      } else {
+        exit(exitCode);
+      }
     });
   }
 
@@ -112,7 +115,7 @@ class IsolateDispatcher {
       isolate = _inactiveIsolates.first;
       _inactiveIsolates.remove(isolate);
     } else {
-      var future = ReusableIsolate.spawn(_isolateMain,
+      var future = ReusableIsolate.spawn(isolateMain,
           onError: (Object error, StackTrace stackTrace) {
         _handleError(error, stackTrace);
       });
@@ -124,11 +127,11 @@ class IsolateDispatcher {
       var fullBuffer = message as Uint8List;
 
       // The first byte of messages from isolates indicates whether the entire
-      // compilation is finished (1) or if it encountered an error (2). Sending
-      // this as part of the message buffer rather than a separate message
-      // avoids a race condition where the host might send a new compilation
-      // request with the same ID as one that just finished before the
-      // [IsolateDispatcher] receives word that the isolate with that ID is
+      // compilation is finished (1) or if it encountered an error (exitCode).
+      // Sending this as part of the message buffer rather than a separate
+      // message avoids a race condition where the host might send a new
+      // compilation request with the same ID as one that just finished before
+      // the [IsolateDispatcher] receives word that the isolate with that ID is
       // done. See sass/dart-sass#2004.
       var category = fullBuffer[0];
       var packet = Uint8List.sublistView(fullBuffer, 1);
@@ -142,9 +145,14 @@ class IsolateDispatcher {
           _inactiveIsolates.add(isolate);
           resource.release();
           _channel.sink.add(packet);
-        case 2:
+        default:
           _channel.sink.add(packet);
-          exit(exitCode);
+          exitCode = category;
+          if (_gracefulShutdown) {
+            _channel.sink.close();
+          } else {
+            exit(exitCode);
+          }
       }
     });
 
@@ -168,7 +176,11 @@ class IsolateDispatcher {
       {int? compilationId, int? messageId}) {
     sendError(compilationId ?? errorId,
         handleError(error, stackTrace, messageId: messageId));
-    _channel.sink.close();
+    if (_gracefulShutdown) {
+      _channel.sink.close();
+    } else {
+      exit(exitCode);
+    }
   }
 
   /// Sends [message] to the host.
@@ -179,7 +191,3 @@ class IsolateDispatcher {
   void sendError(int compilationId, ProtocolError error) =>
       _send(compilationId, OutboundMessage()..error = error);
 }
-
-void _isolateMain(Mailbox mailbox, SendPort sendPort) {
-  CompilationDispatcher(mailbox, sendPort).listen();
-}

lib/src/embedded/isolate_main.dart

@@ -0,0 +1,12 @@
+// Copyright 2024 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'dart:isolate' show SendPort;
+
+import 'compilation_dispatcher.dart';
+import 'sync_receive_port.dart';
+
+void isolateMain(SyncReceivePort receivePort, SendPort sendPort) {
+  CompilationDispatcher(receivePort, sendPort).listen();
+}

lib/src/embedded/js/concurrency.dart

@@ -0,0 +1,10 @@
+// Copyright 2024 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'dart:js_interop';
+
+@JS('os.cpus')
+external JSArray _cpus();
+
+int get concurrencyLimit => _cpus().length;