Fix dart vm lockup during shutdown with pending requests (#2279)

Co-authored-by: Natalie Weizenbaum <[email protected]>

Author: ntkme

CHANGELOG.md

@@ -8,6 +8,9 @@
   intended. Now users can run `npx sass` for local installs or just `sass` when
   `sass-embedded` is installed globally.
 
+* Fix an edge case where the Dart VM could hang when shutting down when requests
+  were in flight.
+
 ## 1.77.8
 
 * No user-visible changes.

lib/src/embedded/compilation_dispatcher.dart

@@ -64,8 +64,12 @@ final class CompilationDispatcher {
   /// Listens for incoming `CompileRequests` and runs their compilations.
   void listen() {
     do {
-      var packet = _mailbox.take();
-      if (packet.isEmpty) break;
+      Uint8List packet;
+      try {
+        packet = _mailbox.take();
+      } on StateError catch (_) {
+        break;
+      }
 
       try {
         var (compilationId, messageBuffer) = parsePacket(packet);
@@ -322,12 +326,14 @@ final class CompilationDispatcher {
     message.id = _outboundRequestId;
     _send(message);
 
-    var packet = _mailbox.take();
-    if (packet.isEmpty) {
+    Uint8List packet;
+    try {
+      packet = _mailbox.take();
+    } on StateError catch (_) {
       // Compiler is shutting down, throw without calling `_handleError` as we
       // don't want to report this as an actual error.
       _requestError = true;
-      throw StateError('Compiler is shutting down.');
+      rethrow;
     }
 
     try {

lib/src/embedded/reusable_isolate.dart

@@ -122,10 +122,8 @@ class ReusableIsolate {
     _receivePort.close();
 
     // If the isolate is blocking on [Mailbox.take], it won't even process a
-    // kill event, so we send an empty message to make sure it wakes up.
-    try {
-      _mailbox.put(Uint8List(0));
-    } on StateError catch (_) {}
+    // kill event, so we closed the mailbox to nofity and wake it up.
+    _mailbox.close();
   }
 }
 

pubspec.yaml

@@ -20,7 +20,7 @@ dependencies:
   http: "^1.1.0"
   js: ^0.6.3
   meta: ^1.3.0
-  native_synchronization: ^0.2.0
+  native_synchronization: ^0.3.0
   node_interop: ^2.1.0
   package_config: ^2.0.0
   path: ^1.8.0