Convert JavaScript uncaught exception stack traces to Dart stacks (#1603)

* Convert JavaScript uncaught exception stack traces to Dart stacks

Fixes #1265
Fixes flutter/flutter#101888

* Built

Author: jason-simmons

dwds/CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 14.0.3-dev
 - Make data types null safe
 - Update `package:vm_service` to 8.3.0.
+- Convert JavaScript stack traces in uncaught exceptions to Dart stack traces.
 
 ## 14.0.2
 - Update the min SDK constraint to 2.17.0.

dwds/lib/src/debugging/debugger.dart

@@ -558,8 +558,10 @@ class Debugger extends Domain {
           if (isNativeJsObject(exception)) {
             if (obj.description != null) {
               // Create a string exception object.
-              exception = await inspector.instanceHelper
-                  .instanceRefFor(obj.description);
+              var description =
+                  await inspector.mapExceptionStackTrace(obj.description);
+              exception =
+                  await inspector.instanceHelper.instanceRefFor(description);
             } else {
               exception = null;
             }

dwds/lib/src/debugging/inspector.dart

@@ -67,6 +67,12 @@ class AppInspector extends Domain {
   final String _root;
   final SdkConfiguration _sdkConfiguration;
 
+  /// JavaScript expression that evaluates to the Dart stack trace mapper.
+  static const stackTraceMapperExpression = '\$dartStackTraceUtility.mapper';
+
+  /// Regex used to extract the message from an exception description.
+  static final exceptionMessageRegex = RegExp(r'^.*$', multiLine: true);
+
   AppInspector._(
     this.appConnection,
     this.isolate,
@@ -223,7 +229,7 @@ class AppInspector extends Domain {
   /// [evalExpression] should be a JS function definition that can accept
   /// [arguments].
   Future<RemoteObject> _jsCallFunction(
-      String evalExpression, List<RemoteObject> arguments,
+      String evalExpression, List<Object> arguments,
       {bool returnByValue = false}) async {
     var jsArguments = arguments.map(callArgumentFor).toList();
     var result =
@@ -550,4 +556,23 @@ function($argsString) {
     handleErrorIfPresent(extensionsResult, evalContents: expression);
     return List.from(extensionsResult.result['result']['value'] as List);
   }
+
+  /// Convert a JS exception description into a description containing
+  /// a Dart stack trace.
+  Future<String> mapExceptionStackTrace(String description) async {
+    RemoteObject mapperResult;
+    try {
+      mapperResult = await _jsCallFunction(
+          stackTraceMapperExpression, <Object>[description]);
+    } catch (_) {
+      return description;
+    }
+    var mappedStack = mapperResult?.value?.toString();
+    if (mappedStack == null || mappedStack.isEmpty) {
+      return description;
+    }
+    var message = exceptionMessageRegex.firstMatch(description)?.group(0);
+    message = (message != null) ? '$message\n' : '';
+    return '$message$mappedStack';
+  }
 }

dwds/lib/src/injected/client.js

@@ -842,15 +842,19 @@ ${globalLoadStrategy.loadModuleSnippet}("dart_sdk").developer.invokeExtension(
           ..timestamp = e.timestamp.toInt());
       });
       if (includeExceptions) {
-        exceptionsSubscription = remoteDebugger.onExceptionThrown.listen((e) {
+        exceptionsSubscription =
+            remoteDebugger.onExceptionThrown.listen((e) async {
           var isolate = _inspector?.isolate;
           if (isolate == null) return;
+          var description = e.exceptionDetails.exception.description;
+          if (description != null) {
+            description = await _inspector.mapExceptionStackTrace(description);
+          }
           controller.add(Event(
               kind: EventKind.kWriteEvent,
               timestamp: DateTime.now().millisecondsSinceEpoch,
               isolate: _inspector.isolateRef)
-            ..bytes = base64.encode(
-                utf8.encode(e.exceptionDetails.exception.description ?? '')));
+            ..bytes = base64.encode(utf8.encode(description ?? '')));
         });
       }
     });

dwds/lib/src/services/chrome_proxy_service.dart

@@ -1129,6 +1129,8 @@ void main() {
         var event = await stream
             .firstWhere((event) => event.kind == EventKind.kPauseException);
         expect(event.exception, isNotNull);
+        // Check that the exception stack trace has been mapped to Dart source files.
+        expect(event.exception.valueAsString, contains('main.dart'));
 
         var stack = await service.getStack(isolateId);
         expect(stack, isNotNull);
@@ -1660,6 +1662,18 @@ void main() {
         await tabConnection.runtime.evaluate('console.error("Error");');
       });
 
+      test('exception stack trace mapper', () async {
+        expect(service.streamListen('Stderr'), completion(_isSuccess));
+        var stderrStream = service.onEvent('Stderr');
+        expect(
+            stderrStream,
+            emitsThrough(predicate((Event event) =>
+                event.kind == EventKind.kWriteEvent &&
+                String.fromCharCodes(base64.decode(event.bytes))
+                    .contains('main.dart'))));
+        await tabConnection.runtime.evaluate('throwUncaughtException();');
+      });
+
       test('VM', () async {
         var status = await service.streamListen('VM');
         expect(status, _isSuccess);

dwds/test/chrome_proxy_service_test.dart

@@ -55,6 +55,10 @@ void main() async {
     log(message, name: 'testLogCategory');
   };
 
+  context['throwUncaughtException'] = () {
+    scheduleMicrotask(() => throw Exception('UncaughtException'));
+  };
+
   Timer.periodic(const Duration(seconds: 1), (_) {
     printCount(); // Breakpoint: callPrintCount
   });

fixtures/_test/example/hello_world/main.dart

@@ -55,6 +55,10 @@ void main() async {
     log(message, name: 'testLogCategory');
   };
 
+  context['throwUncaughtException'] = () {
+    scheduleMicrotask(() => throw Exception('UncaughtException'));
+  };
+
   Timer.periodic(const Duration(seconds: 1), (_) {
     printCount(); // Breakpoint: callPrintCount
   });