Fix error message on expression evaluation for module load error (#1542)

* Fix error message on expression evaluation for module load error

* Fix new analyze warning

* Updated changelog

* Addressed CR Comments

* Fix chrome teardown in tests

Author: Anna Gringauze

dwds/CHANGELOG.md

@@ -12,7 +12,7 @@
   restart.
 - Remove verbose printing on receiving DevTools events.
 - Update `vm_service` version to `^8.2.0`.
-
+- Update error message on expression evaluation using unloaded libraries.
 
 **Breaking changes:**
 - `Dwds.start` and `ExpressionCompilerService` now take

dwds/debug_extension/pubspec.yaml

@@ -1,7 +1,6 @@
 name: extension
 publish_to: none
 version: 1.27.0
-author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/dart-lang/webdev
 description: >-
   A chrome extension for Dart debugging.

dwds/lib/src/services/chrome_proxy_service.dart

@@ -215,7 +215,8 @@ class ChromeProxyService implements VmServiceInterface {
     // the expression compiler service will fail to start.
     // Issue: https://github.com/dart-lang/webdev/issues/1282
     var debugger = await _debugger;
-    await _initializeEntrypoint(appConnection.request.entrypointPath);
+    var entrypoint = appConnection.request.entrypointPath;
+    await _initializeEntrypoint(entrypoint);
     var sdkConfiguration = await _sdkConfigurationProvider.configuration;
 
     debugger.notifyPausedAtStart();
@@ -232,7 +233,13 @@ class ChromeProxyService implements VmServiceInterface {
 
     _expressionEvaluator = _compiler == null
         ? null
-        : ExpressionEvaluator(_inspector, _locations, _modules, _compiler);
+        : ExpressionEvaluator(
+            entrypoint,
+            _inspector,
+            _locations,
+            _modules,
+            _compiler,
+          );
 
     await debugger.reestablishBreakpoints(
         _previousBreakpoints, _disabledBreakpoints);

dwds/lib/src/services/expression_evaluator.dart

@@ -11,6 +11,7 @@ import '../debugging/dart_scope.dart';
 import '../debugging/inspector.dart';
 import '../debugging/location.dart';
 import '../debugging/modules.dart';
+import '../loaders/strategy.dart';
 import '../utilities/objects.dart' as chrome;
 import 'expression_compiler.dart';
 
@@ -23,6 +24,7 @@ class ErrorKind {
   static const ErrorKind reference = ErrorKind._('ReferenceError');
   static const ErrorKind internal = ErrorKind._('InternalError');
   static const ErrorKind invalidInput = ErrorKind._('InvalidInputError');
+  static const ErrorKind loadModule = ErrorKind._('LoadModuleError');
 
   @override
   String toString() => _kind;
@@ -33,17 +35,26 @@ class ErrorKind {
 /// collect context for evaluation (scope, types, modules), and using
 /// ExpressionCompilerInterface to compile dart expressions to JavaScript.
 class ExpressionEvaluator {
+  final String _entrypoint;
   final AppInspector _inspector;
   final Locations _locations;
   final Modules _modules;
   final ExpressionCompiler _compiler;
   final _logger = Logger('ExpressionEvaluator');
 
+  /// Strip synthetic library name from compiler error messages.
   static final _syntheticNameFilterRegex =
       RegExp('org-dartlang-debug:synthetic_debug_expression:.*:.*Error: ');
 
-  ExpressionEvaluator(
-      this._inspector, this._locations, this._modules, this._compiler);
+  /// Find module path from the XHR call network error message received from chrome.
+  ///
+  /// Example:
+  /// NetworkError: Failed to load 'http://<hostname>.com/path/to/module.js?<cache_busting_token>'
+  static final _loadModuleErrorRegex =
+      RegExp(r".*Failed to load '.*\.com/(.*\.js).*");
+
+  ExpressionEvaluator(this._entrypoint, this._inspector, this._locations,
+      this._modules, this._compiler);
 
   RemoteObject _createError(ErrorKind severity, String message) {
     return RemoteObject(
@@ -107,10 +118,10 @@ class ExpressionEvaluator {
           '  return $inner(t);'
           '}';
       result = await _inspector.callFunction(function, scope.values);
-      result = _formatEvaluationError(result);
+      result = await _formatEvaluationError(result);
     } else {
       result = await _inspector.debugger.evaluate(jsResult);
-      result = _formatEvaluationError(result);
+      result = await _formatEvaluationError(result);
     }
 
     _logger.finest('Evaluated "$expression" to "$result"');
@@ -199,7 +210,7 @@ class ExpressionEvaluator {
     // Send JS expression to chrome to evaluate.
     var result = await _inspector.debugger
         .evaluateJsOnCallFrameIndex(frameIndex, jsResult);
-    result = _formatEvaluationError(result);
+    result = await _formatEvaluationError(result);
 
     _logger.finest('Evaluated "$expression" to "$result"');
     return result;
@@ -240,16 +251,26 @@ class ExpressionEvaluator {
     return _createError(ErrorKind.compilation, error);
   }
 
-  RemoteObject _formatEvaluationError(RemoteObject result) {
+  Future<RemoteObject> _formatEvaluationError(RemoteObject result) async {
     if (result.type == 'string') {
       var error = '${result.value}';
       if (error.startsWith('ReferenceError: ')) {
         error = error.replaceFirst('ReferenceError: ', '');
         return _createError(ErrorKind.reference, error);
-      }
-      if (error.startsWith('TypeError: ')) {
+      } else if (error.startsWith('TypeError: ')) {
         error = error.replaceFirst('TypeError: ', '');
         return _createError(ErrorKind.type, error);
+      } else if (error.startsWith('NetworkError: ')) {
+        var modulePath = _loadModuleErrorRegex.firstMatch(error)?.group(1);
+        var module = modulePath != null
+            ? await globalLoadStrategy.moduleForServerPath(
+                _entrypoint, modulePath)
+            : 'unknown';
+        modulePath ??= 'unknown';
+        error = 'Module is not loaded : $module (path: $modulePath). '
+            'Accessing libraries that have not yet been used in the '
+            'application is not supported during expression evaluation.';
+        return _createError(ErrorKind.loadModule, error);
       }
     }
     return result;

dwds/test/build_daemon_evaluate_test.dart

@@ -493,7 +493,7 @@ void main() async {
             });
           });
 
-          test('error', () async {
+          test('compilation error', () async {
             await onBreakPoint(isolate.id, mainScript, 'printLocal', () async {
               var event = await stream.firstWhere(
                   (event) => event.kind == EventKind.kPauseBreakpoint);
@@ -508,6 +508,21 @@ void main() async {
             });
           });
 
+          test('module load error', () async {
+            await onBreakPoint(isolate.id, mainScript, 'printLocal', () async {
+              var event = await stream.firstWhere(
+                  (event) => event.kind == EventKind.kPauseBreakpoint);
+
+              var error = await setup.service.evaluateInFrame(
+                  isolate.id, event.topFrame.index, 'd.deferredPrintLocal()');
+
+              expect(
+                  error,
+                  isA<ErrorRef>().having((instance) => instance.message,
+                      'message', contains('LoadModuleError:')));
+            });
+          }, skip: 'https://github.com/dart-lang/sdk/issues/48587');
+
           test('cannot evaluate in unsupported isolate', () async {
             await onBreakPoint(isolate.id, mainScript, 'printLocal', () async {
               var event = await stream.firstWhere(

dwds/test/frontend_server_evaluate_test.dart

@@ -413,6 +413,21 @@ void main() async {
                   contains('CompilationError:')));
         });
       });
+
+      test('module load error', () async {
+        await onBreakPoint(isolate.id, mainScript, 'printLocal', () async {
+          var event = await stream
+              .firstWhere((event) => event.kind == EventKind.kPauseBreakpoint);
+
+          var error = await setup.service.evaluateInFrame(
+              isolate.id, event.topFrame.index, 'd.deferredPrintLocal()');
+
+          expect(
+              error,
+              isA<ErrorRef>().having((instance) => instance.message, 'message',
+                  contains('LoadModuleError:')));
+        });
+      }, skip: 'https://github.com/dart-lang/sdk/issues/48587');
     });
 
     group('evaluate', () {

fixtures/_test/lib/deferred_library.dart

@@ -0,0 +1,10 @@
+// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// A library that we can import.
+library test_deferred_library;
+
+void deferredPrintLocal() {
+  print('hello from deferred library'); // Breakpoint: DeferredPrintLocal
+}

fixtures/_testPackage/web/main.dart

@@ -8,6 +8,7 @@ import 'dart:async';
 import 'dart:core';
 import 'dart:html';
 
+import 'package:_test/deferred_library.dart' deferred as d;
 import 'package:_test/library.dart';
 import 'package:_test_package/test_library.dart';
 
@@ -94,6 +95,10 @@ void printLoopVariable() {
   }
 }
 
+Future<void> printDeferred() async {
+  d.deferredPrintLocal();
+}
+
 class MainClass {
   final int _field;
   MainClass(this._field);

fixtures/_testPackageSound/web/main.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 import 'dart:core';
 import 'dart:html';
 
+import 'package:_test/deferred_library.dart' deferred as d;
 import 'package:_test/library.dart';
 import 'package:_test_package/test_library.dart';
 
@@ -103,6 +104,10 @@ void printLoopVariable() {
   }
 }
 
+Future<void> printDeferred() async {
+  d.deferredPrintLocal();
+}
+
 class MainClass {
   final int _field;
   MainClass(this._field);

fixtures/_testSound/lib/deferred_library.dart

@@ -0,0 +1,10 @@
+// Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// A library that we can import.
+library test_deferred_library;
+
+void deferredPrintLocal() {
+  print('hello from deferred library'); // Breakpoint: DeferredPrintLocal
+}