Make extension methods more readable on dart2js stacktraces

Change-Id: I776b78c5a8742aad5ccc9aa4ffbc86827aacba96
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118205
Commit-Queue: Sigmund Cherem <sigmund@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

pkg/compiler/lib/src/io/kernel_source_information.dart

@@ -42,6 +42,11 @@ String computeKernelElementNameForSourceMaps(
     [CallStructure callStructure]) {
   MemberDefinition definition = elementMap.getMemberDefinition(member);
   switch (definition.kind) {
+    case MemberKind.regular:
+      ir.Member node = definition.node;
+      if (node.isExtensionMember) return _findExtensionMemberName(node);
+      return computeElementNameForSourceMaps(member, callStructure);
+
     case MemberKind.closureCall:
       ir.TreeNode node = definition.node;
       String name;
@@ -70,6 +75,32 @@ String computeKernelElementNameForSourceMaps(
   }
 }
 
+/// Extract a simple readable name for an extension member.
+String _findExtensionMemberName(ir.Member member) {
+  assert(member.isExtensionMember);
+  for (ir.Extension extension in member.enclosingLibrary.extensions) {
+    for (ir.ExtensionMemberDescriptor descriptor in extension.members) {
+      if (descriptor.member == member.reference) {
+        String extensionName;
+        // Anonymous extensions contain a # on their synthetic name.
+        if (extension.name.contains('#')) {
+          ir.DartType type = extension.onType;
+          if (type is ir.InterfaceType) {
+            extensionName = "${type.classNode.name}.<anonymous extension>";
+          } else {
+            extensionName = "<anonymous extension>";
+          }
+        } else {
+          extensionName = extension.name;
+        }
+        String memberName = descriptor.name.name;
+        return '$extensionName.$memberName';
+      }
+    }
+  }
+  throw StateError('No original name found for extension member $member.');
+}
+
 /// [SourceInformationBuilder] that generates [PositionSourceInformation] from
 /// Kernel nodes.
 class KernelSourceInformationBuilder implements SourceInformationBuilder {

pkg/compiler/testing.json

@@ -16,7 +16,8 @@
     "exclude": [
       "^tests/compiler/dart2js/.*/data/.*",
       "^tests/compiler/dart2js/.*/model_data/.*",
-      "^tests/compiler/dart2js/deferred_loading/libs/.*"
+      "^tests/compiler/dart2js/deferred_loading/libs/.*",
+      "^tests/compiler/dart2js/sourcemaps/stacktrace/extension_method.dart"
     ]
   }
 }

tests/compiler/dart2js/sourcemaps/stacktrace/extension_method.dart

@@ -0,0 +1,72 @@
+class MyClass {
+  MyClass();
+
+  @pragma('dart2js:noInline')
+  set internalSetter(int v) {
+    /*7:MyClass.internalSetter*/ throw "error";
+  }
+}
+
+int q = 3;
+
+extension Ext on MyClass {
+  @pragma('dart2js:noInline')
+  int method() {
+    this./*6:Ext.method*/ internalSetter = 1;
+    // TODO(sigmund): remove once kernel preserves noInline pragmas. #38439
+    if (q > 29) return 3;
+    return 2;
+  }
+
+  @pragma('dart2js:noInline')
+  int get propertyB {
+    /*5:Ext.propertyB*/ method();
+    // TODO(sigmund): remove once kernel preserves noInline pragmas. #38439
+    if (q > 29) return 3;
+    return 2;
+  }
+
+  @pragma('dart2js:noInline')
+  set propertyA(int v) {
+    /*4:Ext.propertyA*/ propertyB;
+    // TODO(sigmund): remove once kernel preserves noInline pragmas. #38439
+    if (q > 29) return null;
+    return null;
+  }
+
+  @pragma('dart2js:noInline')
+  int operator+(int v) {
+    this./*3:Ext.+*/ propertyA = 2;
+    // TODO(sigmund): remove once kernel preserves noInline pragmas. #38439
+    if (q > 30) return 1;
+    return 3;
+  }
+
+  @pragma('dart2js:noInline')
+  int operator[](int v) {
+    this /*2:Ext.[]*/ + 2;
+    // TODO(sigmund): remove once kernel preserves noInline pragmas. #38439
+    if (q > 30) return 1;
+    return 3;
+  }
+}
+
+extension on MyClass {
+  @pragma('dart2js:noInline')
+  int method2() {
+    this/*1:MyClass.<anonymous extension>.method2*/[0];
+    // TODO(sigmund): remove once kernel preserves noInline pragmas. #38439
+    if (q > 29) return 3;
+    return 2;
+  }
+}
+
+@pragma('dart2js:noInline')
+confuse(x) => x;
+
+main() {
+  q++;
+  confuse(null);
+  MyClass x = confuse(new MyClass());
+  x. /*0:main*/method2();
+}

tests/compiler/dart2js/sourcemaps/stacktrace_test.dart

@@ -85,6 +85,7 @@ Future runTest(Test test, String config,
       '--libraries-spec=sdk/lib/libraries.json',
       '--packages=${Platform.packageConfig}',
       Flags.testMode,
+      '--enable-experiment=extension-methods',
       input,
     ]..addAll(options);
     print("Compiling dart2js ${arguments.join(' ')}");