[wasm][debugger] Improvements in debugging in async methods

src/mono/wasm/debugger/BrowserDebugProxy/DebugStore.cs

@@ -320,6 +320,8 @@ public override bool Equals(object obj)
         public static bool operator !=(SourceId a, SourceId b) => !a.Equals(b);
     }
 
+    internal sealed record Scope (int Id, int StartOffset, int EndOffset);
+
     internal sealed class MethodInfo
     {
         private MethodDefinition methodDef;
@@ -350,6 +352,7 @@ internal sealed class MethodInfo
         private ParameterInfo[] _parametersInfo;
         public int KickOffMethod { get; }
         internal bool IsCompilerGenerated { get; }
+        internal List<Scope> AsyncScopes { get; }
 
         public MethodInfo(AssemblyInfo assembly, string methodName, int methodToken, TypeInfo type, MethodAttributes attrs)
         {
@@ -447,7 +450,24 @@ public MethodInfo(AssemblyInfo assembly, MethodDefinitionHandle methodDefHandle,
                 DebuggerAttrInfo.ClearInsignificantAttrFlags();
             }
             if (pdbMetadataReader != null)
+            {
                 localScopes = pdbMetadataReader.GetLocalScopes(methodDefHandle);
+                var scopeDebugInformation =
+                        (from cdiHandle in pdbMetadataReader.GetCustomDebugInformation(methodDefHandle)
+                        let cdi = pdbMetadataReader.GetCustomDebugInformation(cdiHandle)
+                        where pdbMetadataReader.GetGuid(cdi.Kind) == PortableCustomDebugInfoKinds.StateMachineHoistedLocalScopes
+                        select pdbMetadataReader.GetBlobBytes(cdi.Value)).SingleOrDefault();
+
+                if (scopeDebugInformation != null)
+                {
+                    AsyncScopes = new List<Scope>();
+                    for (int i = 0; i < scopeDebugInformation.Length; i += 8) {
+                        var offset = BitConverter.ToInt32 (scopeDebugInformation, i);
+                        var len = BitConverter.ToInt32 (scopeDebugInformation, i + 4);
+                        AsyncScopes.Add(new Scope((i / 8) + 1, offset, offset + len));
+                    }
+                }
+            }
         }
 
         public ParameterInfo[] GetParametersInfo()

src/mono/wasm/debugger/BrowserDebugProxy/MonoProxy.cs

@@ -1406,7 +1406,7 @@ internal async Task<GetMembersResult> GetScopeProperties(SessionId msg_id, int s
 
                 VarInfo[] varIds = scope.Method.Info.GetLiveVarsAt(scope.Location.IlLocation.Offset);
 
-                var values = await context.SdbAgent.StackFrameGetValues(scope.Method, context.ThreadId, scopeId, varIds, token);
+                var values = await context.SdbAgent.StackFrameGetValues(scope.Method, context.ThreadId, scopeId, varIds, scope.Location.IlLocation.Offset, token);
                 if (values != null)
                 {
                     if (values == null || values.Count == 0)

src/mono/wasm/debugger/BrowserDebugProxy/MonoSDBHelper.cs

@@ -804,7 +804,7 @@ internal sealed class MonoSDBHelper
         private SessionId sessionId;
 
         internal readonly ILogger logger;
-        private static readonly Regex regexForAsyncLocals = new (@"\<([^)]*)\>", RegexOptions.Singleline);
+        private static readonly Regex regexForAsyncLocals = new (@"\<([^)]*)\>([^)]*)([_][_])([0-9]*)", RegexOptions.Singleline);
         private static readonly Regex regexForAsyncMethodName = new (@"\<([^>]*)\>([d][_][_])([0-9]*)", RegexOptions.Compiled);
         private static readonly Regex regexForGenericArgs = new (@"[`][0-9]+", RegexOptions.Compiled);
         private static readonly Regex regexForNestedLeftRightAngleBrackets = new ("^(((?'Open'<)[^<>]*)+((?'Close-Open'>)[^<>]*)+)*(?(Open)(?!))[^<>]*", RegexOptions.Compiled);
@@ -1961,7 +1961,7 @@ private static bool IsClosureReferenceField (string fieldName)
                         fieldName.StartsWith ("<>8__", StringComparison.Ordinal);
         }
 
-        public async Task<JArray> GetHoistedLocalVariables(int objectId, IEnumerable<JToken> asyncLocals, CancellationToken token)
+        public async Task<JArray> GetHoistedLocalVariables(MethodInfoWithDebugInformation method, int objectId, IEnumerable<JToken> asyncLocals, int offset, CancellationToken token)
         {
             JArray asyncLocalsFull = new JArray();
             List<int> objectsAlreadyRead = new();
@@ -1982,7 +1982,7 @@ public async Task<JArray> GetHoistedLocalVariables(int objectId, IEnumerable<JTo
                         {
                             var asyncProxyMembersFromObject = await MemberObjectsExplorer.GetObjectMemberValues(
                                 this, dotnetObjectId.Value, GetObjectCommandOptions.WithProperties, token);
-                            var hoistedLocalVariable = await GetHoistedLocalVariables(dotnetObjectId.Value, asyncProxyMembersFromObject.Flatten(), token);
+                            var hoistedLocalVariable = await GetHoistedLocalVariables(method, dotnetObjectId.Value, asyncProxyMembersFromObject.Flatten(), offset, token);
                             asyncLocalsFull = new JArray(asyncLocalsFull.Union(hoistedLocalVariable));
                         }
                     }
@@ -1995,7 +1995,11 @@ public async Task<JArray> GetHoistedLocalVariables(int objectId, IEnumerable<JTo
                 {
                     var match = regexForAsyncLocals.Match(fieldName);
                     if (match.Success)
+                    {
+                        if (!method.Info.AsyncScopes.Where(s => s.Id == Convert.ToInt32(match.Groups[4].Value) && offset >= s.StartOffset && offset <= s.EndOffset).Any())
+                            continue;
                         asyncLocal["name"] = match.Groups[1].Value;
+                    }
                     asyncLocalsFull.Add(asyncLocal);
                 }
                 else
@@ -2006,7 +2010,7 @@ public async Task<JArray> GetHoistedLocalVariables(int objectId, IEnumerable<JTo
             return asyncLocalsFull;
         }
 
-        public async Task<JArray> StackFrameGetValues(MethodInfoWithDebugInformation method, int thread_id, int frame_id, VarInfo[] varIds, CancellationToken token)
+        public async Task<JArray> StackFrameGetValues(MethodInfoWithDebugInformation method, int thread_id, int frame_id, VarInfo[] varIds, int offset, CancellationToken token)
         {
             using var commandParamsWriter = new MonoBinaryWriter();
             commandParamsWriter.Write(thread_id);
@@ -2023,7 +2027,7 @@ public async Task<JArray> StackFrameGetValues(MethodInfoWithDebugInformation met
                 retDebuggerCmdReader.ReadByte(); //ignore type
                 var objectId = retDebuggerCmdReader.ReadInt32();
                 GetMembersResult asyncProxyMembers = await MemberObjectsExplorer.GetObjectMemberValues(this, objectId, GetObjectCommandOptions.WithProperties, token, includeStatic: true);
-                var asyncLocals = await GetHoistedLocalVariables(objectId, asyncProxyMembers.Flatten(), token);
+                var asyncLocals = await GetHoistedLocalVariables(method, objectId, asyncProxyMembers.Flatten(), offset, token);
                 return asyncLocals;
             }
 

src/mono/wasm/debugger/DebuggerTestSuite/AsyncTests.cs

@@ -81,5 +81,30 @@ public async Task AsyncLocalsInNestedContinueWithStaticBlock() => await CheckIns
                      ncs_dt0 = TDateTime(new DateTime(3412, 4, 6, 8, 0, 2))
                  }, "locals");
               });
+
+        [Fact]
+        public async Task InspectVariablesWithSameNameInDifferentScopes()
+        {
+            var expression = $"{{ invoke_static_method('[debugger-test] DebuggerTests.AsyncTests.VariablesWithSameNameDifferentScopes:Run'); }}";
+
+            await EvaluateAndCheck(
+                "window.setTimeout(function() {" + expression + "; }, 1);",
+                "dotnet://debugger-test.dll/debugger-async-test.cs", 249, 16,
+                "DebuggerTests.AsyncTests.VariablesWithSameNameDifferentScopes.RunFirstScope",
+                wait_for_event_fn: async (pause_location) =>
+                {
+                    var id = pause_location["callFrames"][0]["callFrameId"].Value<string>();
+                    await EvaluateOnCallFrameAndCheck(id,
+                        ("testFirstScope", TObject("System.Collections.Generic.List<string>", description: "Count = 2"))
+                    );
+                }
+            );
+            await StepAndCheck(StepKind.Resume, "dotnet://debugger-test.dll/debugger-async-test.cs", 273, 16, "DebuggerTests.AsyncTests.VariablesWithSameNameDifferentScopes.RunSecondScope",
+                locals_fn: async (locals) =>
+                {
+                    await CheckObject(locals, "testSecondScope", "System.Collections.Generic.List<string>", description: "Count = 2");
+                }
+            );
+        }
     }
 }

src/mono/wasm/debugger/tests/debugger-test/debugger-async-test.cs

@@ -230,4 +230,51 @@ await Task.Delay(300).ContinueWith(t2 =>
         }
     }
 
+    public class VariablesWithSameNameDifferentScopes
+    {
+        public static async System.Threading.Tasks.Task Run()
+        {
+            await RunFirstScope();
+            await RunSecondScope();
+        }
+
+        public static async System.Threading.Tasks.Task<System.Collections.Generic.List<string>> RunFirstScope()
+        {
+            await System.Threading.Tasks.Task.Delay(1);
+            int number = 10;
+            if (number < 999)
+            {
+                System.Collections.Generic.List<string> testFirstScope = new System.Collections.Generic.List<string>();
+                testFirstScope.Add("hello");
+                testFirstScope.Add("hi");
+                System.Diagnostics.Debugger.Break();
+                return testFirstScope;
+            }
+            else
+            {
+                System.Collections.Generic.List<string> testFirstScope = new System.Collections.Generic.List<string>();
+                return testFirstScope;
+            }
+        }
+
+        public static async System.Threading.Tasks.Task<System.Collections.Generic.List<string>> RunSecondScope()
+        {
+            await System.Threading.Tasks.Task.Delay(1);
+            int number = 10;
+            if (number < 5)
+            {
+                System.Collections.Generic.List<string> testSecondScope = new System.Collections.Generic.List<string>();
+                return testSecondScope;
+            }
+            else
+            {
+                System.Collections.Generic.List<string> testSecondScope = new System.Collections.Generic.List<string>();
+                testSecondScope.Add("hello");
+                testSecondScope.Add("hi");
+                System.Diagnostics.Debugger.Break();
+                return testSecondScope;
+            }
+        }
+    }
+
 }