[wasm][debugger] Implement support for null-conditional operators in simple expressions

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

@@ -75,10 +75,9 @@ public async Task<JObject> GetValueFromObject(JToken objRet, CancellationToken t
  return null;
  }
 
- public async Task<(JObject containerObject, string remaining)> ResolveStaticMembersInStaticTypes(string varName, CancellationToken token)
+ public async Task<(JObject containerObject, string remaining)> ResolveStaticMembersInStaticTypes(string[] parts, CancellationToken token)
  {
  string classNameToFind = "";
- string[] parts = varName.Split(".", StringSplitOptions.TrimEntries);
  var store = await proxy.LoadStore(sessionId, token);
  var methodInfo = context.CallStack.FirstOrDefault(s => s.Id == scopeId)?.Method?.Info;
 
@@ -175,6 +174,10 @@ async Task<int> FindStaticTypeId(string typeName)
  // Checks Locals, followed by `this`
  public async Task<JObject> Resolve(string varName, CancellationToken token)
  {
+ // question mark at the end of expression is invalid
+ if (varName.LastOrDefault() == '?')
+ throw new ReturnAsErrorException($"Expected expression.", "ReferenceError");
+
  //has method calls
  if (varName.Contains('('))
  return null;
@@ -185,17 +188,25 @@ public async Task<JObject> Resolve(string varName, CancellationToken token)
  if (scopeCache.ObjectFields.TryGetValue(varName, out JObject valueRet))
  return await GetValueFromObject(valueRet, token);
 
- string[] parts = varName.Split(".");
+ string[] parts = varName.Split(".", StringSplitOptions.TrimEntries);
  if (parts.Length == 0)
  return null;
 
  JObject retObject = await ResolveAsLocalOrThisMember(parts[0]);
+ bool isRootNullSafe = parts[0].LastOrDefault() == '?';
  if (retObject != null && parts.Length > 1)
- retObject = await ResolveAsInstanceMember(string.Join('.', parts[1..]), retObject);
+ {
+ // cannot resolve instance member on a primitive type,
+ // try compiling to check if it's not a method on primitive
+ var typeName = retObject["className"]?.Value<string>();
+ if (MonoSDBHelper.IsPrimitiveType(typeName))
+ return null;
+ retObject = await ResolveAsInstanceMember(string.Join('.', parts[1..]), retObject, isRootNullSafe);
+ }
 
  if (retObject == null)
  {
- (retObject, string remaining) = await ResolveStaticMembersInStaticTypes(varName, token);
+ (retObject, string remaining) = await ResolveStaticMembersInStaticTypes(parts, token);
  if (!string.IsNullOrEmpty(remaining))
  {
  if (retObject.IsNullValuedObject())
@@ -205,7 +216,7 @@ public async Task<JObject> Resolve(string varName, CancellationToken token)
  }
  else
  {
- retObject = await ResolveAsInstanceMember(remaining, retObject);
+ retObject = await ResolveAsInstanceMember(remaining, retObject, isRootNullSafe);
  }
  }
  }
@@ -215,7 +226,6 @@ public async Task<JObject> Resolve(string varName, CancellationToken token)
 
  async Task<JObject> ResolveAsLocalOrThisMember(string name)
  {
- var nameTrimmed = name.Trim();
  if (scopeCache.Locals.Count == 0 && !localsFetched)
  {
  Result scope_res = await proxy.GetScopeProperties(sessionId, scopeId, token);
@@ -224,6 +234,11 @@ async Task<JObject> ResolveAsLocalOrThisMember(string name)
  localsFetched = true;
  }
 
+ var nameTrimmed = name.Trim();
+ // remove null-safety, otherwise TryGet by name fails
+ if (nameTrimmed.LastOrDefault() == '?')
+ nameTrimmed = nameTrimmed.Remove(nameTrimmed.Length - 1);
+
  if (scopeCache.Locals.TryGetValue(nameTrimmed, out JObject obj))
  return obj["value"]?.Value<JObject>();
 
@@ -247,8 +262,11 @@ async Task<JObject> ResolveAsLocalOrThisMember(string name)
  return null;
  }
 
- async Task<JObject> ResolveAsInstanceMember(string expr, JObject baseObject)
+ async Task<JObject> ResolveAsInstanceMember(string expr, JObject baseObject, bool isRootNullSafe)
  {
+ // if the prevPart has "?" at the end: true
+ bool isResolvedObjNullSafe = isRootNullSafe;
+ bool isPrevPartNull = false;
  JObject resolvedObject = baseObject;
  string[] parts = expr.Split('.');
  for (int i = 0; i < parts.Length; i++)
@@ -257,16 +275,42 @@ async Task<JObject> ResolveAsInstanceMember(string expr, JObject baseObject)
  if (partTrimmed.Length == 0)
  return null;
 
+ // current value of resolvedObject is on parts[i - 1]
+ if (isPrevPartNull || resolvedObject.IsNullValuedObject())
+ {
+ // trying null.$member
+ if (!isResolvedObjNullSafe)
+ throw new ReturnAsErrorException($"Cannot access member \"{partTrimmed}\" of a null-valued object.", "ReferenceError");
+
+ if (i == parts.Length - 1)
+ {
+ // this is not ideal, it returns the last object
+ // that had objectId and was null-valued,
+ // so the class/description of object are not of the last part
+ return resolvedObject;
+ }
+ // else: trying null?.$member... - allowed operation
+ isPrevPartNull = true;
+ }
+
+ bool isCurrentPartNullSafe = partTrimmed.Last() == '?';
+ isResolvedObjNullSafe = isCurrentPartNullSafe;
+
+ // cannot resolve the members but can check if nullSafety is
+ // correctly applied and if we should throw or return null-object
  if (!DotnetObjectId.TryParse(resolvedObject?["objectId"]?.Value<string>(), out DotnetObjectId objectId))
- return null;
+ continue;
 
- ValueOrError<GetMembersResult> valueOrError = await proxy.RuntimeGetObjectMembers(sessionId, objectId, null, token);
+ var args = JObject.FromObject(new { forDebuggerDisplayAttribute = true });
+ ValueOrError<GetMembersResult> valueOrError = await proxy.RuntimeGetObjectMembers(sessionId, objectId, args, token);
  if (valueOrError.IsError)
  {
  logger.LogDebug($"ResolveAsInstanceMember failed with : {valueOrError.Error}");
  return null;
  }
 
+ if (isCurrentPartNullSafe)
+ partTrimmed = partTrimmed.Remove(partTrimmed.Length - 1);
  JToken objRet = valueOrError.Value.FirstOrDefault(objPropAttr => objPropAttr["name"]?.Value<string>() == partTrimmed);
  if (objRet == null)
  return null;
@@ -275,19 +319,7 @@ async Task<JObject> ResolveAsInstanceMember(string expr, JObject baseObject)
  if (resolvedObject == null)
  return null;
 
- if (resolvedObject.IsNullValuedObject())
- {
- if (i < parts.Length - 1)
- {
- // there is some parts remaining, and can't
- // do null.$remaining
- return null;
- }
-
- return resolvedObject;
- }
  }
-
  return resolvedObject;
  }
  }

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

@@ -751,14 +751,14 @@ internal async Task<ValueOrError<GetMembersResult>> RuntimeGetObjectMembers(Sess
  GetObjectCommandOptions getObjectOptions = GetObjectCommandOptions.WithProperties;
  if (args != null)
  {
- if (args["accessorPropertiesOnly"] != null && args["accessorPropertiesOnly"].Value<bool>())
- {
+ if (args["accessorPropertiesOnly"]?.Value<bool>() == true)
  getObjectOptions |= GetObjectCommandOptions.AccessorPropertiesOnly;
- }
- if (args["ownProperties"] != null && args["ownProperties"].Value<bool>())
- {
+
+ if (args["ownProperties"]?.Value<bool>() == true)
  getObjectOptions |= GetObjectCommandOptions.OwnProperties;
- }
+
+ if (args["forDebuggerDisplayAttribute"]?.Value<bool>() == true)
+ getObjectOptions |= GetObjectCommandOptions.ForDebuggerDisplayAttribute;
  }
  try
  {

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

@@ -1148,6 +1148,54 @@ await EvaluateOnCallFrameAndCheck(id,
  );
  });
 
+ [ConditionalFact(nameof(RunningOnChrome))]
+ public async Task EvaluateNullObjectPropertiesPositive() => await CheckInspectLocalsAtBreakpointSite(
+ $"DebuggerTests.EvaluateNullableProperties", "Evaluate", 6, "Evaluate",
+ $"window.setTimeout(function() {{ invoke_static_method ('[debugger-test] DebuggerTests.EvaluateNullableProperties:Evaluate'); 1 }})",
+ wait_for_event_fn: async (pause_location) =>
+ {
+ var id = pause_location["callFrames"][0]["callFrameId"].Value<string>();
+
+ // we have no way of returning int? for null values, 
+ // so we return the last non-null class name
+ await EvaluateOnCallFrameAndCheck(id,
+ ("list.Count", TNumber(1)),
+ ("list?.Count", TNumber(1)),
+ ("listNull", TObject("System.Collections.Generic.List<int>", is_null: true)),
+ ("listNull?.Count", TObject("System.Collections.Generic.List<int>", is_null: true)),
+ ("tc?.memberList?.Count", TNumber(2)),
+ ("tc?.memberListNull?.Count", TObject("System.Collections.Generic.List<int>", is_null: true)),
+ ("tc.memberListNull?.Count", TObject("System.Collections.Generic.List<int>", is_null: true)),
+ ("tcNull?.memberListNull?.Count", TObject("DebuggerTests.EvaluateNullableProperties.TestClass", is_null: true)));
+ });
+
+ [ConditionalFact(nameof(RunningOnChrome))]
+ public async Task EvaluateNullObjectPropertiesNegative() => await CheckInspectLocalsAtBreakpointSite(
+ $"DebuggerTests.EvaluateNullableProperties", "Evaluate", 6, "Evaluate",
+ $"window.setTimeout(function() {{ invoke_static_method ('[debugger-test] DebuggerTests.EvaluateNullableProperties:Evaluate'); 1 }})",
+ wait_for_event_fn: async (pause_location) =>
+ {
+ var id = pause_location["callFrames"][0]["callFrameId"].Value<string>();
+ var (_, res) = await EvaluateOnCallFrame(id, "listNull.Count", expect_ok: false);
+ AssertEqual("Cannot access member \"Count\" of a null-valued object.", 
+ res.Error["result"]?["description"]?.Value<string>(), "wrong error message");
+ (_, res) = await EvaluateOnCallFrame(id, "tcNull.memberListNull.Count", expect_ok: false);
+ AssertEqual("Cannot access member \"memberListNull\" of a null-valued object.", 
+ res.Error["result"]?["description"]?.Value<string>(), "wrong error message");
+ (_, res) = await EvaluateOnCallFrame(id, "tc.memberListNull.Count", expect_ok: false);
+ AssertEqual("Cannot access member \"Count\" of a null-valued object.", 
+ res.Error["result"]?["description"]?.Value<string>(), "wrong error message");
+ (_, res) = await EvaluateOnCallFrame(id, "tcNull?.memberListNull.Count", expect_ok: false);
+ AssertEqual("Cannot access member \"Count\" of a null-valued object.", 
+ res.Error["result"]?["description"]?.Value<string>(), "wrong error message");
+ (_, res) = await EvaluateOnCallFrame(id, "listNull?.Count.NonExistingProperty", expect_ok: false);
+ AssertEqual("Cannot access member \"NonExistingProperty\" of a null-valued object.", 
+ res.Error["result"]?["description"]?.Value<string>(), "wrong error message");
+ (_, res) = await EvaluateOnCallFrame(id, "listNull?", expect_ok: false);
+ AssertEqual("Expected expression.", 
+ res.Error["result"]?["description"]?.Value<string>(), "wrong error message");
+ });
+
  [Fact]
  public async Task EvaluateMethodsOnPrimitiveTypesReturningPrimitives() => await CheckInspectLocalsAtBreakpointSite(
  "DebuggerTests.PrimitiveTypeMethods", "Evaluate", 11, "Evaluate",

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

@@ -1401,6 +1401,24 @@ public static void Evaluate()
  string localString = "S*T*R";
  }
  }
+
+ public static class EvaluateNullableProperties
+ {
+ class TestClass
+ {
+ public List<int> memberListNull = null;
+ List<int> memberList = new List<int>() {1, 2};
+ }
+ static void Evaluate()
+ {
+ #nullable enable
+ List<int>? listNull = null;
+ #nullable disable
+ List<int> list = new List<int>() {1};
+ TestClass tc = new TestClass();
+ TestClass tcNull = null;
+ }
+ }
 }
 
 namespace DebuggerTestsV2