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

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

@@ -382,13 +382,6 @@ private static async Task<IList<JObject>> ResolveElementAccess(IEnumerable<Eleme
  return values;
  }
 
- internal static string RemoveNullSuppression(string expression)
- {
- expression = expression.Trim();
- expression = expression.Replace("!.", ".").Replace("![", "[").Replace("!(", "(");
- return expression;
- }
-
  internal static async Task<JObject> CompileAndRunTheExpression(
  string expression, MemberReferenceResolver resolver, ILogger logger, CancellationToken token)
  {

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

@@ -98,7 +98,7 @@ public async Task<JObject> GetValueFromObject(JToken objRet, CancellationToken t
  {
  ArraySegment<string> remaining = null;
  if (i < parts.Count - 1)
- remaining = parts[(i + 1)..];
+ remaining = parts[i..];
 
  return (memberObject, remaining);
  }
@@ -190,22 +190,14 @@ public async Task<JObject> Resolve(string varName, CancellationToken token)
  if (scopeCache.ObjectFields.TryGetValue(varName, out JObject valueRet))
  return await GetValueFromObject(valueRet, token);
 
- ArraySegment<string> parts = new ArraySegment<string>(varName.Split(".", StringSplitOptions.TrimEntries));
- if (parts.Count == 0 || string.IsNullOrEmpty(parts[0]))
+ string[] parts = varName.Split(".", StringSplitOptions.TrimEntries);
+ if (parts.Length == 0 || string.IsNullOrEmpty(parts[0]))
  throw new ReturnAsErrorException($"Failed to resolve expression: {varName}", "ReferenceError");
 
  JObject retObject = await ResolveAsLocalOrThisMember(parts[0]);
- bool hasNullCondition = parts[0][^1] == '?';
- if (retObject != null && parts.Count > 1)
- {
- // 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(parts[1..], retObject, hasNullCondition);
- }
+ bool throwOnNullReference = parts[0][^1] != '?';
+ if (retObject != null && parts.Length > 1)
+ retObject = await ResolveAsInstanceMember(parts, retObject, throwOnNullReference);
 
  if (retObject == null)
  {
@@ -219,7 +211,7 @@ public async Task<JObject> Resolve(string varName, CancellationToken token)
  }
  else
  {
- retObject = await ResolveAsInstanceMember(remaining, retObject, hasNullCondition);
+ retObject = await ResolveAsInstanceMember(remaining, retObject, throwOnNullReference);
  }
  }
  }
@@ -238,7 +230,7 @@ async Task<JObject> ResolveAsLocalOrThisMember(string name)
  }
 
  // remove null-condition, otherwise TryGet by name fails
- if (name[^1] == '?')
+ if (name[^1] == '?' || name[^1] == '!')
  name = name.Remove(name.Length - 1);
 
  if (scopeCache.Locals.TryGetValue(name, out JObject obj))
@@ -264,24 +256,27 @@ async Task<JObject> ResolveAsLocalOrThisMember(string name)
  return null;
  }
 
- async Task<JObject> ResolveAsInstanceMember(ArraySegment<string> parts, JObject baseObject, bool hasNullCondition)
+ async Task<JObject> ResolveAsInstanceMember(ArraySegment<string> parts, JObject baseObject, bool throwOnNullReference)
  {
- // if the prevPart has "?" at the end: true
- bool hasResolvedObjNullCondition = hasNullCondition;
- bool isPrevPartNull = false;
  JObject resolvedObject = baseObject;
- for (int i = 0; i < parts.Count; i++)
+ // parts[0] - name of baseObject
+ for (int i = 1; i < parts.Count; i++)
  {
- string partTrimmed = parts[i];
- if (partTrimmed.Length == 0)
+ string part = parts[i];
+ if (part.Length == 0)
  return null;
 
+ if (part[^1] == '!')
+ part = part.Remove(part.Length - 1);
+
+ bool hasCurrentPartNullCondition = part[^1] == '?';
+
  // current value of resolvedObject is on parts[i - 1]
- if (isPrevPartNull || resolvedObject.IsNullValuedObject())
+ if (resolvedObject.IsNullValuedObject())
  {
  // trying null.$member
- if (!hasResolvedObjNullCondition)
- throw new ReturnAsErrorException($"Cannot access member \"{partTrimmed}\" of a null-valued object.", "ReferenceError");
+ if (throwOnNullReference)
+ throw new ReturnAsErrorException($"Expression threw NullReferenceException trying to access \"{part}\" on a null-valued object.", "ReferenceError");
 
  if (i == parts.Count - 1)
  {
@@ -290,17 +285,18 @@ async Task<JObject> ResolveAsInstanceMember(ArraySegment<string> parts, JObject
  // so the class/description of object are not of the last part
  return resolvedObject;
  }
- // else: trying null?.$member... - allowed operation
- isPrevPartNull = true;
- }
 
- bool hasCurrentPartNullCondition = partTrimmed.Last() == '?';
- hasResolvedObjNullCondition = hasCurrentPartNullCondition;
+ // check if null condition is correctly applied: should we throw or return null-object
+ throwOnNullReference = !hasCurrentPartNullCondition;
+ continue;
+ }
 
- // cannot resolve the members but can check if null condition is
- // correctly applied and if we should throw or return null-object
  if (!DotnetObjectId.TryParse(resolvedObject?["objectId"]?.Value<string>(), out DotnetObjectId objectId))
- continue;
+ {
+ if (!throwOnNullReference)
+ throw new ReturnAsErrorException($"Operation '?' not allowed on primitive type - '{parts[i - 1]}'", "ReferenceError");
+ throw new ReturnAsErrorException($"Cannot find member '{part}' on a primitive type", "ReferenceError");
+ }
 
  var args = JObject.FromObject(new { forDebuggerDisplayAttribute = true });
  ValueOrError<GetMembersResult> valueOrError = await proxy.RuntimeGetObjectMembers(sessionId, objectId, args, token);
@@ -311,15 +307,15 @@ async Task<JObject> ResolveAsInstanceMember(ArraySegment<string> parts, JObject
  }
 
  if (hasCurrentPartNullCondition)
- partTrimmed = partTrimmed.Remove(partTrimmed.Length - 1);
- JToken objRet = valueOrError.Value.FirstOrDefault(objPropAttr => objPropAttr["name"]?.Value<string>() == partTrimmed);
+ part = part.Remove(part.Length - 1);
+ JToken objRet = valueOrError.Value.FirstOrDefault(objPropAttr => objPropAttr["name"]?.Value<string>() == part);
  if (objRet == null)
  return null;
 
  resolvedObject = await GetValueFromObject(objRet, token);
  if (resolvedObject == null)
  return null;
-
+ throwOnNullReference = !hasCurrentPartNullCondition;
  }
  return resolvedObject;
  }

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

@@ -1318,7 +1318,6 @@ private async Task<bool> OnEvaluateOnCallFrame(MessageId msg_id, int scopeId, st
 
  var resolver = new MemberReferenceResolver(this, context, msg_id, scopeId, logger);
 
- expression = ExpressionEvaluator.RemoveNullSuppression(expression);
  JObject retValue = await resolver.Resolve(expression, token);
  if (retValue == null)
  {

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

@@ -1163,11 +1163,11 @@ await EvaluateOnCallFrameAndCheck(id,
  ("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!.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)));
+ ("tc?.MemberList?.Count", TNumber(2)),
+ ("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))]
@@ -1177,27 +1177,30 @@ public async Task EvaluateNullObjectPropertiesNegative() => await CheckInspectLo
  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, "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");
+ await CheckEvaluateFail("list.Count.x", "Cannot find member 'x' on a primitive type");
+ await CheckEvaluateFail("listNull.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("listNull!.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tcNull.MemberListNull.Count", GetNullReferenceErrorOn("\"MemberListNull\""));
+ await CheckEvaluateFail("tc.MemberListNull.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tcNull?.MemberListNull.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("listNull?.Count.NonExistingProperty", GetNullReferenceErrorOn("\"NonExistingProperty\""));
+ await CheckEvaluateFail("tc?.MemberListNull! .Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tc?. MemberListNull!.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tc?.MemberListNull.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tc! .MemberListNull!.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tc!.MemberListNull. Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("tcNull?.Sibling.MemberListNull?.Count", GetNullReferenceErrorOn("\"MemberListNull?\""));
+ await CheckEvaluateFail("listNull?", "Expected expression.");
+ await CheckEvaluateFail("listNull!.Count", GetNullReferenceErrorOn("\"Count\""));
+ await CheckEvaluateFail("x?.p", "Operation '?' not allowed on primitive type - 'x?'");
+
+ string GetNullReferenceErrorOn(string name) => $"Expression threw NullReferenceException trying to access {name} on a null-valued object.";
+
+ async Task CheckEvaluateFail(string expr, string message)
+ {
+ (_, Result _res) = await EvaluateOnCallFrame(id, expr, expect_ok: false);
+ AssertEqual(message, _res.Error["result"]?["description"]?.Value<string>(), $"Expression '{expr}' - wrong error message");
+ }
  });
 
  [Fact]

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

@@ -1371,7 +1371,7 @@ public static void Evaluate()
  var test = new TestClass();
  }
  }
- 
+
  public static class PrimitiveTypeMethods
  {
  public class TestClass
@@ -1406,8 +1406,9 @@ public static class EvaluateNullableProperties
  {
  class TestClass
  {
- public List<int> memberListNull = null;
- List<int> memberList = new List<int>() {1, 2};
+ public List<int> MemberListNull = null;
+ public List<int> MemberList = new List<int>() {1, 2};
+ public TestClass Sibling { get; set; }
  }
  static void Evaluate()
  {
@@ -1417,6 +1418,11 @@ static void Evaluate()
  List<int> list = new List<int>() {1};
  TestClass tc = new TestClass();
  TestClass tcNull = null;
+ string str = "str#value";
+ string str_null = null;
+ int x = 5;
+ int? x_null = null;
+ int? x_val = x;
  }
  }
 }