Fix for ValidateBreakpointLocationWorker NFW

src/EditorFeatures/Test/Extensions/ITextSnapshotExtensionsTests.cs

@@ -159,10 +159,17 @@ public void TryGetPositionTest()
         }
 
         [Fact]
-        public void GetPointTest()
+        public void TryGetPointValueTest()
         {
             var snapshot = GetSampleCodeSnapshot();
-            Assert.Equal(new SnapshotPoint(snapshot, 15), snapshot.GetPoint(3, 0));
+            Assert.Equal(new SnapshotPoint(snapshot, 15), snapshot.TryGetPoint(3, 0).Value);
+        }
+
+        [Fact]
+        public void TryGetPointNullTest()
+        {
+            var snapshot = GetSampleCodeSnapshot();
+            Assert.Null(snapshot.TryGetPoint(3000, 0));
         }
 
         [Fact]

src/EditorFeatures/Text/Shared/Extensions/ITextSnapshotExtensions.cs

@@ -11,8 +11,18 @@ internal static partial class ITextSnapshotExtensions
         public static SnapshotPoint GetPoint(this ITextSnapshot snapshot, int position)
             => new SnapshotPoint(snapshot, position);
 
-        public static SnapshotPoint GetPoint(this ITextSnapshot snapshot, int lineNumber, int columnIndex)
-            => new SnapshotPoint(snapshot, snapshot.GetPosition(lineNumber, columnIndex));
+        public static SnapshotPoint? TryGetPoint(this ITextSnapshot snapshot, int lineNumber, int columnIndex)
+        {
+            var position = snapshot.TryGetPosition(lineNumber, columnIndex);
+            if (position.HasValue)
+            {
+                return new SnapshotPoint(snapshot, position.Value);
+            }
+            else
+            {
+                return null;
+            }
+        }
 
         /// <summary>
         /// Convert a <see cref="LinePositionSpan"/> to <see cref="TextSpan"/>.

src/VisualStudio/Core/Def/Implementation/LanguageService/AbstractLanguageService`2.VsLanguageDebugInfo.cs

@@ -92,21 +92,25 @@ public int GetNameOfLocation(IVsTextBuffer pBuffer, int iLine, int iCol, out str
                             var textBuffer = _languageService.EditorAdaptersFactoryService.GetDataBuffer(pBuffer);
                             if (textBuffer != null)
                             {
-                                var point = textBuffer.CurrentSnapshot.GetPoint(iLine, iCol);
-                                var document = point.Snapshot.GetOpenDocumentInCurrentContextWithChanges();
-
-                                if (document != null)
+                                var nullablePoint = textBuffer.CurrentSnapshot.TryGetPoint(iLine, iCol);
+                                if (nullablePoint.HasValue)
                                 {
-                                    // NOTE(cyrusn): We have to wait here because the debuggers' 
-                                    // GetNameOfLocation is a blocking call.  In the future, it 
-                                    // would be nice if they could make it async.
-                                    var debugLocationInfo = _languageDebugInfo.GetLocationInfoAsync(document, point, cancellationToken).WaitAndGetResult(cancellationToken);
+                                    var point = nullablePoint.Value;
+                                    var document = point.Snapshot.GetOpenDocumentInCurrentContextWithChanges();
 
-                                    if (!debugLocationInfo.IsDefault)
+                                    if (document != null)
                                     {
-                                        succeeded = true;
-                                        name = debugLocationInfo.Name;
-                                        lineOffset = debugLocationInfo.LineOffset;
+                                        // NOTE(cyrusn): We have to wait here because the debuggers' 
+                                        // GetNameOfLocation is a blocking call.  In the future, it 
+                                        // would be nice if they could make it async.
+                                        var debugLocationInfo = _languageDebugInfo.GetLocationInfoAsync(document, point, cancellationToken).WaitAndGetResult(cancellationToken);
+
+                                        if (!debugLocationInfo.IsDefault)
+                                        {
+                                            succeeded = true;
+                                            name = debugLocationInfo.Name;
+                                            lineOffset = debugLocationInfo.LineOffset;
+                                        }
                                     }
                                 }
                             }
@@ -146,16 +150,20 @@ public int GetProximityExpressions(IVsTextBuffer pBuffer, int iLine, int iCol, i
                         if (textBuffer != null)
                         {
                             var snapshot = textBuffer.CurrentSnapshot;
-                            Document document = snapshot.GetOpenDocumentInCurrentContextWithChanges();
-                            if (document != null)
+                            var nullablePoint = snapshot.TryGetPoint(iLine, iCol);
+                            if (nullablePoint.HasValue)
                             {
-                                var point = snapshot.GetPoint(iLine, iCol);
-                                var proximityExpressions = _proximityExpressionsService.GetProximityExpressionsAsync(document, point.Position, waitContext.CancellationToken).WaitAndGetResult(waitContext.CancellationToken);
-
-                                if (proximityExpressions != null)
+                                Document document = snapshot.GetOpenDocumentInCurrentContextWithChanges();
+                                if (document != null)
                                 {
-                                    enumBSTR = new VsEnumBSTR(proximityExpressions);
-                                    succeeded = true;
+                                    var point = nullablePoint.Value;
+                                    var proximityExpressions = _proximityExpressionsService.GetProximityExpressionsAsync(document, point.Position, waitContext.CancellationToken).WaitAndGetResult(waitContext.CancellationToken);
+
+                                    if (proximityExpressions != null)
+                                    {
+                                        enumBSTR = new VsEnumBSTR(proximityExpressions);
+                                        succeeded = true;
+                                    }
                                 }
                             }
                         }
@@ -278,10 +286,17 @@ public int ValidateBreakpointLocation(IVsTextBuffer pBuffer, int iLine, int iCol
                 if (textBuffer != null)
                 {
                     var snapshot = textBuffer.CurrentSnapshot;
+                    var nullablePoint = snapshot.TryGetPoint(iLine, iCol);
+                    if (nullablePoint == null)
+                    {
+                        // The point disappeared between sessions. Do not allow a breakpoint here.
+                        return VSConstants.E_FAIL;
+                    }
+
                     Document document = snapshot.AsText().GetDocumentWithFrozenPartialSemantics(cancellationToken);
                     if (document != null)
                     {
-                        var point = snapshot.GetPoint(iLine, iCol);
+                        var point = nullablePoint.Value;
                         var length = 0;
                         if (pCodeSpan != null && pCodeSpan.Length > 0)
                         {