Merge pull request #3170 from heejaechang/errorlist2

fixed a race where build only errors are not cleared correctly

src/VisualStudio/Core/Def/Implementation/TableDataSource/VisualStudioDiagnosticListTable.cs

@@ -144,13 +144,17 @@ private void ConnectToBuildUpdateSource(ExternalErrorDiagnosticUpdateSource erro
 
                 SetStableState(errorSource.IsInProgress);
 
-                errorSource.DiagnosticsUpdated += OnDiagnosticsUpdated;
                 errorSource.BuildStarted += OnBuildStarted;
             }
 
             private void OnBuildStarted(object sender, bool started)
             {
                 SetStableState(started);
+
+                if (!started)
+                {
+                    OnDataAddedOrChanged(this, _buildErrorSource.GetBuildErrors().Length);
+                }
             }
 
             private void SetStableState(bool started)
@@ -163,11 +167,6 @@ private void SetStableState(bool started)
             public override string SourceTypeIdentifier => StandardTableDataSources.ErrorTableDataSource;
             public override string Identifier => IdentifierString;
 
-            private void OnDiagnosticsUpdated(object sender, DiagnosticsUpdatedArgs e)
-            {
-                OnDataAddedOrChanged(this, _buildErrorSource.GetBuildErrors().Length);
-            }
-
             protected void OnDataAddedOrChanged(object key, int itemCount)
             {
                 // reuse factory. it is okay to re-use factory since we make sure we remove the factory before