Make CodeExplorer refresh safer by waiting for things pushed to the UI thread to finish

Otherwise, it is possible to cancel a parse and start a new one, while the UI is still updating.

Author: MDoerner

Rubberduck.CodeAnalysis/CodeMetrics/CodeMetricsAnalyst.cs

@@ -1,5 +1,4 @@
 using Antlr4.Runtime.Tree;
-using Rubberduck.Parsing.Symbols;
 using Rubberduck.Parsing.VBA;
 using Rubberduck.VBEditor;
 using System.Collections.Generic;
@@ -14,11 +13,11 @@ public class CodeMetricsAnalyst : ICodeMetricsAnalyst
     {
         private static readonly Logger Logger = LogManager.GetCurrentClassLogger();
 
-        private readonly CodeMetric[] metrics;
+        private readonly CodeMetric[] _metrics;
 
         public CodeMetricsAnalyst(IEnumerable<CodeMetric> supportedMetrics)
         {
-            metrics = supportedMetrics.ToArray();
+            _metrics = supportedMetrics.ToArray();
         }
 
         public IEnumerable<ICodeMetricResult> GetMetrics(RubberduckParserState state)
@@ -45,7 +44,7 @@ public IEnumerable<ICodeMetricResult> ModuleResults(QualifiedModuleName moduleNa
 
         private IEnumerable<ICodeMetricResult> TraverseModuleTree(IParseTree parseTree, DeclarationFinder declarationFinder, QualifiedModuleName moduleName)
         {
-            var listeners = metrics.Select(metric => metric.TreeListener).ToList();
+            var listeners = _metrics.Select(metric => metric.TreeListener).ToList();
             foreach (var l in listeners)
             {
                 l.Reset();

Rubberduck.CodeAnalysis/CodeMetrics/NestingLevelMetric.cs

@@ -1,12 +1,9 @@
 using Antlr4.Runtime.Misc;
 using Rubberduck.Parsing.Grammar;
 using Rubberduck.Parsing.Symbols;
-using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace Rubberduck.CodeAnalysis.CodeMetrics
 {

Rubberduck.Core/CodeAnalysis/CodeMetrics/CodeMetricsViewModel.cs

@@ -65,7 +65,8 @@ private void Synchronize(IEnumerable<Declaration> declarations)
             var metricResults = _analyst.GetMetrics(_state);
             _resultsByDeclaration = metricResults.GroupBy(r => r.Declaration).ToDictionary(g => g.Key, g => g.ToList());
 
-            _uiDispatcher.Invoke(() =>
+            //We have to wait for the task to guarantee that no new parse starts invalidating all cached components.
+            _uiDispatcher.StartTask(() =>
             {
                 var updates = declarations.ToList();
                 var existing = Projects.OfType<CodeExplorerProjectViewModel>().ToList();
@@ -86,7 +87,7 @@ private void Synchronize(IEnumerable<Declaration> declarations)
                     var model = new CodeExplorerProjectViewModel(project, ref updates, _state, _vbe, false);
                     Projects.Add(model);
                 }
-            });
+            }).Wait();
         }
 
         private ICodeExplorerNode _selectedItem;

Rubberduck.Core/Navigation/CodeExplorer/CodeExplorerViewModel.cs

@@ -231,7 +231,8 @@ private void HandleStateChanged(object sender, ParserStateEventArgs e)
             if (e.State == ParserState.Ready)
             {
                 // Finished up resolving references, so we can now update the reference nodes.
-                _uiDispatcher.Invoke(() =>
+                //We have to wait for the task to guarantee that no new parse starts invalidating all cached components.
+                _uiDispatcher.StartTask(() =>
                 {
                     var referenceFolders = Projects.SelectMany(node =>
                         node.Children.OfType<CodeExplorerReferenceFolderViewModel>());
@@ -243,7 +244,7 @@ private void HandleStateChanged(object sender, ParserStateEventArgs e)
                     Unparsed = !Projects.Any();
                     IsBusy = false;
                     ParserReady = true;
-                });
+                }).Wait();
                 return;
             }
 
@@ -264,7 +265,8 @@ private void HandleStateChanged(object sender, ParserStateEventArgs e)
         /// </param>
         private void Synchronize(IEnumerable<Declaration> declarations)
         {
-            _uiDispatcher.Invoke(() =>
+            //We have to wait for the task to guarantee that no new parse starts invalidating all cached components.
+            _uiDispatcher.StartTask(() =>
             {
                 var updates = declarations.ToList();
                 var existing = Projects.OfType<CodeExplorerProjectViewModel>().ToList();
@@ -287,7 +289,7 @@ private void Synchronize(IEnumerable<Declaration> declarations)
                 }
 
                 CanSearch = Projects.Any();
-            });
+            }).Wait();
         }
 
         private void ParserState_ModuleStateChanged(object sender, ParseProgressEventArgs e)

RubberduckTests/CodeExplorer/CodeExplorerViewModelTests.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 using NUnit.Framework;
 using Moq;
@@ -859,6 +860,7 @@ public void UnparsedSetToTrue_NoProjects()
             var dispatcher = new Mock<IUiDispatcher>();
 
             dispatcher.Setup(m => m.Invoke(It.IsAny<Action>())).Callback((Action argument) => argument.Invoke());
+            dispatcher.Setup(m => m.StartTask(It.IsAny<Action>(), It.IsAny<TaskCreationOptions>())).Returns((Action argument, TaskCreationOptions options) => Task.Factory.StartNew(argument.Invoke, options));
 
             var viewModel = new CodeExplorerViewModel(state, null, null, null, dispatcher.Object, vbe.Object, null, new CodeExplorerSyncProvider(vbe.Object, state));
 

RubberduckTests/CodeExplorer/MockedCodeExplorer.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using System.Windows.Forms;
 using NUnit.Framework;
 using Moq;
@@ -49,6 +50,7 @@ public MockedCodeExplorer()
                 .Returns(new UnitTestSettings(BindingMode.LateBinding,AssertMode.StrictAssert, true, true, false));
 
             _uiDispatcher.Setup(m => m.Invoke(It.IsAny<Action>())).Callback((Action argument) => argument.Invoke());
+            _uiDispatcher.Setup(m => m.StartTask(It.IsAny<Action>(), It.IsAny<TaskCreationOptions>())).Returns((Action argument, TaskCreationOptions options) => Task.Factory.StartNew(argument.Invoke, options));
 
             SaveDialog = new Mock<ISaveFileDialog>();
             SaveDialog.Setup(o => o.OverwritePrompt);