Additional try/catch handling in DocumentsSyncService (#392)

Adds defensive try-catch blocks with error logging to three VS event
handler methods in DocumentsSyncService to prevent unhandled exceptions
from destabilizing Visual Studio.

VS extensibility callbacks must not throw exceptions. Unhandled
exceptions in IVsRunningDocTableEvents can crash Visual Studio or
disable the extension.

Author: PiotrKarczmarz

src/Cody.VisualStudio/Services/DocumentsSyncService.cs

@@ -1,5 +1,6 @@
 using Cody.Core.DocumentSync;
 using Cody.Core.Logging;
+using Cody.Core.Settings;
 using Cody.Core.Trace;
 using Microsoft.VisualStudio;
 using Microsoft.VisualStudio.Editor;
@@ -12,7 +13,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
-using Cody.Core.Settings;
+using System.Threading;
 
 namespace Cody.VisualStudio.Services
 {
@@ -248,67 +249,90 @@ int IVsRunningDocTableEvents.OnAfterSave(uint docCookie)
 
         int IVsRunningDocTableEvents.OnBeforeDocumentWindowShow(uint docCookie, int fFirstShow, IVsWindowFrame pFrame)
         {
-            trace.TraceEvent("OnBeforeDocumentWindowShow");
-            if (lastShowDocCookie != docCookie)
+            try
             {
-                var path = rdt.GetDocumentInfo(docCookie).Moniker;
-                if (path == null) return VSConstants.S_OK;
-
-                if (!isSubscribed.Contains(docCookie))
+                trace.TraceEvent("OnBeforeDocumentWindowShow");
+                if (lastShowDocCookie != docCookie)
                 {
-                    trace.TraceEvent("OnSubscribeDocument", path);
+                    var path = rdt.GetDocumentInfo(docCookie).Moniker;
+                    if (path == null) return VSConstants.S_OK;
 
-                    var content = rdt.GetRunningDocumentContents(docCookie);
-                    if (content == null) return VSConstants.S_OK;
-
-                    var textView = GetVsTextView(pFrame);
-                    if (textView != null)
+                    if (!isSubscribed.Contains(docCookie))
                     {
-                        var wpfTextView = editorAdaptersFactoryService.GetWpfTextView(textView);
-                        if (wpfTextView != null)
-                        {
-                            Subscribe(wpfTextView);
+                        trace.TraceEvent("OnSubscribeDocument", path);
 
-                            if (!openNotificationSend.Contains(docCookie))
-                            {
-
-                                var docRange = GetDocumentSelection(wpfTextView);
-                                var visibleRange = GetVisibleRange(wpfTextView);
+                        var content = rdt.GetRunningDocumentContents(docCookie);
+                        if (content == null) return VSConstants.S_OK;
 
-                                documentActions.OnOpened(path, content, visibleRange, docRange);
-                                openNotificationSend.Add(docCookie);
+                        var textView = GetVsTextView(pFrame);
+                        if (textView != null)
+                        {
+                            var wpfTextView = editorAdaptersFactoryService.GetWpfTextView(textView);
+                            if (wpfTextView != null)
+                            {
+                                Subscribe(wpfTextView, path, docCookie, content);
                             }
-
-                            isSubscribed.Add(docCookie);
                         }
                     }
-                }
 
-                trace.TraceEvent("OnDocumentFocus", path);
-                documentActions.OnFocus(path);
+                    trace.TraceEvent("OnDocumentFocus", path);
+                    documentActions.OnFocus(path);
 
-                lastShowDocCookie = docCookie;
+                    lastShowDocCookie = docCookie;
+                }
+            }
+            catch (Exception ex)
+            {
+                log.Error("OnBeforeDocumentWindowShow failed", ex);
             }
 
             return VSConstants.S_OK;
         }
 
-        private void Subscribe(IWpfTextView textView)
+        private void Subscribe(IWpfTextView textView, string path, uint docCookie, string content)
         {
-            textView.TextBuffer.Properties.AddProperty(typeof(IWpfTextView), textView);
-            textView.Selection.SelectionChanged += OnSelectionChanged;
-            textView.TextBuffer.ChangedLowPriority += OnTextBufferChanged;
-            textView.Closed += UnsubscribeOnClosed;
+            try
+            {
+
+                textView.TextBuffer.Properties.AddProperty(typeof(IWpfTextView), textView);
+                textView.Selection.SelectionChanged += OnSelectionChanged;
+                textView.TextBuffer.ChangedLowPriority += OnTextBufferChanged;
+                textView.Closed += UnsubscribeOnClosed;
+
+                if (!openNotificationSend.Contains(docCookie))
+                {
+
+                    var docRange = GetDocumentSelection(textView);
+                    var visibleRange = GetVisibleRange(textView);
+
+                    documentActions.OnOpened(path, content, visibleRange, docRange);
+                    openNotificationSend.Add(docCookie);
+                }
+
+                isSubscribed.Add(docCookie);
+
+            }
+            catch (Exception ex)
+            {
+                log.Error("Subscribe failed", ex);
+            }
         }
 
         private void UnsubscribeOnClosed(object sender, EventArgs e)
         {
-            var textView = (IWpfTextView)sender;
+            try
+            {
+                var textView = (IWpfTextView)sender;
 
-            textView.TextBuffer.Properties.RemoveProperty(typeof(IWpfTextView));
-            textView.Selection.SelectionChanged -= OnSelectionChanged;
-            textView.TextBuffer.ChangedLowPriority -= OnTextBufferChanged;
-            textView.Closed -= UnsubscribeOnClosed;
+                textView.TextBuffer.Properties.RemoveProperty(typeof(IWpfTextView));
+                textView.Selection.SelectionChanged -= OnSelectionChanged;
+                textView.TextBuffer.ChangedLowPriority -= OnTextBufferChanged;
+                textView.Closed -= UnsubscribeOnClosed;
+            }
+            catch (Exception ex)
+            {
+                log.Error("Unsubscribe failed", ex);
+            }
         }
 
         int IVsRunningDocTableEvents.OnAfterDocumentWindowHide(uint docCookie, IVsWindowFrame pFrame) => VSConstants.S_OK;
@@ -422,7 +446,7 @@ public int OnAfterAttributeChangeEx(uint docCookie, uint grfAttribs, IVsHierarch
             {
                 trace.TraceEvent("OnRename");
                 documentActions.OnRename(pszMkDocumentOld, pszMkDocumentNew);
-    }
+            }
             return VSConstants.S_OK;
         }
     }