completion leaking cancellation exception (#38526)

* completion leaking cancellation exception

* code review feedback

* feedback addressed

* fixing more merge conflicts

* Update CommitManager.cs

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/CommitManager.cs

@@ -164,16 +164,13 @@ internal CommitManager(ITextView textView, RecentItemsManager recentItemsManager
 
             // Commit with completion service assumes that null is provided is case of invoke. VS provides '\0' in the case.
             var commitChar = typeChar == '\0' ? null : (char?)typeChar;
-            var commitBehavior = Commit(
+            return Commit(
                 triggerDocument, completionService, session.TextView, subjectBuffer,
                 roslynItem, completionListSpan, commitChar, triggerLocation.Snapshot, serviceRules,
                 filterText, cancellationToken);
-
-            _recentItemsManager.MakeMostRecentItem(roslynItem.FilterText);
-            return new AsyncCompletionData.CommitResult(isHandled: true, commitBehavior);
         }
 
-        private AsyncCompletionData.CommitBehavior Commit(
+        private AsyncCompletionData.CommitResult Commit(
             Document document,
             CompletionService completionService,
             ITextView view,
@@ -193,22 +190,37 @@ internal CommitManager(ITextView textView, RecentItemsManager recentItemsManager
             {
                 // We are on the wrong thread.
                 FatalError.ReportWithoutCrash(new InvalidOperationException("Subject buffer did not provide Edit Access"));
-                return AsyncCompletionData.CommitBehavior.None;
+                return new AsyncCompletionData.CommitResult(isHandled: true, AsyncCompletionData.CommitBehavior.None);
             }
 
             if (subjectBuffer.EditInProgress)
             {
                 FatalError.ReportWithoutCrash(new InvalidOperationException("Subject buffer is editing by someone else."));
-                return AsyncCompletionData.CommitBehavior.None;
+                return new AsyncCompletionData.CommitResult(isHandled: true, AsyncCompletionData.CommitBehavior.None);
             }
 
+            CompletionChange change;
+
+            // We met an issue when external code threw an OperationCanceledException and the cancellationToken is not cancelled.
+            // Catching this scenario for further investigations.
+            // See https://github.com/dotnet/roslyn/issues/38455.
+            try
+            {
+                change = completionService.GetChangeAsync(document, roslynItem, completionListSpan, commitCharacter, cancellationToken).WaitAndGetResult(cancellationToken);
+            }
+            catch (OperationCanceledException e) when (e.CancellationToken != cancellationToken && FatalError.ReportWithoutCrash(e))
+            {
+                return CommitResultUnhandled;
+            }
+
+            cancellationToken.ThrowIfCancellationRequested();
+
             if (GetCompletionProvider(completionService, roslynItem) is ICustomCommitCompletionProvider provider)
             {
                 provider.Commit(roslynItem, view, subjectBuffer, triggerSnapshot, commitCharacter);
-                return AsyncCompletionData.CommitBehavior.None;
+                return new AsyncCompletionData.CommitResult(isHandled: true, AsyncCompletionData.CommitBehavior.None);
             }
 
-            var change = completionService.GetChangeAsync(document, roslynItem, completionListSpan, commitCharacter, cancellationToken).WaitAndGetResult(cancellationToken);
             var textChange = change.TextChange;
             var triggerSnapshotSpan = new SnapshotSpan(triggerSnapshot, textChange.Span.ToSpan());
             var mappedSpan = triggerSnapshotSpan.TranslateTo(subjectBuffer.CurrentSnapshot, SpanTrackingMode.EdgeInclusive);
@@ -267,17 +279,19 @@ internal CommitManager(ITextView textView, RecentItemsManager recentItemsManager
                 }
             }
 
+            _recentItemsManager.MakeMostRecentItem(roslynItem.FilterText);
+
             if (includesCommitCharacter)
             {
-                return AsyncCompletionData.CommitBehavior.SuppressFurtherTypeCharCommandHandlers;
+                return new AsyncCompletionData.CommitResult(isHandled: true, AsyncCompletionData.CommitBehavior.SuppressFurtherTypeCharCommandHandlers);
             }
 
             if (commitCharacter == '\n' && SendEnterThroughToEditor(rules, roslynItem, filterText))
             {
-                return AsyncCompletionData.CommitBehavior.RaiseFurtherReturnKeyAndTabKeyCommandHandlers;
+                return new AsyncCompletionData.CommitResult(isHandled: true, AsyncCompletionData.CommitBehavior.RaiseFurtherReturnKeyAndTabKeyCommandHandlers);
             }
 
-            return AsyncCompletionData.CommitBehavior.None;
+            return new AsyncCompletionData.CommitResult(isHandled: true, AsyncCompletionData.CommitBehavior.None);
         }
 
         internal static bool IsCommitCharacter(CompletionRules completionRules, CompletionItem item, char ch, string textTypedSoFar)