Update nuget version to 19

Updte editor nuget to 15.7.111-preview-g28b775fb96

9 files changed, 201 insertions, 106 deletions

diff --git a/src/Language/Impl/Language/Completion/AsyncCompletionBroker.cs b/src/Language/Impl/Language/Completion/AsyncCompletionBroker.cs
index 440c3a3..d38044c 100644
--- a/src/Language/Impl/Language/Completion/AsyncCompletionBroker.cs
+++ b/src/Language/Impl/Language/Completion/AsyncCompletionBroker.cs
@@ -28,9 +28,6 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         internal IGuardedOperations GuardedOperations { get; set; }
 
         [Import]
-        internal ITextStructureNavigatorSelectorService TextStructureNavigatorSelectorService { get; set; }
-
-        [Import]
         private JoinableTaskContext JoinableTaskContext;
 
         [Import]
@@ -69,7 +66,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             session.TextView.Properties.RemoveProperty(typeof(IAsyncCompletionSession));
         }
 
-        IAsyncCompletionSession IAsyncCompletionBroker.TriggerCompletion(ITextView view, SnapshotSpan applicableSpan)
+        IAsyncCompletionSession IAsyncCompletionBroker.TriggerCompletion(ITextView view, SnapshotPoint triggerLocation, SnapshotSpan applicableSpan)
         {
             var session = GetSession(view);
             if (session != null)
@@ -77,16 +74,23 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 return session;
             }
 
-            // TODO: Need to map applicableSpan to respective buffers
-            var sourcesWithLocations = CompletionUtilities.GetCompletionSourcesWithMappedSpans(view, applicableSpan, GetCompletionItemSourceProviders);
+            var sourcesWithLocations = CompletionUtilities.GetCompletionSourcesWithMappedPoints(view, triggerLocation, GetCompletionItemSourceProviders);
             if (!sourcesWithLocations.Any())
             {
                 // There is no completion source available for this buffer
                 return null;
             }
 
-            // TODO: use applicableSpan
-            var buffers = CompletionUtilities.GetBuffersForSpan(view, applicableSpan).ToImmutableArray();
+            var potentialCommitCharsBuilder = ImmutableArray.CreateBuilder<char>();
+            foreach (var source in sourcesWithLocations.Keys)
+            {
+                // Unfortunately we can't use for loop here because IDictionary.Keys is ICollection which can't be accessed with an indexer
+                GuardedOperations.CallExtensionPoint(
+                    errorSource: source,
+                    call: () => potentialCommitCharsBuilder.AddRange(source.GetPotentialCommitCharacters()));
+            }
+
+            var buffers = CompletionUtilities.GetBuffersForPoint(view, triggerLocation).ToImmutableArray();
             var service = buffers
                 .Select(b => GetCompletionService(b.ContentType))
                 .FirstOrDefault(s => s != null)
@@ -109,7 +113,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             }
             var telemetry = GetOrCreateTelemetry(view);
 
-            session = new AsyncCompletionSession(applicableSpan, JoinableTaskContext.Factory, uiFactory, sourcesWithLocations, service, this, view, telemetry);
+            session = new AsyncCompletionSession(applicableSpan, potentialCommitCharsBuilder.ToImmutable(), JoinableTaskContext.Factory, uiFactory, sourcesWithLocations, service, this, view, telemetry);
             view.Properties.AddProperty(typeof(IAsyncCompletionSession), session);
             view.Closed += TextView_Closed;
 
@@ -269,9 +273,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             }
         }
 
-        internal string GetItemSourceName(IAsyncCompletionItemSource source) => OrderedCompletionItemSourceProviders.FirstOrDefault(n => n.Value == source)?.Metadata.Name ?? string.Empty;
-        internal string GetCompletionServiceName(IAsyncCompletionService service) => OrderedCompletionServiceProviders.FirstOrDefault(n => n.Value == service)?.Metadata.Name ?? string.Empty;
-        internal string GetCompletionPresenterProviderName(ICompletionPresenterProvider provider) => OrderedPresenterProviders.FirstOrDefault(n => n.Value == provider)?.Metadata.Name ?? string.Empty;
+        internal string GetItemSourceName(IAsyncCompletionItemSource source) => OrderedCompletionItemSourceProviders.FirstOrDefault(n => n.IsValueCreated && n.Value == source)?.Metadata.Name ?? string.Empty;
+        internal string GetCompletionServiceName(IAsyncCompletionService service) => OrderedCompletionServiceProviders.FirstOrDefault(n => n.IsValueCreated && n.Value == service)?.Metadata.Name ?? string.Empty;
+        internal string GetCompletionPresenterProviderName(ICompletionPresenterProvider provider) => OrderedPresenterProviders.FirstOrDefault(n => n.IsValueCreated && n.Value == provider)?.Metadata.Name ?? string.Empty;
 
         // Parity with legacy telemetry
         private void EmulateLegacyCompletionTelemetry(IContentType contentType, ITextView textView)
diff --git a/src/Language/Impl/Language/Completion/AsyncCompletionSession.cs b/src/Language/Impl/Language/Completion/AsyncCompletionSession.cs
index a0dd3ca..b7a49ba 100644
--- a/src/Language/Impl/Language/Completion/AsyncCompletionSession.cs
+++ b/src/Language/Impl/Language/Completion/AsyncCompletionSession.cs
@@ -22,15 +22,15 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
     internal class AsyncCompletionSession : IAsyncCompletionSession, ICompletionComputationCallbackHandler<CompletionModel>
     {
         // Available data and services
-        private readonly IDictionary<IAsyncCompletionItemSource, SnapshotSpan> _completionSources;
+        private readonly IDictionary<IAsyncCompletionItemSource, SnapshotPoint> _completionSources;
         private readonly IAsyncCompletionService _completionService;
         private readonly SnapshotSpan _initialApplicableSpan;
         private readonly JoinableTaskFactory _jtf;
         private readonly ICompletionPresenterProvider _presenterProvider;
         private readonly AsyncCompletionBroker _broker;
         private readonly ITextView _view;
-        private readonly ITextStructureNavigator _textStructureNavigator;
         private readonly IGuardedOperations _guardedOperations;
+        private readonly ImmutableArray<char> _potentialCommitChars;
 
         // Presentation:
         ICompletionPresenter _gui; // Must be accessed from GUI thread
@@ -67,18 +67,18 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
 
         public bool IsDismissed => _isDismissed;
 
-        public AsyncCompletionSession(SnapshotSpan applicableSpan, JoinableTaskFactory jtf, ICompletionPresenterProvider presenterProvider,
-            IDictionary<IAsyncCompletionItemSource, SnapshotSpan> completionSources,
+        public AsyncCompletionSession(SnapshotSpan applicableSpan, ImmutableArray<char> potentialCommitChars, JoinableTaskFactory jtf,
+            ICompletionPresenterProvider presenterProvider, IDictionary<IAsyncCompletionItemSource, SnapshotPoint> completionSources,
             IAsyncCompletionService completionService, AsyncCompletionBroker broker, ITextView view, CompletionTelemetryHost telemetryHost)
         {
             _initialApplicableSpan = applicableSpan;
+            _potentialCommitChars = potentialCommitChars;
             _jtf = jtf;
             _presenterProvider = presenterProvider;
             _broker = broker;
             _completionSources = completionSources;
             _completionService = completionService;
             _view = view;
-            _textStructureNavigator = broker.TextStructureNavigatorSelectorService?.GetTextStructureNavigator(view.TextBuffer);
             _guardedOperations = broker.GuardedOperations;
             _telemetry = new CompletionSessionTelemetry(telemetryHost, completionService, presenterProvider);
             PageStepSize = presenterProvider?.ResultsPerPage ?? 1;
@@ -87,6 +87,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
 
         bool IAsyncCompletionSession.CommitIfUnique(CancellationToken token)
         {
+            if (_isDismissed)
+                return false;
+
             // Note that this will deadlock if OpenOrUpdate wasn't called ahead of time.
             var lastModel = _computation.WaitAndGetResult();
             if (lastModel.UniqueItem != null)
@@ -133,7 +136,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 // Commit the suggestion mode item
                 return Commit(typedChar, lastModel.SuggestionModeItem, token);
             }
-            else if (!lastModel.PresentedItems.Any())
+            else if (lastModel.PresentedItems.IsDefaultOrEmpty)
             {
                 // There is nothing to commit
                 Dismiss();
@@ -149,6 +152,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         private CustomCommitBehavior Commit(char typedChar, CompletionItem itemToCommit, CancellationToken token)
         {
             CustomCommitBehavior result = CustomCommitBehavior.None;
+            if (_isDismissed)
+                return result;
+
             var lastModel = _computation.WaitAndGetResult();
 
             if (!_jtf.Context.IsOnMainThread)
@@ -195,8 +201,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             _broker.DismissSession(this);
             _guardedOperations.RaiseEvent(this, Dismissed);
             _view.Caret.PositionChanged -= OnCaretPositionChanged;
-            _computationCancellation.Cancel();
             _computation = null;
+            _computationCancellation.Cancel();
 
             if (_gui != null)
             {
@@ -218,6 +224,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
 
         void IAsyncCompletionSession.OpenOrUpdate(ITextView view, CompletionTrigger trigger, SnapshotPoint triggerLocation)
         {
+            if (_isDismissed)
+                return;
+
             if (_computation == null)
             {
                 _computation = new ModelComputation<CompletionModel>(PrioritizedTaskScheduler.AboveNormalInstance, _computationCancellation.Token, _guardedOperations, this);
@@ -230,6 +239,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
 
         internal void InvokeAndCommitIfUnique(ITextView view, CompletionTrigger trigger, SnapshotPoint triggerLocation, CancellationToken token)
         {
+            if (_isDismissed)
+                return;
+
             ((IAsyncCompletionSession)this).OpenOrUpdate(view, trigger, triggerLocation);
             if (((IAsyncCompletionSession)this).CommitIfUnique(token))
             {
@@ -305,18 +317,17 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             Dismiss();
         }
 
+        /// <summary>
+        /// Determines whether the commit code path should be taken. Since this method is on a typing hot path,
+        /// we return quickly if the character is not found in the predefined list of potential commit characters.
+        /// </summary>
+        /// <remarks>This method runs on UI thread. ShouldCommit performs mapping which requires UI thread.</remarks>
         bool IAsyncCompletionSession.ShouldCommit(ITextView view, char typeChar, SnapshotPoint triggerLocation)
         {
-            foreach (var contentType in CompletionUtilities.GetBuffersForPoint(view, triggerLocation).Select(b => b.ContentType))
+            if (_potentialCommitChars.Contains(typeChar))
             {
-                if (_broker.TryGetKnownCommitCharacters(contentType, view, out var commitChars))
-                {
-                    if (commitChars.Contains(typeChar))
-                    {
-                        if (ShouldCommit(view, typeChar, triggerLocation))
-                            return true;
-                    }
-                }
+                if (ShouldCommit(view, typeChar, triggerLocation))
+                    return true;
             }
             return false;
         }
@@ -392,7 +403,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 _completionSources.Select(
                     p => _guardedOperations.CallExtensionPointAsync<CompletionContext>(
                         errorSource: p.Key,
-                        asyncCall: () => p.Key.GetCompletionContextAsync(trigger, p.Value, token),
+                        asyncCall: () => p.Key.GetCompletionContextAsync(trigger, triggerLocation, _initialApplicableSpan, token),
                         valueOnThrow: null
                     )));
             var initialCompletionItems = nestedResults.Where(n => n != null && !n.Items.IsDefaultOrEmpty).SelectMany(n => n.Items).ToImmutableArray();
@@ -467,17 +478,29 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             // Always record keystrokes, even if filtering is preempted
             _telemetry.RecordKeystroke();
 
-            // Filtering got preempted, so store the most recent snapshot for the next time we filter
-            if (token.IsCancellationRequested || thisId != _lastFilteringTaskId)
-                return model.WithSnapshot(triggerLocation.Snapshot);
+            // Completion got cancelled
+            if (token.IsCancellationRequested || model == null)
+                return default(CompletionModel);
 
             // Dismiss if we are outside of the applicable span
-            // TODO: dismiss if applicable span was reduced to zero AND moved again (e.g. first backspace keeps completion open, second backspace closes it)
-            if (triggerLocation < model.ApplicableSpan.GetStartPoint(triggerLocation.Snapshot) || triggerLocation > model.ApplicableSpan.GetEndPoint(triggerLocation.Snapshot))
+            var currentlyApplicableSpan = model.ApplicableSpan.GetSpan(triggerLocation.Snapshot);
+            if (triggerLocation < currentlyApplicableSpan.Start
+                || triggerLocation > currentlyApplicableSpan.End)
+            {
+                ((IAsyncCompletionSession)this).Dismiss();
+                return model;
+            }
+            // Record the first time the span is empty. If it is empty the second time we're here, and user is deleting, then dismiss
+            if (currentlyApplicableSpan.IsEmpty && model.ApplicableSpanWasEmpty && trigger.Reason == CompletionTriggerReason.Deletion)
             {
                 ((IAsyncCompletionSession)this).Dismiss();
                 return model;
             }
+            model = model.WithApplicableSpanEmptyRecord(currentlyApplicableSpan.IsEmpty);
+
+            // Filtering got preempted, so store the most recent snapshot for the next time we filter
+            if (thisId != _lastFilteringTaskId)
+                return model.WithSnapshot(triggerLocation.Snapshot);
 
             ComputationStopwatch.Restart();
 
@@ -515,7 +538,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 model = model.WithSoftSelection(false);
 
             // Prepare the suggestionModeItem if we ever change the mode
-            var enteredText = model.ApplicableSpan.GetText(triggerLocation.Snapshot);
+            var enteredText = currentlyApplicableSpan.GetText();
             var suggestionModeItem = new CompletionItem(enteredText, SuggestionModeCompletionItemSource.Instance);
 
             _guardedOperations.RaiseEvent(this, ItemsUpdated, new CompletionItemsWithHighlightEventArgs(returnedItems));
@@ -654,6 +677,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         /// </summary>
         public bool ShouldCommit(ITextView view, char typeChar, SnapshotPoint triggerLocation)
         {
+            if (!_jtf.Context.IsOnMainThread)
+                throw new InvalidOperationException($"This method must be callled on the UI thread.");
+
             var mappingPoint = view.BufferGraph.CreateMappingPoint(triggerLocation, PointTrackingMode.Negative);
             return _completionSources
                 .Select(p => (p, mappingPoint.GetPoint(p.Value.Snapshot.TextBuffer, PositionAffinity.Predecessor)))
diff --git a/src/Language/Impl/Language/Completion/CompletionCommandHandlers.cs b/src/Language/Impl/Language/Completion/CompletionCommandHandlers.cs
index 7451582..2e14382 100644
--- a/src/Language/Impl/Language/Completion/CompletionCommandHandlers.cs
+++ b/src/Language/Impl/Language/Completion/CompletionCommandHandlers.cs
@@ -1,6 +1,7 @@
 using System;
 using System.ComponentModel.Composition;
 using Microsoft.VisualStudio.Commanding;
+using Microsoft.VisualStudio.Text;
 using Microsoft.VisualStudio.Text.Editor;
 using Microsoft.VisualStudio.Text.Editor.Commanding.Commands;
 using Microsoft.VisualStudio.Text.Operations;
@@ -120,7 +121,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             var applicableSpan = Broker.ShouldTriggerCompletion(args.TextView, default(char), location);
             if (applicableSpan.HasValue)
             {
-                var session = Broker.TriggerCompletion(args.TextView, applicableSpan.Value);
+                var session = Broker.TriggerCompletion(args.TextView, location, applicableSpan.Value);
                 session?.OpenOrUpdate(args.TextView, trigger, location);
                 return true;
             }
@@ -137,7 +138,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             var applicableSpan = Broker.ShouldTriggerCompletion(args.TextView, default(char), location);
             if (applicableSpan.HasValue)
             {
-                var session = Broker.TriggerCompletion(args.TextView, applicableSpan.Value) as AsyncCompletionSession;
+                var session = Broker.TriggerCompletion(args.TextView, location, applicableSpan.Value) as AsyncCompletionSession;
                 session?.InvokeAndCommitIfUnique(args.TextView, trigger, location, executionContext.OperationContext.UserCancellationToken);
                 return true;
             }
@@ -252,19 +253,30 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         void IChainedCommandHandler<TypeCharCommandArgs>.ExecuteCommand(TypeCharCommandArgs args, Action nextCommandHandler, CommandExecutionContext executionContext)
         {
             var initialTextSnapshot = args.TextView.TextSnapshot;
+            var view = args.TextView;
 
-            // Execute other commands in the chain to see the change in the buffer.
-            nextCommandHandler();
-
-            // We are only inteterested in the top buffer. Currently, commanding implementation calls us multiple times, once per each buffer.
-            if (args.TextView.BufferGraph.TopBuffer != args.SubjectBuffer)
+            if (args.TextView.TextBuffer != args.SubjectBuffer)
+            {
+                // We are only inteterested in the top buffer. Currently, commanding implementation calls us multiple times, once per each buffer.
+                // Allow other command handlers to act.
+                nextCommandHandler();
                 return;
+            }
 
-            var view = args.TextView;
             var location = view.Caret.Position.BufferPosition;
+            // Call ShouldCommit before nextCommandHandler so that extenders
+            // get the same view of the buffer in both ShouldCommit and Commit
             var sessionToCommit = Broker.GetSession(args.TextView);
-            if (sessionToCommit?.ShouldCommit(view, args.TypedChar, location) == true)
+            var shouldCommit = sessionToCommit?.ShouldCommit(view, args.TypedChar, location);
+
+            if (shouldCommit == true)
             {
+                // Execute other commands in the chain to see the change in the buffer.
+                nextCommandHandler();
+
+                // Buffer has changed, update the snapshot
+                location = view.Caret.Position.BufferPosition;
+
                 using (var undoTransaction = new CaretPreservingEditTransaction("Completion", view, UndoHistoryRegistry, EditorOperationsFactoryService))
                 {
                     UndoUtilities.RollbackToBeforeTypeChar(initialTextSnapshot, args.SubjectBuffer);
@@ -272,15 +284,20 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
 
                     var customBehavior = sessionToCommit.Commit(executionContext.OperationContext.UserCancellationToken, args.TypedChar);
 
-                    if ((customBehavior & CustomCommitBehavior.SurpressFurtherCommandHandlers) == 0)
+                    if ((customBehavior & CustomCommitBehavior.SuppressFurtherCommandHandlers) == 0)
                         nextCommandHandler(); // Replay the key, so that we get brace completion.
 
                     // Complete the transaction before stopping it.
                     undoTransaction.Complete();
                 }
-                // Snapshot has changed when committing. Update it for when we try to trigger new session.
-                location = view.Caret.Position.BufferPosition;
             }
+            else
+            {
+                nextCommandHandler();
+            }
+
+            // Buffer might have changed. Update it for when we try to trigger new session.
+            location = view.Caret.Position.BufferPosition;
 
             var trigger = new CompletionTrigger(CompletionTriggerReason.Insertion, args.TypedChar);
             var session = Broker.GetSession(args.TextView);
@@ -293,7 +310,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 var applicableSpan = Broker.ShouldTriggerCompletion(view, args.TypedChar, location);
                 if (applicableSpan.HasValue)
                 {
-                    var newSession = Broker.TriggerCompletion(view, applicableSpan.Value);
+                    var newSession = Broker.TriggerCompletion(view, location, applicableSpan.Value);
                     newSession?.OpenOrUpdate(view, trigger, location);
                 }
             }
diff --git a/src/Language/Impl/Language/Completion/CompletionModel.cs b/src/Language/Impl/Language/Completion/CompletionModel.cs
index 111b580..84d18f3 100644
--- a/src/Language/Impl/Language/Completion/CompletionModel.cs
+++ b/src/Language/Impl/Language/Completion/CompletionModel.cs
@@ -85,6 +85,12 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         public readonly CompletionItem UniqueItem;
 
         /// <summary>
+        /// When completion starts, its <see cref="ApplicableSpan"/> may be empty. Initially, don't dismiss.
+        /// Further, the span is empty if user removes characters. We would like to dismiss then.
+        /// </summary>
+        public readonly bool ApplicableSpanWasEmpty;
+
+        /// <summary>
         /// Constructor for the initial model
         /// </summary>
         public CompletionModel(ImmutableArray<CompletionItem> initialItems, ImmutableArray<CompletionItem> sortedItems,
@@ -104,6 +110,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             SuggestionModeDescription = suggestionModeDescription;
             SuggestionModeItem = suggestionModeItem;
             UniqueItem = null;
+            ApplicableSpanWasEmpty = false;
         }
 
         /// <summary>
@@ -111,7 +118,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         /// </summary>
         private CompletionModel(ImmutableArray<CompletionItem> initialItems, ImmutableArray<CompletionItem> sortedItems, ITrackingSpan applicableSpan, CompletionTriggerReason initialTriggerReason,
             ITextSnapshot snapshot, ImmutableArray<CompletionFilterWithState> filters, ImmutableArray<CompletionItemWithHighlight> presentedItems, bool useSoftSelection, bool useSuggestionMode,
-            string suggestionModeDescription, int selectedIndex, bool selectSuggestionMode, CompletionItem suggestionModeItem, CompletionItem uniqueItem)
+            string suggestionModeDescription, int selectedIndex, bool selectSuggestionMode, CompletionItem suggestionModeItem, CompletionItem uniqueItem, bool applicableSpanWasEmpty)
         {
             InitialItems = initialItems;
             SortedItems = sortedItems;
@@ -126,6 +133,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             SelectSuggestionMode = selectSuggestionMode;
             SuggestionModeDescription = suggestionModeDescription;
             SuggestionModeItem = suggestionModeItem;
+            ApplicableSpanWasEmpty = applicableSpanWasEmpty;
         }
 
         public CompletionModel WithPresentedItems(ImmutableArray<CompletionItemWithHighlight> newPresentedItems, int newSelectedIndex)
@@ -144,7 +152,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: newSelectedIndex, // Updated
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -164,7 +173,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: SelectedIndex,
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -184,7 +194,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: SelectedIndex,
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -204,7 +215,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: newIndex, // Updated
                 selectSuggestionMode: false, // Explicit selection of regular item
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -224,7 +236,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: -1, // Deselect regular item
                 selectSuggestionMode: true, // Explicit selection of suggestion item
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -244,7 +257,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: SelectedIndex,
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -267,7 +281,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: SelectedIndex,
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: newSuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -291,7 +306,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: SelectedIndex,
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: newUniqueItem
+                uniqueItem: newUniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -311,7 +327,8 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: SelectedIndex,
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: SuggestionModeItem,
-                uniqueItem: UniqueItem
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
             );
         }
 
@@ -331,7 +348,29 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
                 selectedIndex: selectedIndex, // Updated
                 selectSuggestionMode: SelectSuggestionMode,
                 suggestionModeItem: suggestionModeItem, // Updated
-                uniqueItem: uniqueItem // Updated
+                uniqueItem: uniqueItem, // Updated
+                applicableSpanWasEmpty: ApplicableSpanWasEmpty
+            );
+        }
+
+        internal CompletionModel WithApplicableSpanEmptyRecord(bool applicableSpanIsEmpty)
+        {
+            return new CompletionModel(
+                initialItems: InitialItems,
+                sortedItems: SortedItems,
+                applicableSpan: ApplicableSpan,
+                initialTriggerReason: InitialTriggerReason,
+                snapshot: Snapshot,
+                filters: Filters,
+                presentedItems: PresentedItems,
+                useSoftSelection: UseSoftSelection,
+                useSuggestionMode: DisplaySuggestionMode,
+                suggestionModeDescription: SuggestionModeDescription,
+                selectedIndex: SelectedIndex,
+                selectSuggestionMode: SelectSuggestionMode,
+                suggestionModeItem: SuggestionModeItem,
+                uniqueItem: UniqueItem,
+                applicableSpanWasEmpty: applicableSpanIsEmpty // Updated
             );
         }
     }
diff --git a/src/Language/Impl/Language/Completion/CompletionUtilities.cs b/src/Language/Impl/Language/Completion/CompletionUtilities.cs
index c1da8e3..0703cb6 100644
--- a/src/Language/Impl/Language/Completion/CompletionUtilities.cs
+++ b/src/Language/Impl/Language/Completion/CompletionUtilities.cs
@@ -100,45 +100,6 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             return pointsInBuffers;
         }
 
-        internal static IDictionary<IAsyncCompletionItemSource, SnapshotSpan> GetCompletionSourcesWithMappedSpans(ITextView textView, SnapshotSpan originalSpan, Func<IContentType, ImmutableArray<IAsyncCompletionItemSourceProvider>> completionItemSourceProviders)
-        {
-            // See comment in GetCompletionSourcesWithMappedPoints for explanation
-
-            var sortedContentTypes = new SortedSet<IContentType>(ContentTypeComparer.Instance);
-            var result = new Dictionary<IAsyncCompletionItemSource, SnapshotSpan>();
-
-            var mappedSpans = GetSpansOnAvailableBuffers(textView, originalSpan);
-            foreach (var mappedSpan in mappedSpans)
-            {
-                AddContentTypeHierarchy(sortedContentTypes, mappedSpan.Snapshot.ContentType);
-            }
-
-            foreach (var contentType in sortedContentTypes)
-            {
-                foreach (var mappedSpan in mappedSpans)
-                {
-                    if (mappedSpan.Snapshot.ContentType.IsOfType(contentType.TypeName))
-                    {
-                        foreach (var sourceProvider in completionItemSourceProviders(contentType))
-                        {
-                            var source = sourceProvider.GetOrCreate(textView);
-                            if (!result.ContainsKey(source))
-                                result.Add(source, mappedSpan);
-                        }
-                    }
-                }
-            }
-            return result;
-        }
-
-        private static IEnumerable<SnapshotSpan> GetSpansOnAvailableBuffers(ITextView textView, SnapshotSpan span)
-        {
-            var mappingSpan = textView.BufferGraph.CreateMappingSpan(span, SpanTrackingMode.EdgePositive);
-            var buffers = textView.BufferGraph.GetTextBuffers(b => mappingSpan.GetSpans(b).Any());
-            var spansInBuffers = buffers.Select(b => mappingSpan.GetSpans(b).First()); // TODO: What if there is more than one span?
-            return spansInBuffers;
-        }
-
         private static void AddContentTypeHierarchy(SortedSet<IContentType> sortedContentTypes, IContentType contentType)
         {
             sortedContentTypes.Add(contentType);
diff --git a/src/Language/Impl/Language/Completion/DefaultCompletionService.cs b/src/Language/Impl/Language/Completion/DefaultCompletionService.cs
index 563eb4d..50f3728 100644
--- a/src/Language/Impl/Language/Completion/DefaultCompletionService.cs
+++ b/src/Language/Impl/Language/Completion/DefaultCompletionService.cs
@@ -161,7 +161,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             return CustomCommitBehavior.None;
         }
 
-        async Task<CompletionContext> IAsyncCompletionItemSource.GetCompletionContextAsync(CompletionTrigger trigger, SnapshotSpan triggerLocation, CancellationToken token)
+        async Task<CompletionContext> IAsyncCompletionItemSource.GetCompletionContextAsync(CompletionTrigger trigger, SnapshotPoint triggerLocation, SnapshotSpan triggerLocation, CancellationToken token)
         {
             return await Task.FromResult(new CompletionContext(
                 ImmutableArray.Create(
@@ -193,7 +193,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         SnapshotSpan? IAsyncCompletionItemSource.ShouldTriggerCompletion(char typeChar, SnapshotPoint triggerLocation)
         {
             var charBeforeCaret = triggerLocation.Subtract(1).GetChar();
-            if (commitCharacters.Contains(charBeforeCaret))
+            if (commitCharacters.Contains(charBeforeCaret) || triggerLocation.Position == 0)
             {
                 // skip the typed character. the applicable span starts at the caret
                 return new SnapshotSpan(triggerLocation, 0);
@@ -206,6 +206,9 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         }
     }
 
+#endif
+#if DEBUG && true
+
     [Export(typeof(IAsyncCompletionItemSourceProvider))]
     [Name("Debug HTML completion item source")]
     [Order(After = "default")]
@@ -231,7 +234,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             return CustomCommitBehavior.None;
         }
 
-        async Task<CompletionContext> IAsyncCompletionItemSource.GetCompletionContextAsync(CompletionTrigger trigger, SnapshotSpan applicableSpan, CancellationToken token)
+        async Task<CompletionContext> IAsyncCompletionItemSource.GetCompletionContextAsync(CompletionTrigger trigger, SnapshotPoint triggerLocation, SnapshotSpan applicableSpan, CancellationToken token)
         {
             return await Task.FromResult(new CompletionContext(ImmutableArray.Create(new CompletionItem("html", this), new CompletionItem("head", this), new CompletionItem("body", this), new CompletionItem("header", this))));
         }
@@ -254,7 +257,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
         SnapshotSpan? IAsyncCompletionItemSource.ShouldTriggerCompletion(char typeChar, SnapshotPoint triggerLocation)
         {
             var charBeforeCaret = triggerLocation.Subtract(1).GetChar();
-            if (commitCharacters.Contains(charBeforeCaret))
+            if (commitCharacters.Contains(charBeforeCaret) || triggerLocation.Position == 0)
             {
                 // skip the typed character. the applicable span starts at the caret
                 return new SnapshotSpan(triggerLocation, 0);
diff --git a/src/Language/Impl/Language/Completion/ImportBucket.cs b/src/Language/Impl/Language/Completion/ImportBucket.cs
new file mode 100644
index 0000000..ba631d0
--- /dev/null
+++ b/src/Language/Impl/Language/Completion/ImportBucket.cs
@@ -0,0 +1,45 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.VisualStudio.Text.Utilities;
+
+namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
+{
+    /// <summary>
+    /// Lightweight stack-like view over a readonly ordered list of command handlers.
+    /// </summary>
+    internal class ImportBucket<T>
+    {
+        private int _currentImportSetting;
+        private readonly IReadOnlyList<Lazy<T, IOrderableContentTypeMetadata>> _imports;
+
+        public ImportBucket(IReadOnlyList<Lazy<T, IOrderableContentTypeMetadata>> imports)
+        {
+            _imports = imports ?? throw new ArgumentNullException(nameof(imports));
+        }
+
+        public bool IsEmpty => _currentImportSetting >= _imports.Count;
+
+        public Lazy<T, IOrderableContentTypeMetadata> Peek()
+        {
+            if (!IsEmpty)
+            {
+                return _imports[_currentImportSetting];
+            }
+
+            throw new InvalidOperationException($"{nameof(ImportBucket<T>)} is empty.");
+        }
+
+        internal Lazy<T, IOrderableContentTypeMetadata> Pop()
+        {
+            if (!IsEmpty)
+            {
+                return _imports[_currentImportSetting++];
+            }
+
+            throw new InvalidOperationException($"{nameof(ImportBucket<T>)} is empty.");
+        }
+    }
+}
diff --git a/src/Language/Impl/Language/Completion/SuggestionModeCompletionItemSource.cs b/src/Language/Impl/Language/Completion/SuggestionModeCompletionItemSource.cs
index dc5b31e..a5b34e4 100644
--- a/src/Language/Impl/Language/Completion/SuggestionModeCompletionItemSource.cs
+++ b/src/Language/Impl/Language/Completion/SuggestionModeCompletionItemSource.cs
@@ -28,7 +28,7 @@ namespace Microsoft.VisualStudio.Language.Intellisense.Implementation
             return CustomCommitBehavior.None;
         }
 
-        Task<CompletionContext> IAsyncCompletionItemSource.GetCompletionContextAsync(CompletionTrigger trigger, SnapshotSpan applicableSpan, CancellationToken token)
+        Task<CompletionContext> IAsyncCompletionItemSource.GetCompletionContextAsync(CompletionTrigger trigger, SnapshotPoint triggerLocation, SnapshotSpan applicableSpan, CancellationToken token)
         {
             throw new NotImplementedException("This item source is not meant to be registered. It is used only to provide tooltip.");
         }
diff --git a/src/Microsoft.VisualStudio.Text.Implementation.csproj b/src/Microsoft.VisualStudio.Text.Implementation.csproj
index 13cdb29..2b7377c 100644
--- a/src/Microsoft.VisualStudio.Text.Implementation.csproj
+++ b/src/Microsoft.VisualStudio.Text.Implementation.csproj
@@ -5,10 +5,10 @@
     <SignAssembly>true</SignAssembly>
     <AssemblyOriginatorKeyFile>key.snk</AssemblyOriginatorKeyFile>
     <DelaySign>false</DelaySign>
-    <Version>15.0.18-pre</Version>
+    <Version>15.0.19-pre</Version>
     <AssemblyVersion>15.0.0.0</AssemblyVersion>
-    <NuGetVersionEditor>15.7.95-preview-gf6780a6ebe</NuGetVersionEditor>
-    <NuGetVersionLanguage>15.7.95-preview-gf6780a6ebe</NuGetVersionLanguage>
+    <NuGetVersionEditor>15.7.111-preview-g28b775fb96</NuGetVersionEditor>
+    <NuGetVersionLanguage>15.7.111-preview-g28b775fb96</NuGetVersionLanguage>
   </PropertyGroup>
 
   <PropertyGroup>