Simplified provisional completion implementation (#1749)

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/CSharpVirtualDocument.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using System.Diagnostics;
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.VisualStudio.Text;
 
@@ -12,11 +11,8 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
     internal class CSharpVirtualDocument : VirtualDocument
     {
         private long? _hostDocumentSyncVersion;
-        private CSharpVirtualDocumentSnapshot _previousSnapshot;
         private CSharpVirtualDocumentSnapshot _currentSnapshot;
 
-        private bool _hasProvisionalChanges = false;
-
         public CSharpVirtualDocument(Uri uri, ITextBuffer textBuffer)
         {
             if (uri is null)
@@ -31,7 +27,6 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             Uri = uri;
             TextBuffer = textBuffer;
-            _previousSnapshot = null;
             _currentSnapshot = UpdateSnapshot();
         }
 
@@ -43,7 +38,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
         public override VirtualDocumentSnapshot CurrentSnapshot => _currentSnapshot;
 
-        public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional = false)
+        public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion)
         {
             if (changes is null)
             {
@@ -52,16 +47,13 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             _hostDocumentSyncVersion = hostDocumentVersion;
 
-            TryRevertProvisionalChanges();
-            _hasProvisionalChanges = provisional;
-
             if (changes.Count == 0)
             {
                 _currentSnapshot = UpdateSnapshot();
                 return _currentSnapshot;
             }
 
-            using var edit = TextBuffer.CreateEdit();
+            using var edit = TextBuffer.CreateEdit(EditOptions.None, reiteratedVersionNumber: null, InviolableEditTag.Instance);
             for (var i = 0; i < changes.Count; i++)
             {
                 var change = changes[i];
@@ -90,42 +82,6 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             return _currentSnapshot;
         }
 
-        private bool TryRevertProvisionalChanges()
-        {
-            if (!_hasProvisionalChanges)
-            {
-                return false;
-            }
-
-            Debug.Assert(_previousSnapshot != null);
-
-            using var revertEdit = TextBuffer.CreateEdit(EditOptions.None, _previousSnapshot.Snapshot.Version.VersionNumber, InviolableEditTag.Instance);
-            var previousChanges = _previousSnapshot.Snapshot.Version.Changes;
-            for (var i = 0; i < previousChanges.Count; i++)
-            {
-                var change = previousChanges[i];
-                revertEdit.Replace(change.NewSpan, change.OldText);
-            }
-
-            revertEdit.Apply();
-
-            _hasProvisionalChanges = false;
-
-            return true;
-        }
-
-        private CSharpVirtualDocumentSnapshot UpdateSnapshot()
-        {
-            _previousSnapshot = _currentSnapshot;
-            return new CSharpVirtualDocumentSnapshot(Uri, TextBuffer.CurrentSnapshot, HostDocumentSyncVersion);
-        }
-
-        // This indicates that no other entity should respond to the edit event associated with this tag.
-        private class InviolableEditTag : IInviolableEditTag
-        {
-            private InviolableEditTag() { }
-
-            public readonly static IInviolableEditTag Instance = new InviolableEditTag();
-        }
+        private CSharpVirtualDocumentSnapshot UpdateSnapshot() => new CSharpVirtualDocumentSnapshot(Uri, TextBuffer.CurrentSnapshot, HostDocumentSyncVersion);
     }
 }

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/DefaultLSPDocument.cs

@@ -58,14 +58,14 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             }
         }
 
-        public override LSPDocumentSnapshot UpdateVirtualDocument<TVirtualDocument>(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional = false)
+        public override LSPDocumentSnapshot UpdateVirtualDocument<TVirtualDocument>(IReadOnlyList<TextChange> changes, long hostDocumentVersion)
         {
             if (!TryGetVirtualDocument<TVirtualDocument>(out var virtualDocument))
             {
                 throw new InvalidOperationException($"Cannot update virtual document of type {typeof(TVirtualDocument)} because LSP document {Uri} does not contain a virtual document of that type.");
             }
 
-            virtualDocument.Update(changes, hostDocumentVersion, provisional);
+            virtualDocument.Update(changes, hostDocumentVersion);
 
             _currentSnapshot = UpdateSnapshot();
 

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/DefaultLSPDocumentManager.cs

@@ -101,8 +101,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
         public override void UpdateVirtualDocument<TVirtualDocument>(
             Uri hostDocumentUri,
             IReadOnlyList<TextChange> changes,
-            long hostDocumentVersion,
-            bool provisional = false)
+            long hostDocumentVersion)
         {
             if (hostDocumentUri is null)
             {
@@ -133,7 +132,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             var old = lspDocument.CurrentSnapshot;
             var oldVirtual = virtualDocument.CurrentSnapshot;
-            var @new = lspDocument.UpdateVirtualDocument<TVirtualDocument>(changes, hostDocumentVersion, provisional);
+            var @new = lspDocument.UpdateVirtualDocument<TVirtualDocument>(changes, hostDocumentVersion);
 
             if (old == @new)
             {

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/HtmlCSharp/CompletionHandler.cs

@@ -78,37 +78,40 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
                 return null;
             }
 
-            var completionParams = new CompletionParams()
-            {
-                Context = request.Context,
-                Position = projectionResult.Position,
-                TextDocument = new TextDocumentIdentifier()
-                {
-                    Uri = projectionResult.Uri
-                }
-            };
+            
 
             var serverKind = projectionResult.LanguageKind == RazorLanguageKind.CSharp ? LanguageServerKind.CSharp : LanguageServerKind.Html;
 
-            var provisionalCompletionParams = await GetProvisionalCompletionParamsAsync(request, documentSnapshot, projectionResult, cancellationToken).ConfigureAwait(false);
-            if (provisionalCompletionParams != null)
+            var (succeeded, result) = await TryGetProvisionalCompletionsAsync(request, documentSnapshot, projectionResult, cancellationToken).ConfigureAwait(false);
+            if (succeeded)
             {
                 // This means the user has just typed a dot after some identifier such as (cursor is pipe): "DateTime.| "
                 // In this case Razor interprets after the dot as Html and before it as C#.
                 // We use this criteria to provide a better completion experience for what we call provisional changes.
-                completionParams = provisionalCompletionParams;
-                serverKind = LanguageServerKind.CSharp;
             }
             else if (!TriggerAppliesToProjection(request.Context, projectionResult.LanguageKind))
             {
                 return null;
             }
+            else
+            {
+                // This is a valid non-provisional completion request.
+                var completionParams = new CompletionParams()
+                {
+                    Context = request.Context,
+                    Position = projectionResult.Position,
+                    TextDocument = new TextDocumentIdentifier()
+                    {
+                        Uri = projectionResult.Uri
+                    }
+                };
 
-            var result = await _requestInvoker.RequestServerAsync<CompletionParams, SumType<CompletionItem[], CompletionList>?>(
-                Methods.TextDocumentCompletionName,
-                serverKind,
-                completionParams,
-                cancellationToken).ConfigureAwait(false);
+                result = await _requestInvoker.RequestServerAsync<CompletionParams, SumType<CompletionItem[], CompletionList>?>(
+                    Methods.TextDocumentCompletionName,
+                    serverKind,
+                    completionParams,
+                    cancellationToken).ConfigureAwait(false);
+            }
 
             if (result.HasValue)
             {
@@ -119,43 +122,43 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
             return result;
         }
 
-        internal async Task<CompletionParams> GetProvisionalCompletionParamsAsync(CompletionParams request, LSPDocumentSnapshot documentSnapshot, ProjectionResult projection, CancellationToken cancellationToken)
+        internal async Task<(bool, SumType<CompletionItem[], CompletionList>?)> TryGetProvisionalCompletionsAsync(CompletionParams request, LSPDocumentSnapshot documentSnapshot, ProjectionResult projection, CancellationToken cancellationToken)
         {
+            SumType<CompletionItem[], CompletionList>? result = null;
             if (projection.LanguageKind != RazorLanguageKind.Html ||
                 request.Context.TriggerKind != CompletionTriggerKind.TriggerCharacter ||
                 request.Context.TriggerCharacter != ".")
             {
-                return null;
+                return (false, result);
             }
 
             if (projection.Position.Character == 0)
             {
                 // We're at the start of line. Can't have provisional completions here.
-                return null;
+                return (false, result);
             }
 
             var previousCharacterPosition = new Position(projection.Position.Line, projection.Position.Character - 1);
             var previousCharacterProjection = await _projectionProvider.GetProjectionAsync(documentSnapshot, previousCharacterPosition, cancellationToken).ConfigureAwait(false);
             if (previousCharacterProjection == null || previousCharacterProjection.LanguageKind != RazorLanguageKind.CSharp)
             {
-                return null;
+                return (false, result);
             }
 
             if (!(_documentManager is TrackingLSPDocumentManager trackingDocumentManager))
             {
-                return null;
+                return (false, result);
             }
 
             // Edit the CSharp projected document to contain a '.'. This allows C# completion to provide valid
             // completion items for moments when a user has typed a '.' that's typically interpreted as Html.
-            var changes = new[]
-            {
-                new TextChange(TextSpan.FromBounds(previousCharacterProjection.PositionIndex, previousCharacterProjection.PositionIndex), "."),
-            };
+            var addProvisionalDot = new TextChange(
+                TextSpan.FromBounds(previousCharacterProjection.PositionIndex, previousCharacterProjection.PositionIndex),
+                ".");
 
             await _joinableTaskFactory.SwitchToMainThreadAsync();
 
-            trackingDocumentManager.UpdateVirtualDocument<CSharpVirtualDocument>(documentSnapshot.Uri, changes, previousCharacterProjection.HostDocumentVersion, provisional: true);
+            trackingDocumentManager.UpdateVirtualDocument<CSharpVirtualDocument>(documentSnapshot.Uri, new[] { addProvisionalDot }, previousCharacterProjection.HostDocumentVersion);
 
             var provisionalCompletionParams = new CompletionParams()
             {
@@ -164,7 +167,20 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
                 TextDocument = new TextDocumentIdentifier() { Uri = previousCharacterProjection.Uri }
             };
 
-            return provisionalCompletionParams;
+            result = await _requestInvoker.RequestServerAsync<CompletionParams, SumType<CompletionItem[], CompletionList>?>(
+                Methods.TextDocumentCompletionName,
+                LanguageServerKind.CSharp,
+                provisionalCompletionParams,
+                cancellationToken).ConfigureAwait(true);
+
+            // We have now obtained the necessary completion items. We no longer need the provisional change. Revert.
+            var removeProvisionalDot = new TextChange(
+                TextSpan.FromBounds(previousCharacterProjection.PositionIndex, previousCharacterProjection.PositionIndex + 1),
+                string.Empty);
+
+            trackingDocumentManager.UpdateVirtualDocument<CSharpVirtualDocument>(documentSnapshot.Uri, new[] { removeProvisionalDot }, previousCharacterProjection.HostDocumentVersion);
+
+            return (true, result);
         }
 
         // Internal for testing

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/HtmlVirtualDocument.cs

@@ -38,7 +38,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
         public override VirtualDocumentSnapshot CurrentSnapshot => _currentSnapshot;
 
-        public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional = false)
+        public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion)
         {
             if (changes is null)
             {
@@ -53,7 +53,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
                 return _currentSnapshot;
             }
 
-            using var edit = TextBuffer.CreateEdit();
+            using var edit = TextBuffer.CreateEdit(EditOptions.None, reiteratedVersionNumber: null, InviolableEditTag.Instance);
             for (var i = 0; i < changes.Count; i++)
             {
                 var change = changes[i];

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/InviolableEditTag.cs

@@ -0,0 +1,15 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using Microsoft.VisualStudio.Text;
+
+namespace Microsoft.VisualStudio.LanguageServerClient.Razor
+{
+    // Used to indicate that no other entity should respond to the edit event associated with this tag.
+    internal class InviolableEditTag : IInviolableEditTag
+    {
+        private InviolableEditTag() { }
+
+        public readonly static IInviolableEditTag Instance = new InviolableEditTag();
+    }
+}

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/LSPDocument.cs

@@ -20,7 +20,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
         public abstract IReadOnlyList<VirtualDocument> VirtualDocuments { get; }
 
-        public abstract LSPDocumentSnapshot UpdateVirtualDocument<TVirtualDocument>(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional = false) where TVirtualDocument : VirtualDocument;
+        public abstract LSPDocumentSnapshot UpdateVirtualDocument<TVirtualDocument>(IReadOnlyList<TextChange> changes, long hostDocumentVersion) where TVirtualDocument : VirtualDocument;
 
         public bool TryGetVirtualDocument<TVirtualDocument>(out TVirtualDocument virtualDocument) where TVirtualDocument : VirtualDocument
         {

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/TrackingLSPDocumentManager.cs

@@ -17,7 +17,6 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
         public abstract void UpdateVirtualDocument<TVirtualDocument>(
             Uri hostDocumentUri,
             IReadOnlyList<TextChange> changes,
-            long hostDocumentVersion,
-            bool provisional = false) where TVirtualDocument : VirtualDocument;
+            long hostDocumentVersion) where TVirtualDocument : VirtualDocument;
     }
 }

src/Razor/src/Microsoft.VisualStudio.LanguageServerClient.Razor/VirtualDocument.cs

@@ -18,6 +18,6 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
         public abstract long? HostDocumentSyncVersion { get; }
 
-        public abstract VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional = false);
+        public abstract VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion);
     }
 }

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/CSharpVirtualDocumentTest.cs

@@ -119,7 +119,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             edit.Setup(e => e.Replace(replace.Span.Start, replace.Span.Length, replace.NewText));
             var textBuffer = new Mock<ITextBuffer>();
             var textBufferSnapshot = Mock.Of<ITextSnapshot>();
-            textBuffer.Setup(buffer => buffer.CreateEdit())
+            textBuffer.Setup(buffer => buffer.CreateEdit(EditOptions.None, null, It.IsAny<IInviolableEditTag>()))
                 .Returns(edit.Object);
             textBuffer.Setup(buffer => buffer.CurrentSnapshot)
                 .Returns(() => textBufferSnapshot);
@@ -138,55 +138,9 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             Assert.Same(editedSnapshot, document.CurrentSnapshot.Snapshot);
         }
 
-        [Fact]
-        public void Update_Provisional_AppliesAndRevertsProvisionalChanges()
+        public static ITextBuffer CreateTextBuffer(ITextEdit edit)
         {
-            // Arrange
-            var insert = new TextChange(new TextSpan(123, 0), ".");
-            var edit = new Mock<ITextEdit>();
-            edit.Setup(e => e.Insert(insert.Span.Start, insert.NewText)).Verifiable();
-            edit.Setup(e => e.Apply()).Verifiable();
-
-            var revertEdit = new Mock<ITextEdit>();
-            revertEdit.Setup(e => e.Replace(new Span(123, 1), string.Empty)).Verifiable();
-            revertEdit.Setup(e => e.Apply()).Verifiable();
-
-            var textBuffer = CreateTextBuffer(edit.Object, revertEdit.Object, new[] { insert });
-            var document = new CSharpVirtualDocument(Uri, textBuffer);
-
-            // Make a provisional edit followed by another edit.
-
-            // Act 1
-            document.Update(new[] { insert }, hostDocumentVersion: 1, provisional: true);
-
-            // Assert 1
-            edit.VerifyAll();
-
-            // Act 2
-            document.Update(new[] { new TextChange(new TextSpan(125, 0), "Some other edit") }, hostDocumentVersion: 2, provisional: false);
-
-            // Assert 2
-            revertEdit.VerifyAll();
-        }
-
-        public static ITextBuffer CreateTextBuffer(ITextEdit edit, ITextEdit revertEdit = null, TextChange[] provisionalChanges = null)
-        {
-            var changes = new TestTextChangeCollection();
-            if (provisionalChanges != null)
-            {
-                foreach (var provisionalChange in provisionalChanges)
-                {
-                    var change = new Mock<ITextChange>();
-                    change.SetupGet(c => c.NewSpan).Returns(new Span(provisionalChange.Span.Start, provisionalChange.NewText.Length));
-                    change.SetupGet(c => c.OldText).Returns(string.Empty);
-                    changes.Add(change.Object);
-                }
-            }
-
-            var textBuffer = Mock.Of<ITextBuffer>(
-                buffer => buffer.CreateEdit() == edit &&
-                buffer.CreateEdit(EditOptions.None, It.IsAny<int?>(), It.IsAny<IInviolableEditTag>()) == revertEdit &&
-                buffer.CurrentSnapshot == Mock.Of<ITextSnapshot>(s => s.Version.Changes == changes));
+            var textBuffer = Mock.Of<ITextBuffer>(buffer => buffer.CreateEdit(EditOptions.None, null, It.IsAny<IInviolableEditTag>()) == edit && buffer.CurrentSnapshot == Mock.Of<ITextSnapshot>());
             return textBuffer;
         }
 

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/DefaultLSPDocumentManagerTest.cs

@@ -27,7 +27,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
                 document.Uri == Uri &&
                 document.CurrentSnapshot == LSPDocumentSnapshot &&
                 document.VirtualDocuments == new[] { new TestVirtualDocument() } &&
-                document.UpdateVirtualDocument<TestVirtualDocument>(It.IsAny<IReadOnlyList<TextChange>>(), It.IsAny<long>(), It.IsAny<bool>()) == Mock.Of<LSPDocumentSnapshot>());
+                document.UpdateVirtualDocument<TestVirtualDocument>(It.IsAny<IReadOnlyList<TextChange>>(), It.IsAny<long>()) == Mock.Of<LSPDocumentSnapshot>());
             LSPDocumentFactory = Mock.Of<LSPDocumentFactory>(factory => factory.Create(TextBuffer) == LSPDocument);
         }
 
@@ -146,7 +146,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             var changes = new[] { new TextChange(new TextSpan(1, 1), string.Empty) };
 
             // Act
-            manager.UpdateVirtualDocument<TestVirtualDocument>(Uri, changes, 123, provisional: true);
+            manager.UpdateVirtualDocument<TestVirtualDocument>(Uri, changes, 123);
 
             // Assert
             Assert.True(changedCalled);
@@ -207,7 +207,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             public override long? HostDocumentSyncVersion => 123;
 
-            public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional)
+            public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion)
             {
                 throw new NotImplementedException();
             }

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/DefaultLSPDocumentTest.cs

@@ -31,12 +31,11 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             var originalSnapshot = document.CurrentSnapshot;
 
             // Act
-            document.UpdateVirtualDocument<TestVirtualDocument>(changes, hostDocumentVersion: 1337, provisional: true);
+            document.UpdateVirtualDocument<TestVirtualDocument>(changes, hostDocumentVersion: 1337);
 
             // Assert
             Assert.Equal(1337, virtualDocument.HostDocumentSyncVersion);
             Assert.Same(changes, virtualDocument.Changes);
-            Assert.True(virtualDocument.Provisional);
             Assert.NotEqual(originalSnapshot, document.CurrentSnapshot);
         }
 
@@ -46,8 +45,6 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             public IReadOnlyList<TextChange> Changes { get; private set; }
 
-            public bool Provisional { get; private set; }
-
             public override Uri Uri => throw new NotImplementedException();
 
             public override ITextBuffer TextBuffer => throw new NotImplementedException();
@@ -56,11 +53,10 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             public override long? HostDocumentSyncVersion => _hostDocumentVersion;
 
-            public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional)
+            public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion)
             {
                 _hostDocumentVersion = hostDocumentVersion;
                 Changes = changes;
-                Provisional = provisional;
 
                 return null;
             }

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/DefaultRazorLanguageServerCustomMessageTargetTest.cs

@@ -53,7 +53,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
         {
             // Arrange
             var documentManager = new Mock<TrackingLSPDocumentManager>();
-            documentManager.Setup(manager => manager.UpdateVirtualDocument<CSharpVirtualDocument>(It.IsAny<Uri>(), It.IsAny<IReadOnlyList<TextChange>>(), 1337, false /* UpdateCSharpBuffer request should never be provisional */))
+            documentManager.Setup(manager => manager.UpdateVirtualDocument<CSharpVirtualDocument>(It.IsAny<Uri>(), It.IsAny<IReadOnlyList<TextChange>>(), 1337))
                 .Verifiable();
             var target = new DefaultRazorLanguageServerCustomMessageTarget(documentManager.Object);
             var request = new UpdateBufferRequest()

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/HtmlCSharp/CompletionHandlerTest.cs

@@ -343,7 +343,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
         }
 
         [Fact]
-        public async Task GetProvisionalCompletionParamsAsync_CSharpProjection_ReturnsNull()
+        public async Task TryGetProvisionalCompletionsAsync_CSharpProjection_ReturnsFalse()
         {
             // Arrange
             var completionRequest = new CompletionParams()
@@ -371,14 +371,15 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
             var completionHandler = new CompletionHandler(JoinableTaskContext, requestInvoker.Object, documentManager, projectionProvider.Object);
 
             // Act
-            var result = await completionHandler.GetProvisionalCompletionParamsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
+            var (succeeded, result) = await completionHandler.TryGetProvisionalCompletionsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
 
             // Assert
+            Assert.False(succeeded);
             Assert.Null(result);
         }
 
         [Fact]
-        public async Task GetProvisionalCompletionParamsAsync_TriggerCharacterNotDot_ReturnsNull()
+        public async Task TryGetProvisionalCompletionsAsync_TriggerCharacterNotDot_ReturnsFalse()
         {
             // Arrange
             var completionRequest = new CompletionParams()
@@ -406,14 +407,15 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
             var completionHandler = new CompletionHandler(JoinableTaskContext, requestInvoker.Object, documentManager, projectionProvider.Object);
 
             // Act
-            var result = await completionHandler.GetProvisionalCompletionParamsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
+            var (succeeded, result) = await completionHandler.TryGetProvisionalCompletionsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
 
             // Assert
+            Assert.False(succeeded);
             Assert.Null(result);
         }
 
         [Fact]
-        public async Task GetProvisionalCompletionParamsAsync_PreviousCharacterHtml_ReturnsNull()
+        public async Task TryGetProvisionalCompletionsAsync_PreviousCharacterHtml_ReturnsFalse()
         {
             // Arrange
             var completionRequest = new CompletionParams()
@@ -447,14 +449,15 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
             var completionHandler = new CompletionHandler(JoinableTaskContext, requestInvoker.Object, documentManager, projectionProvider.Object);
 
             // Act
-            var result = await completionHandler.GetProvisionalCompletionParamsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
+            var (succeeded, result) = await completionHandler.TryGetProvisionalCompletionsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
 
             // Assert
+            Assert.False(succeeded);
             Assert.Null(result);
         }
 
         [Fact]
-        public async Task GetProvisionalCompletionParamsAsync_ProjectionAtStartOfLine_ReturnsNull()
+        public async Task TryGetProvisionalCompletionsAsync_ProjectionAtStartOfLine_ReturnsFalse()
         {
             // Arrange
             var completionRequest = new CompletionParams()
@@ -488,14 +491,15 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
             var completionHandler = new CompletionHandler(JoinableTaskContext, requestInvoker.Object, documentManager, projectionProvider.Object);
 
             // Act
-            var result = await completionHandler.GetProvisionalCompletionParamsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
+            var (succeeded, result) = await completionHandler.TryGetProvisionalCompletionsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
 
             // Assert
+            Assert.False(succeeded);
             Assert.Null(result);
         }
 
         [Fact]
-        public async Task GetProvisionalCompletionParamsAsync_AtCorrectProvisionalCompletionPoint_ReturnsCorrectParams()
+        public async Task TryGetProvisionalCompletionsAsync_AtCorrectProvisionalCompletionPoint_ReturnsExpectedResult()
         {
             // Arrange
             var completionRequest = new CompletionParams()
@@ -513,7 +517,18 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
 
             var documentManager = new TestDocumentManager();
 
-            var requestInvoker = new Mock<LSPRequestInvoker>();
+            var languageServerCalled = false;
+            var expectedItem = new CompletionItem() { InsertText = "DateTime" };
+            var requestInvoker = new Mock<LSPRequestInvoker>(MockBehavior.Strict);
+            requestInvoker
+                .Setup(r => r.RequestServerAsync<CompletionParams, SumType<CompletionItem[], CompletionList>?>(It.IsAny<string>(), LanguageServerKind.CSharp, It.IsAny<CompletionParams>(), It.IsAny<CancellationToken>()))
+                .Callback<string, LanguageServerKind, CompletionParams, CancellationToken>((method, serverKind, completionParams, ct) =>
+                {
+                    Assert.Equal(Methods.TextDocumentCompletionName, method);
+                    Assert.Equal(LanguageServerKind.CSharp, serverKind);
+                    languageServerCalled = true;
+                })
+                .Returns(Task.FromResult<SumType<CompletionItem[], CompletionList>?>(new[] { expectedItem }));
 
             var projectionResult = new ProjectionResult()
             {
@@ -533,15 +548,15 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
             var completionHandler = new CompletionHandler(JoinableTaskContext, requestInvoker.Object, documentManager, projectionProvider.Object);
 
             // Act
-            var result = await completionHandler.GetProvisionalCompletionParamsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
+            var (succeeded, result) = await completionHandler.TryGetProvisionalCompletionsAsync(completionRequest, Mock.Of<LSPDocumentSnapshot>(), projectionResult, CancellationToken.None).ConfigureAwait(false);
 
             // Assert
-            Assert.True(documentManager.UpdateVirtualDocumentCalled);
+            Assert.True(succeeded);
+            Assert.True(languageServerCalled);
+            Assert.Equal(2, documentManager.UpdateVirtualDocumentCallCount);
             Assert.NotNull(result);
-            Assert.Same(completionRequest.Context, result.Context);
-            Assert.Equal(virtualDocumentUri, result.TextDocument.Uri);
-            Assert.Equal(previousCharacterProjection.Position.Line, result.Position.Line);
-            Assert.Equal(previousCharacterProjection.Position.Character + 1, result.Position.Character);
+            var item = Assert.Single((CompletionItem[])result.Value);
+            Assert.Equal(expectedItem.InsertText, item.InsertText);
         }
 
         private class TestDocumentManager : TrackingLSPDocumentManager
@@ -550,7 +565,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
 
             public override event EventHandler<LSPDocumentChangeEventArgs> Changed;
 
-            public bool UpdateVirtualDocumentCalled { get; private set; }
+            public int UpdateVirtualDocumentCallCount { get; private set; }
 
             public override bool TryGetDocument(Uri uri, out LSPDocumentSnapshot lspDocumentSnapshot)
             {
@@ -574,9 +589,9 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor.HtmlCSharp
                 throw new NotImplementedException();
             }
 
-            public override void UpdateVirtualDocument<TVirtualDocument>(Uri hostDocumentUri, IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional = false)
+            public override void UpdateVirtualDocument<TVirtualDocument>(Uri hostDocumentUri, IReadOnlyList<TextChange> changes, long hostDocumentVersion)
             {
-                UpdateVirtualDocumentCalled = true;
+                UpdateVirtualDocumentCallCount++;
             }
         }
     }

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/HtmlVirtualDocumentTest.cs

@@ -118,7 +118,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
             edit.Setup(e => e.Replace(replace.Span.Start, replace.Span.Length, replace.NewText));
             var textBuffer = new Mock<ITextBuffer>();
             var textBufferSnapshot = Mock.Of<ITextSnapshot>();
-            textBuffer.Setup(buffer => buffer.CreateEdit())
+            textBuffer.Setup(buffer => buffer.CreateEdit(EditOptions.None, null, It.IsAny<IInviolableEditTag>()))
                 .Returns(edit.Object);
             textBuffer.Setup(buffer => buffer.CurrentSnapshot)
                 .Returns(() => textBufferSnapshot);
@@ -139,7 +139,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
         public static ITextBuffer CreateTextBuffer(ITextEdit edit)
         {
-            var textBuffer = Mock.Of<ITextBuffer>(buffer => buffer.CreateEdit() == edit && buffer.CurrentSnapshot == Mock.Of<ITextSnapshot>());
+            var textBuffer = Mock.Of<ITextBuffer>(buffer => buffer.CreateEdit(EditOptions.None, null, It.IsAny<IInviolableEditTag>()) == edit && buffer.CurrentSnapshot == Mock.Of<ITextSnapshot>());
             return textBuffer;
         }
     }

src/Razor/test/Microsoft.VisualStudio.LanguageServerClient.Razor.Test/LSPDocumentTest.cs

@@ -58,7 +58,7 @@ namespace Microsoft.VisualStudio.LanguageServerClient.Razor
 
             public override VirtualDocumentSnapshot CurrentSnapshot => throw new NotImplementedException();
 
-            public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion, bool provisional)
+            public override VirtualDocumentSnapshot Update(IReadOnlyList<TextChange> changes, long hostDocumentVersion)
             {
                 throw new NotImplementedException();
             }