Move TagHelperCompletionService to VS.Editor.Razor and export it.

- Moved service poco types: `AttributeCompletionContext`, `AttributeCompletionResult`, `ElementCompletionContext` and `ElementCompletionResult`.
- Exported DefaultTagHelperCompletionService.

#1762

src/Microsoft.CodeAnalysis.Razor.Workspaces/DefaultTagHelperCompletionServiceFactory.cs

@@ -1,18 +0,0 @@
-// 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.CodeAnalysis.Host;
-using Microsoft.CodeAnalysis.Host.Mef;
-
-namespace Microsoft.CodeAnalysis.Razor
-{
-    [ExportLanguageServiceFactory(typeof(TagHelperCompletionService), RazorLanguage.Name, ServiceLayer.Default)]
-    internal class DefaultTagHelperCompletionServiceFactory : ILanguageServiceFactory
-    {
-        public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
-        {
-            var tagHelperFactsService = languageServices.GetRequiredService<TagHelperFactsServiceInternal>();
-            return new DefaultTagHelperCompletionService(tagHelperFactsService);
-        }
-    }
-}

src/Microsoft.VisualStudio.Editor.Razor/AttributeCompletionContext.cs

@@ -5,7 +5,7 @@ using System;
 using System.Collections.Generic;
 using Microsoft.AspNetCore.Razor.Language;
 
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
     public class AttributeCompletionContext
     {

src/Microsoft.VisualStudio.Editor.Razor/AttributeCompletionResult.cs

@@ -5,7 +5,7 @@ using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
     public abstract class AttributeCompletionResult
     {

src/Microsoft.VisualStudio.Editor.Razor/DefaultTagHelperCompletionService.cs

@@ -3,18 +3,30 @@
 
 using System;
 using System.Collections.Generic;
+using System.ComponentModel.Composition;
 using System.Diagnostics;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Razor;
 
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
+    [System.Composition.Shared]
+    [Export(typeof(TagHelperCompletionService))]
     internal class DefaultTagHelperCompletionService : TagHelperCompletionService
     {
         private readonly TagHelperFactsServiceInternal _tagHelperFactsService;
         private static readonly HashSet<TagHelperDescriptor> _emptyHashSet = new HashSet<TagHelperDescriptor>();
 
-        public DefaultTagHelperCompletionService(TagHelperFactsServiceInternal tagHelperFactsService)
+        [ImportingConstructor]
+        public DefaultTagHelperCompletionService(VisualStudioWorkspaceAccessor workspaceAccessor)
+        {
+            var razorLanguageServices = workspaceAccessor.Workspace.Services.GetLanguageServices(RazorLanguage.Name);
+            _tagHelperFactsService = razorLanguageServices.GetRequiredService<TagHelperFactsServiceInternal>();
+        }
+
+        // Internal for testing
+        internal DefaultTagHelperCompletionService(TagHelperFactsServiceInternal tagHelperFactsService)
         {
             _tagHelperFactsService = tagHelperFactsService;
         }

src/Microsoft.VisualStudio.Editor.Razor/ElementCompletionContext.cs

@@ -5,7 +5,7 @@ using System;
 using System.Collections.Generic;
 using Microsoft.AspNetCore.Razor.Language;
 
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
     public sealed class ElementCompletionContext
     {

src/Microsoft.VisualStudio.Editor.Razor/ElementCompletionResult.cs

@@ -5,7 +5,7 @@ using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
 
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
     public abstract class ElementCompletionResult
     {

src/Microsoft.VisualStudio.Editor.Razor/TagHelperCompletionService.cs

@@ -1,11 +1,9 @@
 // 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.CodeAnalysis.Host;
-
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
-    public abstract class TagHelperCompletionService : ILanguageService
+    public abstract class TagHelperCompletionService
     {
         public abstract AttributeCompletionResult GetAttributeCompletions(AttributeCompletionContext completionContext);
 

test/Microsoft.VisualStudio.Editor.Razor.Test/DefaultTagHelperCompletionServiceTest.cs

@@ -4,9 +4,10 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.Razor;
 using Xunit;
 
-namespace Microsoft.CodeAnalysis.Razor
+namespace Microsoft.VisualStudio.Editor.Razor
 {
     public class DefaultTagHelperCompletionServiceTest
     {