Add TextBufferProjectService Mac implementation.

- Was unable to test the text buffer project service class due to signing issues with the MonoDevelop.Sdk dependency.

#1789

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/Editor/DefaultTextBufferProjectService.cs

@@ -0,0 +1,98 @@
+// 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 System;
+using System.Diagnostics;
+using System.Linq;
+using Microsoft.CodeAnalysis.Razor;
+using Microsoft.VisualStudio.Editor.Razor;
+using Microsoft.VisualStudio.Text;
+using MonoDevelop.Ide;
+using MonoDevelop.Projects;
+
+namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor.Editor
+{
+    /// <summary>
+    /// Infrastructure methods to find project information from an <see cref="ITextBuffer"/>.
+    /// </summary>
+    internal class DefaultTextBufferProjectService : TextBufferProjectService
+    {
+        private readonly ITextDocumentFactoryService _documentFactory;
+        private readonly ErrorReporter _errorReporter;
+
+        public DefaultTextBufferProjectService(
+            ITextDocumentFactoryService documentFactory,
+            ErrorReporter errorReporter)
+        {
+            if (documentFactory == null)
+            {
+                throw new ArgumentNullException(nameof(documentFactory));
+            }
+
+            if (errorReporter == null)
+            {
+                throw new ArgumentNullException(nameof(errorReporter));
+            }
+
+            _documentFactory = documentFactory;
+            _errorReporter = errorReporter;
+        }
+
+        public override object GetHostProject(ITextBuffer textBuffer)
+        {
+            if (textBuffer == null)
+            {
+                throw new ArgumentNullException(nameof(textBuffer));
+            }
+
+            // If there's no document we can't find the FileName, or look for an associated project.
+            if (!_documentFactory.TryGetTextDocument(textBuffer, out var textDocument))
+            {
+                return null;
+            }
+
+            var projectsContainingFilePath = IdeApp.Workspace.GetProjectsContainingFile(textDocument.FilePath);
+            foreach (var project in projectsContainingFilePath)
+            {
+                if (!(project is DotNetProject))
+                {
+                    continue;
+                }
+
+                var projectFile = project.GetProjectFile(textDocument.FilePath);
+                if (!projectFile.IsHidden)
+                {
+                    return project;
+                }
+            }
+
+            return null;
+        }
+
+        public override string GetProjectPath(object project)
+        {
+            if (project == null)
+            {
+                throw new ArgumentNullException(nameof(project));
+            }
+
+            var dotnetProject = (DotNetProject)project;
+            return dotnetProject.FileName.FullPath;
+        }
+
+        // VisualStudio for Mac only supports ASP.NET Core Razor.
+        public override bool IsSupportedProject(object project) => true;
+
+        public override string GetProjectName(object project)
+        {
+            if (project == null)
+            {
+                throw new ArgumentNullException(nameof(project));
+            }
+
+            var dotnetProject = (DotNetProject)project;
+
+            return dotnetProject.Name;
+        }
+    }
+}

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/Editor/DefaultTextBufferProjectServiceFactory.cs

@@ -0,0 +1,44 @@
+// 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 System;
+using System.Composition;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Razor;
+using Microsoft.VisualStudio.Editor.Razor;
+using Microsoft.VisualStudio.Text;
+using MonoDevelop.Ide.TypeSystem;
+
+namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor.Editor
+{
+    [Shared]
+    [ExportLanguageServiceFactory(typeof(TextBufferProjectService), RazorLanguage.Name, ServiceLayer.Default)]
+    internal class DefaultTextBufferProjectServiceFactory : ILanguageServiceFactory
+    {
+        private readonly ITextDocumentFactoryService _documentFactory;
+
+        [ImportingConstructor]
+        public DefaultTextBufferProjectServiceFactory(ITextDocumentFactoryService documentFactory)
+        {
+            if (documentFactory == null)
+            {
+                throw new ArgumentNullException(nameof(documentFactory));
+            }
+
+            _documentFactory = documentFactory;
+        }
+
+        public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
+        {
+            if (languageServices == null)
+            {
+                throw new ArgumentNullException(nameof(languageServices));
+            }
+
+            var errorReporter = languageServices.WorkspaceServices.GetRequiredService<ErrorReporter>();
+
+            return new DefaultTextBufferProjectService(_documentFactory, errorReporter);
+        }
+    }
+}