Generalize project system interactions to CPS

We can share behavior across all CPS projects for handling files additions/removals.  CPS is much more efficient for bulk edits - they work from the file system automatically, so we don't have to do batched edits on the UI thread in VS. This is something we should take advantage of for as many project types as possible, not limited to DotNetCoreWeb.

Addresses aspnet#710

src/LibraryManager.Vsix/Constants.cs

@@ -14,6 +14,13 @@ internal static class Constants
         public const string ErrorCodeLink = "https://github.com/aspnet/LibraryManager/wiki/Error-codes#{0}";
         public const string WAP = "{349C5851-65DF-11DA-9384-00065B846F21}";
         public const string WebsiteProject = "{E24C65DC-7377-472B-9ABA-BC803B73C61A}";
+        /// <summary>
+        /// Project capability for .NET web projects. Used only for UI context rules.
+        /// </summary>
         public const string DotNetCoreWebCapability = "DotNetCoreWeb";
+        /// <summary>
+        /// Project capability for CPS-based projects. Used to determine how to add/remove items to the project.
+        /// </summary>
+        public const string CpsCapability = "CPS";
     }
 }

src/LibraryManager.Vsix/Contracts/HostInteraction.cs

@@ -85,9 +85,9 @@ public async Task<bool> DeleteFilesAsync (IEnumerable<string> relativeFilePaths,
 
             //Delete from project
             Project project = VsHelpers.GetDTEProjectFromConfig(_configFilePath);
-            bool isCoreProject = await VsHelpers.IsDotNetCoreWebProjectAsync(project);
+            bool isCpsProject = await VsHelpers.IsCpsProject(project);
 
-            if (!isCoreProject)
+            if (!isCpsProject)
             {
                 var logAction = new Action<string, LogLevel>((message, level) => { Logger.Log(message, level); });
                 bool deleteFromProject = await VsHelpers.DeleteFilesFromProjectAsync(project, absolutePaths, logAction, cancellationToken);

src/LibraryManager.Vsix/Shared/VsHelpers.cs

@@ -109,7 +109,7 @@ public static async Task AddFileToProjectAsync(this Project project, string file
         {
             await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
 
-            if (IsCapabilityMatch(project, Constants.DotNetCoreWebCapability))
+            if (IsCapabilityMatch(project, Constants.CpsCapability))
             {
                 return;
             }
@@ -140,7 +140,7 @@ public static async Task AddFilesToProjectAsync(Project project, IEnumerable<str
         {
             await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken);
 
-            if (project == null || IsCapabilityMatch(project, Constants.DotNetCoreWebCapability))
+            if (project == null || IsCapabilityMatch(project, Constants.CpsCapability))
             {
                 return;
             }
@@ -244,11 +244,19 @@ public static bool IsKind(this Project project, params string[] kindGuids)
             return false;
         }
 
-        public static async Task<bool> IsDotNetCoreWebProjectAsync(Project project)
+        /// <summary>
+        /// Returns whether the DTE project is a CPS-based project
+        /// </summary>
+        /// <remarks>
+        /// This is used for taking advantage of some shortcuts. For example, CPS projects can automatically
+        /// reflect files on disk, so that rather than using legacy project system APIs on the UI thread,
+        /// we can interact with the filesystem on a background thread.
+        /// </remarks>
+        public static async Task<bool> IsCpsProject(Project project)
         {
             await ThreadHelper.JoinableTaskFactory.SwitchToMainThreadAsync();
 
-            if (project == null || IsCapabilityMatch(project, Constants.DotNetCoreWebCapability))
+            if (project == null || IsCapabilityMatch(project, Constants.CpsCapability))
             {
                 return true;
             }