Make sure MultiSelectWindow for different purposes are unique.

EditorWindow.GetWindow() only create a new window or return an
existing one per type.  As a result, when CreateMultiSelectWindow()
is called for different purposes at the same time, the same window
instance can be filled with data from the different code path, and
causes error.

This change make sure the MultiSelectWindow created for different
purposes are unique.

Change-Id: I7dafdb49ef714def221afcc359561ec5cff886ed

Author: chkuang-g

source/PackageManagerResolver/src/PackageManagerResolver.cs

@@ -24,6 +24,10 @@ namespace Google {
 
 [InitializeOnLoad]
 public class PackageManagerResolver : AssetPostprocessor {
+    /// <summary>
+    /// A unique class to create the multi-select window to add registries.
+    /// </summary>
+    class PackageManagerResolverWindow : MultiSelectWindow {}
 
     /// <summary>
     /// Name of the plugin.
@@ -406,7 +410,9 @@ internal static void UpdateManifest(ManifestModificationMode mode,
                 }
 
                 // Optional when prompting is enabled or forced.
-                var window = MultiSelectWindow.CreateMultiSelectWindow(PLUGIN_NAME);
+                var window =
+                        MultiSelectWindow.CreateMultiSelectWindow<PackageManagerResolverWindow>(
+                                PLUGIN_NAME);
                 window.minSize = new Vector2(1024, 500);
                 window.AvailableItems = registryItems;
                 window.Sort(1);

source/PackageManagerResolver/src/PackageMigrator.cs

@@ -29,6 +29,10 @@ namespace Google {
 /// </summary>
 [InitializeOnLoad]
 internal class PackageMigrator {
+    /// <summary>
+    /// A unique class to create the multi-select window to migrate packages.
+    /// </summary>
+    private class PackageMigratorWindow : MultiSelectWindow {}
 
     /// <summary>
     /// Map of Version Handler determined package to Package Manager Package ID and version.
@@ -943,7 +947,7 @@ public static void DisplaySelectionWindow(ICollection<PackageMap> packageMaps,
                               pkg.PackageManagerPackageId)));
         }
 
-        var window = MultiSelectWindow.CreateMultiSelectWindow(WindowTitle);
+        var window = MultiSelectWindow.CreateMultiSelectWindow<PackageMigratorWindow>(WindowTitle);
         window.minSize = new UnityEngine.Vector2(800, 400);
         window.SelectedItems = new HashSet<string>(packageMapsByPackageId.Keys);
         window.AvailableItems = items;

source/VersionHandlerImpl/src/MultiSelectWindow.cs

@@ -263,11 +263,26 @@ protected virtual void OnGUI() {
         /// </summary>
         /// <param name="title">Title to display on the window.</param>
         /// <returns>Reference to this class</returns>
+        [Obsolete("This method deprecated. Please use CreateMultiSelectWindow<T>() instead.")]
         public static MultiSelectWindow CreateMultiSelectWindow(string title) {
             MultiSelectWindow window = (MultiSelectWindow)EditorWindow.GetWindow(
                 typeof(MultiSelectWindow), true, title, true);
             window.Initialize();
             return window;
         }
+
+        /// <summary>
+        /// Get the existing multi-select window or create a new one.
+        /// To create an unique MultiSelectWindow, pass a type derived from MultiSelectWindow
+        /// as the type parameter.
+        /// </summary>
+        /// <typeparam name="T">A type that inherits from the MultiSelectWindow.</typeparam>
+        /// <param name="title">Title to display on the window.</param>
+        /// <returns>Reference to this class</returns>
+        public static T CreateMultiSelectWindow<T>(string title) where T : MultiSelectWindow {
+            T window = (T)EditorWindow.GetWindow(typeof(T), true, title, true);
+            window.Initialize();
+            return window;
+        }
     }
 }

source/VersionHandlerImpl/src/PackageUninstallWindow.cs

@@ -20,8 +20,13 @@
 using UnityEditor;
 
 namespace Google {
+
+/// <summary>
+/// A unique class to create the multi-select window to uninstall packages managed by
+/// VersionHandler.
+/// </summary>
 [InitializeOnLoad]
-public class PackageUninstallWindow : EditorWindow {
+public class PackageUninstallWindow : MultiSelectWindow {
     // Hardcoded text for the window.
     private static string windowTitle = "Uninstall Managed Packages";
     private static string caption =
@@ -36,7 +41,7 @@ public class PackageUninstallWindow : EditorWindow {
     [MenuItem("Assets/External Dependency Manager/Version Handler/Uninstall Managed Packages")]
     public static void UninstallPackage() {
         // Display MultiSelectWindow
-        MultiSelectWindow window = MultiSelectWindow.CreateMultiSelectWindow(windowTitle);
+        var window =MultiSelectWindow.CreateMultiSelectWindow<PackageUninstallWindow>(windowTitle);
         window.AvailableItems = GetSelectionList();
         window.Sort(1);
         window.Caption = caption;

source/VersionHandlerImpl/src/VersionHandlerImpl.cs

@@ -27,6 +27,11 @@ namespace Google {
 
 [InitializeOnLoad]
 public class VersionHandlerImpl : AssetPostprocessor {
+    /// <summary>
+    /// A unique class to create the multi-select window to obsolete files.
+    /// </summary>
+    private class ObsoleteFilesWindow : MultiSelectWindow {}
+
     /// <summary>
     /// Derives metadata from an asset filename.
     /// </summary>
@@ -2859,7 +2864,7 @@ private static void UpdateVersionedAssetsOnMainThread(bool forceUpdate,
 
         bool cleanupFilesPending = cleanupFiles.Count > 0;
         if (cleanupFilesPending && !Refreshing) {
-            var window = MultiSelectWindow.CreateMultiSelectWindow(PLUGIN_NAME);
+            var window = MultiSelectWindow.CreateMultiSelectWindow<ObsoleteFilesWindow>(PLUGIN_NAME);
             Action<string> logObsoleteFile = (filename) => {
                 Log("Leaving obsolete file: " + filename, verbose: true);
             };