Half completes: U4-2462 Does the app_plugins manager monitor file changes?

src/Umbraco.Core/Manifest/ManifestWatcher.cs

@@ -0,0 +1,49 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Web;
+using Umbraco.Core.Logging;
+
+namespace Umbraco.Core.Manifest
+{
+    internal class ManifestWatcher : DisposableObject
+    {
+        private readonly List<FileSystemWatcher> _fws = new List<FileSystemWatcher>();
+
+        public void Start(params string[] packageFolders)
+        {
+            foreach (var packageFolder in packageFolders)
+            {
+                if (Directory.Exists(packageFolder) && File.Exists(Path.Combine(packageFolder, "package.manifest")))
+                {
+                    //NOTE: for some reason *.manifest doesn't work!
+                    var fsw = new FileSystemWatcher(packageFolder, "*package.*")
+                    {
+                        IncludeSubdirectories = false,
+                        NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite 
+                    };
+                    _fws.Add(fsw);
+                    fsw.Changed += FswChanged;
+                    fsw.EnableRaisingEvents = true;
+                }
+            }
+        }
+
+        void FswChanged(object sender, FileSystemEventArgs e)
+        {
+            if (e.Name.InvariantContains("package.manifest"))
+            {
+                LogHelper.Info<ManifestWatcher>("manifest has changed, app pool is restarting (" + e.FullPath + ")");
+                HttpRuntime.UnloadAppDomain();
+                Dispose();    
+            }
+        }
+
+        protected override void DisposeResources()
+        {
+            foreach (var fw in _fws)
+            {
+                fw.Dispose();
+            }
+        }
+    }
+}

src/Umbraco.Core/Umbraco.Core.csproj

@@ -316,6 +316,7 @@
     <Compile Include="Manifest\ManifestBuilder.cs" />
     <Compile Include="Manifest\ManifestParser.cs" />
     <Compile Include="Manifest\ManifestValidatorConverter.cs" />
+    <Compile Include="Manifest\ManifestWatcher.cs" />
     <Compile Include="Manifest\PackageManifest.cs" />
     <Compile Include="Manifest\ParameterEditorConverter.cs" />
     <Compile Include="Manifest\PreValueFieldConverter.cs" />

src/Umbraco.Web/UmbracoApplication.cs

@@ -1,13 +1,17 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.IO;
 using System.Linq;
 using System.Text;
 using System.Web;
 using System.Web.Hosting;
 using System.Web.Mvc;
 using Umbraco.Core;
+using Umbraco.Core.Configuration;
+using Umbraco.Core.IO;
 using Umbraco.Core.Logging;
+using Umbraco.Core.Manifest;
 using Umbraco.Web.Routing;
 using umbraco.businesslogic;
 
@@ -18,7 +22,25 @@ namespace Umbraco.Web
 	/// </summary>
     public class UmbracoApplication : UmbracoApplicationBase
 	{
-           
+        private readonly ManifestWatcher _mw = new ManifestWatcher();
+
+	    protected override void OnApplicationStarted(object sender, EventArgs e)
+	    {
+	        base.OnApplicationStarted(sender, e);
+
+	        if (ApplicationContext.Current.IsConfigured && GlobalSettings.DebugMode)
+	        {   
+	            _mw.Start(Directory.GetDirectories(IOHelper.MapPath("~/App_Plugins/")));
+	        }
+	    }
+
+	    protected override void OnApplicationEnd(object sender, EventArgs e)
+	    {
+	        base.OnApplicationEnd(sender, e);
+
+            _mw.Dispose();
+	    }
+
 	    protected override IBootManager GetBootManager()
 	    {
             return new WebBootManager(this);