Fix enable feature from command line

If we enable a feature from the command line, we need the host to
recompute it's list of shell topologies on the next request
of the web application.

We enable this by making the OrchardHost watch for file changes
on the "cache.dat" file (topology cache)

--HG--
branch : dev

src/Orchard/Environment/DefaultOrchardHost.cs

@@ -21,6 +21,7 @@ namespace Orchard.Environment {
         private readonly ControllerBuilder _controllerBuilder;
         private readonly IShellSettingsManager _shellSettingsManager;
         private readonly IShellContextFactory _shellContextFactory;
+        private readonly IShellDescriptorCache _shellDescriptorCache;
         private readonly IRunningShellTable _runningShellTable;
         private readonly IProcessingEngine _processingEngine;
         private readonly IExtensionLoaderCoordinator _extensionLoaderCoordinator;
@@ -32,6 +33,7 @@ namespace Orchard.Environment {
         public DefaultOrchardHost(
             IShellSettingsManager shellSettingsManager,
             IShellContextFactory shellContextFactory,
+            IShellDescriptorCache shellDescriptorCache,
             IRunningShellTable runningShellTable,
             IProcessingEngine processingEngine,
             IExtensionLoaderCoordinator extensionLoaderCoordinator,
@@ -40,6 +42,7 @@ namespace Orchard.Environment {
 
             _shellSettingsManager = shellSettingsManager;
             _shellContextFactory = shellContextFactory;
+            _shellDescriptorCache = shellDescriptorCache;
             _runningShellTable = runningShellTable;
             _processingEngine = processingEngine;
             _extensionLoaderCoordinator = extensionLoaderCoordinator;
@@ -149,6 +152,7 @@ namespace Orchard.Environment {
             _cacheManager.Get("OrchardHost_Extensions",
                               ctx => {
                                   _extensionLoaderCoordinator.MonitorExtensions(ctx.Monitor);
+                                  _shellDescriptorCache.Monitor(ctx.Monitor);
                                   _current = null;
                                   return "";
                               });

src/Orchard/Environment/Descriptor/ShellDescriptorCache.cs

@@ -2,13 +2,14 @@
 using System.IO;
 using System.Runtime.Serialization;
 using System.Xml;
+using Orchard.Caching;
 using Orchard.Environment.Descriptor.Models;
 using Orchard.FileSystems.AppData;
 using Orchard.Localization;
 using Orchard.Logging;
 
 namespace Orchard.Environment.Descriptor {
-        /// <summary>
+    /// <summary>
     /// Single service instance registered at the host level. Provides storage
     /// and recall of shell descriptor information. Default implementation uses
     /// app_data, but configured replacements could use other per-host writable location.
@@ -26,6 +27,11 @@ namespace Orchard.Environment.Descriptor {
         /// Loss of storage is expected.
         /// </summary>
         void Store(string shellName, ShellDescriptor descriptor);
+
+        /// <summary>
+        /// Monitor changes on the persistent storage.
+        /// </summary>
+        void Monitor(Action<IVolatileToken> monitor);
     }
 
     public class ShellDescriptorCache : IShellDescriptorCache {
@@ -55,7 +61,7 @@ namespace Orchard.Environment.Descriptor {
                     var serializer = new DataContractSerializer(typeof(ShellDescriptor));
                     var reader = new StringReader(tenantNode.InnerText);
                     using (var xmlReader = XmlReader.Create(reader)) {
-                        return (ShellDescriptor) serializer.ReadObject(xmlReader, true); 
+                        return (ShellDescriptor)serializer.ReadObject(xmlReader, true);
                     }
                 }
             }
@@ -73,7 +79,7 @@ namespace Orchard.Environment.Descriptor {
             XmlNode rootNode = xmlDocument.DocumentElement;
             foreach (XmlNode tenantNode in rootNode.ChildNodes) {
                 if (String.Equals(tenantNode.Name, name, StringComparison.OrdinalIgnoreCase)) {
-                    var serializer = new DataContractSerializer(typeof (ShellDescriptor));
+                    var serializer = new DataContractSerializer(typeof(ShellDescriptor));
                     var writer = new StringWriter();
                     using (var xmlWriter = XmlWriter.Create(writer)) {
                         serializer.WriteObject(xmlWriter, descriptor);
@@ -98,6 +104,10 @@ namespace Orchard.Environment.Descriptor {
             _appDataFolder.CreateFile(DescriptorCacheFileName, saveWriter.ToString());
         }
 
+        public void Monitor(Action<IVolatileToken> monitor) {
+            monitor(_appDataFolder.WhenPathChanges(DescriptorCacheFileName));
+        }
+
         #endregion
 
         private void VerifyCacheFile() {
@@ -106,8 +116,8 @@ namespace Orchard.Environment.Descriptor {
                 using (XmlWriter xmlWriter = XmlWriter.Create(writer)) {
                     if (xmlWriter != null) {
                         xmlWriter.WriteStartDocument();
-                        xmlWriter.WriteStartElement("Tenants"); 
-                        xmlWriter.WriteEndElement();              
+                        xmlWriter.WriteStartElement("Tenants");
+                        xmlWriter.WriteEndElement();
                         xmlWriter.WriteEndDocument();
                     }
                 }