work on extension loading

* Add a "ExtensionLoaderCoordinator" class
* Rework the way loaders are notified of extensions being loaded,
  (de)activated, etc.

--HG--
branch : dev

src/Orchard.Tests/Environment/Extensions/ExtensionManagerTests.cs

@@ -43,23 +43,19 @@ namespace Orchard.Tests.Environment.Extensions {
             }
         }
 
-        public class StubLoaders : IExtensionLoader {
+        public class StubLoaders : ExtensionLoaderBase {
             #region Implementation of IExtensionLoader
 
-            public int Order {
+            public override int Order {
                 get { return 1; }
             }
 
-            public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+            public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
                 return new ExtensionProbeEntry { Descriptor = descriptor, Loader = this };
             }
 
-            public ExtensionEntry Load(ExtensionProbeEntry entry) {
-                return new ExtensionEntry { Descriptor = entry.Descriptor, ExportedTypes = new[] { typeof(Alpha), typeof(Beta), typeof(Phi) } };
-            }
-
-            public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
-                throw new NotImplementedException();
+            public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
+                return new ExtensionEntry { Descriptor = descriptor, ExportedTypes = new[] { typeof(Alpha), typeof(Beta), typeof(Phi) } };
             }
 
             #endregion

src/Orchard.Web/Orchard.Web.csproj

@@ -143,10 +143,6 @@
       <Project>{17F86780-9A1F-4AA1-86F1-875EEC2730C7}</Project>
       <Name>Orchard.Modules</Name>
     </ProjectReference>
-    <ProjectReference Include="Modules\Orchard.MultiTenancy\Orchard.MultiTenancy.csproj">
-      <Project>{72457126-E118-4171-A08F-9A709EE4B7FC}</Project>
-      <Name>Orchard.MultiTenancy</Name>
-    </ProjectReference>
     <ProjectReference Include="Modules\Orchard.Pages\Orchard.Pages.csproj">
       <Project>{4A9C04A6-0986-4A92-A610-5F59FF273FB9}</Project>
       <Name>Orchard.Pages</Name>

src/Orchard/Environment/DefaultOrchardHost.cs

@@ -23,6 +23,7 @@ namespace Orchard.Environment {
         private readonly IRunningShellTable _runningShellTable;
         private readonly IProcessingEngine _processingEngine;
         private readonly IExtensionManager _extensionManager;
+        private readonly IExtensionLoaderCoordinator _extensionLoaderCoordinator;
         private readonly ICacheManager _cacheManager;
 
         private IEnumerable<ShellContext> _current;
@@ -33,6 +34,7 @@ namespace Orchard.Environment {
             IRunningShellTable runningShellTable,
             IProcessingEngine processingEngine,
             IExtensionManager extensionManager,
+            IExtensionLoaderCoordinator extensionLoaderCoordinator,
             ICacheManager cacheManager,
             ControllerBuilder controllerBuilder) {
             _shellSettingsManager = shellSettingsManager;
@@ -40,6 +42,7 @@ namespace Orchard.Environment {
             _runningShellTable = runningShellTable;
             _processingEngine = processingEngine;
             _extensionManager = extensionManager;
+            _extensionLoaderCoordinator = extensionLoaderCoordinator;
             _cacheManager = cacheManager;
             _controllerBuilder = controllerBuilder;
             Logger = NullLogger.Instance;
@@ -78,10 +81,17 @@ namespace Orchard.Environment {
         }
 
         IEnumerable<ShellContext> BuildCurrent() {
+            if (_current == null) {
                 lock (this) {
-                return _current ?? (_current = CreateAndActivate().ToArray());
+                    if (_current == null) {
+                        SetupExtensions();
+                        MonitorExtensions();
+                        _current = CreateAndActivate().ToArray();
                     }
                 }
+            }
+            return _current;
+        }
 
         IEnumerable<ShellContext> CreateAndActivate() {
             var allSettings = _shellSettingsManager.LoadSettings();
@@ -119,13 +129,21 @@ namespace Orchard.Environment {
             return _shellContextFactory.CreateShellContext(settings);
         }
 
-        protected virtual void BeginRequest() {
+        private void SetupExtensions() {
+            _extensionLoaderCoordinator.SetupExtensions();
+        }
+
+        private void MonitorExtensions() {
             _cacheManager.Get("OrchardHost_Extensions",
                               ctx => {
-                    _extensionManager.Monitor(ctx.Monitor);
+                                  _extensionLoaderCoordinator.MonitorExtensions(ctx.Monitor);
                                   _current = null;
                                   return "";
                               });
+        }
+
+        protected virtual void BeginRequest() {
+            MonitorExtensions();
             BuildCurrent();
         }
 

src/Orchard/Environment/Extensions/ExtensionLoaderCoordinator.cs

@@ -0,0 +1,200 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using Orchard.Caching;
+using Orchard.Environment.Extensions.Loaders;
+using Orchard.Environment.Extensions.Models;
+using Orchard.FileSystems.Dependencies;
+using Orchard.FileSystems.VirtualPath;
+using Orchard.Localization;
+using Orchard.Logging;
+using Orchard.Services;
+
+namespace Orchard.Environment.Extensions {
+    public class ExtensionLoaderCoordinator : IExtensionLoaderCoordinator {
+        private readonly IDependenciesFolder _dependenciesFolder;
+        private readonly IExtensionManager _extensionManager;
+        private readonly IEnumerable<IExtensionLoader> _loaders;
+        private readonly IVirtualPathProvider _virtualPathProvider;
+        private readonly IClock _clock;
+
+        public ExtensionLoaderCoordinator(
+            IDependenciesFolder dependenciesFolder,
+            IExtensionManager extensionManager,
+            IEnumerable<IExtensionLoader> loaders,
+            IVirtualPathProvider virtualPathProvider,
+            IClock clock) {
+            _dependenciesFolder = dependenciesFolder;
+            _extensionManager = extensionManager;
+            _loaders = loaders.OrderBy(l => l.Order);
+            _virtualPathProvider = virtualPathProvider;
+            _clock = clock;
+            T = NullLocalizer.Instance;
+            Logger = NullLogger.Instance;
+        }
+
+        public Localizer T { get; set; }
+        public ILogger Logger { get; set; }
+
+        public void SetupExtensions() {
+            Logger.Information("Loading extensions.");
+
+            var extensions = _extensionManager.AvailableExtensions().Where(d => d.ExtensionType == "Module").ToList();
+            var existingDependencies = _dependenciesFolder.LoadDescriptors().ToList();
+
+            var sameExtensions = extensions.Where(e => existingDependencies.Any(e2 => e2.Name == e.Name)).ToList();
+            var deletedDependencies = existingDependencies.Where(e => !extensions.Any(e2 => e2.Name == e.Name)).ToList();
+            var newExtensions = extensions.Except(sameExtensions).ToList();
+
+            var ctx = new ExtensionLoadingContext { DependenciesFolder = _dependenciesFolder };
+
+            // Notify all loaders about extensions removed from the web site
+            foreach (var dependency in deletedDependencies) {
+                Logger.Information("Extension {0} has been removed from site", dependency.Name);
+                foreach (var loader in _loaders) {
+                    if (dependency.LoaderName == loader.Name) {
+                        loader.ExtensionRemoved(ctx, dependency);
+                    }
+                }
+            }
+
+            // For all existing extensions in the site, ask each loader if they can
+            // load that extension.
+            var newDependencies = new List<DependencyDescriptor>();
+            foreach (var extension in extensions) {
+                bool isNewExtension = newExtensions.Any(e => e.Name == extension.Name);
+                ProcessExtension(ctx, extension, isNewExtension, existingDependencies, newDependencies);
+            }
+
+            // Execute all the work need by "ctx"
+            ProcessContextCommands(ctx);
+
+            // And finally save the new entries in the dependencies folder
+            _dependenciesFolder.StoreDescriptors(newDependencies);
+            Logger.Information("Done loading extensions.");
+        }
+
+        private void ProcessExtension(
+            ExtensionLoadingContext ctx,
+            ExtensionDescriptor extension,
+            bool isNewExtension,
+            IEnumerable<DependencyDescriptor> existingDependencies,
+            List<DependencyDescriptor> newDependencies) {
+
+            var extensionProbes = _loaders
+                .Select(loader => loader.Probe(extension))
+                .Where(probe => probe != null)
+                .OrderByDescending(probe => probe.LastModificationTimeUtc)
+                .ThenBy(probe => probe.Loader.Order)
+                .ToList();
+
+
+            if (Logger.IsEnabled(LogLevel.Debug)) {
+                Logger.Debug("Loaders for extension \"{0}\": ", extension.Name);
+                foreach (var probe in extensionProbes) {
+                    Logger.Debug("  Loader: {0}", probe.Loader.Name);
+                    Logger.Debug("    VirtualPath: {0}", probe.VirtualPath);
+                    Logger.Debug("    DateTimeUtc: {0}", probe.LastModificationTimeUtc);
+                }
+            }
+
+            var activatedExtension = extensionProbes.FirstOrDefault();
+            var previousDependency = existingDependencies.Where(d => d.Name == extension.Name).FirstOrDefault();
+
+            if (activatedExtension == null) {
+                Logger.Warning("No loader found for extension {0}!", extension.Name);
+            }
+
+            foreach (var loader in _loaders) {
+                if (activatedExtension != null && activatedExtension.Loader.Name == loader.Name) {
+                    Logger.Information("Activating extension \"{0}\" with loader \"{1}\"", activatedExtension.Descriptor.Name, loader.Name);
+                    loader.ExtensionActivated(ctx, isNewExtension, extension);
+                }
+                else if (previousDependency != null && previousDependency.LoaderName == loader.Name) {
+                    Logger.Information("Deactivating extension \"{0}\" from loader \"{1}\"", previousDependency.Name, loader.Name);
+                    loader.ExtensionDeactivated(ctx, isNewExtension, extension);
+                }
+            }
+
+            if (activatedExtension != null) {
+                newDependencies.Add(new DependencyDescriptor {
+                    Name = extension.Name,
+                    LoaderName = activatedExtension.Loader.Name,
+                    VirtualPath = activatedExtension.VirtualPath
+                });
+            }
+        }
+
+        private void ProcessContextCommands(ExtensionLoadingContext ctx) {
+            Logger.Information("Executing list of operations needed for loading extensions...");
+            foreach (var fileName in ctx.FilesToDelete) {
+                Logger.Information("Deleting file \"{0}\"", fileName);
+                File.Delete(fileName);
+            }
+            foreach (var entry in ctx.FilesToCopy) {
+                Logger.Information("Copying file from \"{0}\" to \"{1}\"", entry.Key, entry.Value);
+                MakeDestinationFileNameAvailable(entry.Value);
+                File.Copy(entry.Key, entry.Value);
+            }
+            foreach (var entry in ctx.FilesToRename) {
+                Logger.Information("Moving file from \"{0}\" to \"{1}\"", entry.Key, entry.Value);
+                MakeDestinationFileNameAvailable(entry.Value);
+                File.Move(entry.Key, entry.Value);
+            }
+
+            if (ctx.RestartAppDomain || ctx.ResetSiteCompilation) {
+                if (ctx.RestartAppDomain)
+                    Logger.Information("AppDomain restart required.");
+
+                if (ctx.ResetSiteCompilation)
+                    Logger.Information("Reset site compilation state required.");
+
+                // Touch web.config
+                File.SetLastWriteTimeUtc(_virtualPathProvider.MapPath("~/web.config"), _clock.UtcNow);
+            }
+        }
+
+        private void MakeDestinationFileNameAvailable(string destinationFileName) {
+            // Try deleting the destination first
+            try {
+                File.Delete(destinationFileName);
+            } catch {
+                // We land here if the file is in use, for example. Let's move on.
+            }
+
+            // If destination doesn't exist, we are good
+            if (!File.Exists(destinationFileName))
+                return;
+
+            // Try renaming destination to a unique filename
+            const string extension = "deleted";
+            for (int i = 0; i < 100; i++) {
+                var newExtension = (i == 0 ? extension : string.Format("{0}{1}", extension, i));
+                var newFileName = Path.ChangeExtension(destinationFileName, newExtension);
+                try {
+                    File.Delete(newFileName);
+                    File.Move(destinationFileName, newFileName);
+
+                    // If successful, we are done...
+                    return;
+                }
+                catch (Exception) {
+                    // We need to try with another extension
+                }
+            }
+
+            // Everything failed, throw an exception
+            throw new OrchardException(T("Unable to make room for file {0} in dependencies folder: too many conflicts.", destinationFileName).Text);
+        }
+
+        public void MonitorExtensions(Action<IVolatileToken> monitor) {
+            var extensions = _extensionManager.AvailableExtensions().Where(d => d.ExtensionType == "Module").ToList();
+            foreach (var extension in extensions) {
+                foreach (var loader in _loaders) {
+                    loader.Monitor(extension, monitor);
+                }
+            }
+        }
+    }
+}

src/Orchard/Environment/Extensions/ExtensionLoadingContext.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using Orchard.FileSystems.Dependencies;
+
+namespace Orchard.Environment.Extensions {
+    public class ExtensionLoadingContext {
+        public ExtensionLoadingContext() {
+            FilesToDelete = new HashSet<string>();
+            FilesToCopy = new Dictionary<string, string>();
+            FilesToRename = new Dictionary<string, string>();
+        }
+
+        public IDependenciesFolder DependenciesFolder { get; set; }
+        public HashSet<string> FilesToDelete { get; set; }
+        public Dictionary<string, string> FilesToCopy { get; set; }
+        public Dictionary<string, string> FilesToRename { get; set; }
+        public bool RestartAppDomain { get; set; }
+        public bool ResetSiteCompilation { get; set; }
+    }
+}

src/Orchard/Environment/Extensions/ExtensionManager.cs

@@ -4,7 +4,6 @@ using System.IO;
 using System.Linq;
 using System.Web;
 using ICSharpCode.SharpZipLib.Zip;
-using Orchard.Caching;
 using Orchard.Environment.Extensions.Folders;
 using Orchard.Environment.Extensions.Helpers;
 using Orchard.Environment.Extensions.Loaders;
@@ -154,33 +153,13 @@ namespace Orchard.Environment.Extensions {
             Directory.Delete(targetFolder, true);
         }
 
-        public void Monitor(Action<IVolatileToken> monitor) {
-            foreach (var descriptor in AvailableExtensions()) {
-                if (string.Equals(descriptor.ExtensionType, "Module", StringComparison.OrdinalIgnoreCase)) {
-                    foreach (var loader in _loaders) {
-                        loader.Monitor(descriptor, monitor);
-                    }
-                }
-            }
-        }
-
         private ExtensionEntry BuildEntry(ExtensionDescriptor descriptor) {
-            var loaders = _loaders.ToList();
-
-            var moreRecentEntry = loaders
-                .Select(loader => loader.Probe(descriptor))
-                .Where(entry => entry != null)
-                .OrderByDescending(entry => entry.LastModificationTimeUtc)
-                .FirstOrDefault();
-
-            ExtensionEntry result = null;
-            foreach (var loader in loaders) {
-                ExtensionEntry entry = loader.Load(moreRecentEntry);
-                if (entry != null && result == null) {
-                    result = entry;
+            foreach (var loader in _loaders) {
+                ExtensionEntry entry = loader.Load(descriptor);
+                if (entry != null)
+                    return entry;
             }
-            }
-            return result;
+            return null;
         }
     }
 }

src/Orchard/Environment/Extensions/IExtensionLoaderCoordinator.cs

@@ -0,0 +1,9 @@
+using System;
+using Orchard.Caching;
+
+namespace Orchard.Environment.Extensions {
+    public interface IExtensionLoaderCoordinator {
+        void SetupExtensions();
+        void MonitorExtensions(Action<IVolatileToken> monitor);
+    }
+}

src/Orchard/Environment/Extensions/IExtensionManager.cs

@@ -1,7 +1,5 @@
-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Web;
-using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
 
 namespace Orchard.Environment.Extensions {
@@ -10,6 +8,5 @@ namespace Orchard.Environment.Extensions {
         IEnumerable<Feature> LoadFeatures(IEnumerable<FeatureDescriptor> featureDescriptors);
         void InstallExtension(string extensionType, HttpPostedFileBase extensionBundle);
         void UninstallExtension(string extensionType, string extensionName);
-        void Monitor(Action<IVolatileToken> monitor);
     }
 }

src/Orchard/Environment/Extensions/Loaders/AreaExtensionLoader.cs

@@ -1,29 +1,21 @@
 using System;
 using System.Linq;
 using System.Reflection;
-using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
 using Orchard.FileSystems.Dependencies;
 using Orchard.FileSystems.VirtualPath;
 
 namespace Orchard.Environment.Extensions.Loaders {
-    public class AreaExtensionLoader : IExtensionLoader {
+    public class AreaExtensionLoader : ExtensionLoaderBase {
         private readonly IDependenciesFolder _dependenciesFolder;
-        private readonly IVirtualPathProvider _virtualPathProvider;
 
-        public AreaExtensionLoader(IDependenciesFolder dependenciesFolder, IVirtualPathProvider virtualPathProvider) {
+        public AreaExtensionLoader(IDependenciesFolder dependenciesFolder) {
             _dependenciesFolder = dependenciesFolder;
-            _virtualPathProvider = virtualPathProvider;
         }
 
-        public int Order { get { return 50; } }
+        public override int Order { get { return 50; } }
 
-        public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
-            // We don't need to monitor anything since we are loaded
-            // from the application assembly itself.
-        }
-
-        public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+        public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
             if (descriptor.Location == "~/Areas") {
                 return new ExtensionProbeEntry {
                     Descriptor = descriptor,
@@ -35,25 +27,20 @@ namespace Orchard.Environment.Extensions.Loaders {
             return null;
         }
 
-        public ExtensionEntry Load(ExtensionProbeEntry entry) {
-            if (entry.Loader == this) {
+        public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
+            var dependency = _dependenciesFolder.GetDescriptor(descriptor.Name);
+            if (dependency != null && dependency.LoaderName == this.Name) {
+
                 var assembly = Assembly.Load("Orchard.Web");
 
-                _dependenciesFolder.Store(new DependencyDescriptor { ModuleName = entry.Descriptor.Name, LoaderName = this.GetType().FullName});
-
                 return new ExtensionEntry {
-                    Descriptor = entry.Descriptor,
+                    Descriptor = descriptor,
                     Assembly = assembly,
-                    ExportedTypes = assembly.GetExportedTypes().Where(x => IsTypeFromModule(x, entry.Descriptor))
+                    ExportedTypes = assembly.GetExportedTypes().Where(x => IsTypeFromModule(x, descriptor))
                 };
             }
-            else {
-                // If the extension is not loaded by us, there is no cached state 
-                // we need to invalidate
-                _dependenciesFolder.Remove(entry.Descriptor.Name, this.GetType().FullName);
             return null;
         }
-        }
 
         private static bool IsTypeFromModule(Type type, ExtensionDescriptor descriptor) {
             return (type.Namespace + ".").StartsWith("Orchard.Web.Areas." + descriptor.Name + ".");

src/Orchard/Environment/Extensions/Loaders/CoreExtensionLoader.cs

@@ -10,23 +10,16 @@ namespace Orchard.Environment.Extensions.Loaders {
     /// <summary>
     /// Load an extension by looking into specific namespaces of the "Orchard.Core" assembly
     /// </summary>
-    public class CoreExtensionLoader : IExtensionLoader {
+    public class CoreExtensionLoader : ExtensionLoaderBase {
         private readonly IDependenciesFolder _dependenciesFolder;
-        private readonly IVirtualPathProvider _virtualPathProvider;
 
-        public CoreExtensionLoader(IDependenciesFolder dependenciesFolder, IVirtualPathProvider virtualPathProvider) {
+        public CoreExtensionLoader(IDependenciesFolder dependenciesFolder) {
             _dependenciesFolder = dependenciesFolder;
-            _virtualPathProvider = virtualPathProvider;
         }
 
-        public int Order { get { return 10; } }
+        public override int Order { get { return 10; } }
 
-        public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
-            // We don't need to monitor anything since we are loaded
-            // from the core assembly.
-        }
-
-        public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+        public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
             if (descriptor.Location == "~/Core") {
                 return new ExtensionProbeEntry {
                     Descriptor = descriptor,
@@ -38,25 +31,20 @@ namespace Orchard.Environment.Extensions.Loaders {
             return null;
         }
 
-        public ExtensionEntry Load(ExtensionProbeEntry entry) {
-            if (entry.Loader == this) {
+        public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
+            var dependency = _dependenciesFolder.GetDescriptor(descriptor.Name);
+            if (dependency != null && dependency.LoaderName == this.Name) {
+
                 var assembly = Assembly.Load("Orchard.Core");
 
-                _dependenciesFolder.Store(new DependencyDescriptor { ModuleName = entry.Descriptor.Name, LoaderName = this.GetType().FullName });
-
                 return new ExtensionEntry {
-                    Descriptor = entry.Descriptor,
+                    Descriptor = descriptor,
                     Assembly = assembly,
-                    ExportedTypes = assembly.GetExportedTypes().Where(x => IsTypeFromModule(x, entry.Descriptor))
+                    ExportedTypes = assembly.GetExportedTypes().Where(x => IsTypeFromModule(x, descriptor))
                 };
             }
-            else {
-                // If the extension is not loaded by us, there is no cached state 
-                // we need to invalidate
-                _dependenciesFolder.Remove(entry.Descriptor.Name, this.GetType().FullName);
             return null;
         }
-        }
 
         private static bool IsTypeFromModule(Type type, ExtensionDescriptor descriptor) {
             return (type.Namespace + ".").StartsWith("Orchard.Core." + descriptor.Name + ".");

src/Orchard/Environment/Extensions/Loaders/DynamicExtensionLoader.cs

@@ -4,36 +4,60 @@ using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
 using Orchard.FileSystems.Dependencies;
 using Orchard.FileSystems.VirtualPath;
+using Orchard.Logging;
 
 namespace Orchard.Environment.Extensions.Loaders {
-    public class DynamicExtensionLoader : IExtensionLoader {
-        private readonly IHostEnvironment _hostEnvironment;
+    public class DynamicExtensionLoader : ExtensionLoaderBase {
         private readonly IBuildManager _buildManager;
         private readonly IVirtualPathProvider _virtualPathProvider;
         private readonly IVirtualPathMonitor _virtualPathMonitor;
         private readonly IDependenciesFolder _dependenciesFolder;
 
-        public DynamicExtensionLoader(IHostEnvironment hostEnvironment, 
+        public DynamicExtensionLoader(
             IBuildManager buildManager,
             IVirtualPathProvider virtualPathProvider,
             IVirtualPathMonitor virtualPathMonitor,
             IDependenciesFolder dependenciesFolder) {
-            _hostEnvironment = hostEnvironment;
+
             _buildManager = buildManager;
             _virtualPathProvider = virtualPathProvider;
             _virtualPathMonitor = virtualPathMonitor;
             _dependenciesFolder = dependenciesFolder;
+            Logger = NullLogger.Instance;
         }
 
-        public int Order { get { return 100; } }
+        public ILogger Logger { get; set; }
 
-        public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
+        public override int Order { get { return 100; } }
+
+        public override string GetAssemblyDirective(DependencyDescriptor dependency) {
+            return string.Format("<%@ Assembly Src=\"{0}\"%>", dependency.VirtualPath);
+        }
+
+        public override void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
+            // We need to monitor the path to the ".csproj" file.
             string projectPath = GetProjectPath(descriptor);
-            if (projectPath != null)
+            if (projectPath != null) {
+                Logger.Information("Monitoring virtual path {0}", projectPath);
                 monitor(_virtualPathMonitor.WhenPathChanges(projectPath));
             }
+        }
 
-        public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+        public override void ExtensionRemoved(ExtensionLoadingContext ctx, DependencyDescriptor dependency) {
+            // Since a dynamic assembly is not active anymore, we need to notify ASP.NET
+            // that a new site compilation is needed (since ascx files may be referencing
+            // this now removed extension).
+            ctx.ResetSiteCompilation = true;
+        }
+
+        public override void ExtensionDeactivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension) {
+            // Since a dynamic assembly is not active anymore, we need to notify ASP.NET
+            // that a new site compilation is needed (since ascx files may be referencing
+            // this now removed extension).
+            ctx.ResetSiteCompilation = true;
+        }
+
+        public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
             string projectPath = GetProjectPath(descriptor);
             if (projectPath == null)
                 return null;
@@ -46,6 +70,21 @@ namespace Orchard.Environment.Extensions.Loaders {
             };
         }
 
+        public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
+            var dependency = _dependenciesFolder.GetDescriptor(descriptor.Name);
+            if (dependency != null && dependency.LoaderName == this.Name) {
+
+                var assembly = _buildManager.GetCompiledAssembly(dependency.VirtualPath);
+
+                return new ExtensionEntry {
+                    Descriptor = descriptor,
+                    Assembly = assembly,
+                    ExportedTypes = assembly.GetExportedTypes(),
+                };
+            }
+            return null;
+        }
+
         private string GetProjectPath(ExtensionDescriptor descriptor) {
             string projectPath = _virtualPathProvider.Combine(descriptor.Location, descriptor.Name,
                                                        descriptor.Name + ".csproj");
@@ -56,33 +95,5 @@ namespace Orchard.Environment.Extensions.Loaders {
 
             return projectPath;
         }
-
-
-        public ExtensionEntry Load(ExtensionProbeEntry entry) {
-            if (entry.Loader == this) {
-                var assembly = _buildManager.GetCompiledAssembly(entry.VirtualPath);
-
-                _dependenciesFolder.Store(new DependencyDescriptor {
-                    ModuleName = entry.Descriptor.Name, 
-                    LoaderName = this.GetType().FullName,
-                    VirtualPath = entry.VirtualPath,
-                    FileName = assembly.Location
-                });
-
-                return new ExtensionEntry {
-                    Descriptor = entry.Descriptor,
-                    Assembly = assembly,
-                    ExportedTypes = assembly.GetExportedTypes(),
-                };
-            }
-            else {
-                // If the extension is not loaded by us, there is some cached state we need to invalidate
-                // 1) The webforms views which have been compiled with ".csproj" assembly source
-                // 2) The modules which contains features which depend on us
-                //TODO
-                _dependenciesFolder.Remove(entry.Descriptor.Name, this.GetType().FullName);
-                return null;
-            }
-        }
     }
 }

src/Orchard/Environment/Extensions/Loaders/ExtensionLoaderBase.cs

@@ -0,0 +1,33 @@
+using System;
+using System.IO;
+using System.Linq;
+using Orchard.Caching;
+using Orchard.Environment.Extensions.Models;
+using Orchard.FileSystems.Dependencies;
+
+namespace Orchard.Environment.Extensions.Loaders {
+    public abstract class ExtensionLoaderBase : IExtensionLoader {
+        public abstract int Order { get; }
+        public string Name { get { return this.GetType().Name; } }
+
+        public abstract ExtensionProbeEntry Probe(ExtensionDescriptor descriptor);
+        public abstract ExtensionEntry Load(ExtensionDescriptor descriptor);
+
+        public virtual void ExtensionActivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension) {}
+        public virtual void ExtensionDeactivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension){}
+        public virtual void ExtensionRemoved(ExtensionLoadingContext ctx, DependencyDescriptor dependency) { }
+        public virtual void Monitor(ExtensionDescriptor extension, Action<IVolatileToken> monitor) { }
+        public virtual string GetAssemblyDirective(DependencyDescriptor dependency) { return null; }
+
+        public static bool FileIsNewer(string sourceFileName, string destinationFileName) {
+            if (!File.Exists(destinationFileName))
+                return true;
+
+            return File.GetLastWriteTimeUtc(sourceFileName) > File.GetLastWriteTimeUtc(destinationFileName);
+        }
+
+        public static bool IsAssemblyLoaded(string moduleName) {
+            return AppDomain.CurrentDomain.GetAssemblies().Any(a => a.GetName().Name == moduleName);
+        }
+    }
+}

src/Orchard/Environment/Extensions/Loaders/IExtensionLoader.cs

@@ -1,19 +1,29 @@
 using System;
 using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
+using Orchard.FileSystems.Dependencies;
 
 namespace Orchard.Environment.Extensions.Loaders {
-    public interface IExtensionLoader {
-        int Order { get; }
-        ExtensionProbeEntry Probe(ExtensionDescriptor descriptor);
-        ExtensionEntry Load(ExtensionProbeEntry descriptor);
-        void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor);
-    }
-
     public class ExtensionProbeEntry {
         public ExtensionDescriptor Descriptor { get; set; }
         public IExtensionLoader Loader { get; set; }
         public string VirtualPath { get; set; }
         public DateTime LastModificationTimeUtc { get; set; }
     }
+
+    public interface IExtensionLoader {
+        int Order { get; }
+        string Name { get; }
+
+        ExtensionProbeEntry Probe(ExtensionDescriptor descriptor);
+        ExtensionEntry Load(ExtensionDescriptor descriptor);
+
+        void ExtensionActivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension);
+        void ExtensionDeactivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension);
+        void ExtensionRemoved(ExtensionLoadingContext ctx, DependencyDescriptor dependency);
+
+        void Monitor(ExtensionDescriptor extension, Action<IVolatileToken> monitor);
+
+        string GetAssemblyDirective(DependencyDescriptor dependency);
+    }
 }

src/Orchard/Environment/Extensions/Loaders/PrecompiledExtensionLoader.cs

@@ -1,16 +1,18 @@
 using System;
 using System.IO;
+using System.Linq;
 using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
 using Orchard.FileSystems.Dependencies;
 using Orchard.FileSystems.VirtualPath;
+using Orchard.Logging;
 
 namespace Orchard.Environment.Extensions.Loaders {
     /// <summary>
     /// Load an extension by looking into the "bin" subdirectory of an
     /// extension directory.
     /// </summary>
-    public class PrecompiledExtensionLoader : IExtensionLoader {
+    public class PrecompiledExtensionLoader : ExtensionLoaderBase {
         private readonly IDependenciesFolder _dependenciesFolder;
         private readonly IVirtualPathProvider _virtualPathProvider;
         private readonly IVirtualPathMonitor _virtualPathMonitor;
@@ -19,26 +21,64 @@ namespace Orchard.Environment.Extensions.Loaders {
             _dependenciesFolder = dependenciesFolder;
             _virtualPathProvider = virtualPathProvider;
             _virtualPathMonitor = virtualPathMonitor;
+            Logger = NullLogger.Instance;
         }
 
-        public int Order { get { return 30; } }
+        public ILogger Logger { get; set; }
 
-        public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
+        public override int Order { get { return 30; } }
+
+        public override string GetAssemblyDirective(DependencyDescriptor dependency) {
+            return string.Format("<%@ Assembly Name=\"{0}\"%>", dependency.Name);
+        }
+
+        public override void ExtensionRemoved(ExtensionLoadingContext ctx, DependencyDescriptor dependency) {
+            var assemblyFileName = _dependenciesFolder.GetProbingAssemblyPhysicalFileName(dependency.Name);
+            if (File.Exists(assemblyFileName)) {
+                ctx.FilesToDelete.Add(assemblyFileName);
+
+                // We need to restart the appDomain if the assembly is loaded
+                if (IsAssemblyLoaded(dependency.Name)) {
+                    Logger.Information("Extension removed: Setting AppDomain for restart because assembly {0} is loaded", dependency.Name);
+                    ctx.RestartAppDomain = true;
+                }
+            }
+        }
+
+        public override void ExtensionActivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension) {
+            string sourceFileName = _virtualPathProvider.MapPath(GetAssemblyPath(extension));
+            string destinationFileName = _dependenciesFolder.GetProbingAssemblyPhysicalFileName(extension.Name);
+            if (FileIsNewer(sourceFileName, destinationFileName)) {
+                ctx.FilesToCopy.Add(sourceFileName, destinationFileName);
+                // We need to restart the appDomain if the assembly is loaded
+                if (IsAssemblyLoaded(extension.Name)) {
+                    Logger.Information("Extension activated: Setting AppDomain for restart because assembly {0} is loaded", extension.Name);
+                    ctx.RestartAppDomain = true;
+                }
+            }
+        }
+
+        public override void ExtensionDeactivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension) {
+            var assemblyFileName = _dependenciesFolder.GetProbingAssemblyPhysicalFileName(extension.Name);
+            if (File.Exists(assemblyFileName)) {
+                ctx.FilesToDelete.Add(assemblyFileName);
+                // We need to restart the appDomain if the assembly is loaded
+                if (IsAssemblyLoaded(extension.Name)) {
+                    Logger.Information("Extension deactivated: Setting AppDomain for restart because assembly {0} is loaded", extension.Name);
+                    ctx.RestartAppDomain = true;
+                }
+            }
+        }
+
+        public override void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
             string assemblyPath = GetAssemblyPath(descriptor);
-            if (assemblyPath != null)
+            if (assemblyPath != null) {
+                Logger.Information("Monitoring virtual path \"{0}\"", assemblyPath);
                 monitor(_virtualPathMonitor.WhenPathChanges(assemblyPath));
             }
-
-        public string GetAssemblyPath(ExtensionDescriptor descriptor) {
-            var assemblyPath = _virtualPathProvider.Combine(descriptor.Location, descriptor.Name, "bin",
-                                                              descriptor.Name + ".dll");
-            if (!_virtualPathProvider.FileExists(assemblyPath))
-                return null;
-
-            return assemblyPath;
         }
 
-        public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+        public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
             var assemblyPath = GetAssemblyPath(descriptor);
             if (assemblyPath == null)
                 return null;
@@ -51,28 +91,30 @@ namespace Orchard.Environment.Extensions.Loaders {
             };
         }
 
-        public ExtensionEntry Load(ExtensionProbeEntry entry) {
-            if (entry.Loader == this) {
-                _dependenciesFolder.StorePrecompiledAssembly(entry.Descriptor.Name, entry.VirtualPath, this.GetType().FullName);
+        public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
+            var dependency = _dependenciesFolder.GetDescriptor(descriptor.Name);
+            if (dependency != null && dependency.LoaderName == this.Name) {
 
-                var assembly = _dependenciesFolder.LoadAssembly(entry.Descriptor.Name);
+                var assembly = _dependenciesFolder.GetProbingAssembly(descriptor.Name);
                 if (assembly == null)
                     return null;
 
                 return new ExtensionEntry {
-                    Descriptor = entry.Descriptor,
-                    Assembly = assembly,
-                    ExportedTypes = assembly.GetExportedTypes()
+                    Descriptor = descriptor,
+                    Assembly = assembly.Assembly(),
+                    ExportedTypes = assembly.Assembly().GetExportedTypes()
                 };
             }
-            else {
-                // If the extension is not loaded by us, there is some cached state we need to invalidate
-                // 1) The webforms views which have been compiled with ".csproj" assembly source
-                // 2) The modules which contains features which depend on us
-                //TODO
-                _dependenciesFolder.Remove(entry.Descriptor.Name, this.GetType().FullName);
             return null;
         }
+
+        public string GetAssemblyPath(ExtensionDescriptor descriptor) {
+            var assemblyPath = _virtualPathProvider.Combine(descriptor.Location, descriptor.Name, "bin",
+                                                            descriptor.Name + ".dll");
+            if (!_virtualPathProvider.FileExists(assemblyPath))
+                return null;
+
+            return assemblyPath;
         }
     }
 }

src/Orchard/Environment/Extensions/Loaders/ProbingExtensionLoader.cs

@@ -1,32 +1,62 @@
 using System;
 using System.IO;
+using System.Linq;
 using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
 using Orchard.FileSystems.Dependencies;
 using Orchard.FileSystems.VirtualPath;
+using Orchard.Logging;
 
 namespace Orchard.Environment.Extensions.Loaders {
     /// <summary>
     /// Load an extension using the "Assembly.Load" method if the
     /// file can be found in the "App_Data/Dependencies" folder.
     /// </summary>
-    public class ProbingExtensionLoader : IExtensionLoader {
+    public class ProbingExtensionLoader : ExtensionLoaderBase {
         private readonly IDependenciesFolder _dependenciesFolder;
+        private readonly IVirtualPathProvider _virtualPathProvider;
 
-        public ProbingExtensionLoader(IDependenciesFolder dependenciesFolder) {
+        public ProbingExtensionLoader(IDependenciesFolder dependenciesFolder, IVirtualPathProvider virtualPathProvider) {
             _dependenciesFolder = dependenciesFolder;
+            _virtualPathProvider = virtualPathProvider;
+            Logger = NullLogger.Instance;
         }
 
-        public int Order { get { return 40; } }
+        public ILogger Logger { get; set; }
 
-        public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
-            // We don't monitor assemblies loaded from this probing directory,
-            // because they are just a copy of the assemblies from the module
-            // bin directory.
+        public override int Order { get { return 40; } }
+
+        public override string GetAssemblyDirective(DependencyDescriptor dependency) {
+            return string.Format("<%@ Assembly Name=\"{0}\"%>", dependency.Name);
         }
 
-        public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
-            if (!_dependenciesFolder.HasPrecompiledAssembly(descriptor.Name))
+        public override void ExtensionRemoved(ExtensionLoadingContext ctx, DependencyDescriptor dependency) {
+            var assemblyFileName = _dependenciesFolder.GetProbingAssemblyPhysicalFileName(dependency.Name);
+            if (File.Exists(assemblyFileName)) {
+                ctx.FilesToDelete.Add(assemblyFileName);
+                // We need to restart the appDomain if the assembly is loaded
+                if (IsAssemblyLoaded(dependency.Name)) {
+                    Logger.Information("Extension removed: Setting AppDomain for restart because assembly {0} is loaded", dependency.Name);
+                    ctx.RestartAppDomain = true;
+                }
+            }
+        }
+
+        public override void ExtensionDeactivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension) {
+            var assemblyFileName = _dependenciesFolder.GetProbingAssemblyPhysicalFileName(extension.Name);
+            if (File.Exists(assemblyFileName)) {
+                ctx.FilesToDelete.Add(assemblyFileName);
+                // We need to restart the appDomain if the assembly is loaded
+                if (IsAssemblyLoaded(extension.Name)) {
+                    Logger.Information("Extension deactivated: Setting AppDomain for restart because assembly {0} is loaded", extension.Name);
+                    ctx.RestartAppDomain = true;
+                }
+            }
+        }
+
+        public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+            var probingAssembly = _dependenciesFolder.GetProbingAssembly(descriptor.Name);
+            if (probingAssembly == null)
                 return null;
 
             var desc = _dependenciesFolder.GetDescriptor(descriptor.Name);
@@ -35,33 +65,27 @@ namespace Orchard.Environment.Extensions.Loaders {
 
             return new ExtensionProbeEntry {
                     Descriptor = descriptor,
-                    LastModificationTimeUtc = File.GetLastWriteTimeUtc(desc.FileName),
+                    LastModificationTimeUtc = probingAssembly.LastWriteTimeUtc(),
                     Loader = this,
                     VirtualPath = desc.VirtualPath
                 };
         }
 
-        public ExtensionEntry Load(ExtensionProbeEntry entry) {
-            if (entry.Loader == this) {
-                var assembly = _dependenciesFolder.LoadAssembly(entry.Descriptor.Name);
+        public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
+            var dependency = _dependenciesFolder.GetDescriptor(descriptor.Name);
+            if (dependency != null && dependency.LoaderName == this.Name) {
+
+                var assembly = _dependenciesFolder.GetProbingAssembly(descriptor.Name);
                 if (assembly == null)
                     return null;
 
                 return new ExtensionEntry {
-                    Descriptor = entry.Descriptor,
-                    Assembly = assembly,
-                    ExportedTypes = assembly.GetExportedTypes()
+                    Descriptor = descriptor,
+                    Assembly = assembly.Assembly(),
+                    ExportedTypes = assembly.Assembly().GetExportedTypes()
                 };
             }
-            else {
-                // If the extension is not loaded by us, there is some cached state we need to invalidate
-                // 1) The webforms views which have been compiled with "Assembly Name=""" directive
-                // 2) The modules which contains features which depend on us
-                // 3) The binary from the App_Data directory
-                //TODO
-                _dependenciesFolder.Remove(entry.Descriptor.Name, this.GetType().FullName);
             return null;
         }
     }
-    }
 }

src/Orchard/Environment/Extensions/Loaders/ReferencedExtensionLoader.cs

@@ -1,32 +1,35 @@
-using System;
-using System.IO;
+using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Web.Compilation;
 using System.Web.Hosting;
-using Orchard.Caching;
 using Orchard.Environment.Extensions.Models;
 using Orchard.FileSystems.Dependencies;
+using Orchard.FileSystems.VirtualPath;
 
 namespace Orchard.Environment.Extensions.Loaders {
     /// <summary>
     /// Load an extension by looking through the BuildManager referenced assemblies
     /// </summary>
-    public class ReferencedExtensionLoader : IExtensionLoader {
+    public class ReferencedExtensionLoader : ExtensionLoaderBase {
         private readonly IDependenciesFolder _dependenciesFolder;
+        private readonly IVirtualPathProvider _virtualPathProvider;
 
-        public ReferencedExtensionLoader(IDependenciesFolder dependenciesFolder) {
+        public ReferencedExtensionLoader(IDependenciesFolder dependenciesFolder, IVirtualPathProvider virtualPathProvider) {
             _dependenciesFolder = dependenciesFolder;
+            _virtualPathProvider = virtualPathProvider;
         }
 
-        public int Order { get { return 20; } }
+        public override int Order { get { return 20; } }
 
-        public void Monitor(ExtensionDescriptor descriptor, Action<IVolatileToken> monitor) {
-            // We don't monitor assemblies loaded from the "~/bin" directory,
-            // because they are monitored by the ASP.NET runtime.
+        public override void ExtensionDeactivated(ExtensionLoadingContext ctx, bool isNewExtension, ExtensionDescriptor extension) {
+            var assemblyPath = _virtualPathProvider.Combine("~/bin", extension.Name + ".dll");
+            if (_virtualPathProvider.FileExists(assemblyPath)) {
+                ctx.FilesToDelete.Add(_virtualPathProvider.MapPath(assemblyPath));
+            }
         }
 
-        public ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
+        public override ExtensionProbeEntry Probe(ExtensionDescriptor descriptor) {
             if (HostingEnvironment.IsHosted == false)
                 return null;
 
@@ -45,36 +48,24 @@ namespace Orchard.Environment.Extensions.Loaders {
             };
         }
 
-        public ExtensionEntry Load(ExtensionProbeEntry entry) {
+        public override ExtensionEntry Load(ExtensionDescriptor descriptor) {
             if (HostingEnvironment.IsHosted == false)
                 return null;
 
-            if (entry.Loader == this) {
+            var dependency = _dependenciesFolder.GetDescriptor(descriptor.Name);
+            if (dependency != null && dependency.LoaderName == this.Name) {
 
                 var assembly = BuildManager.GetReferencedAssemblies()
                     .OfType<Assembly>()
-                    .FirstOrDefault(x => x.GetName().Name == entry.Descriptor.Name);
-
-                _dependenciesFolder.Store(new DependencyDescriptor {
-                    ModuleName = entry.Descriptor.Name, 
-                    LoaderName = this.GetType().FullName,
-                    VirtualPath = entry.VirtualPath,
-                    FileName = assembly.Location
-                });
-
+                    .FirstOrDefault(x => x.GetName().Name == descriptor.Name);
 
                 return new ExtensionEntry {
-                    Descriptor = entry.Descriptor,
+                    Descriptor = descriptor,
                     Assembly = assembly,
                     ExportedTypes = assembly.GetExportedTypes()
                 };
             }
-            else {
-                // If the extension is not loaded by us, there is no cached state 
-                // we need to invalidate
-                _dependenciesFolder.Remove(entry.Descriptor.Name, this.GetType().FullName);
             return null;
         }
     }
-    }
 }

src/Orchard/Environment/OrchardStarter.cs

@@ -57,6 +57,7 @@ namespace Orchard.Environment {
                         .As<ICompositionStrategy>()
                         .SingleInstance();
                     {
+                        builder.RegisterType<ExtensionLoaderCoordinator>().As<IExtensionLoaderCoordinator>().SingleInstance();
                         builder.RegisterType<ExtensionManager>().As<IExtensionManager>().SingleInstance();
                         {
                             builder.RegisterType<ModuleFolders>().As<IExtensionFolders>()

src/Orchard/FileSystems/Dependencies/DefaultDependenciesFolder.cs

@@ -6,11 +6,12 @@ using System.Reflection;
 using System.Xml.Linq;
 using Orchard.Caching;
 using Orchard.FileSystems.AppData;
+using Orchard.Localization;
 
 namespace Orchard.FileSystems.Dependencies {
     public class DefaultDependenciesFolder : IDependenciesFolder {
-        private readonly string _basePath = "Dependencies";
-        private readonly string _persistanceFileName = "dependencies.xml";
+        private const string BasePath = "Dependencies";
+        private const string FileName = "dependencies.xml";
         private readonly ICacheManager _cacheManager;
         private readonly IAppDataFolder _appDataFolder;
         private readonly InvalidationToken _writeThroughToken;
@@ -19,11 +20,14 @@ namespace Orchard.FileSystems.Dependencies {
             _cacheManager = cacheManager;
             _appDataFolder = appDataFolder;
             _writeThroughToken = new InvalidationToken();
+            T = NullLocalizer.Instance;
         }
 
+        public Localizer T { get; set; }
+
         private string PersistencePath {
             get {
-                return _appDataFolder.Combine(_basePath, _persistanceFileName);
+                return _appDataFolder.Combine(BasePath, FileName);
             }
         }
 
@@ -31,106 +35,47 @@ namespace Orchard.FileSystems.Dependencies {
             get {
                 return _cacheManager.Get(PersistencePath,
                                          ctx => {
-                                             _appDataFolder.CreateDirectory(_basePath);
+                                             _appDataFolder.CreateDirectory(BasePath);
 
                                              ctx.Monitor(_appDataFolder.WhenPathChanges(ctx.Key));
                                              ctx.Monitor(_writeThroughToken);
 
-                                             _appDataFolder.CreateDirectory(_basePath);
+                                             _appDataFolder.CreateDirectory(BasePath);
                                              return ReadDependencies(ctx.Key).ToList();
                                          });
             }
         }
 
-        public class InvalidationToken : IVolatileToken {
-            public bool IsCurrent { get; set; }
+        public IEnumerable<DependencyDescriptor> LoadDescriptors() {
+            return Descriptors;
         }
 
-        public void StorePrecompiledAssembly(string moduleModuleName, string virtualPath, string loaderName) {
-            _appDataFolder.CreateDirectory(_basePath);
-
-            // Only store assembly if it's more recent that what we have stored already (if anything)
-            var assemblyFileName = _appDataFolder.MapPath(virtualPath);
-            if (IsNewerAssembly(moduleModuleName, assemblyFileName)) {
-                var destinationFileName = Path.GetFileName(assemblyFileName);
-                var destinationPath = _appDataFolder.MapPath(_appDataFolder.Combine(_basePath, destinationFileName));
-                File.Copy(assemblyFileName, destinationPath, true);
-
-                StoreDepencyInformation(new DependencyDescriptor {
-                    ModuleName = moduleModuleName,
-                    LoaderName = loaderName,
-                    VirtualPath = virtualPath,
-                    FileName = destinationFileName
-                });
-            }
-        }
-
-        public void Remove(string moduleName, string loaderName) {
-            Func<DependencyDescriptor, bool> predicate = (d => d.ModuleName == moduleName && d.LoaderName == loaderName);
-            if (Descriptors.Any(predicate)) {
-                var newDescriptors = Descriptors.Where(e => !predicate(e));
-
-                WriteDependencies(PersistencePath, newDescriptors);
-            }
-        }
-
-        public void Store(DependencyDescriptor descriptor) {
-            StoreDepencyInformation(descriptor);
+        public void StoreDescriptors(IEnumerable<DependencyDescriptor> dependencyDescriptors) {
+            WriteDependencies(PersistencePath, dependencyDescriptors);
         }
 
         public DependencyDescriptor GetDescriptor(string moduleName) {
-            return Descriptors.SingleOrDefault(d => d.ModuleName == moduleName);
+            return Descriptors.SingleOrDefault(d => d.Name == moduleName);
         }
 
-        private bool IsNewerAssembly(string moduleName, string assemblyFileName) {
-            var dependency = Descriptors.SingleOrDefault(d => d.ModuleName == moduleName);
-            if (dependency == null) {
-                return true;
-            }
-
-            var existingFileName = _appDataFolder.MapPath(_appDataFolder.Combine(_basePath, dependency.FileName));
-            if (!File.Exists(existingFileName)) {
-                return true;
-            }
-
-            return (File.GetLastWriteTimeUtc(existingFileName) < File.GetLastWriteTimeUtc(assemblyFileName));
-        }
-
-        private void StoreDepencyInformation(DependencyDescriptor descriptor) {
-            var dependencies = Descriptors.ToList();
-            int index = dependencies.FindIndex(d => d.ModuleName == descriptor.ModuleName);
-            if (index < 0) {
-                dependencies.Add(descriptor);
-            }
-            else {
-                dependencies[index] = descriptor;
-            }
-
-            WriteDependencies(PersistencePath, dependencies);
-        }
-
-        public Assembly LoadAssembly(string moduleName) {
-            _appDataFolder.CreateDirectory(_basePath);
-
-            var dependency = Descriptors.SingleOrDefault(d => d.ModuleName == moduleName);
-            if (dependency == null)
+        public ProbingAssembly GetProbingAssembly(string moduleName) {
+            var path = PrecompiledAssemblyPath(moduleName);
+            if (!_appDataFolder.FileExists(path))
                 return null;
 
-            if (!_appDataFolder.FileExists(_appDataFolder.Combine(_basePath, dependency.FileName)))
-                return null;
-
-            return Assembly.Load(Path.GetFileNameWithoutExtension(dependency.FileName));
+            return new ProbingAssembly {
+                Path = path,
+                Assembly = () => Assembly.Load(moduleName),
+                LastWriteTimeUtc = () => File.GetLastWriteTimeUtc(_appDataFolder.MapPath(path)),
+            };
         }
 
-        public bool HasPrecompiledAssembly(string moduleName) {
-            var dependency = Descriptors.SingleOrDefault(d => d.ModuleName == moduleName);
-            if (dependency == null)
-                return false;
+        public string GetProbingAssemblyPhysicalFileName(string moduleName) {
+            return _appDataFolder.MapPath(PrecompiledAssemblyPath(moduleName));
+        }
 
-            if (!_appDataFolder.FileExists(_appDataFolder.Combine(_basePath, dependency.FileName)))
-                return false;
-
-            return true;
+        private string PrecompiledAssemblyPath(string moduleName) {
+            return _appDataFolder.Combine(BasePath, moduleName + ".dll");
         }
 
         private IEnumerable<DependencyDescriptor> ReadDependencies(string persistancePath) {
@@ -146,9 +91,8 @@ namespace Orchard.FileSystems.Dependencies {
                     .Elements(ns("Dependencies"))
                     .Elements(ns("Dependency"))
                     .Select(e => new DependencyDescriptor {
-                        ModuleName = elem(e, "ModuleName"),
+                        Name = elem(e, "ModuleName"),
                         VirtualPath = elem(e, "VirtualPath"),
-                        FileName = elem(e, "FileName"),
                         LoaderName = elem(e, "LoaderName")
                     })
                     .ToList();
@@ -161,10 +105,9 @@ namespace Orchard.FileSystems.Dependencies {
             var document = new XDocument();
             document.Add(new XElement(ns("Dependencies")));
             var elements = dependencies.Select(d => new XElement("Dependency",
-                                                                 new XElement(ns("ModuleName"), d.ModuleName),
+                                                                 new XElement(ns("ModuleName"), d.Name),
                                                                  new XElement(ns("VirtualPath"), d.VirtualPath),
-                                                                 new XElement(ns("LoaderName"), d.LoaderName),
-                                                                 new XElement(ns("FileName"), d.FileName)));
+                                                                 new XElement(ns("LoaderName"), d.LoaderName)));
             document.Root.Add(elements);
 
             using (var stream = _appDataFolder.CreateFile(persistancePath)) {
@@ -174,5 +117,9 @@ namespace Orchard.FileSystems.Dependencies {
             // Ensure cache is invalidated right away, not waiting for file change notification to happen
             _writeThroughToken.IsCurrent = false;
         }
+
+        private class InvalidationToken : IVolatileToken {
+            public bool IsCurrent { get; set; }
+        }
     }
 }

src/Orchard/FileSystems/Dependencies/IDependenciesFolder.cs

@@ -1,20 +1,27 @@
-using System.Reflection;
+using System;
+using System.Collections.Generic;
+using System.Reflection;
 using Orchard.Caching;
 
 namespace Orchard.FileSystems.Dependencies {
     public class DependencyDescriptor {
-        public string ModuleName { get; set; }
+        public string Name { get; set; }
         public string LoaderName { get; set; }
         public string VirtualPath { get; set; }
-        public string FileName { get; set; }
+    }
+
+    public class ProbingAssembly {
+        public string Path { get; set; }
+        public Func<DateTime> LastWriteTimeUtc { get; set; }
+        public Func<Assembly> Assembly { get; set; }
     }
 
     public interface IDependenciesFolder : IVolatileProvider {
-        void Store(DependencyDescriptor descriptor);
-        void StorePrecompiledAssembly(string moduleName, string virtualPath, string loaderName);
-        void Remove(string moduleName, string loaderName);
         DependencyDescriptor GetDescriptor(string moduleName);
-        bool HasPrecompiledAssembly(string moduleName);
-        Assembly LoadAssembly(string moduleName);
+        IEnumerable<DependencyDescriptor> LoadDescriptors();
+        void StoreDescriptors(IEnumerable<DependencyDescriptor> dependencyDescriptors);
+
+        ProbingAssembly GetProbingAssembly(string moduleName);
+        string GetProbingAssemblyPhysicalFileName(string moduleName);
     }
 }

src/Orchard/FileSystems/Dependencies/WebFormsExtensionsVirtualFile.cs

@@ -1,16 +1,15 @@
 using System.IO;
 using System.Web.Hosting;
-using Orchard.Environment.Extensions.Loaders;
 
 namespace Orchard.FileSystems.Dependencies {
     public class WebFormsExtensionsVirtualFile : VirtualFile {
-        private readonly DependencyDescriptor _dependencyDescriptor;
         private readonly VirtualFile _actualFile;
+        private readonly string _assemblyDirective;
 
-        public WebFormsExtensionsVirtualFile(string virtualPath, DependencyDescriptor dependencyDescriptor, VirtualFile actualFile)
+        public WebFormsExtensionsVirtualFile(string virtualPath, VirtualFile actualFile, string assemblyDirective)
             : base(virtualPath) {
-            _dependencyDescriptor = dependencyDescriptor;
             _actualFile = actualFile;
+            _assemblyDirective = assemblyDirective;
         }
 
         public override string Name {
@@ -37,7 +36,7 @@ namespace Orchard.FileSystems.Dependencies {
                     for (var line = reader.ReadLine(); line != null; line = reader.ReadLine()) {
 
                         if (!string.IsNullOrWhiteSpace(line) && !assemblyDirectiveAdded) {
-                            line += GetAssemblyDirective();
+                            line += _assemblyDirective;
                             assemblyDirectiveAdded = true;
                         }
 
@@ -49,14 +48,5 @@ namespace Orchard.FileSystems.Dependencies {
                 return new MemoryStream(memoryStream.GetBuffer(), 0, length);
             }
         }
-
-        private string GetAssemblyDirective() {
-            if (_dependencyDescriptor.LoaderName == typeof(DynamicExtensionLoader).FullName) {
-                return string.Format("<%@ Assembly Src=\"{0}\"%>", _dependencyDescriptor.VirtualPath);
-            }
-            else {
-                return string.Format("<%@ Assembly Name=\"{0}\"%>", _dependencyDescriptor.ModuleName);
-            }
-        }
     }
 }

src/Orchard/FileSystems/Dependencies/WebFormsExtensionsVirtualPathProvider.cs

@@ -1,16 +1,20 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Web.Hosting;
+using Orchard.Environment.Extensions.Loaders;
 using Orchard.FileSystems.VirtualPath;
 
 namespace Orchard.FileSystems.Dependencies {
     public class WebFormsExtensionsVirtualPathProvider : VirtualPathProvider, ICustomVirtualPathProvider {
         private readonly IDependenciesFolder _dependenciesFolder;
+        private readonly IEnumerable<IExtensionLoader> _loaders;
         private readonly string[] _prefixes = { "~/Modules/", "/Modules/" };
         private readonly string[] _extensions = { ".ascx", ".aspx", ".master" };
 
-        public WebFormsExtensionsVirtualPathProvider(IDependenciesFolder dependenciesFolder) {
+        public WebFormsExtensionsVirtualPathProvider(IDependenciesFolder dependenciesFolder, IEnumerable<IExtensionLoader> loaders) {
             _dependenciesFolder = dependenciesFolder;
+            _loaders = loaders;
         }
 
         public override bool DirectoryExists(string virtualDir) {
@@ -24,27 +28,35 @@ namespace Orchard.FileSystems.Dependencies {
         public override VirtualFile GetFile(string virtualPath) {
             var actualFile = Previous.GetFile(virtualPath);
 
+            return GetCustomVirtualFile(virtualPath, actualFile) ?? actualFile;
+        }
+
+        private VirtualFile GetCustomVirtualFile(string virtualPath, VirtualFile actualFile) {
             var prefix = PrefixMatch(virtualPath, _prefixes);
             if (prefix == null)
-                return actualFile;
+                return null;
 
             var extension = ExtensionMatch(virtualPath, _extensions);
             if (extension == null)
-                return actualFile;
+                return null;
 
             var moduleName = ModuleMatch(virtualPath, prefix);
             if (moduleName == null)
-                return actualFile;
+                return null;
 
-            // It looks like we have a module name. Is this one of this modules
-            // with its assembly stored in the "App_Data/Dependencies" folder?
             var dependencyDescriptor = _dependenciesFolder.GetDescriptor(moduleName);
             if (dependencyDescriptor == null)
-                return actualFile;
+                return null;
 
-            // Yes: we need to wrap the VirtualFile to add the <%@ Assembly Name=".."%> directive
-            // in the content.
-            return new WebFormsExtensionsVirtualFile(virtualPath, dependencyDescriptor, actualFile);
+            var loader = _loaders.Where(l => l.Name == dependencyDescriptor.LoaderName).FirstOrDefault();
+            if (loader == null)
+                return null;
+
+            var directive = loader.GetAssemblyDirective(dependencyDescriptor);
+            if (string.IsNullOrEmpty(directive))
+                return null;
+
+            return new WebFormsExtensionsVirtualFile(virtualPath, actualFile, directive);
         }
 
         private string ModuleMatch(string virtualPath, string prefix) {

src/Orchard/Orchard.Framework.csproj

@@ -353,6 +353,10 @@
     <Compile Include="Data\DataModule.cs" />
     <Compile Include="Data\Orderable.cs" />
     <Compile Include="Environment\DefaultOrchardShell.cs" />
+    <Compile Include="Environment\Extensions\ExtensionLoaderCoordinator.cs" />
+    <Compile Include="Environment\Extensions\ExtensionLoadingContext.cs" />
+    <Compile Include="Environment\Extensions\IExtensionLoaderCoordinator.cs" />
+    <Compile Include="Environment\Extensions\Loaders\ExtensionLoaderBase.cs" />
     <Compile Include="FileSystems\AppData\IAppDataFolderRoot.cs" />
     <Compile Include="FileSystems\Dependencies\DefaultDependenciesFolder.cs" />
     <Compile Include="FileSystems\VirtualPath\DefaultVirtualPathMonitor.cs" />