Fixed #4905: Taxonomy term counter does not decrease.

I think the problem is that the TermsPartHandler triggers the TermCountProcessor as a Task async and the TermCountProcessor used the ContentTypeId as a parameter.
If a ContentItem gets deleted, the TermCountProcessor cannot access it anymore and the Terms won't getting reprocessed which results in a wrong count.
I altered the ITermCountProcessor interface to accept TermPartRecordId's instead of the ContentTypeId and use this id's directly.
I also had to add a call for the ITermCountProcessor in the TermService UpdateTerm method. This is because when you re-publish a ContentItem only the new Terms are available in the PublishedEvent - but also terms from the previous version needed to be processed.

src/Orchard.Web/Modules/Orchard.Taxonomies/Handlers/TermsPartHandler.cs

@@ -91,7 +91,8 @@ namespace Orchard.Taxonomies.Handlers {
         
         // Fires off a processing engine task to run the count processing after the request so it's non-blocking.
         private void RecalculateCount(IProcessingEngine processingEngine, ShellSettings shellSettings, IShellDescriptorManager shellDescriptorManager, TermsPart part) {
-            processingEngine.AddTask(shellSettings, shellDescriptorManager.GetShellDescriptor(), "ITermCountProcessor.Process", new Dictionary<string, object> { { "termsPartId", part.ContentItem.Id } });
+            var termPartRecordIds = part.Terms.Select(t => t.TermRecord.Id).ToArray();
+            processingEngine.AddTask(shellSettings, shellDescriptorManager.GetShellDescriptor(), "ITermCountProcessor.Process", new Dictionary<string, object> { { "termPartRecordIds", termPartRecordIds } });
 
         }
 

src/Orchard.Web/Modules/Orchard.Taxonomies/Services/ITermCountProcessor.cs

@@ -7,6 +7,6 @@ using Orchard.Events;
 
 namespace Orchard.Taxonomies.Services {
     public interface ITermCountProcessor : IEventHandler {
-        void Process(int termsPartId);
+        void Process(params int[] termPartRecordIds);
     }
 }

src/Orchard.Web/Modules/Orchard.Taxonomies/Services/TaxonomyService.cs

@@ -9,6 +9,9 @@ using Orchard.ContentManagement.MetaData;
 using Orchard.Core.Common.Models;
 using Orchard.Core.Title.Models;
 using Orchard.Data;
+using Orchard.Environment.Configuration;
+using Orchard.Environment.Descriptor;
+using Orchard.Environment.State;
 using Orchard.Localization;
 using Orchard.Logging;
 using Orchard.Security;
@@ -23,6 +26,10 @@ namespace Orchard.Taxonomies.Services {
         private readonly IAuthorizationService _authorizationService;
         private readonly IContentDefinitionManager _contentDefinitionManager;
         private readonly IOrchardServices _services;
+        private readonly IProcessingEngine _processingEngine;
+        private readonly ShellSettings _shellSettings;
+        private readonly IShellDescriptorManager _shellDescriptorManager;
+
 
         public TaxonomyService(
             IRepository<TermContentItem> termContentItemRepository,
@@ -30,13 +37,20 @@ namespace Orchard.Taxonomies.Services {
             INotifier notifier,
             IContentDefinitionManager contentDefinitionManager,
             IAuthorizationService authorizationService,
-            IOrchardServices services) {
+            IOrchardServices services, 
+            IProcessingEngine processingEngine, 
+            ShellSettings shellSettings, 
+            IShellDescriptorManager shellDescriptorManager)
+        {
             _termContentItemRepository = termContentItemRepository;
             _contentManager = contentManager;
             _notifier = notifier;
             _authorizationService = authorizationService;
             _contentDefinitionManager = contentDefinitionManager;
             _services = services;
+            _processingEngine = processingEngine;
+            _shellSettings = shellSettings;
+            _shellDescriptorManager = shellDescriptorManager;
 
             Logger = NullLogger.Instance;
             T = NullLocalizer.Instance;
@@ -208,24 +222,31 @@ namespace Orchard.Taxonomies.Services {
             var termsPart = contentItem.As<TermsPart>();
 
             // removing current terms for specific field
-            var fieldIndexes = termsPart.Terms.Select((t, i) => new {Term = t, Index = i})
+            var termList = termsPart.Terms.Select((t, i) => new {Term = t, Index = i})
                 .Where(x => x.Term.Field == field)
-                .Select(x => x.Index)
+                .Select(x => x)
-                .OrderByDescending(i => i)
+                .OrderByDescending(i => i.Index)
                 .ToList();
-            
+
-            foreach(var x in fieldIndexes) {
+            foreach (var x in termList) {
-                termsPart.Terms.RemoveAt(x);
+                termsPart.Terms.RemoveAt(x.Index);
             }
             
             // adding new terms list
             foreach(var term in terms) {
+                // Remove the newly added terms because they will get processed by the Published-Event
+                termList.RemoveAll(t => t.Term.Id == term.Id);
                 termsPart.Terms.Add( 
                     new TermContentItem {
                         TermsPartRecord = termsPart.Record, 
                         TermRecord = term.Record, Field = field
                     });
             }
+
+            var termPartRecordIds = termList.Select(t => t.Term.TermRecord.Id).ToArray();
+            _processingEngine.AddTask(_shellSettings, _shellDescriptorManager.GetShellDescriptor(), "ITermCountProcessor.Process", new Dictionary<string, object> { { "termPartRecordIds", termPartRecordIds } });
+
+
         }
 
         public IContentQuery<TermsPart, TermsPartRecord> GetContentItemsQuery(TermPart term, string fieldName = null) {

src/Orchard.Web/Modules/Orchard.Taxonomies/Services/TermCountProcessor.cs

@@ -15,16 +15,10 @@ namespace Orchard.Taxonomies.Services {
             _taxonomyService = taxonomyService;
         }
         
-        public void Process(int termsPartId) {
+        public void Process(params int[] termPartRecordIds) {
-            var termsPart = _contentManager.Get<TermsPart>(termsPartId);
 
-            if (termsPart == null) {
+            foreach (var id in termPartRecordIds) {
-                return;
+                var termPart = _taxonomyService.GetTerm(id);
-            }
-
-            // Retrieve the number of associated content items, for the whole hierarchy
-            foreach (var term in termsPart.Terms) {
-                var termPart = _taxonomyService.GetTerm(term.TermRecord.Id);
                 while (termPart != null) {
                     termPart.Count = (int)_taxonomyService.GetContentItemsCount(termPart);