Fix GetInstance(IIdentity) resulting in an exception because of a wrong if clause

src/Moryx.AbstractionLayer/Products/IProductManagement.cs

@@ -94,6 +94,8 @@ public interface IProductManagement : IRecipeProvider, IWorkplans
         /// <summary>
         /// Get an instance with this identity
         /// </summary>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="identity"/> is null</exception>
+        /// <exception cref="InvalidOperationException">Thrown when there is more than one product with the given <paramref name="identity"/></exception>
         ProductInstance GetInstance(IIdentity identity);
 
         /// <summary>

src/Moryx.Products.Management/Facades/ProductManagementFacade.cs

@@ -1,4 +1,4 @@
-// Copyright (c) 2022, Phoenix Contact GmbH & Co. KG
+// Copyright (c) 2024, Phoenix Contact GmbH & Co. KG
 // Licensed under the Apache License, Version 2.0
 
 using System;
@@ -9,6 +9,7 @@
 using Moryx.AbstractionLayer.Identity;
 using Moryx.AbstractionLayer.Products;
 using Moryx.AbstractionLayer.Recipes;
+using Moryx.Logging;
 using Moryx.Runtime.Modules;
 using Moryx.Workflows;
 
@@ -31,6 +32,8 @@ internal class ProductManagementFacade : IFacadeControl, IWorkplansVersions, IPr
 
         public ModuleConfig Config { get; set; }
 
+        public IModuleLogger Logger { get; set; }
+
         #endregion
 
         public void Activate()
@@ -219,10 +222,15 @@ public ProductInstance GetInstance(IIdentity identity)
             if (identity == null)
                 throw new ArgumentNullException(nameof(identity));
 
-            var instance = ProductManager
-                .GetInstances<IIdentifiableObject>(i => identity.Equals(i.Identity))
-                .SingleOrDefault();
-            return (ProductInstance) instance;
+            var instances = ProductManager
+                .GetInstances<IIdentifiableObject>(i => identity.Equals(i.Identity));
+            if (instances.Count > 1)
+            {
+                Logger.Log(LogLevel.Error, "ProductManagement contains more than one {0} with the identity {1}.", nameof(ProductInstance), identity);
+                throw new InvalidOperationException();
+            }
+
+            return (ProductInstance) instances.SingleOrDefault(); ;
         }
 
         public TInstance GetInstance<TInstance>(Expression<Func<TInstance, bool>> selector)

src/Moryx.Products.Management/Implementation/Storage/ProductStorage.cs

@@ -17,6 +17,7 @@
 using Moryx.Model.Repositories;
 using Moryx.Tools;
 using static Moryx.Products.Management.ProductExpressionHelpers;
+using Moryx.Logging;
 
 namespace Moryx.Products.Management
 {
@@ -88,6 +89,11 @@ internal class ProductStorage : IProductRemoveRecipeStorage, IConfiguredTypesPro
         /// </summary>
         public ModuleConfig Config { get; set; }
 
+        /// <summary>
+        /// Logger for the product manager module
+        /// </summary>
+        public IModuleLogger Logger { get; set; }
+
         /// <summary>
         /// Start the storage and load the type strategies
         /// </summary>
@@ -773,6 +779,8 @@ private IReadOnlyList<TInstance> LoadInstancesByType<TInstance>(Expression<Func<
                 else
                 {
                     // TODO: Filter by type specific properties
+                    Logger.Log(LogLevel.Warning, "You tried to load an instance filtering a property ({0}) of the custom type {1}. " +
+                        "This is not supported yet and will always return a negative result.", typeProperty.Name, typeProperty.ReflectedType.Name);
                     var productType = typeProperty.ReflectedType;
                     instanceSelector = i => false;
                 }
@@ -881,6 +889,13 @@ private void TransformInstance(IUnitOfWork uow, ProductInstanceEntity entity, Pr
                     // Update all parts that are also present as entities
                     foreach (var partEntity in partEntityGroups[partGroup.Key.Name])
                     {
+                        if (!partGroup.Value.Any())
+                        {
+                            Logger.Log(LogLevel.Warning, "No reconstruction of the property {1} possible. You have configured the {0} strategy, but the property was null." +
+                                "Please initialize the property in the Initialize method or select the {2} strategy.", 
+                                nameof(PartSourceStrategy.FromPartlink), partGroup.Key.Name, nameof(PartSourceStrategy.FromEntities));
+                            continue;
+                        }
                         var part = partGroup.Value.First(p => p.PartLink.Id == partEntity.PartLinkId);
                         TransformInstance(uow, partEntity, part);
                     }
@@ -895,7 +910,7 @@ private void TransformInstance(IUnitOfWork uow, ProductInstanceEntity entity, Pr
                         partArticles[index].PartLink = partLinks.Find(pl => pl?.Id == partCollection[index].PartLinkId.Value);
                     }
 
-                    if (typeof(ProductInstance).IsAssignableFrom(partGroup.Key.PropertyType) && partArticles.Length == 0)
+                    if (typeof(ProductInstance).IsAssignableFrom(partGroup.Key.PropertyType) && partArticles.Length == 1)
                     {
                         partGroup.Key.SetValue(productInstance, partArticles[0]);
                     }