Allow setting RootNamespace in ResourceLocationAttribute

src/Microsoft.Extensions.Localization/ResourceManagerStringLocalizerFactory.cs

@@ -68,7 +68,7 @@ namespace Microsoft.Extensions.Localization
                 throw new ArgumentNullException(nameof(typeInfo));
             }
 
-            return GetResourcePrefix(typeInfo, new AssemblyName(typeInfo.Assembly.FullName).Name, _resourcesRelativePath);
+            return GetResourcePrefix(typeInfo, GetRootNamespace(typeInfo.Assembly), GetResourcePath(typeInfo.Assembly));
         }
 
         /// <summary>
@@ -94,9 +94,17 @@ namespace Microsoft.Extensions.Localization
                 throw new ArgumentNullException(nameof(baseNamespace));
             }
 
-            return string.IsNullOrEmpty(resourcesRelativePath)
+            if (string.IsNullOrEmpty(resourcesRelativePath))
-                ? typeInfo.FullName
+            {
-                : baseNamespace + "." + resourcesRelativePath + TrimPrefix(typeInfo.FullName, baseNamespace + ".");
+                return typeInfo.FullName;
+            }
+            else
+            {
+                // This expectation is defined by dotnet's automatic resource storage.
+                // We have to conform to "{RootNamespace}.{ResourceLocation}.{FullTypeName - AssemblyName}".
+                var assemblyName = new AssemblyName(typeInfo.Assembly.FullName).Name;
+                return baseNamespace + "." + resourcesRelativePath + TrimPrefix(typeInfo.FullName, assemblyName + ".");
+            }
         }
 
         /// <summary>
@@ -119,8 +127,9 @@ namespace Microsoft.Extensions.Localization
 
             var assemblyName = new AssemblyName(baseNamespace);
             var assembly = Assembly.Load(assemblyName);
+            var rootNamespace = GetRootNamespace(assembly);
             var resourceLocation = GetResourcePath(assembly);
-            var locationPath = baseNamespace + "." + resourceLocation;
+            var locationPath = rootNamespace + "." + resourceLocation;
 
             baseResourceName = locationPath + TrimPrefix(baseResourceName, baseNamespace + ".");
 
@@ -141,11 +150,10 @@ namespace Microsoft.Extensions.Localization
             }
 
             var typeInfo = resourceSource.GetTypeInfo();
-            var assembly = typeInfo.Assembly;
-            var assemblyName = new AssemblyName(assembly.FullName);
-            var resourcePath = GetResourcePath(assembly);
 
-            var baseName = GetResourcePrefix(typeInfo, assemblyName.Name, resourcePath);
+            var baseName = GetResourcePrefix(typeInfo);
+
+            var assembly = typeInfo.Assembly;
 
             return _localizerCache.GetOrAdd(baseName, _ => CreateResourceManagerStringLocalizer(assembly, baseName));
         }
@@ -217,6 +225,23 @@ namespace Microsoft.Extensions.Localization
             return assembly.GetCustomAttribute<ResourceLocationAttribute>();
         }
 
+        /// <summary>Gets a <see cref="RootNamespaceAttribute"/> from the provided <see cref="Assembly"/>.</summary>
+        /// <param name="assembly">The assembly to get a <see cref="RootNamespaceAttribute"/> from.</param>
+        /// <returns>The <see cref="RootNamespaceAttribute"/> associated with the given <see cref="Assembly"/>.</returns>
+        /// <remarks>This method is protected and virtual for testing purposes only.</remarks>
+        protected virtual RootNamespaceAttribute GetRootNamespaceAttribute(Assembly assembly)
+        {
+            return assembly.GetCustomAttribute<RootNamespaceAttribute>();
+        }
+
+        private string GetRootNamespace(Assembly assembly)
+        {
+            var rootNamespaceAttribute = GetRootNamespaceAttribute(assembly);
+
+            return rootNamespaceAttribute?.RootNamespace ??
+                new AssemblyName(assembly.FullName).Name;
+        }
+
         private string GetResourcePath(Assembly assembly)
         {
             var resourceLocationAttribute = GetResourceLocationAttribute(assembly);

src/Microsoft.Extensions.Localization/RootNamespaceAttribute.cs

@@ -0,0 +1,35 @@
+// Copyright (c) .NET Foundation. All rights reserved. 
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.Extensions.Localization
+{
+    /// <summary>
+    /// Provides the RootNamespace of an Assembly. The RootNamespace of the assembly is used by Localization to
+    /// determine the resource name to look for when RootNamespace differs from the AssemblyName.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false, Inherited = false)]
+    public class RootNamespaceAttribute : Attribute
+    {
+        /// <summary>
+        /// Creates a new <see cref="RootNamespaceAttribute"/>.
+        /// </summary>
+        /// <param name="rootNamespace">The RootNamespace for this Assembly.</param>
+        public RootNamespaceAttribute(string rootNamespace)
+        {
+            if (string.IsNullOrEmpty(rootNamespace))
+            {
+                throw new ArgumentNullException(nameof(rootNamespace));
+            }
+
+            RootNamespace = rootNamespace;
+        }
+
+        /// <summary>
+        /// The RootNamespace of this Assembly. The RootNamespace of the assembly is used by Localization to
+        /// determine the resource name to look for when RootNamespace differs from the AssemblyName.
+        /// </summary>
+        public string RootNamespace { get; }
+    }
+}

test/Microsoft.Extensions.Localization.Tests/ResourceManagerStringLocalizerFactoryTest.cs

@@ -17,16 +17,20 @@ namespace Microsoft.Extensions.Localization.Tests
     {
         private ResourceLocationAttribute _resourceLocationAttribute;
 
+        private RootNamespaceAttribute _rootNamespaceAttribute;
+
         public Assembly Assembly { get; private set; }
         public string BaseName { get; private set; }
 
         public TestResourceManagerStringLocalizerFactory(
             IOptions<LocalizationOptions> localizationOptions,
             ResourceLocationAttribute resourceLocationAttribute,
+            RootNamespaceAttribute rootNamespaceAttribute,
             ILoggerFactory loggerFactory)
             : base(localizationOptions, loggerFactory)
         {
             _resourceLocationAttribute = resourceLocationAttribute;
+            _rootNamespaceAttribute = rootNamespaceAttribute;
         }
 
         protected override ResourceLocationAttribute GetResourceLocationAttribute(Assembly assembly)
@@ -34,6 +38,11 @@ namespace Microsoft.Extensions.Localization.Tests
             return _resourceLocationAttribute;
         }
 
+        protected override RootNamespaceAttribute GetRootNamespaceAttribute(Assembly assembly)
+        {
+            return _rootNamespaceAttribute;
+        }
+
         protected override ResourceManagerStringLocalizer CreateResourceManagerStringLocalizer(Assembly assembly, string baseName)
         {
             BaseName = baseName;
@@ -58,11 +67,13 @@ namespace Microsoft.Extensions.Localization.Tests
             var typeFactory = new TestResourceManagerStringLocalizerFactory(
                 options.Object,
                 resourceLocationAttribute,
-                loggerFactory);
+                rootNamespaceAttribute: null,
+                loggerFactory: loggerFactory);
             var stringFactory = new TestResourceManagerStringLocalizerFactory(
                 options.Object,
                 resourceLocationAttribute,
-                loggerFactory);
+                rootNamespaceAttribute: null,
+                loggerFactory: loggerFactory);
             var type = typeof(ResourceManagerStringLocalizerFactoryTest);
             var assemblyName = new AssemblyName(type.GetTypeInfo().Assembly.FullName);
 
@@ -111,6 +122,61 @@ namespace Microsoft.Extensions.Localization.Tests
             Assert.NotSame(result1, result2);
         }
 
+        [Fact]
+        public void Create_ResourceLocationAttribute_RootNamespaceIgnoredWhenNoLocation()
+        {
+            // Arrange
+            var locOptions = new LocalizationOptions();
+            var options = new Mock<IOptions<LocalizationOptions>>();
+            options.Setup(o => o.Value).Returns(locOptions);
+            var loggerFactory = NullLoggerFactory.Instance;
+
+            var resourcePath = Path.Combine("My", "Resources");
+            var rootNamespace = "MyNamespace";
+            var rootNamespaceAttribute = new RootNamespaceAttribute(rootNamespace);
+
+            var typeFactory = new TestResourceManagerStringLocalizerFactory(
+                options.Object,
+                resourceLocationAttribute: null,
+                rootNamespaceAttribute: rootNamespaceAttribute,
+                loggerFactory: loggerFactory);
+
+            var type = typeof(ResourceManagerStringLocalizerFactoryTest);
+            // Act
+            typeFactory.Create(type);
+
+            // Assert
+            Assert.Equal($"Microsoft.Extensions.Localization.Tests.ResourceManagerStringLocalizerFactoryTest", typeFactory.BaseName);
+        }
+
+        [Fact]
+        public void Create_ResourceLocationAttribute_UsesRootNamespace()
+        {
+            // Arrange
+            var locOptions = new LocalizationOptions();
+            var options = new Mock<IOptions<LocalizationOptions>>();
+            options.Setup(o => o.Value).Returns(locOptions);
+            var loggerFactory = NullLoggerFactory.Instance;
+
+            var resourcePath = Path.Combine("My", "Resources");
+            var rootNamespace = "MyNamespace";
+            var resourceLocationAttribute = new ResourceLocationAttribute(resourcePath);
+            var rootNamespaceAttribute = new RootNamespaceAttribute(rootNamespace);
+
+            var typeFactory = new TestResourceManagerStringLocalizerFactory(
+                options.Object,
+                resourceLocationAttribute,
+                rootNamespaceAttribute,
+                loggerFactory);
+
+            var type = typeof(ResourceManagerStringLocalizerFactoryTest);
+            // Act
+            typeFactory.Create(type);
+
+            // Assert
+            Assert.Equal($"MyNamespace.My.Resources.ResourceManagerStringLocalizerFactoryTest", typeFactory.BaseName);
+        }
+
         [Fact]
         public void Create_FromType_ResourcesPathDirectorySeperatorToDot()
         {
@@ -123,6 +189,7 @@ namespace Microsoft.Extensions.Localization.Tests
             var factory = new TestResourceManagerStringLocalizerFactory(
                 options.Object,
                 resourceLocationAttribute: null,
+                rootNamespaceAttribute: null,
                 loggerFactory: loggerFactory);
 
             // Act
@@ -202,6 +269,7 @@ namespace Microsoft.Extensions.Localization.Tests
             var factory = new TestResourceManagerStringLocalizerFactory(
                 options.Object,
                 resourceLocationAttribute: null,
+                rootNamespaceAttribute: null,
                 loggerFactory: loggerFactory);
 
             // Act

test/ResourcesClassLibraryWithAttribute/AssemblyInfo.cs

@@ -5,3 +5,4 @@ using System.Reflection;
 using Microsoft.Extensions.Localization;
 
 [assembly: ResourceLocation("ResourceFolder")]
+[assembly: RootNamespace("Alternate.Namespace")]

test/ResourcesClassLibraryWithAttribute/ResourcesClassLibraryWithAttribute.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <RootNamespace>Alternate.Namespace</RootNamespace>
   </PropertyGroup>
 
   <ItemGroup>