Cache fixes for ResourceManagerStringLocalizer culture walk:

- Make the cache static
- Make the cache key include the assembly name & the resource name
- #15

Author: DamianEdwards

src/Microsoft.Framework.Localization/ResourceManagerStringLocalizer.cs

@@ -21,10 +21,9 @@ public class ResourceManagerStringLocalizer : IStringLocalizer
         private readonly ConcurrentDictionary<string, object> _missingManifestCache =
             new ConcurrentDictionary<string, object>();
 
-        private readonly ConcurrentDictionary<string, IList<string>> _resourceNamesCache =
+        private static readonly ConcurrentDictionary<string, IList<string>> _resourceNamesCache =
             new ConcurrentDictionary<string, IList<string>>();
-
-
+        
         /// <summary>
         /// Creates a new <see cref="ResourceManagerStringLocalizer"/>.
         /// </summary>
@@ -188,7 +187,9 @@ private IList<string> GetResourceNamesForCulture(CultureInfo culture)
             }
             resourceStreamName += ".resources";
 
-            var cultureResourceNames = _resourceNamesCache.GetOrAdd(resourceStreamName, key =>
+            var cacheKey = $"assembly={ResourceAssembly.FullName};resourceStreamName={resourceStreamName}";
+
+            var cultureResourceNames = _resourceNamesCache.GetOrAdd(cacheKey, key =>
             {
                 var names = new List<string>();
                 using (var cultureResourceStream = ResourceAssembly.GetManifestResourceStream(key))

test/Microsoft.Framework.Localization.Test/ResourceManagerStringLocalizerTest.cs

@@ -22,15 +22,20 @@ public void EnumeratorCachesCultureWalk()
             resourceAssembly.Setup(rm => rm.GetManifestResourceStream(It.IsAny<string>()))
                 .Returns(() => MakeResourceStream());
             var baseName = "test";
-            var localizer = new ResourceManagerStringLocalizer(
+            var localizer1 = new ResourceManagerStringLocalizer(
+                resourceManager.Object,
+                resourceAssembly.Object,
+                baseName);
+            var localizer2 = new ResourceManagerStringLocalizer(
                 resourceManager.Object,
                 resourceAssembly.Object,
                 baseName);
 
             // Act
             for (int i = 0; i < 5; i++)
             {
-                localizer.ToList();
+                localizer1.ToList();
+                localizer2.ToList();
             }
 
             // Assert