Add tests for all current BCL cultures, and expand parser to support three-letter locales

Author: baronfel

src/NuGet.Core/NuGet.Packaging/ContentModel/ManagedCodeConventions.cs

@@ -148,7 +148,7 @@ private static object CodeLanguage_Parser(string name, PatternTable table)
             return name;
         }
 
-        private static object Locale_Parser(string name, PatternTable table)
+        internal static object Locale_Parser(string name, PatternTable table)
         {
             if (table != null)
             {
@@ -161,7 +161,8 @@ private static object Locale_Parser(string name, PatternTable table)
 
             // We use a heuristic here for common locale codes. Locale codes are often
             // * two characters for the language: en, es, fr, de
-            if (name.Length == 2)
+            // * three characters for the language: agq
+            if (name.Length == 2 || name.Length == 3)
             {
                 return name;
             }

test/NuGet.Core.Tests/NuGet.Packaging.Test/ContentModelTests/ContentModelResourceTests.cs

@@ -0,0 +1,27 @@
+// 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.Collections.Generic;
+using System.Globalization;
+using System.Linq;
+using Xunit;
+
+namespace NuGet.Client.Test
+{
+    public class ContentModelResourceTests
+    {
+        [MemberData(nameof(AllCultures))]
+        [Theory]
+        public void CanParseEverySystemKnownCultureResource(CultureInfo culture)
+        {
+            var result = ManagedCodeConventions.Locale_Parser(culture.Name, null);
+            Assert.Equal(culture.Name, result as string);
+        }
+
+        public static IEnumerable<object[]> AllCultures()
+        {
+            return CultureInfo.GetCultures(CultureTypes.AllCultures).Where(c => !string.IsNullOrEmpty(c.Name)).Select(culture => new[] { culture });
+        }
+    }
+}
+