Fix languages with a sub-language part not working properly

osu.Game/Extensions/LanguageExtensions.cs

@@ -0,0 +1,33 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Globalization;
+using osu.Game.Localisation;
+
+namespace osu.Game.Extensions
+{
+    /// <summary>
+    /// Conversion utilities for the <see cref="Language"/> enum.
+    /// </summary>
+    public static class LanguageExtensions
+    {
+        /// <summary>
+        /// Returns the culture code of the <see cref="CultureInfo"/> that corresponds to the supplied <paramref name="language"/>.
+        /// </summary>
+        /// <remarks>
+        /// This is required as enum member names are not allowed to contain hyphens.
+        /// </remarks>
+        public static string ToCultureCode(this Language language)
+            => language.ToString().Replace("_", "-");
+
+        /// <summary>
+        /// Attempts to parse the supplied <paramref name="cultureCode"/> to a <see cref="Language"/> value.
+        /// </summary>
+        /// <param name="cultureCode">The code of the culture to parse.</param>
+        /// <param name="language">The parsed <see cref="Language"/>. Valid only if the return value of the method is <see langword="true" />.</param>
+        /// <returns>Whether the parsing succeeded.</returns>
+        public static bool TryParseCultureCode(string cultureCode, out Language language)
+            => Enum.TryParse(cultureCode.Replace("-", "_"), out language);
+    }
+}

osu.Game/OsuGame.cs

@@ -50,6 +50,7 @@ using osu.Game.Updater;
 using osu.Game.Utils;
 using LogLevel = osu.Framework.Logging.LogLevel;
 using osu.Game.Database;
+using osu.Game.Extensions;
 using osu.Game.IO;
 using osu.Game.Localisation;
 using osu.Game.Skinning.Editor;
@@ -580,7 +581,7 @@ namespace osu.Game
 
             foreach (var language in Enum.GetValues(typeof(Language)).OfType<Language>())
             {
-                var cultureCode = language.ToString();
+                var cultureCode = language.ToCultureCode();
                 Localisation.AddLanguage(cultureCode, new ResourceManagerLocalisationStore(cultureCode));
             }
 

osu.Game/Overlays/Settings/Sections/General/LanguageSettings.cs

@@ -1,11 +1,11 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
-using System;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Configuration;
 using osu.Framework.Graphics;
+using osu.Game.Extensions;
 using osu.Game.Localisation;
 
 namespace osu.Game.Overlays.Settings.Sections.General
@@ -35,11 +35,11 @@ namespace osu.Game.Overlays.Settings.Sections.General
                 },
             };
 
-            if (!Enum.TryParse<Language>(frameworkLocale.Value, out var locale))
+            if (!LanguageExtensions.TryParseCultureCode(frameworkLocale.Value, out var locale))
                 locale = Language.en;
             languageSelection.Current.Value = locale;
 
-            languageSelection.Current.BindValueChanged(val => frameworkLocale.Value = val.NewValue.ToString());
+            languageSelection.Current.BindValueChanged(val => frameworkLocale.Value = val.NewValue.ToCultureCode());
         }
     }
 }