From f4ef8419729f4c80ccd8b1a666c180b2267a73f0 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Wed, 10 Nov 2021 18:27:23 +0900
Subject: [PATCH] Add fallback for cases where beatmap has no
 author/title/artist specified

---
 osu.Game.Tests/Models/DisplayStringTest.cs    | 22 +++++++++++++++++++
 .../Beatmaps/BeatmapMetadataInfoExtensions.cs |  8 +++++--
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/osu.Game.Tests/Models/DisplayStringTest.cs b/osu.Game.Tests/Models/DisplayStringTest.cs
index 9a3c32bfb2..754a849ac8 100644
--- a/osu.Game.Tests/Models/DisplayStringTest.cs
+++ b/osu.Game.Tests/Models/DisplayStringTest.cs
@@ -17,6 +17,8 @@ namespace osu.Game.Tests.Models
     {
         private static readonly object[][] test_cases =
         {
+            new object[] { makeNoMetadataMockBeatmapSet(), "unknown artist - unknown title" },
+            new object[] { makeNoAuthorMockBeatmapSet(), "artist - title" },
             new object[] { makeMockBeatmapSet(), "artist - title (author)" },
             new object[] { makeMockBeatmap(), "artist - title (author) [difficulty]" },
             new object[] { makeMockMetadata(), "artist - title (author)" },
@@ -29,6 +31,26 @@ namespace osu.Game.Tests.Models
         [TestCaseSource(nameof(test_cases))]
         public void TestDisplayString(object model, string expected) => Assert.That(model.GetDisplayString(), Is.EqualTo(expected));
 
+        private static IBeatmapSetInfo makeNoAuthorMockBeatmapSet()
+        {
+            var mock = new Mock<IBeatmapSetInfo>();
+
+            mock.Setup(m => m.Metadata.Artist).Returns("artist");
+            mock.Setup(m => m.Metadata.Title).Returns("title");
+            mock.Setup(m => m.Metadata.Author.Username).Returns(string.Empty);
+
+            return mock.Object;
+        }
+
+        private static IBeatmapSetInfo makeNoMetadataMockBeatmapSet()
+        {
+            var mock = new Mock<IBeatmapSetInfo>();
+
+            mock.Setup(m => m.Metadata).Returns(new BeatmapMetadata());
+
+            return mock.Object;
+        }
+
         private static IBeatmapSetInfo makeMockBeatmapSet()
         {
             var mock = new Mock<IBeatmapSetInfo>();
diff --git a/osu.Game/Beatmaps/BeatmapMetadataInfoExtensions.cs b/osu.Game/Beatmaps/BeatmapMetadataInfoExtensions.cs
index 32fb389e9a..7aab6a7a9b 100644
--- a/osu.Game/Beatmaps/BeatmapMetadataInfoExtensions.cs
+++ b/osu.Game/Beatmaps/BeatmapMetadataInfoExtensions.cs
@@ -27,8 +27,12 @@ namespace osu.Game.Beatmaps
         /// </summary>
         public static string GetDisplayTitle(this IBeatmapMetadataInfo metadataInfo)
         {
-            string author = string.IsNullOrEmpty(metadataInfo.Author.Username) ? string.Empty : $"({metadataInfo.Author.Username})";
-            return $"{metadataInfo.Artist} - {metadataInfo.Title} {author}".Trim();
+            string author = string.IsNullOrEmpty(metadataInfo.Author.Username) ? string.Empty : $" ({metadataInfo.Author.Username})";
+
+            string artist = string.IsNullOrEmpty(metadataInfo.Artist) ? "unknown artist" : metadataInfo.Artist;
+            string title = string.IsNullOrEmpty(metadataInfo.Title) ? "unknown title" : metadataInfo.Title;
+
+            return $"{artist} - {title}{author}".Trim();
         }
 
         /// <summary>