From e82d948acc5d9ead0202f78707ff12d5069d08de Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 20 Jun 2022 16:06:22 +0900
Subject: [PATCH 1/2] Add test coverage of import throwing when no valid `.osu`
 files are found

---
 .../Database/BeatmapImporterTests.cs          | 36 +++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/osu.Game.Tests/Database/BeatmapImporterTests.cs b/osu.Game.Tests/Database/BeatmapImporterTests.cs
index f9cd75d8c3..b018a26aec 100644
--- a/osu.Game.Tests/Database/BeatmapImporterTests.cs
+++ b/osu.Game.Tests/Database/BeatmapImporterTests.cs
@@ -291,6 +291,42 @@ namespace osu.Game.Tests.Database
             });
         }
 
+        [Test]
+        public void TestImportDirectoryWithEmptyOsuFiles()
+        {
+            RunTestWithRealmAsync(async (realm, storage) =>
+            {
+                using var importer = new BeatmapImporter(storage, realm);
+                using var store = new RealmRulesetStore(realm, storage);
+
+                string? temp = TestResources.GetTestBeatmapForImport();
+
+                string extractedFolder = $"{temp}_extracted";
+                Directory.CreateDirectory(extractedFolder);
+
+                try
+                {
+                    using (var zip = ZipArchive.Open(temp))
+                        zip.WriteToDirectory(extractedFolder);
+
+                    foreach (var file in new DirectoryInfo(extractedFolder).GetFiles("*.osu"))
+                    {
+                        using (file.Open(FileMode.Create))
+                        {
+                            // empty file.
+                        }
+                    }
+
+                    var imported = await importer.Import(new ImportTask(extractedFolder));
+                    Assert.IsNull(imported);
+                }
+                finally
+                {
+                    Directory.Delete(extractedFolder, true);
+                }
+            });
+        }
+
         [Test]
         public void TestImportThenImportWithReZip()
         {

From d38defada461430817c8e99d21b49840ef769eb3 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 20 Jun 2022 16:07:10 +0900
Subject: [PATCH 2/2] Silence exception and provide more log output when import
 fails due to empty `.osu` files

---
 osu.Game/Beatmaps/BeatmapImporter.cs | 9 +++++++++
 osu.Game/Beatmaps/Formats/Decoder.cs | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/osu.Game/Beatmaps/BeatmapImporter.cs b/osu.Game/Beatmaps/BeatmapImporter.cs
index e463492e2b..237088036c 100644
--- a/osu.Game/Beatmaps/BeatmapImporter.cs
+++ b/osu.Game/Beatmaps/BeatmapImporter.cs
@@ -177,8 +177,17 @@ namespace osu.Game.Beatmaps
             }
 
             Beatmap beatmap;
+
             using (var stream = new LineBufferedReader(reader.GetStream(mapName)))
+            {
+                if (stream.PeekLine() == null)
+                {
+                    Logger.Log($"No content found in first .osu file of beatmap archive ({reader.Name} / {mapName})", LoggingTarget.Database);
+                    return null;
+                }
+
                 beatmap = Decoder.GetDecoder<Beatmap>(stream).Decode(stream);
+            }
 
             return new BeatmapSetInfo
             {
diff --git a/osu.Game/Beatmaps/Formats/Decoder.cs b/osu.Game/Beatmaps/Formats/Decoder.cs
index aad29f46fb..ca1bcc97fd 100644
--- a/osu.Game/Beatmaps/Formats/Decoder.cs
+++ b/osu.Game/Beatmaps/Formats/Decoder.cs
@@ -74,7 +74,7 @@ namespace osu.Game.Beatmaps.Formats
             }
 
             if (line == null)
-                throw new IOException("Unknown file format (null)");
+                throw new IOException("Unknown file format (no content)");
 
             var decoder = typedDecoders.Where(d => line.StartsWith(d.Key, StringComparison.InvariantCulture)).Select(d => d.Value).FirstOrDefault();