Add zero byte check and tests

osu.Game/Rulesets/Edit/Checks/CheckZeroByteFiles.cs

@@ -0,0 +1,41 @@
+// 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.Collections.Generic;
+using System.IO;
+using osu.Game.Rulesets.Edit.Checks.Components;
+
+namespace osu.Game.Rulesets.Edit.Checks
+{
+    public class CheckZeroByteFiles : ICheck
+    {
+        public CheckMetadata Metadata => new CheckMetadata(CheckCategory.Files, "Zero-byte files");
+
+        public IEnumerable<IssueTemplate> PossibleTemplates => new IssueTemplate[]
+        {
+            new IssueTemplateZeroBytes(this)
+        };
+
+        public IEnumerable<Issue> Run(BeatmapVerifierContext context)
+        {
+            var beatmapSet = context.Beatmap.BeatmapInfo.BeatmapSet;
+
+            foreach (var file in beatmapSet.Files)
+            {
+                Stream data = context.WorkingBeatmap.GetStream(file.FileInfo.StoragePath);
+                if (data?.Length == 0)
+                    yield return new IssueTemplateZeroBytes(this).Create(file.Filename);
+            }
+        }
+
+        public class IssueTemplateZeroBytes : IssueTemplate
+        {
+            public IssueTemplateZeroBytes(ICheck check)
+                : base(check, IssueType.Problem, "\"{0}\" is a 0-byte file.")
+            {
+            }
+
+            public Issue Create(string filename) => new Issue(this, filename);
+        }
+    }
+}