Fix commented line check not working with whitespace

osu.Game.Tests/Beatmaps/Formats/LegacyDecoderTest.cs

@@ -0,0 +1,56 @@
+// 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 NUnit.Framework;
+using osu.Game.Beatmaps.Formats;
+using osu.Game.Tests.Resources;
+
+namespace osu.Game.Tests.Beatmaps.Formats
+{
+    [TestFixture]
+    public class LegacyDecoderTest
+    {
+        [Test]
+        public void TestDecodeComments()
+        {
+            var decoder = new LineLoggingDecoder(14);
+
+            using (var resStream = TestResources.OpenResource("comments.osu"))
+            using (var stream = new StreamReader(resStream))
+            {
+                decoder.Decode(stream);
+
+                Assert.That(decoder.ParsedLines, Has.None.EqualTo("// Combo1: 0, 0, 0"));
+                Assert.That(decoder.ParsedLines, Has.None.EqualTo("//Combo2: 0, 0, 0"));
+                Assert.That(decoder.ParsedLines, Has.None.EqualTo(" // Combo3: 0, 0, 0"));
+                Assert.That(decoder.ParsedLines, Has.One.EqualTo("Combo1: 100, 100, 100 // Comment at end of line"));
+            }
+        }
+
+        private class LineLoggingDecoder : LegacyDecoder<TestModel>
+        {
+            public readonly List<string> ParsedLines = new List<string>();
+
+            public LineLoggingDecoder(int version)
+                : base(version)
+            {
+            }
+
+            protected override bool ShouldSkipLine(string line)
+            {
+                var result = base.ShouldSkipLine(line);
+
+                if (!result)
+                    ParsedLines.Add(line);
+
+                return result;
+            }
+        }
+
+        private class TestModel
+        {
+        }
+    }
+}

osu.Game.Tests/Resources/comments.osu

@@ -0,0 +1,9 @@
+osu file format v14
+
+[Colours]
+
+// Combo1: 0, 0, 0
+//Combo2: 0, 0, 0
+ // Combo3: 0, 0, 0
+
+Combo1: 100, 100, 100 // Comment at end of line

osu.Game/Beatmaps/Formats/LegacyDecoder.cs

@@ -54,7 +54,7 @@ namespace osu.Game.Beatmaps.Formats
             }
         }
 
-        protected virtual bool ShouldSkipLine(string line) => string.IsNullOrWhiteSpace(line) || line.StartsWith("//", StringComparison.Ordinal);
+        protected virtual bool ShouldSkipLine(string line) => string.IsNullOrWhiteSpace(line) || line.AsSpan().TrimStart().StartsWith("//".AsSpan(), StringComparison.Ordinal);
 
         protected virtual void ParseLine(T output, Section section, string line)
         {