Add zero-length objects check and tests

osu.Game.Tests/Editing/Checks/CheckZeroLengthObjectsTest.cs

@@ -0,0 +1,94 @@
+// 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.Linq;
+using Moq;
+using NUnit.Framework;
+using osu.Game.Beatmaps;
+using osu.Game.Rulesets.Edit;
+using osu.Game.Rulesets.Edit.Checks;
+using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Types;
+using osu.Game.Rulesets.Osu.Objects;
+using osu.Game.Tests.Beatmaps;
+using osuTK;
+
+namespace osu.Game.Tests.Editing.Checks
+{
+    [TestFixture]
+    public class CheckZeroLengthObjectsTest
+    {
+        private CheckZeroLengthObjects check;
+
+        [SetUp]
+        public void Setup()
+        {
+            check = new CheckZeroLengthObjects();
+        }
+
+        [Test]
+        public void TestCircle()
+        {
+            assertOk(new List<HitObject>
+            {
+                new HitCircle { StartTime = 1000, Position = new Vector2(0, 0) }
+            });
+        }
+
+        [Test]
+        public void TestRegularSlider()
+        {
+            assertOk(new List<HitObject>
+            {
+                getSliderMock(1000).Object
+            });
+        }
+
+        [Test]
+        public void TestZeroLengthSlider()
+        {
+            assertZeroLength(new List<HitObject>
+            {
+                getSliderMock(0).Object
+            });
+        }
+
+        [Test]
+        public void TestNegativeLengthSlider()
+        {
+            assertZeroLength(new List<HitObject>
+            {
+                getSliderMock(-1000).Object
+            });
+        }
+
+        private Mock<Slider> getSliderMock(double duration)
+        {
+            var mockSlider = new Mock<Slider>();
+            mockSlider.As<IHasDuration>().Setup(d => d.Duration).Returns(duration);
+
+            return mockSlider;
+        }
+
+        private void assertOk(List<HitObject> hitObjects)
+        {
+            Assert.That(check.Run(getContext(hitObjects)), Is.Empty);
+        }
+
+        private void assertZeroLength(List<HitObject> hitObjects)
+        {
+            var issues = check.Run(getContext(hitObjects)).ToList();
+
+            Assert.That(issues, Has.Count.EqualTo(1));
+            Assert.That(issues.First().Template is CheckZeroLengthObjects.IssueTemplateZeroLength);
+        }
+
+        private BeatmapVerifierContext getContext(List<HitObject> hitObjects)
+        {
+            var beatmap = new Beatmap<HitObject> { HitObjects = hitObjects };
+
+            return new BeatmapVerifierContext(beatmap, new TestWorkingBeatmap(beatmap));
+        }
+    }
+}

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

@@ -0,0 +1,47 @@
+// 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 osu.Game.Rulesets.Edit.Checks.Components;
+using osu.Game.Rulesets.Objects;
+using osu.Game.Rulesets.Objects.Types;
+
+namespace osu.Game.Rulesets.Edit.Checks
+{
+    public class CheckZeroLengthObjects : ICheck
+    {
+        /// <summary>
+        /// The duration can be this low before being treated as having no length, in case of precision errors. Unit is milliseconds.
+        /// </summary>
+        private const double leniency = 0.5d;
+
+        public CheckMetadata Metadata { get; } = new CheckMetadata(CheckCategory.Compose, "Zero-length hitobjects");
+
+        public IEnumerable<IssueTemplate> PossibleTemplates => new IssueTemplate[]
+        {
+            new IssueTemplateZeroLength(this)
+        };
+
+        public IEnumerable<Issue> Run(BeatmapVerifierContext context)
+        {
+            foreach (var hitObject in context.Beatmap.HitObjects)
+            {
+                if (!(hitObject is IHasDuration hasDuration))
+                    continue;
+
+                if (hasDuration.Duration < leniency)
+                    yield return new IssueTemplateZeroLength(this).Create(hitObject, hasDuration.Duration);
+            }
+        }
+
+        public class IssueTemplateZeroLength : IssueTemplate
+        {
+            public IssueTemplateZeroLength(ICheck check)
+                : base(check, IssueType.Problem, "{0} has a duration of {1:0}.")
+            {
+            }
+
+            public Issue Create(HitObject hitobject, double duration) => new Issue(hitobject, this, hitobject.GetType(), duration);
+        }
+    }
+}