Make sure control points is internally initialised

osu.Game.Rulesets.Osu/Edit/Blueprints/Sliders/Components/PathControlPointPiece.cs

@@ -1,7 +1,6 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
-using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;

osu.Game/Rulesets/Objects/SliderPath.cs

@@ -13,11 +13,6 @@ namespace osu.Game.Rulesets.Objects
 {
     public struct SliderPath : IEquatable<SliderPath>
     {
-        /// <summary>
-        /// The control points of the path.
-        /// </summary>
-        public readonly Vector2[] ControlPoints;
-
         /// <summary>
         /// The user-set distance of the path. If non-null, <see cref="Distance"/> will match this value,
         /// and the path will be shortened/lengthened to match this length.
@@ -29,6 +24,9 @@ namespace osu.Game.Rulesets.Objects
         /// </summary>
         public readonly PathType Type;
 
+        [JsonProperty]
+        private Vector2[] controlPoints;
+
         private List<Vector2> calculatedPath;
         private List<double> cumulativeLength;
 
@@ -46,14 +44,27 @@ namespace osu.Game.Rulesets.Objects
         public SliderPath(PathType type, Vector2[] controlPoints, double? expectedDistance = null)
         {
             this = default;
+            this.controlPoints = controlPoints;
 
-            ControlPoints = controlPoints;
             Type = type;
             ExpectedDistance = expectedDistance;
 
             ensureInitialised();
         }
 
+        /// <summary>
+        /// The control points of the path.
+        /// </summary>
+        [JsonIgnore]
+        public ReadOnlySpan<Vector2> ControlPoints
+        {
+            get
+            {
+                ensureInitialised();
+                return controlPoints.AsSpan();
+            }
+        }
+
         /// <summary>
         /// The distance of the path after lengthening/shortening to account for <see cref="ExpectedDistance"/>.
         /// </summary>
@@ -116,6 +127,7 @@ namespace osu.Game.Rulesets.Objects
                 return;
             isInitialised = true;
 
+            controlPoints = controlPoints ?? Array.Empty<Vector2>();
             calculatedPath = new List<Vector2>();
             cumulativeLength = new List<double>();
 
@@ -166,7 +178,7 @@ namespace osu.Game.Rulesets.Objects
 
                 if (i == ControlPoints.Length - 1 || ControlPoints[i] == ControlPoints[i + 1])
                 {
-                    ReadOnlySpan<Vector2> cpSpan = ControlPoints.AsSpan().Slice(start, end - start);
+                    ReadOnlySpan<Vector2> cpSpan = ControlPoints.Slice(start, end - start);
 
                     foreach (Vector2 t in calculateSubpath(cpSpan))
                         if (calculatedPath.Count == 0 || calculatedPath.Last() != t)