Rework to support obsoletion

osu.Game/Beatmaps/BeatmapConverter.cs

@@ -27,6 +27,8 @@ event Action<HitObject, IEnumerable<HitObject>> IBeatmapConverter.ObjectConverte
 
         public IBeatmap Beatmap { get; }
 
+        private CancellationToken cancellationToken;
+
         protected BeatmapConverter(IBeatmap beatmap, Ruleset ruleset)
         {
             Beatmap = beatmap;
@@ -39,6 +41,8 @@ protected BeatmapConverter(IBeatmap beatmap, Ruleset ruleset)
 
         public IBeatmap Convert(CancellationToken cancellationToken = default)
         {
+            this.cancellationToken = cancellationToken;
+
             // We always operate on a clone of the original beatmap, to not modify it game-wide
             return ConvertBeatmap(Beatmap.Clone(), cancellationToken);
         }
@@ -51,6 +55,19 @@ public IBeatmap Convert(CancellationToken cancellationToken = default)
         /// <returns>The converted Beatmap.</returns>
         protected virtual Beatmap<T> ConvertBeatmap(IBeatmap original, CancellationToken cancellationToken)
         {
+#pragma warning disable 618
+            return ConvertBeatmap(original);
+#pragma warning restore 618
+        }
+
+        /// <summary>
+        /// Performs the conversion of a Beatmap using this Beatmap Converter.
+        /// </summary>
+        /// <param name="original">The un-converted Beatmap.</param>
+        /// <returns>The converted Beatmap.</returns>
+        [Obsolete("Use the cancellation-supporting override")] // Can be removed 20210318
+        protected virtual Beatmap<T> ConvertBeatmap(IBeatmap original)
+        {
             var beatmap = CreateBeatmap();
 
             beatmap.BeatmapInfo = original.BeatmapInfo;
@@ -104,6 +121,21 @@ private List<T> convertHitObjects(IReadOnlyList<HitObject> hitObjects, IBeatmap
         /// <param name="beatmap">The un-converted Beatmap.</param>
         /// <param name="cancellationToken">The cancellation token.</param>
         /// <returns>The converted hit object.</returns>
-        protected abstract IEnumerable<T> ConvertHitObject(HitObject original, IBeatmap beatmap, CancellationToken cancellationToken);
+        protected virtual IEnumerable<T> ConvertHitObject(HitObject original, IBeatmap beatmap, CancellationToken cancellationToken)
+        {
+#pragma warning disable 618
+            return ConvertHitObject(original, beatmap);
+#pragma warning restore 618
+        }
+
+        /// <summary>
+        /// Performs the conversion of a hit object.
+        /// This method is generally executed sequentially for all objects in a beatmap.
+        /// </summary>
+        /// <param name="original">The hit object to convert.</param>
+        /// <param name="beatmap">The un-converted Beatmap.</param>
+        /// <returns>The converted hit object.</returns>
+        [Obsolete("Use the cancellation-supporting override")] // Can be removed 20210318
+        protected virtual IEnumerable<T> ConvertHitObject(HitObject original, IBeatmap beatmap) => Enumerable.Empty<T>();
     }
 }