Variation fallback & add missing chartdata difficulties to metadata

Author: Lasercar

source/funkin/ui/debug/charting/handlers/ChartEditorImportExportHandler.hx

@@ -118,10 +118,31 @@ class ChartEditorImportExportHandler
     state.songMetadata = newSongMetadata;
     state.songChartData = newSongChartData;
 
-    if (!state.songMetadata.exists(state.selectedVariation))
+    var variationMetadata:Null<SongMetadata> = state.songMetadata.get(state.selectedVariation);
+    if (variationMetadata == null)
     {
-      state.selectedVariation = Constants.DEFAULT_VARIATION;
+      // Use the default variation, or the first available variation if that doesn't exist for some reason.
+      if (state.availableDifficulties.indexOf(Constants.DEFAULT_VARIATION) < 0) state.selectedVariation = state.availableVariations[0];
+      else state.selectedVariation = Constants.DEFAULT_VARIATION;
+
+      variationMetadata = state.songMetadata.get(state.selectedVariation);
+    }
+
+    for (variation in state.availableVariations)
+    {
+      var metadata:Null<SongMetadata> = state.songMetadata.get(variation);
+      if(metadata == null) return;
+      var chartdata:Null<SongChartData> = state.songChartData.get(variation);
+      if(chartdata == null) return;
+      // Add the chartdata difficulties to the metadata difficulties if they don't exist so that the editor properly loads them.
+      var keys:Array<String> = [for (x in chartdata.scrollSpeed.keys()) x];
+      keys = keys.concat([for (x in chartdata.notes.keys()) x]);
+      for (key in keys)
+        {
+          metadata.playData.difficulties.pushUnique(key);
+        }
     }
+
     // Use the first available difficulty as a fallback if the currently selected one cannot be found.
     if (state.availableDifficulties.indexOf(state.selectedDifficulty) < 0) state.selectedDifficulty = state.availableDifficulties[0];