[folding] "editor.showFoldingCongrols":"always" not respected. Fixes #35839

src/vs/editor/contrib/folding/folding.css

@@ -24,7 +24,7 @@
 }
 
 .monaco-editor .margin-view-overlays:hover .folding,
-.monaco-editor.alwaysShowFoldIcons .margin-view-overlays .folding {
+.monaco-editor .margin-view-overlays .folding.alwaysShowFoldIcons {
 	opacity: 1;
 }
 

src/vs/editor/contrib/folding/folding.ts

@@ -177,12 +177,14 @@ export class FoldingController {
 	}
 
 	private onModelContentChanged() {
-		this.foldingModelPromise = this.updateScheduler.trigger(() => {
-			if (this.foldingModel) { // null if editor has been disposed, or folding turned off
-				this.foldingModel.update(this.computeRanges(this.foldingModel.textModel));
-			}
-			return this.foldingModel;
-		});
+		if (this.updateScheduler) {
+			this.foldingModelPromise = this.updateScheduler.trigger(() => {
+				if (this.foldingModel) { // null if editor has been disposed, or folding turned off
+					this.foldingModel.update(this.computeRanges(this.foldingModel.textModel));
+				}
+				return this.foldingModel;
+			});
+		}
 	}
 
 	private onHiddenRangesChanges(hiddenRanges: IRange[]) {

src/vs/editor/contrib/folding/foldingDecorations.ts

@@ -18,12 +18,12 @@ export class FoldingDecorationProvider implements IDecorationProvider {
 
 	private EXPANDED_AUTO_HIDE_VISUAL_DECORATION = ModelDecorationOptions.register({
 		stickiness: TrackedRangeStickiness.NeverGrowsWhenTypingAtEdges,
-		linesDecorationsClassName: 'folding autoHide'
+		linesDecorationsClassName: 'folding'
 	});
 
 	private EXPANDED_VISUAL_DECORATION = ModelDecorationOptions.register({
 		stickiness: TrackedRangeStickiness.NeverGrowsWhenTypingAtEdges,
-		linesDecorationsClassName: 'folding'
+		linesDecorationsClassName: 'folding alwaysShowFoldIcons'
 	});
 
 	public autoHideFoldingControls: boolean = true;