only if changed

Update SelectableCanvas.ts

src/canvas/SelectableCanvas.ts

@@ -1104,7 +1104,9 @@ export class SelectableCanvas<EventSpec extends CanvasEvents = CanvasEvents>
       return false;
     }
     this._activeObject = object;
-    if (object instanceof ActiveSelection) {
+
+    if (object instanceof ActiveSelection && this._activeSelection !== object) {
+      this._activeSelection.dispose();
       this._activeSelection = object;
       this._activeSelection.set('canvas', this);
       this._activeSelection.setCoords();

src/shapes/ActiveSelection.spec.ts

@@ -88,18 +88,27 @@ describe('ActiveSelection', () => {
     expect(canvas.getActiveSelection().aCoords).toMatchSnapshot();
   });
 
-  it('`setActiveObject` should update the active selection ref on canvas', () => {
+  it('`setActiveObject` should update the active selection ref on canvas if it changed', () => {
     const canvas = new Canvas(null);
     const obj1 = new FabricObject();
     const obj2 = new FabricObject();
     canvas.add(obj1, obj2);
+    const existingActiveSelection = canvas.getActiveSelection();
+    const disposeSpy = jest.spyOn(existingActiveSelection, 'dispose');
     const activeSelection = new ActiveSelection([obj1, obj2]);
     const spy = jest.spyOn(activeSelection, 'setCoords');
     canvas.setActiveObject(activeSelection);
     expect(canvas.getActiveSelection()).toBe(activeSelection);
     expect(canvas.getActiveObjects()).toEqual([obj1, obj2]);
+    expect(disposeSpy).toHaveBeenCalled();
     expect(spy).toHaveBeenCalled();
     expect(activeSelection.canvas).toBe(canvas);
+
+    spy.mockClear();
+    const disposeSpy2 = jest.spyOn(activeSelection, 'dispose');
+    canvas.setActiveObject(activeSelection);
+    expect(disposeSpy2).not.toHaveBeenCalled();
+    expect(spy).not.toHaveBeenCalled();
   });
 
   it('transferring an object between active selections keeps its owning group', () => {