Avoid unwanted mutation to passed objects array to Group constructor

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [next]
 
+- patch(): Avoid unwanted mutation to passed objects array to Group constructor [#9151](https://github.com/fabricjs/fabric.js/pull/9151)
 - patch(): ActiveSelection initialization + types [#9143](https://github.com/fabricjs/fabric.js/pull/9143)
 - chore(TS): BREAKING remove canvas.interactive, added typings for canvas options [#9140](https://github.com/fabricjs/fabric.js/pull/9140)
 - chore(TS): BREAKING PREVIOUS BETA mv + rename `TProps` => `TOptions` [#9139](https://github.com/fabricjs/fabric.js/pull/9139)

src/shapes/Group.spec.ts

@@ -0,0 +1,15 @@
+import { Group } from './Group';
+import { FabricObject } from './Object/FabricObject';
+
+describe('Group', () => {
+  it('avoid mutations to passed objects array', () => {
+    const objs = [new FabricObject(), new FabricObject()];
+    const group = new Group(objs);
+
+    group.add(new FabricObject());
+
+    expect(group._objects).not.toBe(objs);
+    expect(objs).toHaveLength(2);
+    expect(group._objects).toHaveLength(3);
+  });
+});

src/shapes/Group.ts

@@ -173,7 +173,7 @@ export class Group extends createCollectionMixin(
     objectsRelativeToGroup?: boolean
   ) {
     super();
-    this._objects = objects;
+    this._objects = objects.slice(); // Avoid unwanted mutations of Collection to affect the caller
     this.__objectMonitor = this.__objectMonitor.bind(this);
     this.__objectSelectionTracker = this.__objectSelectionMonitor.bind(
       this,