Undoing remove children change children orders

[chuckn0rris]

Forum post

task-order-bug.mov

Hi Bryntum support,

I found an unexpected behavior when I undo removing children.
Sometimes, undoing removing children can't keep children orders.
It can be reproduced at https://bryntum.com/products/gantt/examples/undoredo/.

I've investigated why it happens. Maybe I found a bug in the RemoveChildAction.undo function.
In the code below, childModels.sort will fail because context.get returns an object, not parentIndex.
Shouldn't it be like context.get(lhs).parentIndex?
If it's a bug, please fix it in the future.

    undo() {
        const { parentModel, context, childModels } = this;

    // Let's sort models by parent index such that models with lesser index
    // were inserted back first, thus making valid parent index of models following.

    childModels.sort((lhs, rhs) => {
        const
            lhsIndex = context.get(lhs),
            rhsIndex = context.get(rhs);

        return (lhsIndex - rhsIndex);
    });

    // Now let's re-insert records back to where they were
    childModels.forEach(m => {
        const ctx = context.get(m);

        parentModel.insertChild(m, ctx.parentIndex, undefined, { orderedParentIndex : ctx.orderedParentIndex });
    });
}