Allow Arrays and Dictionaries to be duplicated or made anew via the inspector

[bojidar-bg]

Closes #13971

I couldn't make the "Changes may be lost" button appearing when the Array comes from another scene though.

[Geequlim]

@bojidar-bg Any idea with #13346 ？

[kubecz3k]

I tested the PR and I'm sorry to say, but I'm still able to observe the issue

[kubecz3k]

Oh I probably misunderstood how the fix works. I assume I should choose 'new array' after creating the scene, in such case it works fine!

[kubecz3k]

But I don't quite understand use-case for those options, are there any cases when I will not want for my array to be separate from the one that is possessed by parent? (pre 3.0 they were automatically cloned I assume)

[bojidar-bg]

@Geequlim No, that other issue appears unrelated to the one solved. I don't know how it should be solved.
@kubecz3k Well, you don't want it to be a separate array in case you are not making changes to it.
Pre 3.0 they might have been saved even if not modified, which would lead to some sort of auto-cloning.

[kubecz3k]

Is there any way to detect if the array is separated or not? I assume the best work-flow would be to duplicate the array automatically at the time of the first modification since no other inspector element need that kind of additional action. Also as far as I understand it's impossible for user to tell if the array is already 'independent' from parent scene or not (so it's hard to tell when it should be duplicated).

[bojidar-bg]

Well, I tried to think of some simple way, but couldn't. Maybe for 3.1.

[bojidar-bg]

After discussion on IRC, it was decided that we can make a more proper workaround.

<reduz> bojidar_bg: we could force duplicating the property in PackedScene when instancing for editing
<reduz> bojidar_bg: and also force duplicating the property on editor duplicate
<reduz> bojidar_bg: i think that may fix the problem
<bojidar_bg> yes, it would fix it as well
[..]
<reduz> bojidar_bg: I suggested adding a deep copy argument to duplicate() in Array and Dictionary, we can call that in Node::duplicate and PackedScene::instance (when used from editor)

I will open another PR when I implement it, but it is likely to land post-3.0.