Reordering locally added items in overridden Collection Property breaks after saving #99924

New Issue

blenderboi · 2022-07-23T03:33:42+02:00

blenderboi commented

2022-07-23 03:33:42 +02:00

System Information
Operating system: Linux-5.18.12-arch1-1-x86_64-with-glibc2.35 64 Bits
Graphics card: NVIDIA GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 515.57

Blender Version
Broken: version: 3.2.1, branch: master, commit date: 2022-07-05 15:44, hash: a2d59b2dac
Worked: (newest version of Blender that worked as expected)

Short description of error

When an object that has a Collection Property which allows Library Overrides, with INSERTION on, one can add new item into it.

I assume it is designed to

cannot remove existing item
cannot move (change the order) of the existing item,

However, while you cannot change the existing item's order directly, you can change its order my moving locally added items
and this will cause things break after you reopen Blender, this only happens if you move added items into slot 1 or slot 2

Exact steps for others to reproduce the error

Install the TestAddon.py as Addon
Open a New Empty Blend File
Link the Cube Object from LinkTest.blend to the new blend file
Create Library Overrides from the Linked Cube Object
Select the Library Overrides Cube and Open N-Panel -> TestPanel
Click Up / Down button in the Addon (Error is Expected as it is not handled in the addon, this is expected behaviour as you cannot move existing items)
Click Add Slot
Click Up with the previously added Slot as active (No Error and You have reordered the Slot that is not suppose to be moved [I assume])
Move the Added Slot to Slot 0 or Slot 1 (Both will cause the problem)
Save the blend file
Reopen the blend file
the Items in the Collection Property is now Messed up, added item is turn into duplicated slot of the existing slot, and cannot to removed / reordered

Test Addon:
TestAddon.py

Test Blend File:
LinkTest.blend

**System Information** Operating system: Linux-5.18.12-arch1-1-x86_64-with-glibc2.35 64 Bits Graphics card: NVIDIA GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 515.57 **Blender Version** Broken: version: 3.2.1, branch: master, commit date: 2022-07-05 15:44, hash: `a2d59b2dac` Worked: (newest version of Blender that worked as expected) **Short description of error** When an object that has a Collection Property which allows Library Overrides, with INSERTION on, one can add new item into it. I assume it is designed to 1. cannot remove existing item 2. cannot move (change the order) of the existing item, However, while you cannot change the existing item's order directly, you can change its order my moving locally added items and this will cause things break after you reopen Blender, this only happens if you move added items into slot 1 or slot 2 **Exact steps for others to reproduce the error** 1. Install the TestAddon.py as Addon 2. Open a New Empty Blend File 3. Link the Cube Object from LinkTest.blend to the new blend file 4. Create Library Overrides from the Linked Cube Object 5. Select the Library Overrides Cube and Open N-Panel -> TestPanel 6. Click Up / Down button in the Addon (Error is Expected as it is not handled in the addon, this is expected behaviour as you cannot move existing items) 7. Click Add Slot 8. Click Up with the previously added Slot as active (No Error and You have reordered the Slot that is not suppose to be moved [I assume]) 9. Move the Added Slot to Slot 0 or Slot 1 (Both will cause the problem) 10. Save the blend file 11. Reopen the blend file 12. the Items in the Collection Property is now Messed up, added item is turn into duplicated slot of the existing slot, and cannot to removed / reordered Test Addon: [TestAddon.py](https://archive.blender.org/developer/F13309346/TestAddon.py) Test Blend File: [LinkTest.blend](https://archive.blender.org/developer/F13309350/LinkTest.blend)

blenderboi commented

2022-07-23 03:33:42 +02:00

Added subscriber: @blenderboi2018

Omar Emara commented

2022-08-02 10:27:23 +02:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-08-02 10:27:23 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Omar Emara commented

2022-08-02 10:27:23 +02:00

As far as I can see in the code, reordering items that are inserted in the local override is allowed. So this looks like a bug.

Omar Emara changed title from ~~Library Overrides and Collection Property~~ to Reordering locally added items in overridden Collection Property breaks after saving

2022-08-02 10:30:20 +02:00

Bastien Montagne commented

2022-08-04 19:08:36 +02:00

Added subscriber: @mont29

Bastien Montagne commented

2022-08-04 19:08:36 +02:00

Changed status from 'Confirmed' to: 'Archived'

Bastien Montagne closed this issue

2022-08-04 19:08:36 +02:00

Bastien Montagne commented

2022-08-04 19:08:36 +02:00

The problem here is that you are using NO_PROPERTY_NAME option for your collection, which means that the diffing code has no way to detect re-ordering, since there is no 'unique identifier' for the items.

So you do can insert items after the existing ones from lib data, but not move them before lib data ones.

In general NO_PROPERTY_NAME should really be avoided, it makes handling of any change in source (lib) data also extremely likely to break things. Without some kind of unique identifier (the name), dealing correctly with changes in a list is close to impossible.

note that if you want the user-visible name to be non-unique, you can always use another hidden string property for your items' names, which you can easily ensure that they are unique.

The problem here is that you are using `NO_PROPERTY_NAME` option for your collection, which means that the diffing code has no way to detect re-ordering, since there is no 'unique identifier' for the items. So you do can insert items after the existing ones from lib data, but not move them before lib data ones. In general `NO_PROPERTY_NAME` should really be avoided, it makes handling of any change in source (lib) data also extremely likely to break things. Without some kind of unique identifier (the name), dealing correctly with changes in a list is close to impossible. note that if you want the user-visible name to be non-unique, you can always use another hidden string property for your items' names, which you can easily ensure that they are unique.

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Reordering locally added items in overridden Collection Property breaks after saving #99924