Collection user counts are set to 1 on file load. Boolean modifier orphans Collections. #89765

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Will · 2021-07-09T21:23:19+02:00

Will commented

2021-07-09 21:23:19 +02:00

System Information
Operating system: Polar Bear Buffet (Linux)
Graphics card: Intel

Blender Version
Broken: 2.93
Worked: N/A

Short description of error

Collection user counts are set to 1 on file load.

So removing a collection from a Boolean modifier decrements that collection's user count to 0, causing it to become orphaned and not be saved.

>>> D.collections["Collection"].users

1

>>> C.object.modifiers[0].collection = None
>>> D.collections["Collection"].users

0

I'm not sure if this also happens with E.G. physics simulations and the like that also have collection properties, and some of which are implemented as modifiers.

Exact steps for others to reproduce the error

In the default scene, add a Boolean modifier to any object.
Set the Boolean modifier to use the default collection.
Save and re-open or "Revert" the file.
Remove the collection from the Boolean modifier.
The collection will now have a "0" next to it in the search template, it will be listed in the "Orphan Data" mode of the Outliner window, .users == 0 on it, and it will not be saved with the file.

Or click the "X" to remove the collection from the Boolean modifier in this file:

CollectionOrphaning.blend

**System Information** Operating system: Polar Bear Buffet (Linux) Graphics card: Intel **Blender Version** Broken: 2.93 Worked: N/A **Short description of error** Collection user counts are set to `1` on file load. So removing a collection from a Boolean modifier decrements that collection's user count to `0`, causing it to become orphaned and not be saved. ``` >>> D.collections["Collection"].users 1 >>> C.object.modifiers[0].collection = None >>> D.collections["Collection"].users 0 ``` I'm not sure if this also happens with E.G. physics simulations and the like that also have collection properties, and some of which are implemented as modifiers. **Exact steps for others to reproduce the error** 1. In the default scene, add a Boolean modifier to any object. 2. Set the Boolean modifier to use the default collection. 2. Save and re-open or "Revert" the file. 3. Remove the collection from the Boolean modifier. 4. The collection will now have a "0" next to it in the search template, it will be listed in the "Orphan Data" mode of the Outliner window, `.users == 0` on it, and it will not be saved with the file. Or click the "X" to remove the collection from the Boolean modifier in this file: [CollectionOrphaning.blend](https://archive.blender.org/developer/F10218624/CollectionOrphaning.blend)

Will commented

2021-07-09 21:23:19 +02:00

Added subscriber: @WCN