How to handle 'fake user' in linked data. #99262

New Issue

Ludvik Koutny · 2022-06-29T10:22:35+02:00

Ludvik Koutny commented

2022-06-29 10:22:35 +02:00

Currently, linked data keep their 'fake user' flag as defined in the source library. This is not editable by the user.

The problem is that this creates linked data that are never automatically/manually purged once unused, user needs to manually delete those IDs.

There are several potential ways to address that issue:

1 Clear Fake User flag on linked data

This would have to be applied in readfile code for all linked data.
It is easy to implement.
One side-effect is that appending would not preserve that information either (unless we add some specific special-case code, which I would rather avoid here).

2 Ignore fake user flag on linked data in purge-like operations

(actual purge operator and/or 'clear on file write' current behavior).

This would not change anything to current behavior, besides removing unused linked data even when it has a (library-defined) fake user.
** One of the questions here is whether 'removal on file write' type of cleanup should also behave that way, or only the actual Purge operator.
It is easy to implement.
The difference with option 1 is that the fake user flag would be automatically preserved when appending (or making linked data local).

3 Allow local definition/storage of 'fake user' flag for linked data

User would be able to set or clear fake user on linked data.
Probably need a specific handling on first linking, e.g. using value from linked data for directly linked ones, and always clearing it for indirectly linked IDs.
Status would be stored in the 'place-holder' ID header used in blendfile to keep reference to the directly linked IDs.
** Implies that indirectly linked IDs would become directly linked if user set a fake user for them (which makes sense anyway I believe).
Probably the most complex/risky option to implement.
** May raise unforeseen issues, and/or have unexpected consequences.

Original report:

Linking data from other blend files leaves the target file with link references which have to be removed manually

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.59

Blender Version
Broken: version: 3.2.2, branch: SelectThrough, commit date: 2022-06-08 07:44, hash: a9ace42a16
Worked: probably never

Short description of error
When linking objects or data from other .blend files, the target blend file is infected with references to the linked file, as well as any files the linked file was linking. These references remain in the target file even after all objects are removed an all the various clean up operators are ran. This is probably due to incorrect handling of linked data blocks if they are fake-usered.

2022-06-29 10-15-50.mp4

Exact steps for others to reproduce the error

Create a blend file with some datablocks, some of which are fake-usered.
Open a new blank file, and link some datablocks from the previous file, which reference some datablocks which have been fake-usered.
Delete any of the data you have just linked, and run all 3 recursive versions of the clean up operators.
Result: The references to the linked files are still present in the target blend file
Expected: The references to the linked files are gone if they are not used

Currently, linked data keep their 'fake user' flag as defined in the source library. This is not editable by the user. The problem is that this creates linked data that are never automatically/manually purged once unused, user needs to manually delete those IDs. There are several potential ways to address that issue: 1 Clear Fake User flag on linked data **** * This would have to be applied in readfile code for all linked data. * It is easy to implement. * One side-effect is that appending would not preserve that information either *(unless we add some specific special-case code, which I would rather avoid here)*. 2 Ignore fake user flag on linked data in purge-like operations **** (actual purge operator and/or 'clear on file write' current behavior). * This would not change anything to current behavior, besides removing unused linked data even when it has a (library-defined) fake user. ** One of the questions here is whether 'removal on file write' type of cleanup should also behave that way, or only the actual Purge operator. * It is easy to implement. * The difference with option **1** is that the fake user flag would be automatically preserved when appending (or making linked data local). 3 Allow local definition/storage of 'fake user' flag for linked data **** * User would be able to set or clear fake user on linked data. * Probably need a specific handling on first linking, e.g. using value from linked data for directly linked ones, and always clearing it for indirectly linked IDs. * Status would be stored in the 'place-holder' ID header used in blendfile to keep reference to the directly linked IDs. ** Implies that indirectly linked IDs would become directly linked if user set a fake user for them *(which makes sense anyway I believe)*. * Probably the most complex/risky option to implement. ** May raise unforeseen issues, and/or have unexpected consequences. ----------------------- **Original report:** *Linking data from other blend files leaves the target file with link references which have to be removed manually* **System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 512.59 **Blender Version** Broken: version: 3.2.2, branch: SelectThrough, commit date: 2022-06-08 07:44, hash: `a9ace42a16` Worked: probably never **Short description of error** When linking objects or data from other .blend files, the target blend file is infected with references to the linked file, as well as any files the linked file was linking. These references remain in the target file even after all objects are removed an all the various clean up operators are ran. This is probably due to incorrect handling of linked data blocks if they are fake-usered. [2022-06-29 10-15-50.mp4](https://archive.blender.org/developer/F13237010/2022-06-29_10-15-50.mp4) **Exact steps for others to reproduce the error** 1. Create a blend file with some datablocks, some of which are fake-usered. 2. Open a new blank file, and link some datablocks from the previous file, which reference some datablocks which have been fake-usered. 3. Delete any of the data you have just linked, and run all 3 recursive versions of the clean up operators. Result: The references to the linked files are still present in the target blend file Expected: The references to the linked files are gone if they are not used

Ludvik Koutny commented

2022-06-29 10:22:35 +02:00

Added subscriber: @Rawalanche

Pratik Borhade commented

2022-06-29 13:59:13 +02:00

Added subscriber: @PratikPB2123

Pratik Borhade commented

2022-06-29 14:05:11 +02:00

I'm seeing that data block is marked as fake user in outliner->orphaned data tab. That's why those cleanup operations are not removing unused data block.
I think Bastien knows if this is working as expected or not

I'm seeing that data block is marked as fake user in `outliner->orphaned data` tab. That's why those cleanup operations are not removing unused data block. I think Bastien knows if this is working as expected or not

Germano Cavalcante commented

2022-06-30 15:50:00 +02:00

Added subscribers: @mont29, @mano-wii

Germano Cavalcante commented

2022-06-30 15:50:00 +02:00

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Germano Cavalcante commented

2022-06-30 15:50:00 +02:00

Okay, if I understand correctly, the problem is that if you link a data-block with fake-user, it will also have fake-user in the new scene and so it won't be removed in any recursive purge operation.

I'm not sure if this should be considered a bug.

Why does the data-block have a fake-user to begin with?

But I agree this behavior is a bit strange. Should the fake-user be removed/ignored in the link?

Needs Information from Developers... (@mont29?)

Okay, if I understand correctly, the problem is that if you link a data-block with fake-user, it will also have fake-user in the new scene and so it won't be removed in any recursive purge operation. I'm not sure if this should be considered a bug. Why does the data-block have a fake-user to begin with? But I agree this behavior is a bit strange. Should the fake-user be removed/ignored in the link? Needs Information from Developers... (@mont29?)

Ludvik Koutny commented

2022-06-30 16:25:23 +02:00

In #99262#1382950, @mano-wii wrote:
Why does the data-block have a fake-user to begin with?

How is that a question? Because I don't want Blender to blatantly delete my data when working with the source file I linked. Isn't that obvious?

Or is your question specifically why does it have a fake user in the file it was linked to? In that case, the answer would be it's a bug. It does not make sense to consider fake user state of a linked datablock, because the target file can not affect/write to the linked file, and therefore delete that data somehow.

> In #99262#1382950, @mano-wii wrote: > Why does the data-block have a fake-user to begin with? How is that a question? Because I don't want Blender to blatantly delete my data when working with the source file I linked. Isn't that obvious? Or is your question specifically why does it have a fake user in the file it was linked to? In that case, the answer would be it's a bug. It does not make sense to consider fake user state of a linked datablock, because the target file can not affect/write to the linked file, and therefore delete that data somehow.

Bastien Montagne commented

2022-07-05 14:59:09 +02:00

Added subscribers: @SimonThommes, @eyecandy, @dfelinto

Bastien Montagne commented

2022-07-05 14:59:09 +02:00

Thanks for the report, however this is not a bug, in the sense that the code is working as intended.

This requires design first, since deciding which behavior would be the best option in that case is not trivial. Will edit the task as such.

Also, CC @dfelinto @eyecandy @SimonThommes

Thanks for the report, however this is not a bug, in the sense that the code is working as intended. This requires design first, since deciding which behavior would be the best option in that case is not trivial. Will edit the task as such. Also, CC @dfelinto @eyecandy @SimonThommes

Bastien Montagne changed title from ~~Linking data from other blend files leaves the target file with link references which have to be removed manually~~ to How to handle 'fake user' in linked data.

2022-07-05 15:16:06 +02:00

Bastien Montagne commented

2022-07-05 15:16:06 +02:00

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

Ludvik Koutny commented

2022-07-05 15:47:54 +02:00

Solution 2. sounds the best. Solution 1 is also acceptable. Solution 3 sounds like a hell. There's already more than enough error prone data management wrangling Blender blatantly offloads onto user's mind. It would be really bad to add even more to it.

Philipp Oeser removed the

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How to handle 'fake user' in linked data. #99262