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Custom Properties for ShaderNodeTree do not save in blend files
Closed, ResolvedPublicBUG

Description

System Information

Operating system: MacOS Catalina 10.15.7 (19H2)
Graphics card: Intel Iris Graphics 6100 1536 MB graphics

Blender Version
Broken: 2.91.0, b0f34eee30c4, master, 2020-10-21
Worked: not sure

Short description of error
The Blender manual describes that Blender can save custom properties to its data blocks (see link). However upon attempting to save a custom property to a ShaderNodeTree type, particularly to the C.scene.world.node_treee, it is clear that the custom property is not saved to the blend file. Other data blocks appear to work just fine.

Exact steps for others to reproduce the error

  1. Create a custom property on the C.scene.world.node_tree or on a material's node_tree;
import bpy
from bpy.props import StringProperty

bpy.types.ShaderNodeTree.uuid= StringProperty(
                    name="Unique Id for hashing",
                    default='')

bpy.context.scene.world.node_tree.uuid = 'hamburgers with cheese'
  1. Save the blend file, close blender
  2. Open the file in blender and inspect the bpy.context.scene.world.node_tree to find the custom property and check its value.
  3. The custom property no longer exists. Its not listed in the data block's keys or items so that
bpy.context.scene.world.node_tree['uuid'] raises a key error

The same approach for saving custom properties to other data blocks, like materials or objects, works as expected.

Event Timeline

I retract my previous comment, you're following the approach outlined here.

Robert Guetzkow (rjg) changed the task status from Needs Triage to Confirmed.Nov 4 2020, 11:19 AM

Since ShaderNodeTree is a subclass of ID, this is supposed to work.

Philipp Oeser (lichtwerk) changed the subtype of this task from "Report" to "Bug".Nov 4 2020, 11:25 AM

Same issue with master collections of scenes actually.

@Bastien Montagne (mont29) @Robert Guetzkow (rjg) @Philipp Oeser (lichtwerk) Thanks guys :) Really appreciate you guys looking into this. Willing to test this as soon as its in a daily build if that will help.

Weird, just checked this issue and can see its closed, but didn't get an update via e-mail, is that expected? I got the initial one about the issue being created!

I got the mail... Yours might have ended up in spams? Got closed by the fixing commit.

I got the mail... Yours might have ended up in spams? Got closed by the fixing commit.

Yeah maybe :) not sure, I had a look in there, nothing. never mind though, glad it got closed :)