Debug assert in uv layer data.foreach_get when called on an Edit Mode mesh #107416

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Thomas Barlow · 2023-04-28T01:16:42+02:00

Thomas Barlow commented

2023-04-28 01:16:42 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 531.41

Blender Version
Broken: version: 3.5.1 and 3.6.0 Alpha, branch: main, commit date: 2023-04-25 23:13, hash: 91020ccde15a
Worked: 3.4.1

Short description of error
Since 3.5, while in Edit Mode, attempting to get all uvs of a MeshUVLoopLayer through uv_layer.data.foreach_get("uv", my_list) will fill my_list with None or fail an assertion in debug builds: https://projects.blender.org/blender/blender/src/tag/v3.5.1/source/blender/python/intern/bpy_rna.c#L5451

In 3.4, unless my_list had zero length, this would fail and raise an Error because the length of the UV layer data is zero while in Edit Mode which is not the same as my_list: https://projects.blender.org/blender/blender/src/tag/v3.4.1/source/blender/makesrna/intern/rna_access.c#L4403

(the newer API of uv_layer.uv.foreach_get("vector", my_list) or using the foreach_get function of the UV layer's attribute fail as expected while in Edit Mode when my_list has non-zero length, so no problems with those.)

Exact steps for others to reproduce the error
Open a mesh with at least one uv_layer in Edit Mode and run the below script. On a debug build, you may need to ctrl+c to stop the script so that the stacktrace from the assertion can be printed.

import bpy

# Enter edit mode with a mesh and then:
me = bpy.context.object.data

# If the mesh weren't in Edit Mode, this would be the correct length of the list
uvs = [0.0] * (len(me.loops) * 2)

uvs_too_long = uvs + [0.0] * 1000

uv_layer = me.uv_layers[0]

# Currently in Edit Mode, so the length gets reported as zero.
assert len(uv_layer.data) == 0

# For a default cube, fails as expected with "Array length mismatch (expected 0, got 48)"
# me.uv_layers[0].uv.foreach_get("vector", uvs)
# For a default cube, fails as expected with "Array length mismatch (expected 0, got 48)"
# me.attributes[uv_layer.name].data.foreach_get("vector", uvs)

# On debug builds, an assertion will fail
uv_layer.data.foreach_get("uv", uvs)

# On release builds, the list will be filled with None
assert all(uv is None for uv in uvs)

# It doesn't seem to matter what size list is used, the entire list is filled with None
uv_layer.data.foreach_get("uv", uvs_too_long)
assert all(uv is None for uv in uvs_too_long)

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 531.41 **Blender Version** Broken: version: 3.5.1 and 3.6.0 Alpha, branch: main, commit date: 2023-04-25 23:13, hash: `91020ccde15a` Worked: 3.4.1 **Short description of error** Since 3.5, while in Edit Mode, attempting to get all uvs of a `MeshUVLoopLayer` through `uv_layer.data.foreach_get("uv", my_list)` will fill `my_list` with `None` or fail an assertion in debug builds: https://projects.blender.org/blender/blender/src/tag/v3.5.1/source/blender/python/intern/bpy_rna.c#L5451 In 3.4, unless `my_list` had zero length, this would fail and raise an Error because the length of the UV layer data is zero while in Edit Mode which is not the same as `my_list`: https://projects.blender.org/blender/blender/src/tag/v3.4.1/source/blender/makesrna/intern/rna_access.c#L4403 (the newer API of `uv_layer.uv.foreach_get("vector", my_list)` or using the `foreach_get` function of the UV layer's attribute fail as expected while in Edit Mode when `my_list` has non-zero length, so no problems with those.) **Exact steps for others to reproduce the error** Open a mesh with at least one uv_layer in Edit Mode and run the below script. On a debug build, you may need to ctrl+c to stop the script so that the stacktrace from the assertion can be printed. ```py import bpy # Enter edit mode with a mesh and then: me = bpy.context.object.data # If the mesh weren't in Edit Mode, this would be the correct length of the list uvs = [0.0] * (len(me.loops) * 2) uvs_too_long = uvs + [0.0] * 1000 uv_layer = me.uv_layers[0] # Currently in Edit Mode, so the length gets reported as zero. assert len(uv_layer.data) == 0 # For a default cube, fails as expected with "Array length mismatch (expected 0, got 48)" # me.uv_layers[0].uv.foreach_get("vector", uvs) # For a default cube, fails as expected with "Array length mismatch (expected 0, got 48)" # me.attributes[uv_layer.name].data.foreach_get("vector", uvs) # On debug builds, an assertion will fail uv_layer.data.foreach_get("uv", uvs) # On release builds, the list will be filled with None assert all(uv is None for uv in uvs) # It doesn't seem to matter what size list is used, the entire list is filled with None uv_layer.data.foreach_get("uv", uvs_too_long) assert all(uv is None for uv in uvs_too_long) ```

Thomas Barlow added the

labels 2023-04-28 01:16:42 +02:00

Pratik Borhade commented

2023-04-28 05:59:19 +02:00

Thanks for the report. I can confirm.

Pratik Borhade added