Cross Version Property Delete

A pair of stage lamps that witnesses the custom ID-property delete contract from cross-version-property-delete.py and custom-properties — not the snippet's __main__, which keys off context.active_object and prints nothing in --background.

The IDs are two stage-lamp housings built with bpy.data.objects.new. The Keep lamp still carries ["accession"] = 42; the Clear lamp had del obj["accession"]. Same del on 4.5 LTS and 5.x; there is no version branch.

What it witnesses: property_unset is a TypeError on a custom ID key and does not remove it. del id_block[key] does. After factory-empty, there is no active_object.

It also witnesses the other half of the split: a registered bpy.props value (Scene.bdt_counter = IntProperty()) is not an ID property on 5.0+. Measured on 4.5.11, 5.1.2 and 5.2.1:

On 5.0+ the raw storage is scene.bl_system_properties_get(). A value saved by 4.5 still loads as the attribute on 5.2.

What failure each check would catch:

• exit 2 — someone set an active object; the snippet __main__ would have been the only path
• exit 3 — the ID property never landed
• exit 4 — property_unset removed the key or failed to raise
• exit 7 — del did not run (--skip-delete / --unset-instead falsify this: measured clear_has=True)
• exit 8 — a registered prop was read or reset the 4.x way, or sits on the wrong side of the ID-property split for this version (--subscript-registered falsifies this on 5.0+)

Staging#

Both lamps hang in U-yokes from one T-stand. The render path reads each housing's keys() after the check has run, so the still is driven by the checked IDs, not staged from the expected outcome. A lamp that still carries the property gets an emissive lens and a real SPOT light along its beam axis, which pools warm light on the placard below it. A lamp without the property keeps a dark lens and casts nothing. Each placard is set in the bundled DejaVu Sans Mono and shows the line of code that produced its lamp's state. Only render-side geometry (stand, yokes, lenses, placards) is added in the render path; the check reads ID properties, never geometry.

Run#

blender --background --python cross_version_property_delete.py --
blender --background --python cross_version_property_delete.py -- --output lamps.png

--skip-delete and --unset-instead are falsification switches: both leave the Clear lamp tagged and exit 7.

The --output render path measures framing against the Layer 1 band via examples/gallery_framing.py (exit 10 on violation) before writing the still.

Exit codes#

Per-script sequential checks. 9 is a valid check code; there is no rule against it. 10 is the shared framing helper.

The blender-smoke workflow runs the check on Blender 5.2 LTS and 4.5 LTS (5.1 on the weekly cron, the needs-5.1 PR label, or manual dispatch). Smoke does not pass --output. Its catalog falsifiers are --skip-delete (expects exit 7); --unset-instead (expects exit 7); --subscript-registered (expects exit 8; 5.0+ only; SKIP on older Blender).