Summary

Fixes #9348. When an IfcOpeningElement voids an element that is the sole occurrence of a shared/typed representation (e.g. a MappedRepresentation from an IfcElementType), the element's Body geometry silently disappeared in downstream Object-mode viewports (observed via Bonsai) — no exception, no warning/error logged, mesh ends up empty. ifcopenshell.geom.create_shape() called directly on the element returns correct, non-empty geometry with the opening properly subtracted, confirming the boolean/CSG kernel itself was never at fault.

Root cause: mapping::reuse_ok_() returned true for any single-product list before ever checking that product for openings. Whenever a caller's include= filter (or the product list naturally) narrowed down to exactly one product — the common case when editing the sole instance of a type — the size-1 fast path bypassed the find_openings() disqualification check entirely. get_representations() then treated the representation as safely shareable and processed it via the reuse/mapped path instead of computing an individual cut shape for the occurrence, and the resulting shape ended up attributed to the wrong product (or the type product, which typically has no consuming scene object downstream).

With two or more products in the list, the existing loop's find_openings() check ran as intended and correctly disqualified reuse — which is why this only manifests for singleton occurrences of a type and is easy to miss in testing (any file with ≥2 instances of the affected type masks it).

Fix

Minimal, targeted change: the products->size() == 1 fast path in reuse_ok_() now checks find_openings() on that single product before returning true, matching what the full loop would do for it anyway. Left the layerset/material checks out of the fast path deliberately, to avoid adding per-representation overhead to the (overwhelmingly common) non-shared, single-product case that has nothing to do with reuse.

Testing

• Full ifcopenshell-python test suite: 2349 passed, 6 pre-existing/environmental failures unrelated to this change (test_mmaped_stream, documented as expected under this repo's USE_MMAP=OFF build config; 5 mathutils-import failures in an unrelated shape-builder test, since mathutils is Blender-only and unavailable to the bare test interpreter).
• Isolated before/after reproduction: on an identical minimal file (one IfcElementType, one occurrence, one opening), the unpatched build keys the resulting shape's geometry id to the shared type-level representation; the patched build keys it to the occurrence's own representation — matching the pattern of every other correctly-working (multi-occurrence) case.
• Confirmed end-to-end against the real-world reproduction that motivated this fix (Bonsai, a single IfcRoofType occurrence with an opening applied) — geometry now regenerates correctly instead of coming back empty.

AI-generated code disclosure

This change (investigation, fix, and this PR description) was produced with the assistance of an AI coding tool, reviewed and tested by the author before submission.