CAD Assembly Exchange

CadQuery is an open-source Python library for parametric CAD built on the Open CASCADE Technology (OCCT) kernel. At the starting commit it cannot read one back: Assembly.load raises NotImplementedError. The agent adds assembly import, matching upstream CadQuery #1779. Reading an assembly is much harder than writing one. XDE separates products from instances and stores names and colors at both levels, so a faithful reader must rebuild CadQuery's tree without flattening or splitting shared parts. Files from other CAD tools lay the same data out differently, adding further cases. Repeated export and load through STEP, XmlXCAF and BinXCAF must still converge.

The agent adds Assembly.load and Assembly.importStep for STEP, XML and XBF, plus XBF export. A loaded assembly reproduces what was written: tree and child order, each node's name, relative placement, geometry and color, and per-node subshape names, colors and layers. Shared parts stay shared, and every component of a foreign file becomes a node. Tolerances are stated: placement entries within 1e-6, volume, area and length within relative 1e-5, and color channels within 1e-6, with XML allowed OCCT's nearest named color. Missing or malformed input raises ValueError without crashing the interpreter, and existing public behavior keeps working. Only the committed HEAD is graded.

The offline sandbox (4 CPUs, 8 GB, 4 hours) holds a CadQuery checkout at the starting commit, installed in editable mode with development dependencies, OCP 7.8.1 (Python bindings to OCCT), Python 3.12 and pytest. Graded checks, fixtures and files imitating other CAD tools are held out.

The branch is rebuilt in a separate environment. Fixtures and foreign files are produced from a trusted starter copy and from raw OCCT before any submitted code runs; an independent XDE reader inspects every exported file. The 67 feature checks cover round trips in each format, per-instance differences, shared geometry, nested assemblies, RGBA colors, non-ASCII names, metadata, foreign files and malformed input. Twelve existing-behavior checks (STEP and exportStepMeta output, glTF colors, building and installing a wheel) and the starter's test suite form a gate. The score is the fraction of feature checks passed; 0 if any gate check fails. A pass requires every check.