BOSL2 for PartCAD

Exposes BOSL2 — the Belfry OpenSCAD Library v2 — as a broad catalog of parametric PartCAD parts, ready to be published in partcad-index side by side with cqwarehouse.

Unlike cqwarehouse (which enumerates every part in YAML), this package is served by an external repository plugin: the parts are generated on demand by parsing BOSL2 module signatures, and the BOSL2 source itself is downloaded the first time a part is listed or built — nothing is vendored into this repo.

What it stacks on

Two PartCAD capabilities are combined here:

1. Parametric OpenSCAD parts. Each part is a scad part with a method (the BOSL2 module) and typed parameters. PartCAD appends a module(name=value, …) call to a throwaway copy of an include-only wrapper and renders it, so a library module that defines geometry but renders nothing on its own becomes an instantiable part.

2. External (plugin-backed) packages. A type: external dependency is served by a repository plugin through a generic key/value protocol. Objects, files and metadata are fetched lazily, so a large library stays cheap to load. Here one plugin (bosl2_repo.py) serves twelve category sub-packages.

Layout

Path	Purpose
partcad.yaml	Declares the bosl2 repository and one external sub-package per BOSL2 category.
bosl2_repo.py	The repository plugin: downloads BOSL2 on demand, parses signatures, serves parts + include wrappers.
test_bosl2_repo.py	Unit tests for the parser/synthesizer and the offline dispatch paths.

Usage

# List the whole generated catalog (downloads BOSL2 on first use).
pc list parts -r //pub/std/metric/bosl2

# Inspect a primitive.
pc inspect //pub/std/metric/bosl2/shapes3d:cuboid

# Override parameters (they flow through the generated module call).
pc inspect -p teeth=30 -p thickness=12 //pub/std/metric/bosl2/gears:spur_gear

The categories exposed are: shapes3d, gears, threading, screws, metric_screws, nema_steppers, ball_bearings, linear_bearings, joiners, cubetruss, bottlecaps and walls — roughly 70 parametric parts.

How parts are generated

For each configured BOSL2 source file, bosl2_repo.py:

1. Parses every top-level module NAME(args) signature.
2. Extracts parameters: scalar-defaulted arguments (bool/int/float/ string) become overridable PartCAD parameters at their BOSL2 defaults.
3. Resolves dimensions: BOSL2 exposes the same dimension through mutually exclusive aliases (r/d/r1+r2, h/l/length, size/size1+ size2). The engine picks a single canonical spelling per family so calls never trip a "define exactly one of …" assertion.
4. Seeds domain arguments the geometry rules cannot infer (gear teeth, thread pitch, bearing trade_size, …) from a small data table.
5. Filters helpers (_-prefixed), 2D modules, masks, and a blocklist of modules that cannot render standalone.

The result is a catalog where every generated part renders out of the box; users can then override any exposed parameter.

Pinning the BOSL2 version

The BOSL2 release is the ref parameter of the bosl2 repository in partcad.yaml (default v2.0.747). The source is cached under ~/.cache/partcad-bosl2/<ref>/ (override the location with PARTCAD_BOSL2_CACHE).

Publishing in partcad-index

This package declares name: //pub/std/metric/bosl2, so standalone development uses the exact addresses consumers will see. To publish it, add an import next to cqwarehouse in the index's std/metric/partcad.yaml:

import:
  cqwarehouse:
    type: git
    url: https://github.com/partcad/partcad-cqwarehouse/
    relPath: metric.yaml
  bosl2:                                   # <-- new, side by side
    desc: Parametric BOSL2 shapes, gears, threading and hardware
    type: git
    url: https://github.com/partcad/partcad-bosl2/

Parts then resolve as //pub/std/metric/bosl2/<category>:<module>.

Note. Because the plugin downloads BOSL2 at build time, a consumer needs network access on first use (subsequently it is cached). This is the deliberate "download-on-demand" design; a future revision could pin BOSL2 as a git submodule instead.

Development

# Fast, offline unit tests of the generation logic:
pytest test_bosl2_repo.py -m "not slow"

# Print the generated catalog directly (downloads BOSL2):
python bosl2_repo.py

Licensing

The code in this repository is Apache-2.0 (see LICENSE). BOSL2 is not bundled here; it is fetched from upstream at build time and remains under its own BSD 2-Clause license. See NOTICE.