scad-etc compatibility audit

Compared the migration against the pre-migration Plexus sources, retaining the existing forward-sampling and entering-cross-section loft fixes in both versions. The scad-etc checkout was not modified.

API surface

The source scan found 73 namespaces with analyzed Plexus imports. No references to public vars removed by this migration were found. The only removed public var in core/transforms/utils is plexus.core/defop; scad-etc does not use it.

22 namespaces have no unresolved Plexus API references. The remaining namespaces include uses of older APIs such as model, backward, spin, iso-hull, plexus.segment, and plexus.math, already absent before this migration. This is a symbol audit, not a claim that every complete namespace loads or builds.

No uses of rebuild, defop, or plexus.impl.Form were found in scad-etc sources. The change from implicit argument re-evaluation to explicit deferred therefore does not require a rebuild call-site migration in this checkout.

Regression found and fixed

scad-etc.utils/calc-right-forward-left-segment passes :n-steps nil when its optional sampling count is omitted. The new positive-integer validation initially rejected this, although the extrusion implementation uses nil to select its default. The schema and static hook now accept nil while rejecting invalid non-nil step counts.

This helper is used by georid-house, lake-house, and several mixer models. Evaluating the actual helper definition in isolation produced identical paths on both versions: 42 points with nil steps, 46 with five steps, ending at approximately [10 40]. The shared JVM/JS tests also cover nil sampling.

clojure -Sdeps '{:paths ["src/main" "resources" "../scad-etc/src/main"]}' \
  -M:local-dev scripts/check-scad-helper.clj

Model tests

Check	Migrated result	Baseline comparison
wave-truss suite	5 tests, 902 assertions, all pass	Also passes
wave-truss + carport-frame suites	8 tests, 923 assertions; 3 failures, 1 error	Same failures/error and assertion count
triangular-truss suite	6 tests, 849 assertions; 2 connector-wall validation errors	Same errors and assertion count
actual shared curve helper	nil and five-step paths pass	Matching point counts and endpoints

The carport failures are fixture/topology expectations in its tests. The triangular-truss errors are its connector-wall checks. Neither was introduced by the migration. The triangular comparison was also performed during the initial migration validation.

A direct require of scad-etc.utils is blocked by an unregistered #dbg reader in scad_etc/offset_polygon.clj:109, independently of Plexus. The helper check reads and evaluates only the selected real function definition with its actual math dependencies. Whole scratch namespaces with top-level exports were not blindly loaded, so this audit does not certify every model in scad-etc.

Source diagnostics

Macro-free constructors cannot automatically capture their call-site source coordinates. plexus.source provides optional operation macros (and at) that preserve file, line, column, and original expression while retaining single argument evaluation. plexus.core/with-source accepts explicit locations without macros, including in SCI. The SCI adapter also exposes plexus.source macros for automatic locations on both JVM and JS hosts. Execution errors include the offending form and cause with either API. See the README for migration examples.