Loft: refuse a section with a hole instead of filling it (#1184) (#1254)

A loft section with a hole is refused with a clear message instead of being lofted as if filled, in both section-to-section and section-to-point lofts. Fixes #1184.

crates/engine/src/tests.rs

@@ -308,6 +308,7 @@ mod boolean_diagnostics;
 mod component_frames;
 mod large_step_import;
 mod loft_cut;
+mod loft_ring;
 mod loft_spacing;
 mod mirror_planes;
 mod path_scope;

crates/engine/src/tests/loft_ring.rs

@@ -0,0 +1,51 @@
+//! A loft section that is a ring (a profile with a hole) is refused (#1184): the loft builds each
+//! section from its outline, so it used to fill the hole and report success.
+
+use super::*;
+
+/// A sketch `name` at height `z` with circles of radius 20 and 12 about the origin.
+fn ring(s: &mut Session, name: &str, z: f64) {
+    run(s, "sketch.create", json!({"plane": "XY", "offset": z, "name": name}));
+    run(s, "sketch.circle.center", json!({"center": [0, 0], "radius": 20}));
+    run(s, "sketch.circle.center", json!({"center": [0, 0], "radius": 12}));
+    run(s, "sketch.finish", json!({}));
+}
+
+fn refused(s: &mut Session, sections: Value) {
+    let saved = s.doc.to_json();
+    let err = s.execute("solid.loft", &json!({"sections": sections, "operation": "new"})).err().map(|e| e.to_string());
+    assert!(err.as_deref().is_some_and(|e| e.contains("not supported yet: a loft section with a hole")), "{err:?}");
+    assert_eq!(s.doc.to_json(), saved);
+}
+
+#[test]
+fn a_ring_section_is_refused_not_filled() {
+    let mut s = Session::default();
+    ring(&mut s, "A", 0.0);
+    ring(&mut s, "B", 20.0);
+    let ring_at = |n: &str| json!({"sketch": n, "profiles": [{"point": [16, 0]}]});
+    refused(&mut s, json!([ring_at("A"), ring_at("B")]));
+    // A ring and a plain disc, in either order.
+    let disc_b = json!({"sketch": "B", "profiles": [{"point": [0, 0]}]});
+    refused(&mut s, json!([ring_at("A"), disc_b]));
+    refused(&mut s, json!([disc_b, ring_at("A")]));
+    // The discs inside the holes still loft into a cylinder of radius 12.
+    run(&mut s, "solid.loft", json!({"sections": [{"sketch": "A", "profiles": [{"point": [0, 0]}]}, disc_b], "operation": "new"}));
+    let want = std::f64::consts::PI * 12.0 * 12.0 * 20.0;
+    let got = volume(&mut s);
+    assert!(rel(got, want) < 1e-3, "{got} vs {want}");
+}
+
+#[test]
+fn a_ring_lofted_to_a_point_is_refused() {
+    let mut s = Session::default();
+    // Square, since lofting curved sections to a point is not supported at all yet.
+    run(&mut s, "sketch.create", json!({"plane": "XY", "name": "A"}));
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0": [-20, -20], "p1": [20, 20]}));
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0": [-12, -12], "p1": [12, 12]}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "sketch.create", json!({"plane": "XY", "offset": 20, "name": "Top"}));
+    run(&mut s, "sketch.point", json!({"point": [0, 0], "id": "apex"}));
+    run(&mut s, "sketch.finish", json!({}));
+    refused(&mut s, json!([{"sketch": "A", "profiles": [{"point": [16, 0]}]}, {"sketch": "Top", "point": "apex"}]));
+}