Persistent naming: shell, draft, offset-face and replace-face faces and hole placements store their faces' names (Feature.face_names) and are moved onto the named face before evaluating (a split face: the nearest piece, with a warning; a vanished face: the picked point, with a warning)

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/engine/src/cmd/edit.rs

@@ -193,6 +193,10 @@ fn edit_feature(s: &mut Session, p: &Value) -> Result<Value> {
         nf.edge_refs = solvecraft_doc::edge_refs(&before, body, a);
         nf.edge_names = solvecraft_doc::edge_names_for(&before, body, a);
     }
+    // New face points: their faces' names now.
+    if nf.kind.face_points() != f.kind.face_points() {
+        nf.face_names = solvecraft_doc::naming::face_names_at(&s.model.state_before(id), &nf.kind.face_points());
+    }
     if let Some(slot) = s.doc_mut().feature_mut(id) {
         *slot = nf;
     }

crates/engine/src/cmd/features.rs

@@ -251,10 +251,15 @@ pub(super) fn add_feature(s: &mut Session, p: &Value, kind: FeatureKind) -> Resu
         }
         _ => (Vec::new(), Vec::new()),
     };
+    let face_names = {
+        let pts = kind.face_points();
+        if pts.is_empty() { Vec::new() } else { solvecraft_doc::naming::face_names_at(&s.model.state(), &pts) }
+    };
     let id = s.doc_mut().add_feature(kind, name)?;
     if let Some(f) = s.doc_mut().feature_mut(id) {
         f.edge_refs = refs;
         f.edge_names = names;
+        f.face_names = face_names;
     }
     s.doc_mut().name_feature_inputs(id);
     let comp = s.active_component;

crates/engine/src/tests.rs

@@ -1325,4 +1325,19 @@ mod naming {
         let sk = s.model.state().sketch(s.doc.find_feature("Top").map(|f| f.id).unwrap_or(0)).map(|x| x.plane.origin.z);
         assert_eq!(sk.map(|z| (z * 1e6).round() / 1e6), Some(10.0));
     }
+
+    #[test]
+    fn shell_and_hole_faces_follow_by_name() {
+        let mut s = Session::default();
+        run(&mut s, "PrimitiveBox", json!({"length": 40, "width": 30, "height": 20, "name": "Base"}));
+        run(&mut s, "FusionShellBodyCommand", json!({"faces": [[20, 15, 20]], "thickness": 2, "name": "Hollow"}));
+        let shell = |h: f64| 40.0 * 30.0 * h - 36.0 * 26.0 * (h - 2.0);
+        assert!((volume(&mut s) - shell(20.0)).abs() < 0.5, "{}", volume(&mut s));
+        // Taller: the picked point is 5 mm under the open face now; its name still finds it.
+        run(&mut s, "timeline.edit", json!({"feature": "Base", "set": {"height": "25"}}));
+        assert!((volume(&mut s) - shell(25.0)).abs() < 0.5, "{}", volume(&mut s));
+        assert_eq!(warning(&s, "Hollow"), None);
+        let h = s.doc.find_feature("Hollow").map(|f| f.face_names.clone()).unwrap_or_default();
+        assert_eq!(h, vec!["F1:+z".to_string()]);
+    }
 }