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/doc/src/document.rs

@@ -885,6 +885,24 @@ impl FeatureKind {
         }
     }
     /// Every expression the feature uses.
+    /// Points on faces the feature refers to (shell, draft, offset and replace faces, a hole's
+    /// placement), for persistent face names.
+    pub fn face_points_mut(&mut self) -> Vec<&mut Vec3> {
+        match self {
+            FeatureKind::Shell { faces, .. }
+            | FeatureKind::Draft { faces, .. }
+            | FeatureKind::OffsetFace { faces, .. }
+            | FeatureKind::ReplaceFace { faces, .. } => faces.iter_mut().collect(),
+            FeatureKind::Hole { position, points: None, .. } => vec![position],
+            _ => Vec::new(),
+        }
+    }
+
+    pub fn face_points(&self) -> Vec<Vec3> {
+        let mut k = self.clone();
+        k.face_points_mut().into_iter().map(|p| *p).collect()
+    }
+
     pub fn expressions(&self) -> Vec<&str> {
         let mut v: Vec<&str> = Vec::new();
         match self {
@@ -1024,6 +1042,9 @@ pub struct Feature {
     /// Persistent names of the picked edges (resolved first; see `naming`).
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub edge_names: Vec<String>,
+    /// Persistent names of the faces at the feature's face points (`FeatureKind::face_points`).
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub face_names: Vec<String>,
     #[serde(flatten)]
     pub kind: FeatureKind,
 }
@@ -1293,6 +1314,7 @@ impl Document {
             component: 0,
             edge_refs: Vec::new(),
             edge_names: Vec::new(),
+            face_names: Vec::new(),
             kind,
         };
         match self.marker {

crates/doc/src/eval.rs

@@ -517,6 +517,33 @@ impl Model {
             let t0 = now();
             let mut next = (*state).clone();
             let mut warning = None;
+            // Face references by name: move each face point onto its named face.
+            let renamed;
+            let f = if f.face_names.iter().any(|n| !n.is_empty()) {
+                let mut g = f.clone();
+                let mut notes = Vec::new();
+                for (p, n) in g.kind.face_points_mut().into_iter().zip(&f.face_names) {
+                    if n.is_empty() {
+                        continue;
+                    }
+                    match crate::naming::point_on_face(&state, n, *p) {
+                        Some((q, split)) => {
+                            if split {
+                                notes.push(format!("face `{n}` was split; using the piece nearest the picked point"));
+                            }
+                            *p = q;
+                        }
+                        None => notes.push(format!("face `{n}` no longer exists; using the face at the picked point")),
+                    }
+                }
+                if !notes.is_empty() {
+                    warning = Some(notes.join("; "));
+                }
+                renamed = g;
+                &renamed
+            } else {
+                f
+            };
             // A parameter with an error fails the features using it, with that error.
             let bad_param = param_names(f).into_iter().find_map(|n| self.param_errors.get(&n).map(|e| format!("parameter `{n}`: {e}")));
             let r = match bad_param {

crates/doc/src/naming.rs

@@ -533,3 +533,44 @@ pub fn edge_names_at(b: &ModelBody, pts: &[Vec3]) -> Vec<String> {
         })
         .collect()
 }
+
+/// Names of the faces holding each point (any body; empty when none does).
+pub fn face_names_at(st: &ModelState, pts: &[Vec3]) -> Vec<String> {
+    pts.iter()
+        .map(|p| {
+            for b in st.bodies.iter().filter(|b| !b.body.is_mesh()) {
+                let tol = (b.body.size() * 1e-3).max(1e-3);
+                let idx = FaceIndex::new(&b.mesh(), face_count(b));
+                if let Some(f) = idx.face_at(*p, tol) {
+                    return face_names(b).get(f).cloned().unwrap_or_default();
+                }
+            }
+            String::new()
+        })
+        .collect()
+}
+
+/// The point on the face with this name nearest `p` (a split face: its nearest piece, with
+/// `true` for "it was split"); `None` when no face has the name.
+pub fn point_on_face(st: &ModelState, name: &str, p: Vec3) -> Option<(Vec3, bool)> {
+    let stem = strip_piece(name);
+    let mut best: Option<(f64, Vec3, bool)> = None;
+    for b in st.bodies.iter().filter(|b| !b.body.is_mesh()) {
+        let names = face_names(b);
+        let m = b.mesh();
+        for (t, f) in m.triangles.iter().zip(&m.tri_face) {
+            let Some(n) = names.get(*f as usize) else { continue };
+            let exact = n == name;
+            if !exact && strip_piece(n) != stem {
+                continue;
+            }
+            let Some([a, bb, c]) = m.tri(t) else { continue };
+            let q = closest(p, a, bb, c);
+            let d = q.dist(p) - if exact { 1e-9 } else { 0.0 };
+            if best.is_none_or(|(bd, _, _)| d < bd) {
+                best = Some((d, q, !exact));
+            }
+        }
+    }
+    best.map(|(_, q, split)| (q, split))
+}

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()]);
+    }
 }