Join keeps exact face attachments on faces it leaves unchanged (#420) (#453)

A Union dropped every construction certificate, so after any join no face
could take a durable sketch: sketch.create failed with "this face has no
exact planar source" even on a face the join never touched (#420, and the
"CREATE SKETCH: operation failed" reports #344, #195).

- kernel: map planar sources through a Union from both operands, with the
  same exact-support rule Cut uses. Coplanar supports of the two operands
  carry distinct identities, so a face merged from both stays without one.
- doc: Join extrude and Join box tools are certified like new bodies; a
  cap moved off its designed height (into the target, or past a curved To
  face) is not certified. Join producers are accepted when certifying.

Tests: both operands' faces attach and follow an upstream edit and a
reopen; a merged coplanar face is refused and fixed:true works; a face a
join covers whole is lost without moving to the new roof. Tests that used
a joined face as their "uncertified" example now use a merged face; the
trimmed-face case in a_sketch_on_a_face_stays_on_that_face now stays
attached to the surviving piece.


Claude-Session: https://claude.ai/code/session_01YDDPmNdRoBgkHcLeUDKVfb

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/cmd/face_tests.rs

@@ -142,7 +142,8 @@ fn legacy_internal_capture_refuses_an_uncaptured_source_in_another_component() {
     let component = run(&mut s, "component.create", json!({"name":"Source"}));
     let occurrence = component["occurrence"].as_u64().unwrap();
     run(&mut s, "solid.box", json!({"length":40,"width":30,"height":20,"body_name":"Stock"}));
-    run(&mut s, "solid.press_pull", json!({"face":[5,5,20],"distance":5}));
+    // A top merged from two joined boxes has no single certified source: the legacy path.
+    run(&mut s, "solid.box", json!({"length":40,"width":30,"height":20,"corner":[40,0,0],"operation":"join"}));
     run(&mut s, "component.activate", json!({"component":0}));
     run(&mut s, "occurrence.move", json!({"occurrence":occurrence,"translate":[30,0,0],"capture":false}));
     let state = s.model.state();
@@ -153,12 +154,12 @@ fn legacy_internal_capture_refuses_an_uncaptured_source_in_another_component() {
         .faces(1e-4)
         .unwrap()
         .iter()
-        .find(|face| face.plane_normal.is_some_and(|normal| normal.z > 0.999) && (face.centroid.z - 25.0).abs() < 1e-6)
+        .find(|face| face.plane_normal.is_some_and(|normal| normal.z > 0.999) && (face.centroid.z - 20.0).abs() < 1e-6)
         .unwrap()
         .index;
     let before = s.doc.to_json();
     let error =
-        super::super::sketch::face::capture_internal(&s, &json!({"face":[35,5,25],"body":"Stock","index":index,"path":[occurrence]}), "internal")
+        super::super::sketch::face::capture_internal(&s, &json!({"face":[35,5,20],"body":"Stock","index":index,"path":[occurrence]}), "internal")
             .unwrap_err();
     assert!(error.to_string().contains("capture the source occurrence position"), "{error}");
     assert_eq!(s.doc.to_json(), before);
@@ -229,3 +230,90 @@ fn blind_cut_inside_a_cylinder_keeps_only_planes_and_cylinders() {
     assert_eq!(body["face_types"], json!({"cylinder": 2, "plane": 12}), "{m}");
     assert_eq!(body["faces"], 14, "{m}");
 }
+
+fn face_anchor(s: &Session, sketch: u64) -> solidcraft_doc::FaceAnchor {
+    let FeatureKind::Sketch { plane: PlaneRef::Face { anchor: Some(anchor), .. }, .. } = &s.doc.feature(sketch).unwrap().kind else {
+        panic!("sketch {sketch} has no face anchor")
+    };
+    (**anchor).clone()
+}
+
+#[test]
+fn join_keeps_exact_face_attachments_from_both_operands() {
+    let mut s = Session::default();
+    run(&mut s, "sketch.create", json!({"plane":"XY"}));
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0":[-10,-10],"p1":[10,10]}));
+    run(&mut s, "sketch.finish", json!({}));
+    let base = run(&mut s, "solid.extrude", json!({"distance":40,"name":"Base"}))["feature"].as_u64().unwrap();
+    // A cross bar joined through the base (the shape of #420) and a boss joined on its top.
+    run(&mut s, "sketch.create", json!({"plane":"YZ"}));
+    run(&mut s, "sketch.circle.center", json!({"center":[0,20],"radius":5}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"distance":20,"symmetric":true,"operation":"join"}));
+    run(&mut s, "sketch.create", json!({"plane":{"face":[0,0,40]}}));
+    run(&mut s, "sketch.circle.center", json!({"center":[0,0],"radius":4}));
+    run(&mut s, "sketch.finish", json!({}));
+    let boss = run(&mut s, "solid.extrude", json!({"distance":10,"operation":"join","name":"Boss"}))["feature"].as_u64().unwrap();
+    assert_eq!(s.model.state().bodies.len(), 1);
+
+    // The base's top around the boss, and the boss's own top (the Union's second operand).
+    let on_base = run(&mut s, "sketch.create", json!({"plane":{"face":[8,8,40]}}))["sketch"].as_u64().unwrap();
+    run(&mut s, "sketch.finish", json!({}));
+    let on_boss = run(&mut s, "sketch.create", json!({"plane":{"face":[0,0,50]}}))["sketch"].as_u64().unwrap();
+    run(&mut s, "sketch.finish", json!({}));
+    assert_eq!(face_anchor(&s, on_base).target.origin_feature, base);
+    assert_eq!(face_anchor(&s, on_boss).target.origin_feature, boss);
+
+    // The attachments follow their faces through an upstream edit and a reopen.
+    run(&mut s, "timeline.edit", json!({"feature":"Base","set":{"extent":{"distance":"50"}}}));
+    s.refresh();
+    assert!(s.model.results.iter().all(|result| result.error.is_none()), "{:?}", s.model.results);
+    let state = s.model.state();
+    assert!((state.sketch(on_base).unwrap().plane.origin.z - 50.0).abs() < 1e-6);
+    assert!((state.sketch(on_boss).unwrap().plane.origin.z - 60.0).abs() < 1e-6);
+    let mut reopened = Session::new(Document::from_json(&s.doc.to_json()).unwrap());
+    reopened.refresh();
+    assert!(reopened.model.results.iter().all(|result| result.error.is_none()), "{:?}", reopened.model.results);
+    assert!((reopened.model.state().sketch(on_boss).unwrap().plane.origin.z - 60.0).abs() < 1e-6);
+}
+
+#[test]
+fn join_leaves_a_face_merged_from_both_operands_without_an_attachment() {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length":20,"width":20,"height":10}));
+    run(&mut s, "solid.box", json!({"length":20,"width":20,"height":10,"corner":[20,0,0],"operation":"join"}));
+    // Both boxes' tops share one support: no single construction identity owns it.
+    let error = s.execute("sketch.create", &json!({"plane":{"face":[10,10,10]}})).unwrap_err().to_string();
+    assert!(error.contains("fixed:true"), "{error}");
+    run(&mut s, "sketch.create", json!({"plane":{"face":[10,10,10],"fixed":true}}));
+    // An unshared support keeps its box role.
+    run(&mut s, "sketch.finish", json!({}));
+    let side = run(&mut s, "sketch.create", json!({"plane":{"face":[0,10,5]}}))["sketch"].as_u64().unwrap();
+    assert!(matches!(face_anchor(&s, side).target.certificate, Some(solidcraft_doc::config::FaceCertificate::Box { axis: 0, high: false })));
+}
+
+#[test]
+fn join_covering_a_whole_attached_face_loses_the_attachment_without_moving_it() {
+    let mut s = Session::default();
+    run(&mut s, "sketch.create", json!({"plane":"XY"}));
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0":[0,0],"p1":[40,30]}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"distance":10,"name":"Block"}));
+    let top = run(&mut s, "sketch.create", json!({"plane":{"face":[30,15,10]},"name":"Top"}))["sketch"].as_u64().unwrap();
+    run(&mut s, "sketch.circle.center", json!({"center":[30,15],"radius":3}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"sketch":"Top","distance":5,"operation":"join","name":"Peg"}));
+    // An earlier join whose roof replaces Block's whole top.
+    run(&mut s, "timeline.roll_to", json!({"feature":"Block"}));
+    run(&mut s, "sketch.create", json!({"plane":"XY","name":"B"}));
+    run(&mut s, "sketch.rectangle.two_point", json!({"p0":[-5,-5],"p1":[45,35]}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.extrude", json!({"sketch":"B","distance":20,"operation":"join","name":"Boss"}));
+    run(&mut s, "timeline.roll_to", json!({}));
+    let failed = |s: &Session, id: u64| s.model.results.iter().find(|r| r.id == id).unwrap().error.is_some();
+    assert!(failed(&s, top), "the attachment never follows the substitute roof");
+    assert!(s.model.state().sketch(top).is_none());
+    run(&mut s, "timeline.suppress", json!({"feature":"Boss","suppressed":true}));
+    assert!(!failed(&s, top));
+    assert!((s.model.state().sketch(top).unwrap().plane.origin.z - 10.).abs() < 1e-9);
+}

crates/engine/src/cmd/sketch_face_tests.rs

@@ -76,7 +76,8 @@ fn explicit_rebind_preserves_geometry_dimensions_context_and_one_undo() {
 fn unsupported_face_has_explicit_fixed_alternative_and_no_live_projection() {
     let mut s = Session::default();
     run(&mut s, "solid.box", json!({"length":10,"width":10,"height":10,"body_name":"Base"}));
-    run(&mut s, "solid.box", json!({"length":2,"width":2,"height":2,"corner":[4,4,10],"operation":"join"}));
+    // The tops of two joined boxes merge into one face that no single construction owns.
+    run(&mut s, "solid.box", json!({"length":10,"width":10,"height":10,"corner":[10,0,0],"operation":"join"}));
     let mut pick = top_pick(&s, "Base");
     let before = s.doc.to_json();
     let error = s.execute("sketch.create", &json!({"plane":pick})).unwrap_err();