Split Face (FusionSplitFaceCommand): a timeline feature dividing the picked faces where a plane, another body's face (its surface extended) or a sketch's curves meet them, through kernel::split_faces; the solid is unchanged and the pieces take the face's name with #k. Rebase fixes: duplicate Chamfer and Combine specs; the Delete selection's face test expects Delete Face's refusal

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/engine/src/split_face_tests.rs

@@ -0,0 +1,64 @@
+//! Split Face: the top of a box divided by a plane, by another body's face and by sketch curves.
+
+use serde_json::{Value, json};
+
+use crate::Session;
+
+fn run(s: &mut Session, id: &str, p: Value) -> Value {
+    match s.execute(id, &p) {
+        Ok(v) => v,
+        Err(e) => panic!("{id} {p}: {e}"),
+    }
+}
+
+/// (kernel faces, volume) of a body: the merged count joins pieces of one surface back up.
+fn faces_volume(s: &mut Session, b: &str) -> (u64, f64) {
+    let m = run(s, "inspect.measure", json!({ "bodies": [b] }))["bodies"][0].clone();
+    (m["kernel"]["faces"].as_u64().unwrap_or(0), m["volume_mm3"].as_f64().unwrap_or(0.0))
+}
+
+fn boxed() -> Session {
+    let mut s = Session::default();
+    run(&mut s, "solid.box", json!({"length": 40, "width": 30, "height": 20, "body_name": "B"}));
+    s
+}
+
+#[test]
+fn split_a_face_by_a_plane() {
+    let mut s = boxed();
+    run(&mut s, "solid.split_face", json!({"faces": [[10, 15, 20]], "plane": {"origin": [20, 0, 0], "normal": [1, 0, 0]}}));
+    let (f, v) = faces_volume(&mut s, "B");
+    assert_eq!(f, 7);
+    assert!((v - 24000.0).abs() < 1e-6 * 24000.0, "{v}");
+    assert_eq!(s.doc.features.last().unwrap().kind.type_name(), "SplitFaceFeature");
+}
+
+#[test]
+fn split_a_face_by_another_bodys_face() {
+    let mut s = boxed();
+    run(&mut s, "solid.box", json!({"corner": [-5, 10, 25], "length": 50, "width": 5, "height": 5, "body_name": "Tool"}));
+    // The tool's face at y = 10, extended down through the box's top.
+    run(&mut s, "solid.split_face", json!({"faces": [[20, 5, 20]], "body": "B", "tool": {"body": "Tool", "point": [20, 10, 27]}}));
+    assert_eq!(faces_volume(&mut s, "B").0, 7);
+}
+
+#[test]
+fn split_a_face_by_sketch_curves() {
+    let mut s = boxed();
+    run(&mut s, "sketch.create", json!({"plane": "XY", "name": "Cuts"}));
+    run(&mut s, "sketch.line", json!({"points": [[10, -5], [10, 35]]}));
+    run(&mut s, "sketch.line", json!({"points": [[30, -5], [30, 35]]}));
+    run(&mut s, "sketch.finish", json!({}));
+    run(&mut s, "solid.split_face", json!({"faces": [[20, 15, 20]], "body": "B", "sketch": "Cuts"}));
+    let (f, v) = faces_volume(&mut s, "B");
+    assert_eq!(f, 8, "two lines make three pieces of the top");
+    assert!((v - 24000.0).abs() < 1e-6 * 24000.0, "{v}");
+}
+
+#[test]
+fn a_tool_that_misses_is_refused() {
+    let mut s = boxed();
+    let n = s.doc.features.len();
+    assert!(s.execute("solid.split_face", &json!({"faces": [[10, 15, 20]], "plane": {"origin": [100, 0, 0], "normal": [1, 0, 0]}})).is_err());
+    assert_eq!(s.doc.features.len(), n);
+}