Booleans are deterministic: result faces keep their shell's order

truck's connected components came out in hash order of face addresses, so a
boolean's faces, and everything built on them (fillet bands, STEP entity
order), changed from run to run. That made the oracle 35 export differ run to
run. Its old step_export flakes came from the orientation check's drifting
search, removed in 2db9e66. The result's shells and faces now keep the
order of the shell they come from (vendored truck-shapeops). Oracle results
are unchanged (73 PASS before and after). Test: the tee of oracle 35 with its
junction fillet exports byte-identical three times in one process (it failed
before).

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

crates/kernel/src/step_in/tests.rs

@@ -484,3 +484,21 @@ fn horn_torus_written_as_one_spline_face() {
     let v = std::f64::consts::PI * 25.0 * std::f64::consts::TAU * 5.0 / 4.0;
     assert!(rel(measure(&imp.bodies[0].body).unwrap().volume, v) < 1e-3);
 }
+
+/// Booleans and blends build the same body every time, so an export is byte-identical from
+/// run to run (truck used to emit a boolean's faces in hash order of their addresses). The
+/// tee of oracle 35 with its rolling-ball fillet round the junction.
+#[test]
+fn tee_fillet_exports_byte_identical() {
+    let main = cylinder(Vec3::new(-40.0, 0.0, 0.0), Vec3::X, 15.0, 80.0).unwrap();
+    let branch = cylinder(Vec3::ZERO, Vec3::Z, 10.0, 35.0).unwrap();
+    let export = || {
+        let tee = boolean(&main, &branch, BoolOp::Union).unwrap().unwrap();
+        let f = fillet(&tee, &[Vec3::new(0.0, 10.0, 125f64.sqrt())], 3.0).unwrap();
+        step_export(&[&f], "tee").unwrap()
+    };
+    let first = export();
+    for _ in 0..2 {
+        assert!(export() == first, "export differs between runs");
+    }
+}

vendor/README.md

@@ -11,6 +11,9 @@ Changes:
   earlier booleans have boundaries that lie on their surface only within tolerance).
 - `transversal/divide_face/mod.rs`: when projecting a loop onto a face's surface, fall back to
   the nearest parameter when the exact search fails (intersection curves are approximations).
+- `transversal/integrate/mod.rs`: the result's shells and faces keep the order of the shell
+  they come from (truck's connected components followed hash order of face addresses, so a
+  boolean's faces came out in a different order on every run).
 - `lib.rs`: `tr!` reports where an operation gives up when `SHAPEOPS_TRACE` is set; compiler
   warnings no longer fail the build.
 

vendor/truck-shapeops/src/transversal/integrate/mod.rs

@@ -120,7 +120,7 @@ pub fn and<C: ShapeOpsCurve<S>, S: ShapeOpsSurface>(
         let [res, _] = process_one_pair_of_shells(&and_shell, shell, tol)?;
         and_shell = res;
     }
-    let boundaries = and_shell.connected_components();
+    let boundaries = components_in_order(&and_shell);
     Some(Solid::new(boundaries))
 }
 
@@ -143,9 +143,27 @@ pub fn or<C: ShapeOpsCurve<S>, S: ShapeOpsSurface>(
         let [_, res] = process_one_pair_of_shells(&or_shell, shell, tol)?;
         or_shell = res;
     }
-    let boundaries = or_shell.connected_components();
+    let boundaries = components_in_order(&or_shell);
     Some(Solid::new(boundaries))
 }
 
+// SolveCraft: truck's connected components come out in hash order of face addresses, so the
+// result's face order changed from run to run. Keep the shell's own order instead.
+fn components_in_order<C, S>(shell: &Shell<Point3, C, S>) -> Vec<Shell<Point3, C, S>> {
+    let pos: rustc_hash::FxHashMap<_, usize> = shell.face_iter().enumerate().map(|(i, f)| (f.id(), i)).collect();
+    let key = |f: &Face<Point3, C, S>| pos.get(&f.id()).copied().unwrap_or(usize::MAX);
+    let mut comps: Vec<Vec<Face<Point3, C, S>>> = shell
+        .connected_components()
+        .into_iter()
+        .map(|c| {
+            let mut faces: Vec<_> = c.into_iter().collect();
+            faces.sort_by_key(|f| key(f));
+            faces
+        })
+        .collect();
+    comps.sort_by_key(|c| c.first().map(|f| key(f)).unwrap_or(usize::MAX));
+    comps.into_iter().map(Shell::from).collect()
+}
+
 #[cfg(test)]
 mod tests;