From 74cbdf7e2ff6c4bde60c55466e6e3d46bbf25999 Mon Sep 17 00:00:00 2001
From: MarekSpodBiedry <73122968+MarekSpodBiedry@users.noreply.github.com>
Date: Sat, 10 Oct 2026 18:13:16 +0200
Subject: [PATCH] Keep selected objects outside the joined chain when using
 JOIN (#86) (#148)

---
 crates/engine/src/cmd/modify.rs        | 13 +++++++++++--
 crates/engine/src/cmd/modify2_tests.rs | 17 +++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/crates/engine/src/cmd/modify.rs b/crates/engine/src/cmd/modify.rs
index 600cea7..46874d1 100644
--- a/crates/engine/src/cmd/modify.rs
+++ b/crates/engine/src/cmd/modify.rs
@@ -1171,6 +1171,8 @@ fn run_breakat(s: &mut Session, p: &Value) -> Result<Value> {
 pub(crate) fn join(s: &mut Session, hs: &[Handle]) -> Result<Option<Handle>> {
     let d = s.doc()?;
     let mut segs: Vec<Segment> = Vec::new();
+    // Source entity of each segment in `segs`, so only entities that end up in the chain are removed.
+    let mut owners: Vec<Handle> = Vec::new();
     let mut common = None;
     for h in hs {
         let Some(e) = d.entity(*h) else { continue };
@@ -1181,12 +1183,14 @@ pub(crate) fn join(s: &mut Session, hs: &[Handle]) -> Result<Option<Handle>> {
             EntityKind::LwPolyline(p) if !p.closed => segs.extend(Polyline { vertices: p.vertices.clone(), closed: false }.segments()),
             _ => {}
         }
+        owners.resize(segs.len(), *h);
     }
     if segs.len() < 2 {
         return Err(EngineError::Other("Select at least two objects to join.".into()));
     }
     // Chain greedily from the first segment.
     let mut chain = vec![segs.remove(0)];
+    let mut used = vec![owners.remove(0)];
     let tol = 1e-6;
     loop {
         let start = chain.first().map(Segment::start).unwrap_or_default();
@@ -1197,6 +1201,7 @@ pub(crate) fn join(s: &mut Session, hs: &[Handle]) -> Result<Option<Handle>> {
             break;
         };
         let s0 = segs.remove(i);
+        used.push(owners.remove(i));
         if s0.start().near(end, tol) {
             chain.push(s0);
         } else if s0.end().near(end, tol) {
@@ -1227,7 +1232,7 @@ pub(crate) fn join(s: &mut Session, hs: &[Handle]) -> Result<Option<Handle>> {
     }
     let space = s.space();
     let doc = s.doc_mut()?;
-    for h in hs {
+    for h in hs.iter().filter(|h| used.contains(*h)) {
         doc.remove_entity(*h);
     }
     let nh = doc.new_handle();
@@ -1318,7 +1323,11 @@ impl SelectThen {
             }
             Op::Join => {
                 match join(s, &self.objs) {
-                    Ok(_) => s.echo(format!("{} objects joined into 1 polyline", self.objs.len())),
+                    Ok(_) => {
+                        // Objects outside the joined chain are kept, so count only the ones JOIN consumed.
+                        let n = s.doc().map(|d| self.objs.iter().filter(|h| d.entity(**h).is_none()).count()).unwrap_or(0);
+                        s.echo(format!("{n} objects joined into 1 polyline"))
+                    }
                     Err(e) => s.echo(e.to_string()),
                 }
                 Ok(Step::Done)
diff --git a/crates/engine/src/cmd/modify2_tests.rs b/crates/engine/src/cmd/modify2_tests.rs
index f7f547e..4746ac6 100644
--- a/crates/engine/src/cmd/modify2_tests.rs
+++ b/crates/engine/src/cmd/modify2_tests.rs
@@ -94,6 +94,23 @@ fn pedit_json_options() {
     assert!(s.execute("pedit", &json!({"handle": c, "option": "close"})).is_err());
 }
 
+#[test]
+fn join_keeps_selected_objects_outside_the_chain() {
+    let mut s = Session::new();
+    let a = h(&s.execute("line", &json!({"points": [[0, 0], [5, 0]]})).unwrap());
+    let b = h(&s.execute("line", &json!({"points": [[5, 0], [5, 5]]})).unwrap());
+    let far = h(&s.execute("line", &json!({"points": [[50, 50], [60, 60]]})).unwrap());
+    let c = h(&s.execute("circle", &json!({"center": [50, 50], "radius": 2})).unwrap());
+    let r = s.execute("join", &json!({"handles": [a, b, far, c]})).unwrap();
+    let joined = r["handle"].as_str().unwrap().to_string();
+    assert_eq!(poly(&kind(&s, &joined)).vertices.len(), 3);
+    let d = s.doc().unwrap();
+    assert!(d.entity(Handle::parse_hex(&a).unwrap()).is_none());
+    assert!(d.entity(Handle::parse_hex(&b).unwrap()).is_none());
+    assert!(d.entity(Handle::parse_hex(&far).unwrap()).is_some(), "unconnected line stays");
+    assert!(d.entity(Handle::parse_hex(&c).unwrap()).is_some(), "unrelated circle stays");
+}
+
 #[test]
 fn pedit_command_line() {
     let mut s = Session::new();