Merge pull request #5303 from storytold/fix/sec-thread-reflow-unique-frames

Threaded text: a frame listed twice flows the story once

crates/engine/src/cmd/threads.rs

@@ -93,7 +93,12 @@ thread_local! {
 /// makes "changed" a pointer comparison). Deleted frames' text flows into the remaining ones; a
 /// frame that is now point type leaves its thread with the text it holds.
 pub(crate) fn reflow(before: &Document, doc: &mut Document) {
-    let threads = std::mem::take(&mut doc.text_threads);
+    // A frame is in one thread, once: a file that lists it again (in its thread or another) would
+    // copy its text into the story each time, and write the grown story back for the next thread
+    // to copy again. Only its first place counts.
+    let mut seen = std::collections::HashSet::new();
+    let threads: Vec<Vec<NodeId>> =
+        std::mem::take(&mut doc.text_threads).into_iter().map(|t| t.into_iter().filter(|id| seen.insert(*id)).collect()).collect();
     let mut kept = vec![];
     for thread in threads {
         let changed = thread.iter().any(|id| match (before.node(*id), doc.node(*id)) {

crates/engine/src/cmd/threads/tests.rs

@@ -40,6 +40,24 @@ fn thread_flows_reflows_on_edit_and_survives_delete() {
     assert_eq!(s.doc().unwrap().doc.text_threads.len(), 1);
 }
 
+/// A file that lists a frame more than once, in its own thread or in another, flows the story
+/// through each frame once: repeated places would copy its text again and again.
+#[test]
+fn frames_listed_twice_flow_the_story_once() {
+    let (mut s, a, b) = setup();
+    s.execute("text.thread.create", &json!({})).unwrap();
+    let mut d = (*s.doc().unwrap().doc).clone();
+    let (fa, fb) = (NodeId(a), NodeId(b));
+    d.text_threads = vec![vec![fa, fb, fa, fb, fa], vec![fb, fa], vec![fa, fb]];
+    reflow(&Document::new(1.0, 1.0), &mut d);
+    assert_eq!(d.text_threads, vec![vec![fa, fb]]);
+    let plain = |id: NodeId| match &d.node(id).unwrap().kind {
+        NodeKind::Text(t) => t.plain_text(),
+        _ => panic!("not text"),
+    };
+    assert_eq!(format!("{}{}", plain(fa), plain(fb)), TEXT.repeat(4));
+}
+
 #[test]
 fn edits_copy_only_the_stories_of_threads_whose_frames_changed() {
     let (mut s, a, b) = setup();