Gap 19: ODT export keeps replies to replies

Export wrote only the direct replies of a comment, so a reply to a reply
was lost on save. Every reply in a comment's thread is written now, each
answering the comment that starts the thread, as LibreOffice's threads
are flat. A reply chain that loops (hostile) is written once.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GBVQLyDnrG8Tn1yDQcUabC

crates/formats/src/model/from_doc.rs

@@ -139,12 +139,21 @@ fn rich_inlines(doc: &Document, o: &InlineObject, f: &Fmt, opts: FlowOpts) -> Op
             let endnote = *kind == wordcraft_doc::para::NoteKind::Endnote;
             vec![Inline::Note { endnote, custom: custom.clone(), blocks }]
         }
-        // The comment, then its replies, which have no place of their own.
+        // The comment, then the replies in its thread (replies to replies too, each answering the
+        // comment that starts the thread), which have no place of their own.
         InlineObject::CommentStart { id } if opts.comments => {
             let Some(c) = doc.comments.get(id) else { return Some(Vec::new()) };
             let mut out = vec![Inline::Comment { id: *id, comment: Box::new(flow_comment(doc, c, None, opts)) }];
-            for (rid, r) in doc.comments.iter().filter(|(_, r)| r.parent == Some(*id)) {
-                out.push(Inline::Comment { id: *rid, comment: Box::new(flow_comment(doc, r, Some(*id), opts)) });
+            let mut thread = std::collections::BTreeSet::from([*id]);
+            let mut k = 0;
+            while let Some(Inline::Comment { id: at, .. }) = out.get(k) {
+                let at = *at;
+                k += 1;
+                for (rid, r) in doc.comments.iter().filter(|(_, r)| r.parent == Some(at)) {
+                    if thread.insert(*rid) {
+                        out.push(Inline::Comment { id: *rid, comment: Box::new(flow_comment(doc, r, Some(*id), opts)) });
+                    }
+                }
             }
             out
         }

crates/formats/src/odt/tests_more/comments.rs

@@ -168,3 +168,20 @@ fn unmatched_and_hostile_comments_do_not_panic() {
         }
     }
 }
+
+#[test]
+fn a_reply_to_a_reply_is_kept() {
+    let xml = concat!(
+        r#"<text:p><office:annotation office:name="a"><dc:creator>A</dc:creator><text:p>Root</text:p></office:annotation>x<office:annotation-end office:name="a"/>"#,
+        r#"<office:annotation office:name="b" loext:parent-name="a"><dc:creator>B</dc:creator><text:p>Reply</text:p></office:annotation>"#,
+        r#"<office:annotation loext:parent-name="b"><dc:creator>C</dc:creator><text:p>Reply to reply</text:p></office:annotation></text:p>"#,
+    );
+    let d = import(&body(xml)).unwrap();
+    assert_eq!(d.comments.len(), 3);
+    // LibreOffice's threads are flat: every reply answers the comment that starts them.
+    let back = import(&export(&d).unwrap()).unwrap();
+    let got = comments(&back);
+    assert_eq!(got.len(), 3, "{got:?}");
+    assert_eq!(got[2].4.as_deref(), Some("Root"));
+    assert_eq!(got[2].5, "Reply to reply");
+}