Integration: a comment listed through a reference chain keeps its replies after an edit (#4061)

crates/annot/src/lib.rs

@@ -2328,6 +2328,18 @@ pub fn is_comment_subtype(subtype: &str) -> bool {
     !matches!(subtype, "Link" | "Widget" | "Popup" | "Screen" | "Movie" | "RichMedia" | "3D" | "PrinterMark" | "TrapNet" | "Watermark")
 }
 
+/// Where a reference to a reference (`5 0 obj 6 0 R endobj`) ends, as `pdfcraft_render::inspect`
+/// follows it, within a few steps (a cycle stops there).
+fn final_ref(doc: &Document, mut r: ObjRef) -> ObjRef {
+    for _ in 0..8 {
+        match &*doc.get(r) {
+            Object::Ref(next) => r = *next,
+            _ => break,
+        }
+    }
+    r
+}
+
 /// Every comment (see [`is_comment_subtype`]), ordered by page and then top edge.
 pub fn summaries(doc: &Document) -> Vec<Summary> {
     let mut out = Vec::new();
@@ -2338,13 +2350,13 @@ pub fn summaries(doc: &Document) -> Vec<Summary> {
     for (page, list) in lists.iter().enumerate() {
         for (index, entry) in list.iter().enumerate() {
             if let Some(r) = entry.as_ref() {
-                slots.entry(r).or_insert((page, index));
+                slots.entry(final_ref(doc, r)).or_insert((page, index));
             }
         }
     }
     for (page, list) in lists.iter().enumerate() {
         for (index, entry) in list.iter().enumerate() {
-            let obj = doc.resolve(entry);
+            let obj = entry.as_ref().map_or_else(|| doc.resolve(entry), |r| doc.get(final_ref(doc, r)));
             let Some(d) = obj.as_dict() else { continue };
             let Some(subtype) = d.name(b"Subtype").map(|s| String::from_utf8_lossy(s).into_owned()) else { continue };
             if !is_comment_subtype(&subtype) {
@@ -2378,8 +2390,9 @@ pub fn summaries(doc: &Document) -> Vec<Summary> {
                 "PolyLine" | "Polygon" => nums(b"Vertices").as_chunks::<2>().0.to_vec(),
                 _ => Vec::new(),
             };
-            let in_reply_to = d.get(b"IRT").map(|o| doc.resolve(o)).and_then(|o| o.as_dict().cloned()).and_then(|p| text_value(doc, &p, b"NM"));
-            let parent = d.get(b"IRT").and_then(Object::as_ref).and_then(|r| slots.get(&r).copied());
+            let irt = d.get(b"IRT").map(|o| o.as_ref().map_or_else(|| doc.resolve(o), |r| doc.get(final_ref(doc, r))));
+            let in_reply_to = irt.and_then(|o| o.as_dict().cloned()).and_then(|p| text_value(doc, &p, b"NM"));
+            let parent = d.get(b"IRT").and_then(Object::as_ref).and_then(|r| slots.get(&final_ref(doc, r)).copied());
             out.push(Summary {
                 page,
                 index,

crates/engine/src/tests.rs

@@ -3839,6 +3839,37 @@ trailer << /Root 1 0 R >>
     check(&s, 2);
 }
 
+/// A comment listed through a reference chain (`/Annots [5 0 R]`, `5 0 obj 6 0 R`) keeps its
+/// replies after an edit, whether their `/IRT` names the comment or the chain, as on open.
+#[test]
+fn replies_thread_through_a_reference_chain_after_an_edit() {
+    let pdf = b"%PDF-1.7
+1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj
+2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj
+3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 300 200] /Annots [5 0 R 7 0 R 8 0 R 9 0 R] >> endobj
+5 0 obj 6 0 R endobj
+6 0 obj << /Type /Annot /Subtype /Text /Rect [20 140 40 160] /NM (one) /Contents (CHAINED) >> endobj
+7 0 obj << /Type /Annot /Subtype /Text /Rect [20 120 40 130] /IRT 6 0 R /Contents (TO THE COMMENT) >> endobj
+8 0 obj << /Type /Annot /Subtype /Text /Rect [20 100 40 110] /IRT 5 0 R /Contents (THROUGH THE CHAIN) >> endobj
+9 0 obj << /Type /Annot /Subtype /Text /Rect [20 60 40 80] /NM (two) /Contents (PLAIN) >> endobj
+trailer << /Root 1 0 R >>
+%%EOF";
+    let mut s = Session::new().with_clock(|| 1_700_000_000);
+    let id = s.open("chain.pdf", None, Arc::new(pdf.to_vec()), None).expect("opens");
+    let check = |s: &Session| {
+        let all = &s.get(id).unwrap().info.annotations;
+        let comment = all.iter().find(|a| a.contents.as_deref() == Some("CHAINED")).expect("listed");
+        assert_eq!((comment.page, comment.index, comment.is_reply()), (0, 0, false), "{all:?}");
+        for reply in ["TO THE COMMENT", "THROUGH THE CHAIN"] {
+            let a = all.iter().find(|a| a.contents.as_deref() == Some(reply)).expect("listed");
+            assert_eq!((a.parent, a.in_reply_to.as_deref()), (Some((0, 0)), Some("one")), "{reply}: {all:?}");
+        }
+    };
+    check(&s);
+    s.apply(id, Edit::ReplyToAnnotation { page: 0, index: 3, text: "LATER".into(), author: "Delta".into() }).unwrap();
+    check(&s);
+}
+
 /// #820: the generated summary includes replies to replies, indented one level deeper.
 #[test]
 fn comment_summary_includes_replies_to_replies() {