Merge remote-tracking branch 'origin/main' into pr-5373

# Conflicts:
#	ROADMAP.md
#	docs/gaps.md

crates/docbin/src/lib.rs

@@ -364,6 +364,11 @@ pub fn read_with_password(bytes: &[u8], password: Option<&str>) -> Result<Docume
     // Sections: each section's properties attach to the paragraph that ends it (its story of
     // header/footer parts included); the section reaching the end of the text is the final one.
     let mut paras = walk(&ctx, 0, fib.ccp.text, &mut pics);
+    // The first paragraph ending at each CP, found once rather than by a scan per section.
+    let mut ending: std::collections::HashMap<u32, usize> = std::collections::HashMap::new();
+    for (i, p) in paras.iter().enumerate() {
+        ending.entry(p.end_cp).or_insert(i);
+    }
     let last = sects.last().map(|s| s.props.clone());
     for (si, sec) in sects.iter().enumerate() {
         let mut props = sec.props.clone();
@@ -374,11 +379,8 @@ pub fn read_with_password(bytes: &[u8], password: Option<&str>) -> Result<Docume
         if is_final {
             continue; // handled below through `last`
         }
-        for p in paras.iter_mut() {
-            if p.end_cp == sec.end_cp {
-                p.para.section = Some(Box::new(props));
-                break;
-            }
+        if let Some(p) = ending.get(&sec.end_cp).and_then(|&i| paras.get_mut(i)) {
+            p.para.section = Some(Box::new(props));
         }
     }
     if let Some(mut l) = last {

crates/docbin/src/tests.rs

@@ -1018,6 +1018,32 @@ fn two_sections_box_the_first() {
     assert!(!doc.last_section.title_page);
 }
 
+#[test]
+fn sections_ending_off_a_paragraph_mark_attach_nowhere() {
+    // Hostile section ends that miss every paragraph mark are skipped; the one that ends a
+    // paragraph still boxes it. Paragraphs are found by their end, not scanned per section.
+    let mut sections: Vec<(u32, Vec<u8>)> = (1..6).map(|cp| (cp, Vec::new())).collect();
+    sections.push((6, grpprl(&[(0x300A, &[0x01])])));
+    sections.push((12, Vec::new()));
+    let spec = StructSpec {
+        text: "first\rsecond\r",
+        header_stories: vec![],
+        sections,
+        chpx_runs: vec![(0, Vec::new())],
+        papx_entries: vec![(0, 0, Vec::new()), (6, 0, Vec::new())],
+        plf_lst: Vec::new(),
+        plf_lfo: Vec::new(),
+        note_stories: vec![],
+        endnote_stories: vec![],
+        extra_pairs: Vec::new(),
+        data_stream: Vec::new(),
+    };
+    let doc = read(&struct_doc(&spec)).expect("opens");
+    let paras: Vec<_> = doc.body.iter().filter_map(|b| b.as_para()).collect();
+    assert!(paras.first().and_then(|p| p.section.as_ref()).expect("first paragraph boxed").title_page);
+    assert_eq!(paras.iter().filter(|p| p.section.is_some()).count(), 1, "the missing ends attach nowhere");
+}
+
 #[test]
 fn header_story_becomes_part() {
     let spec = StructSpec {