From d713a2da0b68e67ab243dfc859f330cd6a4812e7 Mon Sep 17 00:00:00 2001
From: "Dylan M. Taylor" <dylan@dylanmtaylor.com>
Date: Wed, 4 Nov 2026 01:02:19 +0000
Subject: [PATCH] address review: keep the cached value of a follower dropped
 for the shared-formula copy limit inside array ranges

---
 crates/xlsx/src/sheet_read.rs      |  7 ++++++-
 crates/xlsx/src/tests/malformed.rs | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/crates/xlsx/src/sheet_read.rs b/crates/xlsx/src/sheet_read.rs
index 5b2ffe61f..ed176bd5e 100644
--- a/crates/xlsx/src/sheet_read.rs
+++ b/crates/xlsx/src/sheet_read.rs
@@ -47,6 +47,9 @@ struct RowState {
     /// Bytes of unparsable shared-master text copied into follower cells so far: each follower
     /// keeps its own copy, so a long master and many followers must stay bounded together.
     shared_fallback_bytes: u64,
+    /// The cell being read lost its shared formula to the copy limit above: its cached value is
+    /// kept, even inside an array range (where a formula's cached values otherwise give way to it).
+    shared_copy_refused: bool,
     dropped: u64,
     rows: u64,
 }
@@ -575,6 +578,7 @@ fn read_cell(cx: &mut Ctx<'_>, sheet: &mut Sheet, st: &mut RowState, c: &El, pos
         return;
     }
     let dynamic = c.attr("cm").is_some();
+    st.shared_copy_refused = false;
     let formula = c.child("f").and_then(|f| read_formula(cx, st, f, pos, dynamic));
     // A `PY(index,0|1)` formula is a Python cell whose code is a script of the Python part. The
     // older `PY("…",0|1)` form is read from the formula's own text: the formula parser would fold
@@ -595,7 +599,7 @@ fn read_cell(cx: &mut Ctx<'_>, sheet: &mut Sheet, st: &mut RowState, c: &El, pos
     if py.is_some() {
         record_python_spill(st, sheet, pos);
     }
-    let spilled_from = if formula.is_none() && py.is_none() { dynamic_range(st, pos) } else { None };
+    let spilled_from = if formula.is_none() && py.is_none() && !st.shared_copy_refused { dynamic_range(st, pos) } else { None };
     let python_anchor = spilled_from.is_some_and(|r| sheet.cells.get(r.start).is_some_and(|a| a.py.is_some()));
     let value = match spilled_from {
         // A Python cell's spilled values are kept: they are its result until it runs again.
@@ -652,6 +656,7 @@ fn read_formula_text(cx: &mut Ctx<'_>, st: &mut RowState, f: &El, pos: CellRef,
                         let total = st.shared_fallback_bytes.saturating_add(sh.text.len() as u64);
                         if total > MAX_SHARED_FALLBACK_BYTES {
                             cx.warn("some shared formulas could not be parsed and exceed the copy limit; those cells kept their cached values");
+                            st.shared_copy_refused = true;
                             return None;
                         }
                         st.shared_fallback_bytes = total;
diff --git a/crates/xlsx/src/tests/malformed.rs b/crates/xlsx/src/tests/malformed.rs
index 0d232187a..c104de6eb 100644
--- a/crates/xlsx/src/tests/malformed.rs
+++ b/crates/xlsx/src/tests/malformed.rs
@@ -274,6 +274,24 @@ fn unparsable_shared_master_copies_stay_bounded() {
     assert!(rep.warnings.iter().any(|w| w.contains("exceed the copy limit")), "{:?}", rep.warnings);
 }
 
+/// A follower dropped for the copy limit keeps its cached value even where an array range covers it.
+#[test]
+fn followers_past_the_copy_limit_keep_their_values_inside_array_ranges() {
+    let master = format!("1{}", "+1".repeat(40_000));
+    let mut rows = format!(
+        r#"<row r="1"><c r="B1"><f t="array" ref="B1:C2000">1</f><v>1</v></c><c r="C1"><f t="shared" ref="C1:C2000" si="0">{master}</f><v>1</v></c></row>"#
+    );
+    for r in 2..=2000 {
+        rows.push_str(&format!(r#"<row r="{r}"><c r="C{r}"><f t="shared" si="0"/><v>{r}</v></c></row>"#));
+    }
+    let (wb, rep) = read_xlsx(&minimal(&format!("<sheetData>{rows}</sheetData>"), &[], "", "")).unwrap();
+    let s = wb.sheet(0).unwrap();
+    let last = gridcraft_core::CellRef::new(1999, 2);
+    assert!(s.cell(last).is_some_and(|c| c.formula.is_none()), "the limit was reached");
+    assert_eq!(s.value(last), gridcraft_core::Value::Number(2000.0));
+    assert!(rep.warnings.iter().any(|w| w.contains("exceed the copy limit")), "{:?}", rep.warnings);
+}
+
 /// Formula text built to overflow a recursive parser or tree walk (a million `%`, a 200,000-term
 /// sum): the cells keep their formula text and cached value, nothing overflows the stack.
 #[test]