From 48910d71d295322b3ec6ee0ff749d0b0272d2471 Mon Sep 17 00:00:00 2001
From: nihilist-narwhal <240798405+nihilist-narwhal@users.noreply.github.com>
Date: Sat, 10 Oct 2026 04:24:41 -0500
Subject: [PATCH] Recalc: replacing or clearing a spilling formula removes its
 spill

Typing a value over a dynamic array formula, or clearing it, left the
values it had spilled: with =SEQUENCE(3) in A1, typing 2 into A1 kept
2 and 3 in A2:A3, and =SUM(A1:A3) gave 7. Only formulas are evaluated
again, so the old spill of a cell that no longer holds a formula was
never written back. It is now removed when the formula goes, and the
formulas reading its area are recalculated.
---
 crates/calc/src/recalc.rs  | 13 +++++++++++++
 crates/engine/src/tests.rs | 12 ++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/crates/calc/src/recalc.rs b/crates/calc/src/recalc.rs
index 13b47c41c..584339534 100644
--- a/crates/calc/src/recalc.rs
+++ b/crates/calc/src/recalc.rs
@@ -351,6 +351,7 @@ impl Calc {
 
     /// Updates the graph for cells whose content changed and recalculates what depends on them.
     pub fn cells_changed(&mut self, wb: &mut Workbook, changed: &[Key]) {
+        let mut cleared: Vec<(usize, RangeRef)> = Vec::new();
         for &k in changed {
             let formula = wb.sheet(k.0).and_then(|s| s.cell(k.1)).and_then(|c| c.formula.clone());
             match formula.and_then(|f| f.expr()) {
@@ -360,6 +361,15 @@ impl Calc {
                 }
                 None => {
                     self.graph.remove(k);
+                    // A formula replaced by a constant (or cleared) takes its spilled values with it.
+                    if let Some(sh) = wb.sheet_mut(k.0)
+                        && let Some(r) = sh.spill_ranges.remove(&k.1)
+                    {
+                        for c in r.iter() {
+                            sh.spill.remove(&c);
+                        }
+                        cleared.push((k.0, r));
+                    }
                     // A formula that doesn't parse evaluates to #NAME?.
                     if let Some(cell) = wb.sheet_mut(k.0).and_then(|s| s.cells.get_mut(k.1))
                         && cell.formula.is_some()
@@ -398,6 +408,9 @@ impl Calc {
                 seeds.extend(r.iter().take(65536).map(|c| (k.0, c)));
             }
         }
+        for (si, r) in &cleared {
+            seeds.extend(r.iter().take(65536).map(|c| (*si, c)));
+        }
         let t0 = prof_now();
         let dirty = self.dirty_closure(wb, &seeds);
         let t1 = prof_now();
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
index f3e36cdf4..361fbce48 100644
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -153,6 +153,18 @@ fn samples_build() {
     }
 }
 
+#[test]
+fn replacing_a_spilling_formula_clears_its_spill() {
+    let mut s = s();
+    s.execute("cell.set", json!({"cell": "A1", "input": "=SEQUENCE(3)"})).unwrap();
+    s.execute("cell.set", json!({"cell": "B1", "input": "=SUM(A1:A3)"})).unwrap();
+    s.execute("cell.set", json!({"cell": "A1", "input": "2"})).unwrap();
+    assert_eq!((v(&s, "A2"), v(&s, "A3"), v(&s, "B1")), (Value::Empty, Value::Empty, Value::Number(2.0)));
+    s.execute("cell.set", json!({"cell": "A1", "input": "=SEQUENCE(3)"})).unwrap();
+    s.execute("edit.clearContents", json!({"range": "A1"})).unwrap();
+    assert_eq!((v(&s, "A2"), v(&s, "B1")), (Value::Empty, Value::Number(0.0)));
+}
+
 #[test]
 fn every_command_survives_empty_params() {
     let mut s = Session::new();