From 342f4b401d0cb21bea2de64c089032a8922a4bc7 Mon Sep 17 00:00:00 2001
From: ljkx <177671075+ljkx@users.noreply.github.com>
Date: Tue, 3 Nov 2026 04:26:30 +0100
Subject: [PATCH] Check list validation against the list before the entry

A source that takes in the cell being checked (=$A1:$A2 on A2:A3 is A2:A3 at A3) listed the value being typed, so any new value passed. The list is now read from the workbook as it was before the entry, as in Excel.
---
 crates/engine/src/cmd/data/tests.rs      | 20 ++++++++++++++++++++
 crates/engine/src/cmd/data/validation.rs |  5 ++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/crates/engine/src/cmd/data/tests.rs b/crates/engine/src/cmd/data/tests.rs
index 3bca70a87..3c2782444 100644
--- a/crates/engine/src/cmd/data/tests.rs
+++ b/crates/engine/src/cmd/data/tests.rs
@@ -499,6 +499,26 @@ fn a_relative_list_source_is_read_from_the_cell_being_checked() {
     }
 }
 
+#[test]
+fn a_list_source_that_takes_in_the_cell_does_not_list_the_value_being_typed() {
+    // `=$A1:$A2` on A2:A3 is A1:A2 at A2 and A2:A3 at A3. The list is the one before the entry, as
+    // in Excel; a new value used to land in its own source and pass.
+    let mut s = Session::new();
+    s.new_workbook();
+    s.execute("range.setValues", json!({"range": "A1:A2", "values": [["x"], ["y"]]})).unwrap();
+    s.execute("data.validation", json!({"range": "A2:A3", "type": "list", "formula1": "=$A1:$A2"})).unwrap();
+    let wb = &s.doc().unwrap().wb;
+    for (cell, accepted, refused) in [("A2", &["x", "y"][..], &["new"][..]), ("A3", &["y"], &["x", "new"])] {
+        let at = CellRef::parse(cell).unwrap();
+        for v in accepted {
+            assert!(check_validation(wb, 0, at, v).is_none(), "{cell} refuses {v}");
+        }
+        for v in refused {
+            assert!(check_validation(wb, 0, at, v).is_some(), "{cell} accepts {v}");
+        }
+    }
+}
+
 #[test]
 fn a_rule_with_an_unknown_type_operator_or_error_style_is_refused() {
     // A typo used to give a rule that validates nothing (`type="none"`) or the wrong check,
diff --git a/crates/engine/src/cmd/data/validation.rs b/crates/engine/src/cmd/data/validation.rs
index 71b3b2190..2217a372a 100644
--- a/crates/engine/src/cmd/data/validation.rs
+++ b/crates/engine/src/cmd/data/validation.rs
@@ -187,6 +187,7 @@ pub fn check_validation(wb: &Workbook, sheet: usize, at: CellRef, input: &str) -
     // The formulas are written for the top-left cell of all the areas and see the value being entered,
     // as in Excel (a custom `=A1>10` on A1:A9 checks A5's new value at A5).
     let first = RangeRef::top_left(&dv.ranges).unwrap_or(at);
+    let original = wb;
     let entered;
     let wb = if sh.value(at) == v {
         wb
@@ -202,7 +203,9 @@ pub fn check_validation(wb: &Workbook, sheet: usize, at: CellRef, input: &str) -
     let eval = |f: &str| gridcraft_calc::evaluate(wb, sheet, at, &formula_at(f, first, at));
     let num = |f: &str| eval(f).to_number().ok();
     let ok = match dv.kind {
-        ValidationKind::List => list_items(wb, sheet, at, dv).iter().any(|x| x.eq_ignore_ascii_case(input)),
+        // The list is the one the dropdown showed before the entry, as in Excel: a source that takes
+        // in the cell itself (`=$A1:$A2` on A2:A3 is A2:A3 at A3) doesn't list the value being typed.
+        ValidationKind::List => list_items(original, sheet, at, dv).iter().any(|x| x.eq_ignore_ascii_case(input)),
         ValidationKind::Custom => eval(&dv.f1).to_bool().unwrap_or(false),
         ValidationKind::TextLength => {
             let n = input.chars().count() as f64;