From 348d955a0ad669bd3dd12cb188a62b4e5fb14e59 Mon Sep 17 00:00:00 2001
From: wstock <1394687+wstock@users.noreply.github.com>
Date: Thu, 15 Oct 2026 06:57:38 +0000
Subject: [PATCH] Conditional formatting: text rules never match an error value
 (#1162)

In Excel the "contains", "begins with" and "ends with" rules are
SEARCH/LEFT/RIGHT formulas, which fail on an error value, so an error
cell is never formatted by them and always matches "does not contain".
GridCraft matched on the error's display text instead, so #N/A
"contained" a and "began with" #.

Skip error values in the three positive rules and match them in
notContainsText, with a regression test over =NA(), =1/0 and text cells.
---
 crates/engine/src/cf.rs | 40 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 36 insertions(+), 4 deletions(-)

diff --git a/crates/engine/src/cf.rs b/crates/engine/src/cf.rs
index b71ddb8ca..ea5b18ca9 100644
--- a/crates/engine/src/cf.rs
+++ b/crates/engine/src/cf.rs
@@ -147,10 +147,18 @@ impl CfCache {
                 CfRule::Expression { formula, style } => {
                     gridcraft_calc::evaluate(wb, sheet, c, &relative(formula, first, c)).to_bool().unwrap_or(false).then_some(style.as_ref())
                 }
-                CfRule::ContainsText { text: t, style } => text.to_lowercase().contains(&t.to_lowercase()).then_some(style.as_ref()),
-                CfRule::NotContainsText { text: t, style } => (!text.to_lowercase().contains(&t.to_lowercase())).then_some(style.as_ref()),
-                CfRule::BeginsWith { text: t, style } => text.to_lowercase().starts_with(&t.to_lowercase()).then_some(style.as_ref()),
-                CfRule::EndsWith { text: t, style } => text.to_lowercase().ends_with(&t.to_lowercase()).then_some(style.as_ref()),
+                // As in Excel, an error value never contains, begins or ends with anything (its rule
+                // formulas SEARCH/LEFT/RIGHT fail on it), so it always "does not contain" (#1162).
+                CfRule::ContainsText { text: t, style } => {
+                    (!v.is_error() && text.to_lowercase().contains(&t.to_lowercase())).then_some(style.as_ref())
+                }
+                CfRule::NotContainsText { text: t, style } => {
+                    (v.is_error() || !text.to_lowercase().contains(&t.to_lowercase())).then_some(style.as_ref())
+                }
+                CfRule::BeginsWith { text: t, style } => {
+                    (!v.is_error() && text.to_lowercase().starts_with(&t.to_lowercase())).then_some(style.as_ref())
+                }
+                CfRule::EndsWith { text: t, style } => (!v.is_error() && text.to_lowercase().ends_with(&t.to_lowercase())).then_some(style.as_ref()),
                 CfRule::Blanks { style } => (v.is_empty() || text.trim().is_empty()).then_some(style.as_ref()),
                 CfRule::NoBlanks { style } => (!v.is_empty() && !text.trim().is_empty()).then_some(style.as_ref()),
                 CfRule::Errors { style } => v.is_error().then_some(style.as_ref()),
@@ -410,4 +418,28 @@ mod tests {
         let mut look = |a: &str| cache.look(&d.wb, 0, CellRef::parse(a).unwrap()).and_then(|l| l.style).is_some();
         assert_eq!([look("A1"), look("A2")], [true, false]);
     }
+
+    #[test]
+    fn text_rules_skip_error_values() {
+        let mut s = crate::Session::new();
+        s.new_workbook();
+        let values = json!([["=NA()", "=NA()", "=1/0", "=NA()"], ["abc", "#x", "x!", "abc"], ["xyz", "y", "y", "xyz"]]);
+        s.execute("range.setValues", json!({"range": "A1", "values": values})).unwrap();
+        let rule = |range: &str, kind: &str, text: &str| json!({"range": range, "rule": {"type": kind, "text": text, "preset": "lightRedFill"}});
+        s.execute("home.conditionalFormat", rule("A1:A3", "containsText", "a")).unwrap();
+        s.execute("home.conditionalFormat", rule("B1:B3", "beginsWith", "#")).unwrap();
+        s.execute("home.conditionalFormat", rule("C1:C3", "endsWith", "!")).unwrap();
+        s.execute("home.conditionalFormat", rule("D1:D3", "notContainsText", "a")).unwrap();
+        let d = s.doc().unwrap();
+        let mut cache = CfCache::new();
+        let mut look = |a: &str| cache.look(&d.wb, 0, CellRef::parse(a).unwrap()).and_then(|l| l.style).is_some();
+        // Contains "a": abc, never #N/A although its text holds an "a".
+        assert_eq!([look("A1"), look("A2"), look("A3")], [false, true, false]);
+        // Begins with "#": #x, never #N/A.
+        assert_eq!([look("B1"), look("B2"), look("B3")], [false, true, false]);
+        // Ends with "!": x!, never #DIV/0!.
+        assert_eq!([look("C1"), look("C2"), look("C3")], [false, true, false]);
+        // Does not contain "a": #N/A and xyz, not abc.
+        assert_eq!([look("D1"), look("D2"), look("D3")], [true, false, true]);
+    }
 }