Protection: keep hidden formulas hidden

On a protected sheet a formula formatted Hidden still showed with Show
Formulas on, matched Find in formulas, and showed in the formula bar
when a cell of its spill range was selected.

crates/engine/src/cmd/edit.rs

@@ -1175,7 +1175,11 @@ fn find(s: &mut Session, p: &Json) -> Result<Json> {
             .cells
             .iter()
             .filter_map(|(c, cell)| {
-                let text = if values || cell.formula.is_none() { crate::display::cell_text(&d.wb, sh, c) } else { cell.input_text() };
+                let text = if values || cell.formula.is_none() || crate::display::formula_hidden(&d.wb, sh, c) {
+                    crate::display::cell_text(&d.wb, sh, c)
+                } else {
+                    cell.input_text()
+                };
                 matches(&text, &what, case, whole).then_some((c, text))
             })
             .collect();

crates/engine/src/display.rs

@@ -31,11 +31,28 @@ pub fn format(v: &Value, code: &str, wb: &Workbook) -> Formatted {
     format_value(v, &parsed(code), wb.date_system)
 }
 
+/// Whether `c` has a formula that must not be shown: its cell is formatted Hidden on a
+/// protected sheet. A spilled cell follows its anchor.
+pub fn formula_hidden(wb: &Workbook, sheet: &Sheet, c: CellRef) -> bool {
+    if !sheet.is_protected() {
+        return false;
+    }
+    let at = match sheet.cell(c) {
+        Some(x) if x.formula.is_some() => c,
+        _ => match sheet.spill_ranges.iter().find(|(_, r)| r.contains(c)) {
+            Some((anchor, _)) => *anchor,
+            None => return false,
+        },
+    };
+    wb.styles.get(sheet.style_id(at)).protection.hidden
+}
+
 /// The text a cell shows (full precision General; the grid narrows General to fit the column).
 pub fn cell_text(wb: &Workbook, sheet: &Sheet, c: CellRef) -> String {
     let v = sheet.value(c);
     if sheet.show_formulas
         && let Some(f) = sheet.cell(c).and_then(|x| x.formula.as_ref())
+        && !formula_hidden(wb, sheet, c)
     {
         return format!("={}", f.text);
     }

crates/engine/src/tests.rs

@@ -165,6 +165,32 @@ fn protection_allows_permitted_row_and_column_edits() {
     assert!(s.execute("home.deleteColumns", json!({"cols": "Z:Z"})).is_err());
 }
 
+#[test]
+fn hidden_formulas_stay_hidden_on_protected_sheets() {
+    let mut s = s();
+    s.execute("cell.set", json!({"cell": "A1", "input": "=SEQUENCE(3)*7"})).unwrap();
+    s.execute("cell.set", json!({"cell": "B1", "input": "=1+1"})).unwrap();
+    s.execute("home.formatCells", json!({"range": "A1", "style": {"protection": {"locked": true, "hidden": true}}})).unwrap();
+    s.execute("formulas.showFormulas", json!({"on": true})).unwrap();
+    let text = |s: &Session, a: &str| {
+        let d = s.doc().unwrap();
+        let sh = d.wb.active().unwrap();
+        crate::display::cell_text(&d.wb, sh, CellRef::parse(a).unwrap())
+    };
+    assert_eq!(text(&s, "A1"), "=SEQUENCE(3)*7");
+    assert_eq!(s.execute("edit.find", json!({"what": "SEQUENCE", "all": true})).unwrap()["count"], 1);
+    s.execute("review.protectSheet", json!({})).unwrap();
+    assert_eq!(text(&s, "A1"), "7");
+    assert_eq!(text(&s, "B1"), "=1+1");
+    let d = s.doc().unwrap();
+    let sh = d.wb.active().unwrap();
+    assert!(crate::display::formula_hidden(&d.wb, sh, CellRef::parse("A2").unwrap()));
+    assert!(!crate::display::formula_hidden(&d.wb, sh, CellRef::parse("B1").unwrap()));
+    assert!(s.execute("edit.find", json!({"what": "SEQUENCE", "all": true})).is_err());
+    let r = s.execute("edit.find", json!({"what": "7", "all": true})).unwrap();
+    assert_eq!(r["results"][0]["value"], "7");
+}
+
 #[test]
 fn formatting_and_styles() {
     let mut s = s();

crates/ui-egui/src/formula_bar.rs

@@ -77,6 +77,9 @@ fn active_input(app: &SheetApp) -> String {
         if r.contains(a)
             && let Some(f) = sh.cell(*anchor).and_then(|c| c.formula.as_ref())
         {
+            if gridcraft_engine::display::formula_hidden(&d.wb, sh, *anchor) {
+                return String::new();
+            }
             return format!("={}", f.text);
         }
     }