feat(engine): open a saved workbook without recalculating it

DocState::new recalculates the whole workbook, so values saved in the file
change where nothing was edited (volatile functions, functions GridCraft
lacks, cycles). DocState::from_saved builds the dependency graph without
evaluating, so every value stays the file's until an edit reaches it.

crates/engine/src/lib.rs

@@ -266,6 +266,17 @@ impl DocState {
     pub fn new(mut wb: Workbook, path: Option<String>, title: String, trust: Trust) -> DocState {
         let mut calc = Calc::new();
         calc.recalc_all(&mut wb);
+        Self::with_calc(wb, calc, path, title, trust)
+    }
+    /// A workbook as its file saved it: the dependency graph is built but nothing is
+    /// evaluated, so every value is the one the file holds until an edit reaches it. `trust`
+    /// is as for [`DocState::new`].
+    pub fn from_saved(wb: Workbook, path: Option<String>, title: String, trust: Trust) -> DocState {
+        let mut calc = Calc::new();
+        calc.rebuild(&wb);
+        Self::with_calc(wb, calc, path, title, trust)
+    }
+    fn with_calc(wb: Workbook, calc: Calc, path: Option<String>, title: String, trust: Trust) -> DocState {
         let scripts_trusted = !cmd::extra::has_scripts(&wb);
         let wb = Arc::new(wb);
         let sel = Selection::at(wb.active().map(|s| s.view_active).unwrap_or_default());

crates/engine/src/tests.rs

@@ -4661,3 +4661,26 @@ fn a_script_cannot_switch_windows() {
 }
 
 mod seams;
+
+#[test]
+fn a_saved_workbook_keeps_its_values_until_an_edit_reaches_them() {
+    let mut s = s();
+    s.execute("cell.set", json!({"cell": "A1", "input": "2"})).unwrap();
+    s.execute("cell.set", json!({"cell": "B1", "input": "=A1*2"})).unwrap();
+    s.execute("cell.set", json!({"cell": "C1", "input": "=10"})).unwrap();
+    let mut wb = (*s.doc().unwrap().wb).clone();
+    // The values a file would have saved, not the ones the formulas give.
+    for (a, n) in [("B1", 99.0), ("C1", 7.0)] {
+        let sheet = std::sync::Arc::make_mut(&mut wb.sheets[0]);
+        let c = CellRef::parse(a).unwrap();
+        let mut cell = sheet.cells.get(c).unwrap().clone();
+        cell.value = Value::Number(n);
+        sheet.set_cell(c, cell);
+    }
+    let mut saved = Session::new();
+    saved.add_document(crate::DocState::from_saved(wb, None, "saved".into(), crate::Trust::FromFile));
+    assert_eq!(v(&saved, "B1"), Value::Number(99.0));
+    saved.execute("cell.set", json!({"cell": "A1", "input": "3"})).unwrap();
+    assert_eq!(v(&saved, "B1"), Value::Number(6.0));
+    assert_eq!(v(&saved, "C1"), Value::Number(7.0));
+}