Save PDF: ui.savePdfDialog refuses a useArtboards that is not true or false

A value such as "false" or 0 used to open the dialog for the artboards. It is
now refused before the dialog opens, as document.exportPdf refuses it.

crates/ui-egui/src/dialogs/save_pdf.rs

@@ -83,6 +83,11 @@ pub(super) const TOP_LABEL_WIDTH: f32 = LIST_WIDTH + 26.0;
 /// Open the dialog with `params` (`document.exportPdf` options and `path?`) applied over their
 /// preset. `useArtboards: false` makes the page the bounds of the visible art.
 pub fn open(app: &mut VectorcraftApp, params: &Value) -> Result<Value, String> {
+    let art_bounds = match params.get("useArtboards") {
+        None | Some(Value::Null) => false,
+        Some(Value::Bool(b)) => !b,
+        Some(v) => return Err(format!("useArtboards must be true or false, not {v}")),
+    };
     let mut fields = settings_fields(app, params)?;
     let s = |k: &str| params.get(k).and_then(Value::as_str);
     fields.insert("preset".into(), json!(s("preset").unwrap_or(pdf::DEFAULT_PRESET)));
@@ -93,7 +98,7 @@ pub fn open(app: &mut VectorcraftApp, params: &Value) -> Result<Value, String> {
     if let Some(path) = s("path") {
         fields.insert("path".into(), json!(path));
     }
-    if params.get("useArtboards") == Some(&json!(false)) {
+    if art_bounds {
         fields.insert(ART_BOUNDS.into(), json!(true));
     }
     app.ui.dialog = Some(Dialog { kind: KIND.into(), fields });

crates/ui-egui/src/dialogs/save_pdf/tests.rs

@@ -130,6 +130,22 @@ fn a_page_of_the_arts_bounds_has_no_artboards_section_and_takes_the_options() {
     assert!(opened.borrow()[0].0.ends_with("/tmp/art.pdf"));
 }
 
+/// `useArtboards` other than true, false or null is refused, as `document.exportPdf` refuses it,
+/// and no dialog opens.
+#[test]
+fn a_use_artboards_that_is_not_true_or_false_is_refused() {
+    let (mut app, _, _) = app();
+    for bad in [json!("false"), json!(0), json!({})] {
+        let e = app.run("ui.savePdfDialog", json!({"path": "/tmp/x.pdf", "useArtboards": bad})).unwrap_err();
+        assert!(e.contains("useArtboards must be true or false"), "{bad}: {e}");
+        assert!(app.ui.dialog.is_none(), "{bad}: no dialog opens");
+    }
+    for ok in [json!(true), json!(null)] {
+        app.run("ui.savePdfDialog", json!({"path": "/tmp/x.pdf", "useArtboards": ok})).unwrap();
+        assert!(!app.ui.dialog.take().unwrap().bool(ART_BOUNDS), "{ok}: the artboards' dialog");
+    }
+}
+
 /// With Background Export on, a page of the art's bounds is written in the background, as Export
 /// As writes its other formats.
 #[test]