Graphic Styles: addFromLibrary treats ids: null as left out

graphicStyle.addFromLibrary with apply: true and ids: null tried to
apply the style to no objects and failed with "no such objects" when
nothing was selected. A null `ids` now behaves as leaving `ids` out:
the style is applied to the selection when there is one, and only added
otherwise.

crates/engine/src/cmd/stylelib.rs

@@ -194,10 +194,11 @@ fn add(s: &mut Session, p: &Value) -> Result<Value> {
         "existing": existing.iter().map(|g| &g.name).collect::<Vec<_>>(),
     });
     let first = picked.first().map(|g| doc_name(&g.name));
-    let targets = p.get("ids").is_some() || !super::appearance::appearance_targets(s, &json!({}))?.is_empty();
+    let ids = p.get("ids").filter(|v| !v.is_null());
+    let targets = ids.is_some() || !super::appearance::appearance_targets(s, &json!({}))?.is_empty();
     if let Some(name) = first.filter(|_| apply && targets) {
         let mut params = json!({"name": name, "add": add});
-        if let Some(ids) = p.get("ids") {
+        if let Some(ids) = ids {
             params["ids"] = ids.clone();
         }
         s.execute("graphicStyle.apply", &params)?;

crates/engine/src/tests/stylelib.rs

@@ -117,6 +117,35 @@ fn add_with_apply_styles_the_selection_in_the_same_undo_step() {
     assert_eq!(doc(&s).node(id).unwrap().opacity, 0.4);
 }
 
+#[test]
+fn add_with_null_ids_and_no_selection_only_adds_style() {
+    let mut omitted = session();
+    let mut null_ids = session();
+    let params = json!({"library": "shadows-glows", "name": "Halo", "apply": true});
+    let expected = run(&mut omitted, "graphicStyle.addFromLibrary", params.clone());
+    let mut with_null = params;
+    with_null["ids"] = Value::Null;
+    let actual = run(&mut null_ids, "graphicStyle.addFromLibrary", with_null);
+    assert_eq!(actual, expected);
+    assert_eq!(names(&actual["added"]), ["Halo"]);
+    assert!(actual.get("applied").is_none());
+    assert!(doc(&null_ids).graphic_style("Halo").is_some());
+    assert_eq!(undo_len(&null_ids), undo_len(&omitted));
+}
+
+#[test]
+fn add_with_null_ids_applies_to_selection() {
+    let mut s = session();
+    let id = rect(&mut s, 10.0, 20.0, 100.0, 50.0);
+    let before = undo_len(&s);
+    let result = run(&mut s, "graphicStyle.addFromLibrary", json!({"library": "shadows-glows", "name": "Halo", "apply": true, "ids": null}));
+    assert_eq!(result["applied"], "Halo");
+    assert_eq!(undo_len(&s), before + 1);
+    let (style, linked) = s.selection_graphic_style().unwrap();
+    assert_eq!((style.name.as_str(), linked), ("Halo", true));
+    assert_eq!(doc(&s).node(id).unwrap().extras().graphic_style, Some(style.id));
+}
+
 /// A document with pattern `name` (a dot) and its swatch.
 fn add_pattern(s: &mut Session, name: &str, radius: f64) {
     s.edit("Pattern", |d, _| {