M4: text on a path keeps its effects when the path's effect style has none

A path linked to an effect style with no effects gave the text an empty effect list and the style link. The text now takes the path's effects only when there are any.

crates/engine/src/cmd/text.rs

@@ -147,7 +147,7 @@ fn on_path(s: &mut Session, p: &Value) -> Result<Value> {
     let (parent, index) = (pn.parent.ok_or_else(|| bad(CMD, "pages have no path"))?, doc.index_in_parent(path));
     let (transform, w, h) = (pn.transform, pn.width, pn.height);
     let fills = pn.fills.iter().any(|f| f.visible).then(|| (pn.fills.clone(), pn.styles.fill.clone()));
-    let effects = (!pn.effects.is_empty() || pn.styles.effect.is_some()).then(|| (pn.effects.clone(), pn.styles.effect.clone()));
+    let effects = (!pn.effects.is_empty()).then(|| (pn.effects.clone(), pn.styles.effect.clone()));
     let moved = |k: &str| (fills.is_some() && (k == "fill" || k.starts_with("fills/"))) || (effects.is_some() && k.starts_with("effects/"));
     let bound: Vec<(String, VariableId)> = pn.bound.iter().filter(|(k, _)| moved(k)).map(|(k, v)| (k.clone(), v.clone())).collect();
     let mut tp = TextPath::new(&geom);

crates/engine/src/draw_tools_tests.rs

@@ -128,6 +128,20 @@ fn text_put_on_a_stroke_only_path_keeps_its_own_fill_and_effects() {
     assert_eq!((&n.fills, &n.effects, &n.bound), (&text.fills, &text.effects, &text.bound), "a path with no fill or effects to give");
 }
 
+#[test]
+fn text_put_on_a_path_with_an_empty_effect_style_keeps_its_own_effects() {
+    let mut s = Session::new();
+    let (t, v) = text_and_curve(&mut s, json!({"fills": []}));
+    let none = s.execute("style.create", &json!({"type": "effect", "name": "None", "value": []})).unwrap()["id"].clone();
+    s.execute("style.apply", &json!({"ids": [v], "style": none})).unwrap();
+    let path = s.doc().unwrap().node(v).unwrap().clone();
+    assert!(path.effects.is_empty() && path.styles.effect.is_some());
+    let text = s.doc().unwrap().node(t).unwrap().clone();
+    s.execute("text.onPath", &json!({"ids": [t, v]})).unwrap();
+    let n = s.doc().unwrap().node(t).unwrap();
+    assert_eq!((&n.effects, &n.styles.effect), (&text.effects, &text.styles.effect), "a path whose effect style draws no effects");
+}
+
 #[test]
 fn pattern_fills_tile_their_source_live() {
     let mut s = Session::new();