#903: name a new component set from its variants' path, not their first property

A component set took its name from the first variant's name up to the first '/' or '=',
so variants named "State=Default, Size=Small" made a set called "State". The set now
takes the path before the last '/' ("Button/State=Hover" -> "Button",
"Icons/Arrow/Dir=Up" -> "Icons/Arrow"), keeps a plain name as is ("Button"), and
otherwise gets the next numbered default ("Component 1"), as a new component does.

crates/engine/src/cmd/component.rs

@@ -330,6 +330,14 @@ fn create(s: &mut Session, p: &Value) -> Result<Value> {
     Ok(json!({"id": target}))
 }
 
+/// The name a new component set takes from its first variant: the path before the last '/'
+/// ("Button/State=Hover" → "Button"), or a plain name as is ("Button"). A bare "prop=value" name
+/// ("State=Default, Size=Small") names no set.
+fn set_name_from(variant: &str) -> Option<String> {
+    let base = variant.rsplit_once('/').map_or(variant, |(path, _)| path).trim();
+    (!base.is_empty() && !base.contains('=')).then(|| base.to_string())
+}
+
 /// Wrap components in a new component set (named after the first) placed around them.
 fn wrap_in_set(doc: &mut Document, ids: &[NodeId]) -> Result<NodeId> {
     let cmd = "component.combineVariants";
@@ -341,12 +349,7 @@ fn wrap_in_set(doc: &mut Document, ids: &[NodeId]) -> Result<NodeId> {
     let bounds = doc.bounds_of(ids).unwrap_or_default();
     let pw = doc.world_transform(parent);
     let local = figcraft_geom::transform_rect_bbox(pw.inverse(), bounds.inflate(20.0, 20.0));
-    let base = ids
-        .first()
-        .and_then(|i| doc.node(*i))
-        .map(|n| n.name.split(['/', '=']).next().unwrap_or("Component").trim().to_string())
-        .filter(|n| !n.is_empty() && !n.contains(','))
-        .unwrap_or_else(|| "Component".into());
+    let base = ids.first().and_then(|i| doc.node(*i)).and_then(|n| set_name_from(&n.name)).unwrap_or_else(|| doc.next_name("Component"));
     let set = doc.alloc_id();
     let mut n = Node::new(set, NodeKind::ComponentSet { description: String::new() }, base, local.width(), local.height());
     n.transform = figcraft_geom::Affine::translate((local.x0, local.y0));

crates/engine/src/components_behaviour_tests.rs

@@ -879,3 +879,35 @@ fn auto_layout_instances_follow_their_main() {
     assert_eq!(node(&s, i).child_layout.min_w, Some(80.0));
     healthy(&s);
 }
+
+#[test]
+fn a_new_component_set_is_named_after_its_first_variant() {
+    // "Button/State=Hover" groups under "Button": the set takes the path before the last '/'.
+    // A bare property name ("State=Default, Size=Small") names no set, and neither does an empty
+    // name: the set gets the next numbered default, like a new component. A plain name is kept.
+    let rows = [
+        ("Button/State=Hover", "Button", "slash-prefixed: the path before the last '/'"),
+        ("Icons/Arrow/Dir=Up", "Icons/Arrow", "nested path: everything before the last '/'"),
+        ("State=Default, Size=Small", "Component 1", "bare prop=value: not \"State\""),
+        ("", "Component 1", "empty name: the numbered default"),
+    ];
+    for (name, expected, why) in rows {
+        let mut s = Session::new();
+        let f = idv(&ex(&mut s, "frame.create", json!({"x": 0, "y": 0, "width": 40, "height": 20})));
+        ex(&mut s, "node.set", json!({"id": f, "props": {"name": name}}));
+        let c = idv(&ex(&mut s, "component.create", json!({"ids": [f]})));
+        assert_eq!(node(&s, c).name, name, "{why}: the variant keeps its name");
+        let set = idv(&ex(&mut s, "component.combineVariants", json!({"ids": [c]})));
+        assert_eq!(node(&s, set).name, expected, "{why}");
+        healthy(&s);
+    }
+
+    // Add variant on a lone component (a variant property on it) wraps it in a set named after it.
+    let mut s = Session::new();
+    let f = idv(&ex(&mut s, "frame.create", json!({"x": 0, "y": 0, "width": 40, "height": 20, "name": "Button"})));
+    let c = idv(&ex(&mut s, "component.create", json!({"ids": [f]})));
+    let set = idv(&ex(&mut s, "component.addProperty", json!({"id": c, "name": "State", "type": "variant"})));
+    assert_eq!(node(&s, set).name, "Button");
+    assert_eq!(node(&s, c).name, "State=Default");
+    healthy(&s);
+}