Make the existence test depend on the nodelist, not on node values

src/query/atom.rs

@@ -24,22 +24,12 @@ impl Query for FilterAtom {
                         res
                     }
                 } else {
-                    let struct_check = |s: &T| {
-                        if let Some(arr) = s.as_array() {
-                            !arr.is_empty()
-                        } else if let Some(obj) = s.as_object() {
-                            !obj.is_empty()
-                        } else if let Some(str) = s.as_str() {
-                            !str.is_empty()
-                        } else {
-                            true
-                        }
-                    };
-
+                    // RFC 9535 2.3.5.2: a test expression is true when the
+                    // nodelist it produces is non-empty. The value of the nodes
+                    // does not take part in the decision.
                     let struct_presented = match res.data {
-                        Data::Ref(v) => struct_check(v.inner),
-                        Data::Refs(e) if e.is_empty() => false,
-                        Data::Refs(elems) => elems.iter().map(|v| v.inner).all(struct_check),
+                        Data::Ref(_) => true,
+                        Data::Refs(elems) => !elems.is_empty(),
                         _ => false,
                     };
 

src/query/filter.rs

@@ -97,6 +97,28 @@ mod tests {
         );
     }
 
+    #[test]
+    fn existence_of_empty_containers() {
+        let json = json!({
+          "a": {
+            "empty_array": {"b": []},
+            "empty_object": {"b": {}},
+            "empty_string": {"b": ""},
+            "no_b": {"c": 1}
+          }
+        });
+        // RFC 9535 2.3.5.2: a test expression is true when the nodelist it
+        // produces is non-empty, whatever the value of the nodes.
+        assert_eq!(
+            js_path("$.a[?@.b]", &json),
+            Ok(vec![
+                (&json!({"b": []}), "$['a']['empty_array']".to_string()).into(),
+                (&json!({"b": {}}), "$['a']['empty_object']".to_string()).into(),
+                (&json!({"b": ""}), "$['a']['empty_string']".to_string()).into(),
+            ])
+        );
+    }
+
     #[test]
     fn existence_or() {
         let json = json!({