fix evaluation of `empty` with wrapping providers (fixes #366)

json-path/src/main/java/com/jayway/jsonpath/internal/filter/ValueNode.java

@@ -359,20 +359,19 @@ public abstract class ValueNode {
         }
 
         public boolean isArray(Predicate.PredicateContext ctx) {
-            return parse(ctx) instanceof List;
+            return ctx.configuration().jsonProvider().isArray(parse(ctx));
         }
 
         public boolean isMap(Predicate.PredicateContext ctx) {
-            return parse(ctx) instanceof Map;
+            return ctx.configuration().jsonProvider().isMap(parse(ctx));
         }
 
         public int length(Predicate.PredicateContext ctx) {
-            return isArray(ctx) ? ((List) parse(ctx)).size() : -1;
+            return isArray(ctx) ? ctx.configuration().jsonProvider().length(parse(ctx)) : -1;
         }
 
         public boolean isEmpty(Predicate.PredicateContext ctx) {
-            if (isArray(ctx)) return ((List) parse(ctx)).size() == 0;
+            if (isArray(ctx) || isMap(ctx)) return ctx.configuration().jsonProvider().length(parse(ctx)) == 0;
-            else if (isMap(ctx)) return ((Map) parse(ctx)).size() == 0;
             else if((parse(ctx) instanceof String)) return ((String)parse(ctx)).length() == 0;
             return true;
         }

json-path/src/test/java/com/jayway/jsonpath/JacksonJsonNodeJsonProviderTest.java

@@ -109,6 +109,35 @@ public class JacksonJsonNodeJsonProviderTest extends BaseTest {
 
         using(JACKSON_JSON_NODE_CONFIGURATION).parse(JSON).read("$", typeRef);
     }
+    
+    @Test
+    // https://github.com/json-path/JsonPath/issues/366
+    public void empty_array_check_works() throws IOException {
+      String json = "[" +
+          "  {" +
+          "    \"name\": \"a\"," +
+          "    \"groups\": [{" +
+          "      \"type\": \"phase\"," +
+          "      \"name\": \"alpha\"" +
+          "    }, {" +
+          "      \"type\": \"not_phase\"," +
+          "      \"name\": \"beta\"" +
+          "    }]" +
+          "  }, {" +
+          "    \"name\": \"b\"," +
+          "    \"groups\": [{" +
+          "      \"type\": \"phase\"," +
+          "      \"name\": \"beta\"" +
+          "    }, {" +
+          "      \"type\": \"not_phase\"," +
+          "      \"name\": \"alpha\"" +
+          "    }]" +
+          "  }" +
+          "]";
+      ArrayNode node = using(JACKSON_JSON_NODE_CONFIGURATION).parse(json).read("$[?(@.groups[?(@.type == 'phase' && @.name == 'alpha')] empty false)]");
+      assertThat(node.size()).isEqualTo(1);
+      assertThat(node.get(0).get("name").asText()).isEqualTo("a");
+    }
 
     public static class FooBarBaz<T> {
         public T gen;