[2.8.0, 2.9.0] Aggregation function attempted to calculate value using empty array

[anatoly-spb]

Hello!

I have a simple json:

{
 "array": [
   {
    "count": 1
   },
   {
    "count": 2
   },
   {
    "count": 3
   }
 ]
}

Is it possible to use aggregate in the following case:

    @Autowired
    com.jayway.jsonpath.Configuration jsonPathConfiguration;

    @Test
    void parseJson() {
      Object object = jsonPathConfiguration.jsonProvider().parse("{\n"
          + "      \"array\": [ \n"
          + "       {\n"
          + "           \"count\": 1\n"
          + "       },\n"
          + "       {\n"
          + "           \"count\": 2\n"
          + "       },\n"
          + "       {\n"
          + "           \"count\": 3\n"
          + "       }\n"
          + "       ]\n"
          + "   }");
      assertThat(object).isNotNull().isInstanceOf(Map.class);
      JsonPath countSum = JsonPath.compile("$.array[*].count.sum()");
      countSum.read(object);
    }

?

Now I got the exception:

com.jayway.jsonpath.JsonPathException: Aggregation function attempted to calculate value using empty array
    at com.jayway.jsonpath.internal.function.numeric.AbstractAggregation.invoke(AbstractAggregation.java:59)
    at com.jayway.jsonpath.internal.path.FunctionPathToken.evaluate(FunctionPathToken.java:41)
    at com.jayway.jsonpath.internal.path.PathToken.handleObjectProperty(PathToken.java:90)
    at com.jayway.jsonpath.internal.path.PropertyPathToken.evaluate(PropertyPathToken.java:80)
    at com.jayway.jsonpath.internal.path.PathToken.handleArrayIndex(PathToken.java:143)
    at com.jayway.jsonpath.internal.path.WildcardPathToken.evaluate(WildcardPathToken.java:42)
    at com.jayway.jsonpath.internal.path.PathToken.handleObjectProperty(PathToken.java:90)
    at com.jayway.jsonpath.internal.path.PropertyPathToken.evaluate(PropertyPathToken.java:80)
    at com.jayway.jsonpath.internal.path.RootPathToken.evaluate(RootPathToken.java:66)
    at com.jayway.jsonpath.internal.path.CompiledPath.evaluate(CompiledPath.java:99)
    at com.jayway.jsonpath.internal.path.CompiledPath.evaluate(CompiledPath.java:107)
    at com.jayway.jsonpath.JsonPath.read(JsonPath.java:179)
    at com.jayway.jsonpath.JsonPath.read(JsonPath.java:153)

But there is a work around:

Object counts = JsonPath.read(object, "$.array[*].count");
Object countSum = JsonPath.read(counts, "$.sum()"); // 6.0(Double)