non-numeric value used as array index error when nested array predicate is first

[schmurgon]

Using the following as input

{
  "Email": [
    {
      "type": "work",
      "address": [{ "email":"fred.smith@my-work.com"}, {"email":"fsmith@my-work.com"}]
    },
    {
      "type": "home",
      "address": [{"email":"freddy@my-social.com"}, {"email":"frederic.smith@very-serious.com"}]
    }
  ]
}

I'm attempting to select and replace the element that matches the filter predicate:

(
    $emailElement := Email[    
       address[ email="fred.smith@my-work.com" ]
    ][0];

    $selectedEmailElements := {        
        "Email": [$emailElement]
    };
 
    $merge([$, $selectedEmailElements])
)

This works perfectly in the node version and on the demo https://try.jsonata.org/ but results in an exception on jsonata4java 1.7.9

com.api.jsonata4java.expressions.EvaluateException: non-numeric value used as array index
at com.api.jsonata4java.expressions.Expressions.evaluate(Expressions.java:195)
Caused by: com.api.jsonata4java.expressions.NonNumericArrayIndexException: non-numeric value used as array index
at com.api.jsonata4java.expressions.ExpressionsVisitor.visitArray(ExpressionsVisitor.java:1018)
at com.api.jsonata4java.expressions.ExpressionsVisitor.visitArray(ExpressionsVisitor.java:99)
at com.api.jsonata4java.expressions.generated.MappingExpressionParser$ArrayContext.accept(MappingExpressionParser.java:521)

When the expression is changed to include a meaningless predicate prior to the array filter then the correct result is returned as expected:

(
    $emailElement := Email[    
      "1" = "1" and /* HACK */
       address[ email="fred.smith@my-work.com" ]
    ][0];

    $selectedEmailElements := {        
        "Email": [$emailElement]
    };
 
    $merge([$, $selectedEmailElements])
)

Result

{
  "Email" : [ {
    "type" : "work",
    "address" : [ { "email" : "fred.smith@my-work.com" }, { "email" : "fsmith@my-work.com" } ]
  } ]
}

[wnm3]

Hi Ben, we had elected to defer supporting the non-numeric indices as the original use cases envisioned would not have included them. This will take some work. You can look at the ExpressionVisitor.json visitArray method starting on line 885 and see where the exception is being thrown (1018). Quite a bit of additional logic is required to support the filtering you seek.