The `string()` function doesn't work for a context with custom value types

[saig0]

Describe the bug

The string() function doesn't return the expected string representation from a context value if it contains custom value types.

The problem doesn't occur with standard Java/Scala types but with custom types. See the issue here on how to reproduce the issue in Camunda 8.

string(myContextVar)     
// --> "{key1:UnsafeBuffer{addressOffset=16, capacity=12, byteArray=byte[12], byteBuffer=null}}"

To Reproduce Steps to reproduce the behavior:

1. Run the following unit test
2. Verify that the test fails on the second case

case class CustomValue(value: Int)

  class MyCustomValueMapper extends CustomValueMapper {
    def toVal(x: Any, innerValueMapper: Any => Val): Option[Val] = x match {
      case CustomValue(value) => Some(ValNumber(value))
      case _              => None
    }

    override def unpackVal(value: Val, innerValueMapper: Val => Any): Option[Any] = None
  }

  it should "convert a custom context" in {

    val engine = FeelEngineBuilder()
      .withCustomValueMapper(new MyCustomValueMapper())
      .build()

    engine.evaluateExpression(
      expression =  " string(context) ",
      variables = Map("context" -> Map("a" -> CustomValue(1)))
    ) should returnResult("{a:1}") // --> works

    engine.evaluateExpression(
      expression =  " string(context) ",
      variables = Map("context" -> ValContext(new MyCustomContext(Map("a" -> CustomValue(1)))))
    ) should returnResult("{a:1}") // --> fails with "the evaluation didn't returned '{a:1}' but '{a:CustomValue(1)}'"
  }

Expected behavior The string() function returns the string representation for custom value types. It uses the configured value mapper of the engine to transform the custom types.

Environment

• FEEL engine version: 1.17.1
• Affects:
  • Camunda Automation Platform 7: [7.x]
  • Zeebe broker: 8.3.2 https://github.com/camunda/zeebe/issues/15209
  • Support: https://jira.camunda.com/browse/SUPPORT-19836

[mustafadagher]

NVM, that was a problem with my intellij runner, it ran another test after adding the lines.

~~@saig0~~ ~~I was trying the test case attached in the description for curiosity, the problem in the above test case lies in the test setup.~~

~~in the MyCustomValueMapper provided the method unpackVal resolves to None~~

~~while if you change it a tiny bit to match the implementation of DefaultValueMapper as follows, The test will succeed.~~

override def unpackVal(value: Val, innerValueMapper: Val => Any): Option[Any] = value match {
  case ValContext(c: Context) =>
    Some(
      c.variableProvider.getVariables.map { case (key, value) =>
        value match {
          case packed: Val => key -> innerValueMapper(packed)
          case unpacked => key -> unpacked
        }
      }
    )
  case _ => None
}