Description
I was recently parsing a CSV into a target class, where one of the fields of said class wasn't present in the CSV. This resulted in this exception being thrown:
java.lang.ClassCastException: Cannot cast kotlin.Unit to java.lang.String
Upon further analysis this seems to happen because when creating the array of parameters for the constructor of the target class in
Root.kt an empty default value block is specified (the Unit in the exception).
I think this is a corner case with no clear-cut solution, at the same time I think the behaviour towards the user could be improved (it took me a debugging session to understand what was going on).
A couple of ideas:
- setting
nullas the default value for constructor parameters. Since anyway the type ofactualParamsisArray<Any?>this wouldn't cause any inconsistency or incompatibility, allowing for target classes with optional parameters not present in the source CSV to still be initialized correctly - doing a pass over the same array and remove all the values that have
Unittype. This would allow two useful things: supporting target classes with default values on parameters that might not be in the source CSV, and otherwise showing a more meaningful error to the user (as in this case, the finalactualParamswon't have a required argument, hence resulting in Kotlin reflection to clearly state which field is missing rather than throwing the more genericClassCastException)
For now I can solve the problem in my code by removing the offending fields, but I'd love to help alleviate this problem.
Please let me know your thoughts, I'd be happy to PR a solution afterwards.