How do use fuzzy matching validation for either a non-present key or an empty array? - karate

Question

In karate version 0.9.6 I used the following match statement in a .feature file and it worked for validating the value to be an empty array or a key that was not present.
def example = {}
match example.errors == '##[0]'
In 1.0 the documentation example suggests that this should check for the key being present and null or an empty array and testing this fails with a validation error that the value is not present.
From https://karatelabs.github.io/karate/#schema-validation
# should be null or an array of strings
* match foo == '##[] #string'
This appears to be an undocumented breaking change from pre-1.0 to 1.0.
My question is: how do I construct a validator to cover this case correctly when the key is allowed to be absent but if it is present it must be an empty array?

Answer 1

I've found an undesirable solution for now but am leaving this open in case someone has a better answer.
I'm validating the entire parent object with a minimal schema:
Replace
match $.errors == '##[0]'
With
* match $ == { data: '#object', extensions: '##object', errors: '##[0]' }
While more brittle and verbose it is technically working.

Answer 2

This indeed looks like an in-intended breaking change. Here is another workaround:
* def example = {}
* def expected = example.errors ? '#[0]' : '#notpresent'
* match example.errors == expected
I see you have opened an issue here: https://github.com/karatelabs/karate/issues/1825
EDIT: this might be an improvement over the workaround you came up with in your answer:
* match example contains { errors: '##[0]' }