building dynamic json

I need to only include the json field if there is a field other than blank
associated with that field's value...

for example, I set out trying to solve this by doing...

values
json_object(
case when :myVal <> ' '
then key 'myVal'
value trim(:myVal)
)

... but no go... compiler does not like this.

So on a field by field basis, how can I continue using the sql json
functions but condition which fields should be included in the json?

tia

Jay