The function fails with nil input. Currently, I'm using guards to check for non-nil values before invoking the function.

if  payment_status,
do:  payment_status |> Recase.to_sentence() ,
else:  ""

What's wrong with that? You can pattern match on your own inputs instead. This operation "recase" only makes sense on binary input, not on nil.

Agreed, you can.

The disadvantage though is that my code is littered with checks preceding each call to recase. An optional default parameter would be great. Alternatively, we could wrap all of our calls to recase internally within our project.
Thanks