Strange behavior with :function output translations and custom output-files method

Hi,

I reduced a testcase from the metacopy-with-contextl .asd file. It defines an output-files method to rename the .fasl so that it can compile the same lisp files with different features set.

This worked fine when I was using normal output translations, but when I switched to a :function output translation, it failed. I'm not sure if this is a bug in asdf, a bug in my output translation function or a bug in metacopy, so I'm posting it here for some advice.

Test-case is in a tarball below. There is a shell script "test.sh" which invokes sbcl twice. The first time the output translation is left unaltered, the second time it specifies a :function translator for all paths, and this causes an error.

-Jason

https://phab.jasomfiles.org/orfiles/asdtest.tar.gz