styx sets invalid value for LANG environment variable

[juliapath]

How to reproduce

1. Create a styx project

   $ mkdir test
   $ cd test
   $ cabal init -n
   ...
   $ cat <<here > styx.yaml
   local-packages:
     test:
       location: .
   here
   $ styx configure
   

2. Watch the problems

   $ nix-shell .styx/shell.nix --pure
   nix$ echo $LANG
   en_US.UTF-8
   nix$ locale -a
   locale: Cannot set LC_CTYPE to default locale: No such file or directory
   locale: Cannot set LC_MESSAGES to default locale: No such file or directory
   locale: Cannot set LC_COLLATE to default locale: No such file or directory
   C
   C.utf8
   POSIX
   nix$ ghci
   Prelude> getLine
   ä*** Exception: <stdin>: hGetLine: invalid argument (invalid byte sequence)
   

   Note how en_US.UTF-8 is not listed in the available locales given by locale -a. The Cannot set ... error messages by locale -a are also due to the invalid value of LANG. Furthermore Haskell functions like getLine will assume the character encoding to be ASCI, causing them to throw exceptions on non ASCI characters.

Solutions

There are two possible solutions:

1. Set LANG=C.UTF-8
2. Add glibcLocales to buildInputs to make more locales available. This can be done easily as a workaround by adding glibcLocales to non-haskell-deps in styx.yaml.