This folder contains an example of a very simple ppx rewriter that will expand
[%get_env "SOME_ENV_VAR"] into the value of the env variable SOME_ENV_VAR at compile time,
as a string.
E.g., assuming we set MY_VAR="foo", it will turn:
let () = print_string [%get_env "foo"]into:
let () = print_string "foo"Note that this is just a toy example and we'd actually advise you against this type of ppx that have side effects or rely heavily on the file system or env variables unless you absolutely what your doing.
In particular in this case it won't work well with dune since dune won't know about the dependency on the env variables specified in the extension's payload.