hello-ppx-esy

A project that includes the minimum configuration for a ppx called ppx_42, a project that uses Reason and Esy.

ppx_42 implements a very basic ppx that transforms the [%gimme] extension into the number literal 42.

So, the code:

let fourtyTwo = string_of_int([%gimme]);

Is transformed into:

let fourtyTwo = string_of_int(42);

Files and folders

The example contains a couple of different targets that will be handled by dune (an OCaml build system) to use the ppx in different projects:

• The library: located under lib folder. It is used directly by native projects, and indirectly by BuckleScript projects
• The standalone binary: BuckleScript does not provide a way to compose multiple ppxs together, so each ppx gets called individually, getting a serialized version of the AST, using the -ppx compiler flag behind the scenes. This can be configured in BuckleScript projects by using the ppx-flags key in bsconfig.json (see "Examples" section below).

For this reason, ppx_42 exposes an executable that can be consumed by BuckleScript projects.

Examples

The repo contains a couple of demo examples that show one way to consume the ppx from both BuckleScript and native environments.

Check the readmes on each example folder:

• BuckleScript
• Native