Built-in PPX Rewriters

Pa_ppx comes with a number of PPX rewriters. In this section we’ll document them all, and describe their commonalities and differences where relevant.

Type-Decl-Related Rewriters (deriving and import)

There are two kinds of type-decl-related rewriters: pa_ppx.deriving and pa_ppx.import. The former are documented (here (ppx_deriving, here (ppx_deriving_yojson), and here (ppx_sexp_conv)). They comprise:

1. enum, eq, ord, fold, iter, make, map, show

   These are all part of ppx_deriving and implement things like automated generation of equality/compare operators, prety-printing, etc.

2. yojson, sexp

   conversion to/from json and sexpressions

3. import

   import of types from some CMI or MLI so they can be used for the above rewriters.

There are inconsistencies in some of the standard PPX rewriters, and specifically in the way they deal with extensible variants and exceptions: those have been remedied in the pa_ppx implementation.

Similarly, ppx_import is able to import single types from other modules, but not entire groups of recursively-defined types; this has been remedied in pa_ppx.import.

Test-Related Rewriters

There are three rewriters related to tests that we’ve implemented:

1. pa_ppx.assert: based on `ppx_assert<https://github.com/janestreet/ppx_assert>`_
2. pa_ppx.inline_test: based on `ppx_inline_test<https://github.com/janestreet/ppx_inline_test>`_
3. pa_ppx.expect_test: based on `ppx_expect<https://github.com/janestreet/ppx_expect>`_

These are all works-in-progress, though they do work.

Miscellaneous Standard Rewriters

pa_ppx.here is the only miscellaneous standard rewriter we’ve implemented.

Useful Pa_ppx-only Rewriters