Dear guix,

I am trying to build js-of-ocaml. I have created an updated version of
ocaml-compiler-libs, ocaml-migrate-parsetree and ocaml-ppxlib, and
tried to build the latest js_of_ocaml with that, but I get the
following error when building the updated ppxlib:

starting phase `build'
File "_build/default/.ppx/0224ad3443a846e54f1637fccb074e7d/ppx.exe",
line 1, characters 0-0:
Error: Failed to create on-demand ppx rewriter for ppxlib.metaquot; too
many
incompatible ppx drivers were found: ppxlib and ocaml-migrate-
parsetree.
File "_build/default/.ppx/3134a5298fb2c80808cc94dd434856cb/ppx.exe",
line 1, characters 0-0:
Error: Failed to create on-demand ppx rewriter for ppxlib.traverse; too
many
incompatible ppx drivers were found: ppxlib and ocaml-migrate-
parsetree.
File "traverse/dune", line 7, characters 13-48:
7 |  (preprocess (pps ppxlib_metaquot ppxlib.runner)))
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error: Too many incompatible ppx drivers were found: ppxlib and
ocaml-migrate-parsetree.
File "ast/ast_helper_lite.mli", line 18, characters 0-17:
18 | open Ocaml_common
     ^^^^^^^^^^^^^^^^^
Error (warning 33): unused open Ocaml_common.
command "dune" "build" "@install" failed with status 1
builder for `/gnu/store/k7wfvxqbp07f8idjsbzi699v5y163j24-ocaml-ppxlib-
0.20.0.drv' failed with exit code 1

Why are these two packages "incompatible"? Do you understand what is
happening?