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Ppx_deriving becomes an optional dependency of ppx_type_conv

There are two ways of using the ppx_sexp_conv ppx rewriter:

  • the legacy way, with:

    $ ocamlfind ocamlc -package ppx_sexp_conv ...
    
  • the new way, with a driver. Since the v0.9.0 version of ppx_sexp_conv one can use either the ocaml-migrate-parsetree driver or ppx_driver. Before v0.9.0 one could only use ppx_driver

Using the legacy way requires using ppx_deriving. ppx_deriving used to be a hard dependency of ppx_sexp_conv through ppx_type_conv. Since v0.9.0 it is an optional one. As a result pacakges building using the legacy way must declare an explicit dependency on ppx_deriving.

Many packages didn't at the time ppx_sexp_conv v0.9.0 was released. To fix builds failure, a ppx_deriving dependency was added to all packages depending on ppx_sexp_conv but not ppx_deriving.

Camlp4 syntax extensions split from Jane Street packages (2016-01-11)

Jane Street packages no longer support camlp4 after the 113.09.00 series.

For Jane Street packages that contain both a library and a camlp4 syntax extension, the latter is extracted to its own package.

The following table summarize the changes:

Package Old findlib name of syntax New camlp4-only package version
sexplib sexplib.syntax pa_sexp_conv 113.00.00
bin_prot bin_prot.syntax pa_bin_prot 113.00.00
typerep typerep.syntax pa_typerep_conv 113.00.00
fieldslib fieldslib.syntax pa_fields_conv 113.00.00
variantslib variantslib.syntax pa_variants_conv 109.15.03

Upgrading

For the long term it is recommended to switch to the corresponding ppx alternative (replace the pa_ prefix by ppx_ to get the ppx package name).

Until then packages that are using one of the camlp4 syntax extension must upgrade their build system to refer to the new package name. Simply replace the name in the second column by the one in the third column.

Running the following shell command on the sources should do:

sed -ri 's/\<sexplib\.syntax\>/pa_sexp_conv/g;
         s/\<bin_prot\.syntax\>/pa_bin_prot/g;
         s/\<typerep\.syntax\>/pa_typerep_conv/g;
         s/\<fieldslib\.syntax\>/pa_fields_conv/g;
         s/\<variantslib\.syntax\>/pa_variants_conv/g' \
  `ag -l .`

The new dependency must also be added to the opam file.

Automatic upgrade of the opam-repository

To avoid the opam-repository being in a inconsistent state once the camlp4-free Jane Street packages are released, the following automatic change is applied to the opam repository:

for js_pkg in "sexplib" "bin_prot" "type_conv" "variantslib" "fieldslib":
  for pkg in all_packages():
    if pkg depends on js_pkg and "type_conv":
      pkg.add_constraint(js_pkg < next-version-of(js_pkg))

This is an over-approximation as some package might not use the syntax extension at all.

Following this automatic change maintainers should:

  • just remove the constraint if the package doesn't use the syntax extension
  • do a new release that depend on the new camlp4-only package