FLG -ppx missing

[Khady]

We have a project that was using dune 1.8 and was working fine. Since we upgraded to 1.9.3, the generation of the .merlin file is broken. the FLG directive is missing. And dune does not print a warning.

The code to reproduce:

https://gist.github.com/Khady/4ffc822f6b127c1bd4862701de0868f1

[Khady]

#2208 fixes the testcase from this issue. Thanks.

But we also have another problem on master/your branch. We have this dune file (that is not at the root of the project, if it matters). It has 2 occurrences of preprocess that are the same. Despite those 2 proprocess being identical, dune is unhappy. dune_gen.sexp does not contain any library or executable. Only some rules for atdgen as pasted bellow.

Everything was working fine under dune 1.8.

Compilation message:

File "api/src/dune", line 24, characters 13-43:
24 |  (preprocess (pps lwt_ppx ppx_deriving.std)))
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Warning: .merlin generated is inaccurate. Cannot mix preprocessed and non preprocessed specificiations.
Split the stanzas into different directories or silence this warning by adding (allow_approximate_merlin) to your dune-project.
File "api/src/dune", line 30, characters 13-43:
30 |  (preprocess (pps lwt_ppx ppx_deriving.std)))
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Warning: .merlin generated is inaccurate. Cannot mix preprocessed and non preprocessed specificiations.
Split the stanzas into different directories or silence this warning by adding (allow_approximate_merlin) to your dune-project.

The dune file:

(copy_files# "gen/*.ml{i,}")
(copy_files# "request/*")
(copy_files# "shared/*")
(copy_files# "keywordsExplorer/*")

(library
 (name apicore)
 (modules (:standard \ main))
 (flags (:standard -w -33)) ; because of EsMapping in atd files
 (libraries
  threads                       ; must be first
  ahrefskit
  angstrom
  atdgen
  bigstringaf
  billing.billing_client
  csv
  devkit
  elastic
  extlib
  fmt
  yojson
 )
 (preprocess (pps lwt_ppx ppx_deriving.std)))

(executable
 (name main)
 (modules main)
 (libraries extlib apicore ahrefskit.version)
 (preprocess (pps lwt_ppx ppx_deriving.std)))

;;; Dune files generation for atdgen
(rule
 (targets dune_gen.sexp.gen)
 (action (with-stdout-to dune_gen.sexp.gen (run ./gen_dune.sh)))
 (deps (glob_files *.atd)))

(alias
  (name gen_dune)
  (action
    (diff dune_gen.sexp dune_gen.sexp.gen)))

(include dune_gen.sexp)

(data_only_dirs gen)

One of the rules in dune_gen.sexp:

(rule
  (targets config_t.mli config_t.ml config_j.mli config_j.ml)
  (deps config.atd)
  (action (progn (run %{bin:atdgen} -j -j-std %{deps}) (run %{bin:atdgen} -t %{deps}))))

[rgrinberg]

Does dune_gen.sexp define any executable, test, or library stanazs?

[Khady]

No, only rules that similar to the one pasted previously. There is one rule per atd file in the project. That's it.

Also to be more precise:

• 1.8 works fine
• 1.9.3 does not generate the FLG -ppx directive and does not display a warning
• master does not generate the FLG -ppx directive but DOES display a warning

[rgrinberg]

And what about my PR?

[Khady]

Same as master

[rgrinberg]

Okay, thanks. I understand what the issue is.