Alert floating attributes in mli are ignored

[david-maison-TrustInSoft]

Reproduction

With the following files:

$ cat dune
(executable
 (name bar)
 (flags (-alert +all))
 (modules foo bar))

$ cat dune-project
(lang dune 2.7)

$ cat bar.ml
let () = print_endline Foo.x

$ cat foo.ml
let x = "Hello"

$ cat foo.mli
[@@@alert unsafe "Reason: it's not safe."]

val x : string

Run dune build.

Expected Behavior

dune build should exit 0 (or 1 if alerts are fatal) with an error message as we can observe with the following command line:

$ ocamlc -c -alert +all foo.mli foo.ml bar.ml
File "bar.ml", line 1, characters 23-28:
1 | let () = print_endline Foo.x
                           ^^^^^
Alert unsafe: module Foo
Reason: it's not safe.

Actual Behavior

dune build exits 0 without printing anything.

Specifications

• Version of dune (output of dune --version): 3.6.1
• Version of ocaml (output of ocamlc --version): 4.14.0
• Operating system (distribution and version): Ubuntu 22.04.1 LTS

Additional information

If the attribute is attached to the val x declaration, it works correctly. A workaround would be to remove the floating attribute and add an item attribute for each declaration.

Same problem with deprecated or ocaml.deprecated attributes.

[Alizter]

I checked and ocamlopt doesn't output any warning either, so perhaps this is really an upstream OCaml bug.

[Alizter]

Here is a self contained test btw:

  $ cat > dune << EOF
  > (executable
  >  (name bar)
  >  (flags (-alert +all))
  >  (modules foo bar))
  > EOF

  $ cat > dune-project << EOF
  > (lang dune 2.7)
  > EOF

  $ cat > bar.ml << EOF
  > let () = print_endline Foo.x
  > EOF

  $ cat > foo.ml << EOF
  > let x = "Hello"
  > EOF

  $ cat > foo.mli << EOF
  > [@@@alert unsafe "Reason: it's not safe."]
  > 
  > val x : string
  > EOF

  $ ocamlc foo.mli
  $ ocamlc foo.ml

  $ ls
  a.out
  bar.ml
  dune
  dune-project
  foo.cmi
  foo.cmo
  foo.ml
  foo.mli

  $ dune build bar.exe --display=short
      ocamldep .bar.eobjs/bar.ml.d
      ocamldep .bar.eobjs/foo.mli.d
      ocamldep .bar.eobjs/foo.ml.d
        ocamlc .bar.eobjs/byte/dune__exe.{cmi,cmo,cmt}
      ocamlopt .bar.eobjs/native/dune__exe.{cmx,o}
        ocamlc .bar.eobjs/byte/dune__exe__Foo.{cmi,cmti}
        ocamlc .bar.eobjs/byte/dune__exe__Bar.{cmi,cmo,cmt}
      ocamlopt .bar.eobjs/native/dune__exe__Foo.{cmx,o}
      ocamlopt .bar.eobjs/native/dune__exe__Bar.{cmx,o}
      ocamlopt bar.exe

  $ ls _build/default
  bar.exe
  bar.ml
  foo.ml
  foo.mli

[nojb]

Is this an instance of #6115?

[nojb]

Is this an instance of #6115?

Answering to myself: no, it is a side-effect of the "wrapped executables" feature of Dune (so a bug). You will see the alert if you add (wrapped_executables false) to your dune-project.

[david-maison-TrustInSoft]

Thanks for your prompt responses! I confirm that (wrapped_executables false) (resp. (wrapped false) in the dune file for libraries) can be used as a workaround.

[nojb]

See ocaml/ocaml#11867 for the upstream report.