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.