dune 2.8.0 test issue

[kit-ty-kate]

Issues detected in ocaml/opam-repository#17967

The CI hasn't finished, but so far at least one issue already arose. Here is a test case:

$ cat dune
(rule
 (with-stdout-to
  test1.output
  (run cat test1.expected)))

(rule
 (alias runtest)
 (action
  (diff test1.expected test1.output)))
$ dune runtest
         cat test1.output (exit 1)
(cd _build/default && /usr/bin/cat test1.expected) > _build/default/test1.output
/usr/bin/cat: test1.expected: No such file or directory

This pattern is used in drom and other packages from ocamlpro.

Specifications

• Version of dune (output of dune --version): 2.8.0 ([new release] dune-build-info, dune, dune-configurator, dune-site, dune-action-plugin, dune-private-libs and dune-glob (2.8.0) opam-repository#17967)

[rgrinberg]

I have no idea how this worked before, the rule that produces test1.output does not specify a dependency on test1.expected. So it must have worked by accident previously?

[rgrinberg]

I confirmed that fixing the rule:

(rule
 (deps test1.expected)
 (action
  (with-stdout-to
   test1.output
   (run cat test1.expected))))

fixes the problem

[kit-ty-kate]

Oh, I always thought dune automatically inferred the file dependency from the arguments.
So I'll just make those packages incompatible with dune 2.8.0 (for the tests only). Thanks a lot!

[rgrinberg]

Oh, I always thought dune automatically inferred the file dependency from the arguments.

This works only for primitive actions that dune understands, like with-stdout-to in that example.

You could also rewrite the above to be:

(rule (with-stdout-to test1.output (echo %{read:test1.expected})))

and then dune will be smart enough to infer the dependency. But since cat is just a random binary in the original rule, dune assumes knowing about its dependencies or targets.

[nojb]

You could also rewrite the above to be:

(rule (with-stdout-to test1.output (echo %{read:test1.expected})))

Or even simpler

(rule (with-stdout-to test1.output (cat test1.expected)))

[bobot]

You can also use run cat %{dep:test1.expected} to add dependencies directly in an action.