The Problem

Trying to learn more about ReasonML, OCaml, and Dune to better understand how to troubleshoot build issues and understand how all these tools work together.

To that end I have been working on creating an ocaml project to use for coding exercises. An executable doesn’t make the most sense to me for this kind of usage, so creating the project as a library.

With a src/dune file set to the below snippet the build would fail. First the snippet:

1
2
3
4
(include_subdirs qualified)

(library
 (name ocaml_coding_exercises))

And here’s the error it produces:

1
2
3
4
5
6
7
8
opam exec -- dune build
Error: The package ocaml_coding_exercises does not have any user defined
stanzas attached to it. If this is intentional, add (allow_empty) to the
package definition in the dune-project file
-> required by _build/default/ocaml_coding_exercises.install
-> required by alias all
-> required by alias default
make: *** [Makefile:18: build] Error 1

Googling for does not have any user defined stanzas attached to it lead to this page on the ocaml discuss forums. The last comment turned out to be the key:

“Just ran into this. Very confusing error message. Would be much better if it mentioned the public_name issue directly.” (direct link to message)

Which in turn lead to the library stanza reference on the dune docs. Looks like library project (as opposed to a library IN an application project) needs to have a public name specified to build.

The Solution

Simply add a public_name stanza inside the library stanza like so:

1
2
3
4
5
(include_subdirs qualified)

(library
 (name ocaml_coding_exercises)
 (public_name ocaml_coding_exercises))