I am new to OCaml, and I followed the tutorial to set up a developpement environment. I then tried the helloworld example with dune and OCaml but encoutered the following error:
$ dune init exe helloworld
Success: initialized executable component named helloworld
$ dune build
Error: I cannot find the root of the current workspace/project.
If you would like to create a new dune project, you can type:
dune init project NAME
Otherwise, please make sure to run dune inside an existing project or
workspace. For more information about how dune identifies the root of the
current workspace/project, please refer to
https://dune.readthedocs.io/en/stable/usage.html#finding-the-root
Directory structure:
.
├── _build
│ └── log
├── dune
└── helloworld.ml
dune: 3.0.2
ocaml: 4.11.1
You can fix this situation by adding a dune-project file at the root of your project filled with this line:
(lang dune 3.0)
However, as per the documentation, dune init exec is not intended for creating projects: it only creates the boilerplate for an executable component within an existing project (see dune init --help or the dune cli manual for details).
To initialize a project, you should run
dune init proj helloworld
This will also generate a template dune-project file along with the recommended project file structure.
NOTE: Prior to dune 3.0 dune build would have created the file for you if it was absent:
❯ dune init exe helloworld
Success: initialized executable component named helloworld
❯ ls
_build dune helloworld.ml
❯ dune build
Info: Creating file dune-project with this contents:
| (lang dune 2.9)
❯ ls
_build dune dune-project helloworld.ml
However, since dune 3.0, dune-project is not added automatically when not found in the project.