package ocamlc-loc

Dune - A Composable Build System

Dune is a build system designed for OCaml/Reason projects only. It focuses on providing the user with a consistent experience and takes care of most low-level details of OCaml compilations. It's merely necessary to provide a description of your project, and Dune will do the rest.

It implements a scheme that's inspired from the one used inside Jane Street and adapted to the open source world. It has matured over a long time and is used daily by hundreds of developers, meaning it's highly tested and productive.

Dune comes with a manual. If you want to get started without reading too much, look at the quick start guide or watch this introduction video.

The example directory contains examples of projects using dune.

Overview

Dune reads project metadata from dune files, which are either static files in a simple S-expression syntax or OCaml scripts. It uses this information to setup build rules, generate configuration files for development tools such as Merlin, handle installation, etc.

Dune itself is fast, has very low overhead, and supports parallel builds on all platforms. It has no system dependencies. OCaml is all you need to build Dune and packages using Dune. You don't need make or bash, as long as the packages themselves don't use bash explicitly.

In particular, one can install OCaml on Windows with a binary installer and then use only the Windows Console to build Dune and packages using Dune.

Strengths

Composable

Take n repositories that use Dune and arrange them in any way on the file system. The result is still a single repository that Dune knows how to build at once.

This make simultaneous development on multiple packages trivial.

Gracefully Handles Multi-Package Repositories

Dune knows how to handle repositories containing several packages. When building via Opam, it is able to correctly use libraries that were previously installed, even if they are already present in the source tree.

The magic invocation is:

$ dune build --only-packages <package-name> @install

Building Against Several Configurations at Once

Dune can build a given source code repository against several configurations simultaneously. This helps maintaining packages across several versions of OCaml, as you can test them all at once without hassle.

In particular, this makes it easy to handle cross-compilation.

This feature requires Opam.

Requirements

Dune requires OCaml version 4.08.0 to build itself and can build OCaml projects using OCaml 4.02.3 or greater.

Installation

We recommended installing Dune via the Opam package manager:

$ opam install dune

If you are new to Opam, make sure to run eval $(opam config env) to make dune available in your PATH. The dune binary is self-contained and relocatable, so you can safely copy it somewhere else to make it permanently available.

You can also build it manually with:

$ make release
$ make install

If you do not have make, you can do the following:

$ ocaml bootstrap.ml
$ ./dune.exe build -p dune --profile dune-bootstrap
$ ./dune.exe install dune

The first command builds the dune.exe binary. The second builds the additional files installed by Dune, such as the man pages, and the last simply installs all of that on the system.

Please note: unless you ran the optional ./configure script, you can simply copy dune.exe anywhere and it will just work. dune is fully relocatable and discovers its environment at runtime rather than hard-coding it at compilation time.

Support

If you have questions about Dune, you can send an email to ocaml-core@googlegroups.com or open a ticket on GitHub.

Migration from Jbuilder

Dune was formerly known as Jbuilder. Migration from Jbuilder to Dune is described in the manual.

Status

Dune is fairly stable and used by the majority of packages on Opam. Note that Dune retains backward compatibility with Jbuilder, and in particular, existing Jbuilder projects will continue to be buildable with Dune.