Dune can be set up to run automatic formatters for source code.
It can use OCamlformat to format OCaml source code (*.ml and *.mli
files) and refmt to format Reason source code (*.re and *.rei files).
Furthermore it can be used to format code of any defined dialect (see :ref:`dialect`).
If using (lang dune 2.0), there is nothing to setup in Dune, as formatting will
be set up by default. However, OCamlformat will still refuse to format sources
without an .ocamlformat file present in the project root.
By default, formatting will be enabled for all languages and dialects present in the project that Dune knows about. This is not always desirable. For example, if in a mixed Reason/OCaml project, one only wants to format the Reason files to avoid pulling OCamlformat as a dependency.
It is possible to restrict the languages considered for formatting or disable it altogether by using the :ref:`formatting` stanza.
When this feature is active, an alias named fmt is defined. When built, it
will format the source files in the corresponding project and display the
differences:
$ dune build @fmt --- hello.ml +++ hello.ml.formatted @@ -1,3 +1 @@ -let () = - print_endline - "hello, world" +let () = print_endline "hello, world"
Then it's possible to accept the correction by calling dune promote to
replace the source files with the corrected versions.
$ dune promote Promoting _build/default/hello.ml.formatted to hello.ml.
As usual with promotion, it's possible to combine these two steps by running
dune build @fmt --auto-promote.
Note
This section applies only to projects with (lang dune 1.x).
In (lang dune 1.x), there is no default formatting. This feature is
enabled by adding the following to the dune-project file:
(using fmt 1.2)Languages can be configured using the following syntax:
(using fmt 1.2 (enabled_for reason))- Formatting is enabled by default.
- Format dialects (see :ref:`dialect`).
- Format Dune files.
- Format OCaml (using ocamlformat) and Reason (using refmt) source code.