On behalf of the dune team, I’m delighted to announce the release of dune 2.0. This release is the culmination of 4 months of hard work by the dune team and contains new features, bug fixes, and performance improvements . Here’s a selection of new features that I personally find interesting:

Refer to the change log for an exhaustive list.

We strive for a good out of the box experience that requires no configuration, so we’ve also tweaked a few defaults. In particular, $ dune build will now build @all instead of @install , and ocamlformat rules are setup by default.

Lastly, dune 2.0 sheds all the legacy related to jbuilder and will no longer build jbuilder projects. This change is necessary to ease maintenance and make it easier to add new features down the line. There are a few other minor breaking changes. Refer to the change log for the full list. We apologize in advance for any convenience this might cause.

Happy Hacking!

Remove existing destination files in install before installing the new

ones. (#2885, fixes #2883, @bschommer)

The action field in the alias stanza is not available starting lang dune 2.0 . The alias field in the rule stanza is a replacement. (#2846, fixes

2681, @rgrinberg)

Introduce alias and package fields to the rule stanza. This is the

preferred way of attaching rules to aliases. (#2744, @rgrinberg)

Add field (optional) for executable stanzas (#2463, fixes #2433, @bobot)

Infer targets for rule stanzas expressed in long form (#2494, fixes #2469,

@NathanReb)

Indicate the progress of the initial file tree loading (#2459, fixes #2374,

@bobot)

Build .cm[ox] files for executables more eagerly. This speeds up builds at

the cost of building unnecessary artifacts in some cases. Some of these extra

artifacts can fail to built, so this is a breaking change. (#2268, @rgrinberg)

Do not put the <package>.install files in the source tree unless -p or

--promote-install-files is passed on the command line (#2329, @jeremiedimino)

Compilation units of user defined executables are now mangled by default. This

is done to prevent the accidental collision with library dependencies of the

executable. (#2364, fixes #2292, @rgrinberg)

Enable (explicit_js_mode) by default. (#1941, @nojb)

Add an option to clear the console in-between builds with

--terminal-persistence=clear-on-rebuild

Stop symlinking object files to main directory for stanzas defined jbuild

files (#2440, @rgrinberg)

Library names are now validated in a strict fashion. Previously, invalid names

would be allowed for unwrapped libraries (#2442, @rgrinberg)

mli only modules must now be explicitly declared. This was previously a

warning and is now an error. (#2442, @rgrinberg)

Modules filtered out from the module list via the Ordered Set Language must

now be actual modules. (#2442, @rgrinberg)

Actions which introduce targets where new targets are forbidden (e.g.

preprocessing) are now an error instead of a warning. (#2442, @rgrinberg)

No longer install a jbuilder binary. (#2441, @jeremiedimino)

Stub names are no longer allowed relative paths. This was previously a warning

and is now an error (#2443, @rgrinberg).

Define (paths …) fields in (context …) definitions in order to set or

extend any PATH-like variable in the context environment. (#2426, @nojb)

The diff action will always normalize newlines before diffing. Perviousy, it

would not do this normalization for rules defined in jbuild files. (#2457,

@rgrinberg)

Modules may no longer belong to more than one stanza. This was previously

allowed only in stanzas defined in jbuild files. (#2458, @rgrinberg)

Remove support for jbuild-ignore files. They have been replaced by the the

dirs stanza in dune files. (#2456, @rgrinberg)

Add a new config option sandboxing_preference , the cli argument --sandbox ,

and the dep spec sandbox in dune language. These let the user control the level of

sandboxing done by dune per rule and globally. The rule specification takes precedence.

The global configuration merely specifies the default.

(#2213, @aalekseyev, @jeremiedimino)

Remove support for old style subsystems. Dune will now emit a warning to

reinstall the library with the old style subsystem. (#2480, @rgrinberg)

Add action (with-stdin-from ) to redirect input from

when performing . (#2487, @nojb)

Change the automatically generated odoc index to only list public modules.

This only affects unwrapped libraries (#2479, @rgrinberg)

Set up formatting rules by default. They can be configured through a new

(formatting) stanza in dune-project (#2347, fixes #2315, @emillon)

Change default target from @install to @all . (#2449, fixes #1220,

@rgrinberg)

Include building stubs in @check rules. (@rgrinberg, #2530)

Get rid of ad-hoc rules for guessing the version. Dune now only

relies on the version written in the dune-project file and no

longer read VERSION or similar files (#2541, @jeremiedimino)

In (diff? x y) action, require x to exist and register a

dependency on that file. (#2486, @aalekseyev)

On Windows, an .exe suffix is no longer added implicitly to binary names that

already end in .exe. Second, when resolving binary names, .opt variants are no

longer chosen automatically. (#2543, @nojb)

Make (diff? x y) move the correction file ( y ) away from the build

directory to promotion staging area. This makes corrections work with

sandboxing and in general reduces build directory pollution. (#2486,

@aalekseyev, fixes #2482)

c_flags , c_names and cxx_names are now supported in executable

and executables stanzas. (#2562, @nojb)

Note: this feature has been subsequently extended into a separate

foreign_stubs field. (#2659, RFC #2650, @snowleopard)

Remove git integration from $ dune upgrade (#2565, @rgrinberg)

Add a --disable-promotion to disable all modification to the source

directory. There’s also a corresponding DUNE_DISABLE_PROMOTION environment

variable. (#2588, fix #2568, @rgrinberg)

Add a forbidden_libraries field to prevent some library from being

linked in an executable. This help detecting who accidently pulls in

unix for instance (#2570, @jeremiedimino)

Fix incorrect error message when a variable is expanded in static context:

%{lib:lib:..} when the library does not exist. (#2597, fix #1541,

@rgrinberg)

Add --sections option to $ dune install to install subsections of .install

files. This is useful for installing only the binaries in a workspace for

example. (#2609, fixes #2554, @rgrinberg)

Drop support for jbuild and jbuild-ignore files (#2607, @jeremiedimino)

Add a dune-action-plugin library for describing dependencies direcly in

the executable source. Programs that use this feature can be run by a new

action (dynamic-run …). (#2635, @staronj, @aalekseyev)

Stop installing the ocaml-syntax-shims binary. In order to use

future_syntax , one now need to depend on the ocaml-syntax-shims

package (#2654, @jeremiedimino)

Add support for dependencies that are re-exported. Such dependencies

are marked with re_export and will automatically be provided to

users of a library (#2605, @rgrinberg)

Add a deprecated_library_name stanza to redirect old names after a

library has been renamed (#2528, @jeremiedimino)

Error out when a preprocessor_deps field is present but not

preprocess field is. It is a warning with Dune 1.x projects

(#2660, @Julow)

Dune will use -output-complete-exe instead of -custom when compiling

self-contained bytecode executables whenever this options is available

(OCaml version >= 4.10) (#2692, @nojb)

Add action (with-accepted-exit-codes <pred> <action>) to specify the set of

successful exit codes of <action> . <pred> is specified using the predicate

language. (#2699, @nojb)

Do not setup rules for disabled libraries (#2491, fixes #2272, @bobot)

Configurator: filter out empty flags from pkg-config (#2716, @AltGr)

no_keep_locs is a no-op for projects that use lang dune older than 2.0. In

projects where the language is at least 2.0 , the field is now forbidden.

(#2752, fixes #2747, @rgrinberg)

Extend support for foreign sources and archives via the (foreign_library ...)

stanza as well as the (foreign_stubs ...) and (foreign_archives ...) fields.

(#2659, RFC #2650, @snowleopard)

Add (deprecated_package_names) field to (package) declaration in

dune-project. The names declared here can be used in the (old_public_name)

field of (deprecated_library_name) stanza. These names are interpreted as

library names (not prefixed by a package name) and appropiate redirections are

setup in their META files. This feaure is meant to migrate old libraries which

do not follow Dune’s convention of prefixing libraries with the package

name. (#2696, @nojb)

The fields license , authors , maintainers , source , bug_reports ,

homepage , and documentation of dune-project can now be overriden on a

per-package basis. (#2774, @nojb)

Change the default modes field of executables to (mode exe) . If

one wants to build a bytecode program, it now needs to be explicitly

requested via (modes byte exe) . (#2851, @jeremiedimino)

Allow ccomp_type as a variable for evaluating enabled_if . (#2855, @dra27,

@rgrinberg)

Stricter validation of file names in select . The file names of conditional

sources must match the prefix and the extension of the resultant filename.

(#2867, @rgrinberg)

Add flag disable_dynamically_linked_foreign_archives to the workspace file.

If the flag is set to true then: (i) when installing libraries, we do not

install dynamic foreign archives dll*.so ; (ii) when building executables in

the byte mode, we statically link in foreign archives into the runtime

system; (iii) we do not generate any dll*.so rules. (#2864, @snowleopard)

Reimplement the bootstrap procedure. The new procedure is faster and

should no longer stack overflow (#2854, @dra27, @jeremiedimino)