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Dune 3.20.0~alpha0

Dune 3.20.0~alpha0 is now available with several user-facing improvements and fixes.

Summary of Changes

Testing improvements: Individual tests can now be run using named aliases (@runtest-<name>), dune runtest accepts absolute paths and can target specific build contexts, and cram tests have better process cleanup.

New command-line features: dune exec works concurrently with watch mode, dune promote runs while watch mode is active, dune describe location shows executable paths, and --alias/--alias-rec flags provide alternatives to @/@@ syntax.

New variables: Added %{os}, %{os_version}, %{os_distribution}, and %{os_family} variables matching opam equivalents.

Fixes: dune subst properly handles version fields in opam files and works when no version control is detected.

Under the hood: Switched from MD5 to BLAKE3 for better performance, improved s-expression formatting, and added smart handling of transitive dependencies based on compiler capabilities.

Installation

opam install dune.3.20.0~alpha0

This is an alpha release for testing. Report issues on GitHub.

See full backstage

Fixed

  • Stop re-running cram tests after promotion when it's not necessary (#11994,
    @rgrinberg)

  • fix: $ dune subst should not fail when adding the version field in opam
    files (#11801, fixes #11045, @btjorge)

  • Kill all processes in the process group after the main process has
    terminated; in particular this avoids background processes in cram tests to
    stick around after the test finished (#11841, fixes #11820, @Alizter,
    @Leonidas-from-XIV)

Added

  • (tests) stanzas now generate aliases with the test name. To run
    (test (name a)) you can do dune build @runtest-a. (#11558, grants part of #10239,
    @Alizter)

  • Inline test libraries now produce aliases runtest-name_of_lib
    allowing users to run specific inline tests as dune build @runtest-name_of_lib. (#11109, partially fixes #10239, @Alizter)

  • feature: $ dune subst use version from dune-project when no version
    control repository has been detected (#11801, @btjorge)

  • Allow dune exec to run concurrently with another instance of dune in watch
    mode (#11840, @gridbugs)

  • Introduce %{os}, %{os_version}, %{os_distribution}, and %{os_family}
    percent forms. These have the same values as their opam counterparts.
    (#11863, @rgrinberg)

  • Introduce option (implicit_transitive_deps false-if-hidden-includes-supported)
    that is equivalent to (implicit_transitive_deps false) when -H is
    supported by the compiler (OCaml >= 5.2) and equivalent to
    (implicit_transitive_deps true) otherwise. (#11866, fixes #11212, @nojb)

  • Add dune describe location for printing the path to the executable that
    would be run (#11905, @gridbugs)

  • dune runtest can now understand absolute paths as well as run tests in
    specific build contexts (#11936, @Alizter).

  • Added 'empty' alias which contains no targets. (#11556 #11952 #11955 #11956,
    grants #4161, @Alizter and @rgrinberg)

  • Allow dune promote to properly run while a watch mode server is running
    (#12010, @ElectreAAS)

  • Add --alias and --alias-rec flags as an alternative to the @ and @@
    syntax in the command line (#12043, fixes #5775, @rgrinberg)

Changed

  • Format long lists in s-expressions to fill the line instead of
    formatting them in a vertical way (#10892, fixes #10860, @nojb)

  • Switch from MD5 to BLAKE3 for digesting targets and rules. BLAKE3 is both more
    performant and difficult to break than MD5 (#11735, @rgrinberg, @Alizter)

  • Print a warning when dune build runs over RPC (#11836, @gridbugs)

  • Stop emitting empty module group wrapper .js file in melange.emit
    (#11987, fixes #11986, @anmonteiro)