Custom Repositories¶

By default when locking package versions, Dune looks up packages from two sources:

The upstream, community maintained opam-repository at ocaml/opam-repository for most packages
An overlay repository with patched software to allow usage in Dune at ocaml-dune/opam-overlays

To change the presets, the dune-workspace file has to be edited (and created if it didn’t exist):

In this case, we want to select a specific revision of the community repository instead of always using the most recent one as it would do by default. We define a new repository and configure the Dune solver to use this repository.

For more information about the stanzas refer to the repositories stanza as well as the lock_dir stanza.

The next time the build system is run, instead of using the default repositories at their newest versions, the solver will check out the configured repositories at the defined revisions. These will then be used to determine the new solution, which will get used for downloading and building the dependencies.

dune build

will thus log a new solution in _build/log. Note that a lot of package versions are different, as the state of the opam-repository is frozen at the specific commit:

...
# Dependency solution for
# _build/.sandbox/<sandbox-hash>/_private/default/.lock/dune.lock:
# - base-unix.base
# - fmt.0.9.0
# - ocaml.5.0.0
# - ocaml-base-compiler.5.0.0
# - ocaml-config.3
# - ocamlbuild.0.16.1+dune
# - ocamlfind.1.9.8+dune
# - topkg.1.0.7
...

Note

This feature can also be used to make sure the locked dependencies are reproducible, as fixing all the package repository versions will lead to equivalent locking results.