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We are extremely happy to announce the release of opam 2.4.0 and encourage all users to upgrade. Please read on for installation and upgrade instructions.

Try it!

The upgrade instructions are unchanged:

1. Either from binaries: run

For Unix systems

bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.4.0"

or from PowerShell for Windows systems

Invoke-Expression "& { $(Invoke-RestMethod https://opam.ocaml.org/install.ps1) } -Version 2.4.0"

or download manually from the Github "Releases" page to your PATH.

1. Or from source, manually: see the instructions in the README.

You should then run:

opam init --reinit -ni

Major changes

• On opam init the compiler chosen for the default switch will no longer be ocaml-system (#3509) This was done because the system compiler (as-is your ocaml installed system wide, e.g. /usr/bin/ocaml) is known to be under-tested and prone to a variety of bugs and configuration issues. Removing it from the default compiler allows new-comers a more smooth experience. Note: if you wish to use it anyway, you are always able to do it explicitly using opam init --compiler=ocaml-system

• GNU patch and the diff command are no longer runtime dependencies. Instead the OCaml patch library is used (#6019, #6052, #3782, ocaml/setup-ocaml#933) Doing this we've removed some rarely used features of GNU Patch such as the support of Context diffs. The new implementation only supports Unified diffs including the git extended headers, however file permission changes via said extended headers have no effect.

• Add Nix support for external dependencies (depexts) by adding support for stateless package managers (#5982). Thanks to @RyanGibb for this contribution

• Fix opam install <local_dir> with and without options like --deps-only or --show-action having unexpected behaviours (#6248, #5567) such as:

  • reporting Nothing to do despite dependencies or package not being up-to-date

  • asking to install the wrong dependencies

• opam switch create [name] <version> will not include compiler packages flagged with avoid-version/deprecated in the generated invariant anymore, unless compiler flagged avoid-version/deprecated are the only ones available (#6494). This will allow opam to avoid the use of the ocaml-system package unless actually explicitly requested by the user. The opam experience when the ocaml-system compiler is used is known to be prone to a variety of bugs and configuration issues.

• opam install --deps-only no longer requires unicity of package version between the request and the installed packages. In other words, if you have pkg.1 installed, installing the dependencies of pkg.2 no longer removes pkg.1 if the installed packages are compatible. This also allows to install dependencies of conflicting packages when their dependencies are compliant. (#6520)

UI changes

• opam show now displays the version number of packages flagged with avoid-version/deprecated gray (#6354)

• opam upgrade: Do not show the message about packages "not up-to-date" when the package is tagged with avoid-version/deprecated (#6271)

• Fail when trying to pin a package whose definition could not be found instead of forcing interactive edition (e.g. this could happen when making a typo in the package name of a pin-depends) (#6322)

New commands / options

• Add opam admin compare-versions to compare package versions for sanity checks. Thanks to @mbarbin for this contribution

• Add opam lock --keep-local to keep local pins url in pin-depends field (#4897)

• Add opam admin migrate-extrafiles which moves all extra-files of an existing opam repository into extra-sources. Thanks to @hannesm for this contribution

• The -i/--ignore-test-doc argument has been removed from opam admin check (#6335)

Other noteworthy changes

• opam pin/opam pin list now displays the current revision of a pinned repository in a new column. Thanks to @desumn for this contribution

• The prebuilt Windows binary now includes Cygwin's setup-x86_64.exe in the binary itself as fallback in case cygwin.com is inaccessible (#6538). Opam will also no longer fail if cygwin.com is inaccessible when checking for upgrades of setup-x86_64.exe (#6495, partial fix for #6474)

• Symlinks in repositories are no longer supported (#5892)

• Fix sandboxing support in NixOS (#6333)

• Add the OPAMSOLVERTOLERANCE environment variable to allow users to fix solver timeouts for good (#3230)

• Fix a regression on opam upgrade <package> upgrading unrelated packages (#6373). Thanks to @AltGr for this contribution

• Fix pin-depends for with-* dependencies when creating a lock file (#5428)

• opam admin check now sets with-test and with-doc to false instead of true

• Add apt-rpm/ALTLinux family support for depexts. Thanks to @RiderALT for this contribution

• Remove handling of the OPAMSTATS environment variable (#6485). Thanks to @hannesm for this contribution

• Fix the detection of installed external packages on OpenBSD to not just consider manually installed packages (#6362). Thanks to @semarie for this contribution

• Disable the detection of available system packages on SUSE-based distributions (#6426)

And many other general, performance and UI improvements were made and bugs were fixed. You can take a look to previous blog posts. API changes and a more detailed description of the changes are listed in:

• the release note for 2.4.0~alpha1
• the release note for 2.4.0~alpha2
• the release note for 2.4.0~beta1
• the release note for 2.4.0~rc1
• the release note for 2.4.0

This release also includes PRs improving the documentation and improving and extending the tests.

Please report any issues to the bug-tracker.

We hope you will enjoy the new features of opam 2.4!