Feedback on this post is welcomed on Discuss!

We are indescribably thrilled to announce the second beta release of opam 2.2.0.

It contains everything required to be able to make opam-repository compatible with Windows, as well as a whole bunch of fixes. You can view the full list of changes in the release note.

We'll post another blog post very soon with more directions on how to test opam on Windows with this release.

This version is a beta, we invite users to test it to spot previously unnoticed bugs as we head towards the stable release.

Changes

Windows support

This beta introduces a handful of changes necessary to be able to make the default opam-repository support Windows out of the box:

• Add a new sys-ocaml-system init default global eval variable
• Hijack the "%{var?string-if-true:string-if-false-or-undefined}%" syntax to support extending the variables of packages with + in their name (conf-c++ and conf-g++ already exist) using "%{?pgkname:var:}%"
• Add winsymlinks:native to the CYGWIN environment variable when installing a package on Windows. In particular, this provides a workaround when extracting ocamlbuild's sources.
• Internal Cygwin installation's bin directory is placed as far down PATH as is necessary not to shadow bash, tar, sort or git
• Disable ACL in Cygwin internal install to avoid permission mismatch errors

We expect to be able to show the proposed changed to opam-repository very soon to take advantage of all these changes.

opam-repository scalability

The current draft resolution resulting from the discussion in ocaml/opam-repository#23789 about the scalability of opam-repository includes the removal of some packages. However currently, opam uses the patch system command to apply changes from a repository. The behaviour of that command is thus very important and it is a known behaviour for the macOS and BSDs patch command to not be able to delete files which leads to failures and inconsistencies for opam. Package managers on those platforms installing opam already make opam depend on GNU patch, however a certain number of people do not install opam via a system package manager (e.g. our own install script!) and end up using their system version of patch. This is in particular a problem on macOS as the name of the GNU patch command is not gpatch like on BSDs but simply patch when installed via Homebrew.

This issue is surprisingly tricky to fix, and after many trials and errors, we've decided to:

• Warn if GNU patch is not detected when a patch is applied
• Use gpatch by default instead of patch on NetBSD and DragonFlyBSD
• Use gpatch if it exists and is detected as GNU patch when patch is not GNU patch

These changes will make their way to the upcoming opam 2.1.6, in a few weeks.

Other noteworthy changes

• Recommend enabling Developer Mode on Windows. This allows the creation of symlinks without requiring elevation. Longer-term, the aim is that we should never require Developer Mode, but at the moment more things work with it than without it!
• Mark the internal Cygwin installation as recommended. Please don't try to maintain your own Cygwin install for use with opam unless you really know what you're doing!
• Fix MSYS2 support. For 2.2.0, the focus has been on Cygwin, so configuring opam to use MSYS2 is quite manual. Please note that even if opam can use a MSYS2 installation, it is not yet officially supported and opam repository is not yet MSYS2 compatible. Use opam with MSYS2 only if you really really know what you're doing!
• Fix issues when using fish
• Improve the internal Cygwin installation during init on Windows
• Unixify Windows paths in init shells scripts
• Disable Software Heritage fallback by default as there currently no CI job in opam-repository to check validity of proposed swhid regarding release archive (neither publication tools support) and some concerns were raised regarding the degree of trust of the hashing method used by Software Heritage (sha1).
• Make sure opam source --dev with git sources, clones the whole repository instead of using --depth=1
• Sandbox: Mark the user temporary directory (as returned by getconf DARWIN_USER_TEMP_DIR) as writable when TMPDIR is not defined on macOS
• Add Warning 69: Warn for new syntax when package name in variable in string interpolation contains several '+' (this is related to the "hijack" item above)
• Add support for Wolfi OS, treat it like Alpine family as it also uses apk
• Upgrade the vendored dune package to 3.14.2 to allow to compile opam when the environment contains unicode characters on Windows (in particular, this means opam now works if your username contains accented characters)
• Upgrade other vendored packages (cmdliner 1.2.0, re 1.11.0, ocamlgraph 2.1.0, opam-file-format 2.1.6)

Various other general and performance improvements were made and bugs were fixed. API changes are denoted in the release note. This release also includes PRs improving the documentation and improving and extending the tests.

Windows Support

As we've said above we're writing a separate blog post to present how to test this new release of opam on Windows.

Stay tuned!

Try it!

In case you plan a possible rollback, you may want to first backup your ~/.opam directory.

The upgrade instructions are unchanged:

1. Either from binaries: run

   bash -c "sh <(curl -fsSL https://opam.ocaml.org/install.sh) --version 2.2.0~beta2"

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

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

You should then run:

opam init --reinit -ni

Please report any issues to the bug-tracker.

Thanks for trying this new release out, and we hope you will enjoy the new features!