Opam 2.2 init with MSYS2

[rjbou]

Opam 2.2 init on Windows is focused on resolving a pre-existent Cygwin install, or install opam internal one. Functions that detect if a Cygwin install is present are strictly checking a Cygwin one. This behaviour broke opam usage under MSYS2. As MSYS2 Cygwin is a Cygwin variant, it is not detected, and no specific handling of paths, syscall, etc. are done.

MSYS2 is not officially supported (not testing it in a regular basis), we should ensure that we can keep MSYS2 users to have a way to use opam.

This PR fixes that behaviour by relaxing Cygwin install checks to accept variants. As for Cygwin setup for opam init, a check of the install is done, and to keep the information, the config file is appended with

global-variables: [os-distribution "msys2" "Set by opam init"]

to be sure that further invocations of opam we don't loose that we are in an MSYS2 context (related to #5348).

ftm in the PR, there is no sys-package-manager-cmd setting, user can set it by hand using opam option. It is an open question.

fixes #5683

/cc @jonahbeckford

[kit-ty-kate]

I have trouble testing this PR.

• opam init --bare won't work because setting C:\msys64 as a manual cygwin install fails with cygcheck.exe not found
• opam init --bare --no-cygwin-setup won't work because of Broken use of curl in 2.2.0~alpha3 on native Windows #5681

How are users of MSYS2 expected to use opam?

[jonahbeckford]

Thanks!

I am going to set expectations that I won't be able to look at this for at least a week. Most likely two weeks. But I will get to it!

[jonahbeckford]

Yep, same issues that @kit-ty-kate reported.

WDAGUtilityAccount@37bfe102-8339-4958-b1e5-11ac3588b96d CLANG64 /c/Users/WDAGUtilityAccount/Tools/opam
# ./opam init --yes --no-setup --bare --disable-sandboxing '--git-location=/c/Program Files/Git/cmd' --cygwin-location=/c/msys64 default https://opam.ocaml.org
[WARNING] Flag --cygwin-location is experimental, there is no guarantee that it will be kept; avoid using it in scripts.
[WARNING] Flag --git-location is experimental, there is no guarantee that it will be kept; avoid using it in scripts.
No configuration file found, using built-in defaults.

<><> Git ><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>  🐫
Using Git from C:\Program Files\Git\cmdYou can change that later with 'opam option "git-location=C:\A\Path\bin"'
<><> Unix support infrastructure ><><><><><><><><><><><><><><><><><><><><><>  🐫
[ERROR] Error while checking Cygwin install (C:\cygwin64): bin\cygcheck.exe not found in C:\msys64

It clearly though is using cygpath to translate paths which is the main thing we wanted.

Test Apparatus (for me)

• https://gitlab.com/dkml/distributions/dkml
• Package-WindowsSandbox target from pkg\bump\WindowsSandbox\CMakeLists.txt

.\install-vcruntime.cmd
.\install-msys2.cmd
.\install-winget.cmd
.\install-git.cmd
cd opam # Unpack the .zip from GitHub Actions
C:\msys64\msys2_shell.cmd -here -clang64

[rjbou]

From dev meeting, there is 2 todos in this PR:

• lookup for cygcheck in <path>/usr/bin too (ftm is is only in <path> and <path>/bin)
• add a lookup mechanism for determining pacman location, and confirm with user.

[rjbou]

Updated PR, previous 2 points resolved.

[kit-ty-kate]

Thanks a lot! It works really well as far as i tested! (being: opam init --bare, opam switch create --empty, opam install conf-autoconf)

[kit-ty-kate]

Thanks!

[s5bug]

When this makes it to a build, what will the procedure be for ripping out the OPAM Cygwin and configuring it to use my MSYS2?

[kit-ty-kate]

@s5bug something like:

opam init '--cygwin-location=C:\msys64'

and without the option (a simple opam init) you'll be asked if you want to install the default Cygwin (recommended) or provide a custom location.