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# Upgrading MSYS2

When installing GHC on Windows, Stack will also install
[MSYS2](http://www.msys2.org/). MSYS2 provides a Unix shell and environment, and
is necessary for such things as running configure scripts. This section explains
the steps required to upgrade the MSYS2 version used by Stack.

1.  Download latest installer(s) from MSYS2's website. Historically, there were
    separate installers for 32 bit (`i686`) and 64 bit (`x86_64`). On
    17 May 2020, the MSYS2 project announced it did not plan to release any
    further `i686` installers. An installer is an executable, versioned by a
    date in the format YYYYMMDD - for example, `msys2-x86_64-20220503.exe`.

2.  Run the installer and install to the default location (`C:\msys64` for the
    64 bit version; the location for the 32 bit version was `C:\msys32`). Do not
    use the installed version; it will create a `.bash_history` file if you do.

3.  Create an `.tar.xz` archive file for each relevant directory (eg
    `C:\msys64`). That is best done using the same `7z` executable in Stack's
    'programs' directory (`stack path --programs`) that will be used to extract
    files from the archive. That can be done in two steps: the first to create a
    `.tar` archive, and the second to create a `.tar.xz` archive. If the current
    working directory is Stack's 'programs' directory:

    ~~~text
    ./7z a msys2-YYYYMMDD-x86_64.tar C:\msys64
    ./7z a msys2-YYYYMMDD-x86_64.tar.xz msys2-YYYYMMDD-x86_64.tar
    rm msys2-YYYYMMDD-x86_64.tar # Tidy up
    ~~~

    !!! note

        Previously, the advice was that creating the archive file required a
        version of [`tar`](https://www.gnu.org/software/tar/tar.html) that
        supported the compression option `--xz`. The version of `tar` that is
        supplied with Windows (`C:\Windows\System32\tar.exe`) does not support
        that option, but MSYS2 can supply a
        [version](https://packages.msys2.org/package/tar) that does (using its
        `pacman` tool). Using the existing Stack-supplied MSYS2, in PowerShell
        and located in a folder with write permissions (so the `.tar.xz` file
        can be created), it was advised to command:

        ~~~text
        stack exec -- pacman -S tar
        stack exec -- tar cJf msys2-YYYYMMDD-x86_64.tar.xz C:\msys64
        ~~~

        However, in the case of `msys2-20220503` that resulted in an archive
        that could not extracted on a terminal that did not have elevated rights
        ('Run as administrator') due to errors
        `ERROR: Cannot create symbolic link : A required privilege is not held by the client`.

4.  Test that the Stack-supplied `7z` executable can extract the files in the
    archive that has been created without error:

    ~~~test
    ./7z x msys2-YYYYMMDD-x86_64.tar.xz
    ./7z x msys2-YYYYMMDD-x86_64.tar
    ~~~

5.  Create a new release tagged and named `msys2-YYYYMMDD` in the `master`
    branch of the
    [commercialhaskell/stackage-content](https://github.com/commercialhaskell/stackage-content)
    GitHub repository, uploading the tarball file(s) into that release.

6.  Changes need to be made to the
    [stackage-content/stack/stack-setup-2.yaml](https://github.com/commercialhaskell/stackage-content/blob/master/stack/stack-setup-2.yaml)
    file, to switch over to using the newly uploaded files. For example
    (extract):

    ~~~yaml
    # For upgrade instructions, see: https://github.com/commercialhaskell/stack/blob/stable/doc/maintainers/msys.md
    msys2:
      windows32:
        version: "20200517"
        url: "https://github.com/fpco/stackage-content/releases/download/20200517/msys2-20200517-i686.tar.xz"
        content-length: 79049224
        sha256: 9152ddf50c6bacfae33c1436338235f8db4b10d73aaea63adefd96731fb0bceb
      windows64:
        version: "20220503"
        url: "https://github.com/commercialhaskell/stackage-content/releases/download/msys2-20220503/msys2-20220503-x86_64.tar.xz"
        content-length: 93835868
        sha256: c918f66e984f70add313ee3a5c5b101132cd93d5a3f8e3555e129e2d3dcb3718
    ~~~

    The `content-length:` key's value is the size of the file in bytes. It can
    be obtained from the `Length` field of the `dir` command. The `sha256:`
    key's value can be obtained from the command (in PowerShell):

    ~~~text
    (Get-FileHash msys2-YYYYMMDD-x86_64.tar.xz -Algorithm SHA256).Hash.ToLower()
    ~~~

    The `sha256:` key only accepts lowercase hash results as values.

7.  The changed `stack-setup-2.yaml` file should be tested locally. This can be
    done by:

    * temporarily disabling the existing local copy of MSYS2 by changing the
      name of the `msys2-YYYYMMDD.installed` file in the `stack path --programs`
      directory; and

    * executing the command:

        ~~~text
        stack setup --setup-info-yaml <path to local copy of stack-setup-2.yaml>
        ~~~

    If all is well, the command should proceed to download the updated version
    of MSYS2 that has been specified.

8.  Raise a pull request on `commercialhaskell/stackage-contents` for the
    changes to the locally-tested `stack-setup-2.yaml` file.