setup-r-dependencies: document 'pak-version: none', add 'repo'

[gaborcsardi]

'repo' is a better option for environments like in #918.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.61%. Comparing base (108c7a6) to head (4fde540).
Report is 1 commits behind head on v2-branch.

Additional details and impacted files

@@            Coverage Diff             @@
##           v2-branch     #919   +/-   ##
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  Coverage      84.61%   84.61%           
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  Files              3        3           
  Lines             13       13           
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  Hits              11       11           
  Misses             2        2           

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[jeroen]

Is it possible to use pak-version: none and use pak from the default library (without a custom R_LIB_FOR_PAK)? I tried the workflow below but that fails. I was expecting R_LIB_FOR_PAK to just default to R_LIBS_USER?

      - name: pre-install pak
        run: |
          install.packages("pak", repos = "https://r-lib.r-universe.dev")
        shell: Rscript {0}

      - uses: r-lib/actions/setup-r-dependencies@feature/pak-from-repo
        with:
          extra-packages: any::rcmdcheck
          needs: check
          pak-version: none

[gaborcsardi]

It defaults to R_LIBS_SITE, if unset, but you can set it to whatever you like.

[jeroen]

So why does it fail above?

[gaborcsardi]

Because you didn't install it there:

Installing package into 'D:/a/_temp/Library'

You need to install it in $R_LIB_FOR_PAK

[gaborcsardi]

Why would you pre-install it, though, if you have access to the default repo that setup-r-dependencies uses?

[gaborcsardi]

I have a number of workflows that do this, e.g. for FreeBSD:
https://github.com/r-lib/ps/blob/1e8305b0f5194d40f7bb854d2d5dde14dcca809b/.github/workflows/freebsd.yaml#L36

And the action that sets up the VM pre-installs pak:
https://github.com/r-hub/actions/blob/b6718c51780280f1cfb5afc1cfa1008a4ae8498e/setup-r-freebsd/action.yaml#L49
and makes sure that the env var is set:
https://github.com/r-hub/actions/blob/b6718c51780280f1cfb5afc1cfa1008a4ae8498e/setup-r-freebsd/Rscript#L20

Although the last one is probably not needed, because it is the default, anyway.

[jeroen]

Why would you pre-install it, though, if you have access to the default repo that setup-r-dependencies uses?

Just trying to test what I thought was the intended use case of pak-version: none. The comment says Use this if you want to install pak yourself manually. so that is what I test.

Not sure why we would need a third package library R_LIB_FOR_PAK just for pak. Anyway maybe I don't understand the use case, if this is the intended behavior, it works as advertised.

[gaborcsardi]

Not sure why we would need a third package library R_LIB_FOR_PAK just for pak.

Because installing it into the user library causes issues if a package depends on pak, and needs a different version. Installing it into the system library causes permission issues on some systems.

[gaborcsardi]

Thanks for the testing!

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