Prevent installing the package itself in setup-r-dependencies

[riccardoporreca]

Is your feature request related to a problem? Please describe.
When installing package dependencies, it might be desirable / convenient not to install the package itself, which is also the approach of e.g. pak::local_install_dev_deps(). Action setup-r-dependencies however does install the package.

• A use-case we have is a package that needs to be checked (and installed) headlessly.
• For a CI workflow running R CMD check, the installation is unneccessary and might waste some precious time (e.g. with compiled code).

Describe the solution you'd like

• Allow not installing the package itself in setup-r-dependencies, driven e.g. by a new "parameter" under with:.
• Consider whether not installing the package might be the sensible default behavior (given R CMD check considerations from above).

Describe alternatives you've considered
The alternative is to not use setup-r-dependencies and go for the old, lengthy approach taking explicit care of caching in the workflows, like in the pre-setup-r-dependencies examples, e.g. https://github.com/r-lib/actions/blob/a880f739a14aad0d50888cb746c1bc2db2257257/examples/check-standard.yaml

Additional context
NULL

[jimhester]

I think this will be resolved eventually by r-lib/pak#319 (comment)

But possibly we could in the meantime explicitly filter local::. from the dependencies.

[riccardoporreca]

Thanks for the prompt reply @jimhester!

If this is already considered the way forward for setup-r-dependencies (through the new pak functionality once available), I agree you may want to already start by explicitly filtering out local::. in the "Install dependencies" step.

[burgerga]

Another use case for this is if you setup a shiny app using shiny::shinyAppTemplate(),
and use a DESCRIPTION file to manage the package dependencies (as suggested by https://usethis.r-lib.org/reference/use_description.html).

Then https://github.com/rstudio/shiny-testing-gha-example can be greatly simplified by using setup-r-dependencies, but currently, it tries to install the shiny app as a package and this can fail (because it is not a package)

[gaborcsardi]

This is now fixed in the v2 tag.

[github-actions]

This issue has been automatically locked. If you believe you have found a related problem, please file a new issue and include a link to this issue