[R-package] [ci] Add option to skip installation in build_r.R

[jameslamb]

Right now, Rscript build_r.R will build a source distribution of the R package and install it. In this PR, I propose an addition to the script to tell build_r.R to just build the package tarball but not install it.

This should allow us to cut a few minutes out of the r-package tasks in CI!

Right now we are doing this:

Rscript build_r.R
R CMD check lightgbm_*.tar.gz

That means we're building lib_lightgbm twice, without getting any extra testing benefit. In fact, I think that the scenario of checking a source tarball on a system where lightgbm hasn't been installed already is an even better test of the experience for our users!

Note that this PR won't change the existing behavior for anyone using build_r.R. The default will still be to both build and install.

[StrikerRUS]

Linking #2441 for example of commandArgs usage.

[StrikerRUS]

LGTM! Really huge difference it time! 🎉

[jameslamb]

Seeing this on the linux CI task in Azure DevOps and I am very confused

I don't understand how this could be failing on Azure DevOps but not Travis 🤔

My best guess is that some very new version of one of our dependencies previously relied on Matrix and just factored it out, and maybe we got a slightly newer version on Linux because we get source packages there and binary packages on Mac.

Either way, we probably should have been installing Matrix all along since it is listed in Imports, so I'll just add it.

EDIT: wait no we already install Matrix! I see this in the logs:

ERROR: dependency ‘lattice’ is not available for package ‘Matrix’

And further up:

I hope this was just transient. Pushing another small commit to test.

[jameslamb]

This PR is ready to merge, but I think we're facing a bug Travis faced a few days ago and thought they'd fixed.

Successful build: https://travis-ci.org/github/microsoft/LightGBM/builds/669022302

Details on the issue from https://www.traviscistatus.com/:

[jameslamb]

close-reopen to retrigger CI to try to get past transient issues

[jameslamb]

This seems to be working! Going to merge it so we can start getting the benefits in our CI 😀

[StrikerRUS]

@jameslamb
Just curious: what is the default set of options?

[jameslamb]

This set is the default set. From ?install.packages

The default, NA, means c("Depends", "Imports", "LinkingTo").

Those are the minimum ones needed to load a package. In case you're not familiar with them:

• Depends: Has to be present to install your package. Will be loaded whenever your package is loaded.
• Imports: Has to be present to install your package. Will only be loaded when your package calls code from them.
• LinkingTo: Has to be present to install your package. These are usually header-only packages that your code links to, e.g. the BH package for Boost.

This commit just makes that explicit.

[StrikerRUS]

Got it, thanks a lot for the detailed explanation!