Add Option to Sync renv Cache

[nateybear]

What problem did you solve?

I frequently run into issues where the language or help server will start up and then crash because it cannot find packages (usually jsonlite). There is the option to add .libPaths in the extension currently, but the renv package cache is unstable and liable to change with different architectures and versions of renv.

Users can get "lucky" when the extension starts an R process in a directory where an .Rprofile bootstraps the renv environment correctly, but for situations where this does not happen (which I find happens often for me), the user is out of luck.

This pull request adds a boolean option to the extension where users can opt into automatically adding the renv package cache to .libPaths when these R processes start up. The mechanism is to write an environment variable on the typescript side that is then parsed as a boolean on the R side, following patterns elsewhere in the code. We then ensure that renv is in fact installed—issuing a warning but not crashing if it isn't—and then read the package cache path from renv::paths$cache() and add this to our .libPaths.

Screenshot

When the language server starts up and renv is bootstrapped, the .libPaths look like this:

When the language server starts up somewhere that does not bootstrap renv, .libPaths looks like this:

Is it a problem that we see packages that the user doesn't?

This change does not automatically bootstrap renv when an R terminal is created. Hence, the language and help servers may have more packages visible to them than the user's terminal does. Users familiar with renv should know how to rectify this, and the user who "accidentally" activates this option without knowing anything about renv can just install the missing packages. The major problem that this change overcomes is that jsonlite and httpgd often get installed into the renv package cache by the extension, and this is a problem that can't be overcome as easily as the accidental user error mentioned above.

[nateybear]

I should add that even when renv is bootstrapped, you have to manually maintain a dependencies.R file and make sure to add jsonlite, httpgd et al. to it, since .libPaths will point to the sandbox not the cache. This is another pain point for me that this pull request fixes.

[renkun-ken]

LGTM
Many thanks for working on this!

[nateybear]

LGTM

Many thanks for working on this!

Very welcome! I enjoyed working on it.