RTools42 support

[rok-cesnovar]

Submission Checklist

• Run unit tests
• Declare copyright holder and agree to license (see below)

Summary

Closes #637

Will post the final summary and reasons behind the fixes once we can confirm this is it - I am 90% certain that it is, but want a few others to test as well.

Copyright and Licensing

Please list the copyright holder for the work you are submitting
(this will be you or your assignee, such as a university or company):
Rok Češnovar

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[rok-cesnovar]

TODO:

• get some additional confirmation this is good for R 4.2 on Windows
• test that it works with Github Actions
• do the same processx env trick for Rtools 4.0 (avoid writing to user's .Renviron)
• bump minor version

[rok-cesnovar]

Everything should now be working for R 4.2 users on Windows. I confirmed this on Github Actions as well as some additional systems I can access. @tjmahr has confirmed that it works (with some warnings/error) in the issue. I was able to replicate his issues and fixed them.

@jgabry do you mind if I merge this assuming tests pass? I would like to make a Stan blog post warning users about what is going on. I bumped the package version as well.

The only really big change is the new withr dependency - each call to processx is now wrapped into a withr() call that makes sure all the right paths are set up. We previously did this by manipulating the PATH with Sys.setenv() and writing to .renviron in the toolchain check. I think this is cleaner and safer now. Do let me know if you disagree.

[rok-cesnovar]

I would like to merge this soon because the 4.2 release is now officially out.

[rok-cesnovar]

@jgabry do you mind if I go ahead and merge this PR with the bumped version? R 4.2 has been released and I want to put out a blog post with the news on how to address Stan+Windows+R4.2 issues.

I can rebuild the website once the PR is merged.

[jgabry]

Sorry for the delay, I've been away. Fine to merge if you think it's ready!

[rok-cesnovar]

Great, can you let me know what you run to rebuild the website?

[jgabry]

To rebuild the whole site:

withr::with_envvar(c("NOT_CRAN" = "true"), pkgdown::build_site(run_dont_run = TRUE, seed = 1234))

Do you want to do add an entry to the Releases page too? https://github.com/stan-dev/cmdstanr/releases

Thanks for fixing the windows issues!

[jgabry]

I have some time now so I can update the NEWS and add to the releases page

[rok-cesnovar]

Thanks!