with_makevars() does not keep contents of existing ~/.R/Makevars

[scanisius]

When I use with_makevars() in the presence of an existing ~/.R/Makevars file, the contents of the latter is simply ignored.

> readLines("~/.R/Makevars")
[1] "CC=/usr/local/bin/gcc"

> with_makevars(c(FC="/usr/local/bin/gfortran"), readLines(Sys.getenv("R_MAKEVARS_USER")))
[1] "FC=/usr/local/bin/gfortran"

The source of this issue is the delayed evaluation of the path = makevars_user() default argument. makevars_user() is only evaluated in set_makevars(), where the environment variable R_MAKEVARS_USER has already been changed to point to a temporary filename. If I pass the filename explicitly, the contents of Makevars are correctly retained.

> with_makevars(c(FC="/usr/local/bin/gfortran"), readLines(Sys.getenv("R_MAKEVARS_USER")), path="~/.R/Makevars")
[1] "CC=/usr/local/bin/gcc"      "FC=/usr/local/bin/gfortran"

So this issue can be fixed by forcing the evaluation of the path argument before passing it to set_makevars().

This issue affects local_makevars() too.

[jimhester]

Thank you for opening the issue and for supplying a reproducible example, it is a big help!