Can we set keep.source to true by default when package is installed?

[jaspercooper]

@nfultz has outlined the problem very nicely here

Basically, construct_design_code() is using getSrcref() to grab the source code of the designer functions in the package. That's great and works fine locally because we can set the project to run R CMD INSTALL --no-multiarch --with-keep.source DesignLibrary by default.

The problem arises in two instances:

1. I don't think that R CMD CHECK has keep.source as an option, so our checks will always break. Is there a way to set global variables when the check runs, before the package is installed?
2. When users don't specify that source should be kept when installing, the package breaks massively.
   This breaks bigly:

   detach("package:DesignLibrary", unload = TRUE)
   devtools::install_github("DeclareDesign/DesignLibrary")
   library(DesignLibrary)
   simple_two_arm_designer()

   This works:

   detach("package:DesignLibrary", unload = TRUE)
   devtools::install_github("DeclareDesign/DesignLibrary", keep_source = TRUE)
   library(DesignLibrary)
   simple_two_arm_designer()

@nfultz is there a way to ensure that keep.source is always true when the package is built? Can we set R_KEEP_PKG_SOURCE=yes as a side effect before installing the package on the user's computer, for example?

[jaspercooper]

OK I fixed 1 in 6a56044

[jaspercooper]

This is breaking everything too often -- I think we need to remove reliance on getSrcref()

[jaspercooper]

This has been fixed using the handler by @clabima and @nfultz