run_onload(pkg = ".")as.package for more informationonLoad is created in the
package's devtools metdata to indicate that it's
attached. When a package is loaded with library() it calls
.onLoad(libpath, pkg), where libpath is the
library path for package, and pkg is the name of
the package. Because in-development packages are not
installed to a library, this function can't call
.onLoad with a proper libpath, so it uses
NULL instead.