When a package Depends on data.table (and does not import it), sometimes using devtools::test on the package can break some functions that use data.table. I filed a bug report for data.table, but it's not clear that is a data.table issue. Here is the link to the data.table bug report: https://r-forge.r-project.org/tracker/?func=detail&atid=975&aid=2367&group_id=240

I don't see a way to attach files to this, but here is a link (that should be a direct download) to the package that I attached to the data.table bug report: https://r-forge.r-project.org/tracker/download.php/240/975/2367/275/anRpackage_1.0.tar.gz

The package has 2 functions: myFun assigns some values to a column of a data.table by reference. myFun2() creates a data.table, and then calls myFun() to change the values of one of the columns of the data.table myFun2() created.

The package also has a testthat test that simply tests that myFun2 returns a data.table.

The package passes R CMD check, and test_dir. However, if I use devtools::test, I get an error, and for the remainder of the R session, myFun() and myFun2() will fail with the same error.

Here is a link to the output from an interactive session (attached to the data.table bug report) showing the problem: https://r-forge.r-project.org/tracker/download.php/240/975/2367/276/interactive.txt