setDT Fails to Detect Locked Objects In Corner Case

[brodieG]

Warning, running the following code will modify objects in locked namespaces:

mtcars2 <- mtcars
setDT(mtcars2)
mtcars                         # this is now a data.table

Obviously this happens because mtcars is never copied since mtcars2 is not touched. This bypasses the setDT safety check because the name mtcars2 is defined in .RGlobalEnv and is not locked, even though the associated SEXP is still the one in package:datasets.

This actual issue came up in the following example:

library(magrittr)
mtcars %>% setDT

Where magrittr "copies" mtcars to ., but since . isn't modified, it still points to the original mtcars SEXP.

[arunsrinivasan]

Unfortunately locked binding allows an object to be modified by reference. setDT checks if an environment is locked, and if so errors. But mtcars2 isn't. I don't think there's anything we can do about this.

[brodieG]

You could check whether NAMED() == 2 and refuse to apply setDT, with a warning on how to circumvent, and possibly an argument in setDT(force=TRUE) to override. Not a huge deal in my books though.

Alternatively, duplicate the object if NAMED() == 2?

[arunsrinivasan]

Brodie, those won't work since all data.frames have NAMED() = 2 upon creation.

[brodieG]

Didn't realize that. Do you want me to close this or just leave it here as wontfix for reference?

[arunsrinivasan]

It's better to have it open, since it's still an issue. I labelled it just for easier searching.