usethis::use_lifecycle() creates R CMD check note

[florianm]

Problem

First reported at r-lib/lifecycle#22

usethis::use_lifecycle() allows to use \lifecycle{...} in function docs. If lifecycle is not referenced anywhere else in the package, R CMD check will raise a NOTE.

# develop a package
usethis::use_lifecycle()
# add \lifecycle{...} to some function docs
goodpractice::goodpractice() # raises R CMD check NOTE on unused library `lifecycle`:

N  checking dependencies in R code (401ms)
   Namespace in Imports field not imported from: ‘lifecycle’
     All declared Imports should be used.

@lionel- suggested to include a NOOP anywhere in the code:

if (FALSE) lifecycle::deprecate_soft()

This expression can live in a stand-alone file like R/utils-lifecycle.R.
To preserve test coverage, depending on the coverage tool used, this file should be excluded. For codecov.io, this could look like this. Thinking out loud: it is fine to exclude from tests, as the expression will never run.

As a feature request to usethis::use_lifecycle(), could I suggest to

• generate a file containing a NOOP like if (FALSE) lifecycle::deprecate_soft(), and
• exclude that file from whichever test coverage tool is used (or at least message to do so).