[R-pkg-devel] Undocumented requirement for CRAN

[Jiří Moravec]

There are quite a lot of undocumented requirement for CRAN.
This bite me several times already.

They are not documented in the 
https://cran.r-project.org/doc/manuals/R-exts.html
Nor they are marked by `R CMD check`

Ideally, these would be documented AND flagged by R CMD check.
Otherwise, it is a waste of time for both CRAN team and package developers.

So far, the undocumented requirements that were flagged for me are:

* Documenting return value even for functions without return value
   -- This is even contrary to the base code (i.e., many graphical 
functions do not document return values)

* Commented code in examples

* Examples for non-exported internal functions
   -- I understand that this is related to the fact that any ::: is 
highly discouraged (which is documented) and that examples for 
unexported functions cannot be run without ::: .
      But I like the idea of using properly documented internal 
functions and usage of examples as for rudimentary testing.


Are there any other undocumented requirements?

(we could maybe create PR for `.check_packages*` so that these problems 
are flagged by `R CMD check`)

-- Jirka