Silently loading and Depends: versus NAMESPACE imports

Sat, Jan 28, 2012 7:52 AM

On 27.01.2012 15:57, Dirk Eddelbuettel wrote:

On 12 January 2012 at 12:12, Herv? Pag?s wrote:
| Hi Dirk,
|
| On 01/11/2012 11:42 AM, Dirk Eddelbuettel wrote:
|>
|>  R CMD check really hates it when my .onLoad() function contains
|>       suppressMessages(library(foo))
|
| Note that you can always fool 'R CMD check' by doing something like:
|
|      sillyname<- library
|      suppressMessages(sillyname("foo"))
|
| Also isn't suppressPackageStartupMessages() more appropriate?
|
|>
|>  However, _and for non-public packages not going to CRAN_ I prefer doing this
|>  over using explicit Depends or import statements in the NAMESPACE file as the
|>  latter do not give me an ability to make the loading less verbose.  With the
|>  R universe of packages being as vast as at is, a simple (non-public) package
|>  I have loads about five or six other packages explicitly, each of which loads
|>  even more.  The net result is totally intimidating _sixty lines full_ of
|>  verbose noise that is meaningful to me as an R programmer, but not for the
|>  colleagues expected to use the packages. It looks rather uninviting, frankly.
|>
|>  How do I use imports via NAMESPACE, and yet keep the noise level down to zero?
|
| If you only need to import foo (i.e. and actually don't need to attach
| it to the search path) then putting foo in Imports and using import
| statements in NAMESPACE will keep the noise level down to zero.

I don't think so.

I have an internal package, call it fooUtils, that (among other things) needs
to figure at startup whether it runs on this or that OS.

So that package fooUtils does

     .onLoad<- function(libname, pkgname) {

         if (.Platform$OS.type == "windows") {
             packageStartupMessage("Running on Windows")
     	# [... more stuff here ... ]
         } else if (.Platform$OS.type == "unix") {
             packageStartupMessage("Running on Linux")
     	# [... more stuff here ... ]
         } else {
             warning("Platform ", .Platform$OS.type, " not recognised")
             drives<- NULL
         }

         # ....

     }

Are you sure you want the messages in .onLoad rather than .onAttach?

See ?.onLoad and its "Good practice" section:

"Loading a namespace should where possible be silent, with startup 
messages given by .onAttach. These messages (and any essential ones from 
.onLoad) should use packageStartupMessage so they can be silenced where 
they would be a distraction."

Best,
Uwe

Silently loading and Depends: versus NAMESPACE imports

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