[Bioc-devel] requireNamespace() / loadNamespace() vs. Imports: / Depends: / Suggests:

[Michael Lawrence]

Modularization is a useful tool for managing complexity. In this case,
you could implement modularity in a number of ways, two obvious ones
are splitting functionality into different packages and wrapping code
in a conditional call based on requireNamespace(). It is not always
obvious which approach to take for a given module. If it's
sufficiently complex, it probably belongs in its own package. One
advantage of requireNamespace() is that it advertises the
functionality while still controlling complexity. Like having a
separate package, it still requires the user to take an extra step,
but discovering the functionality may have been easier.

Michael

On Thu, Apr 27, 2017 at 10:01 AM, Tim Triche, Jr. <tim.triche at gmail.com> wrote:
> Today I stumbled across requireNamespace() as a suggested approach to
> managing sprawling dependencies, particularly in packages that are meant to
> be "core" building blocks in e.g. BioC.
>
> http://r-pkgs.had.co.nz/namespace.html
>
> My reading (which may be very, very far off) is that when a desirable piece
> of code is "optional" in the sense of "the user can opt not to install
> these other 90 packages" but "suggested" in the sense of "it is suggested
> that the user bite the bullet anyways", a compromise is to Suggest:
> installation and then fail at runtime with a message from
> requireNamespace("suggestedPackage") if the suggestion is not heeded.  Is
> this considered good practice?
>
> Mulling it over, my initial reaction of "hey, that's cheating!" has given
> way to "this is a clever way not to overburden users".  Am I reading the
> underlying logic correctly?  I can think of numerous applications for this
> approach in packages I have developed, not the least of which is patching
> an ancient piece of code that performs a generalized Gamma deconvolution
> and once required C++ (hence I ended up commenting out the dependency,
> which broke most Windows users' installation of the entire package).
>
> Thanks,
>
> --t
>
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