[Rd] declare and validate options

[Antoine Fabri]

>
> I think there are too many packages that would need changes under this
> scheme.


There would be zero if the registration of options is not required for
packages first uploaded on CRAN before the feature is implemented.
If an option is not registered no validation is triggered and nothing
breaks even if we opt in the behavior.


> If those functions could be made simple enough and bulletproof and were
> widely adopted, maybe they'd be copied into one of the base packages,
>

Sure but realistically few maintainers will opt-in for more restrictions.
if posit did something on those lines maybe it would have a chance but
otherwise I don't see an optional feature like this spread very far.
Or we need this package to make working with options really really much
easier for themselves as developers, not just beneficial for users in the
long run.

Le ven. 29 mars 2024 à 16:25, Duncan Murdoch <murdoch.duncan using gmail.com> a
écrit :

> On 29/03/2024 10:52 a.m., Antoine Fabri wrote:
> > Dear r-devel,
> >
> > options() are basically global variables and they come with several
> issues:
> > * they're not really truly owned by a package aside from loose naming
> > conventions
> > * they're not validated
> > * their documentation is not standard, and they're often not documented
> at
> > all, it's hard to know what options exist
> > * in practice they're sometimes used for internal purposes, which is at
> > odds with their global nature and contribute to the mess, I think they
> can
> > almost always be replaced by objects under a `globals` environment in the
> > namespace, it's just a bit more work
> >
> > I tried to do as much as possible with static analysis using my package
> opt
> > but it can only go so far : https://github.com/moodymudskipper/opt
> >
> > I think we can do a bit better and that it's not necessarily so complex,
> > here's a draft of possible design :
> >
> > We could have something like this in a package to register options along
> > with an optional validator, triggered on `options(..)` (or a new
> function).
> >
> > # similar to registerS3method() :
> > registerOption("mypkg.my_option1")
> > registerOption("mypkg.my_option2", function(x) stopifnot(is.numeric(x))
> > # maybe a `default` arg too to avoid the .onLoad() gymnastics and
> invisible
> > NULL options
> >
> > * validation is a breaking change so we'd have an environment variable to
> > opt in
> > * validation occurs when an option is set AND the namespace is already
> > loaded (so we can still set options without loading a namespace) OR it
> > occurs later when an applicable namespace is loaded
> > * if we register an option that has already been registered by another
> > package, we get a message, the validator of the last loaded namespace is
> > used, in practice due to naming conventions it doesn't really happen,
> CRAN
> > could also enforce naming conventions for new packages
> > * New packages must use registerOption() if they define options, and
> there
> > must be a standard documentation page for those, separately or together
> > (with aliases), accessible with `?mypkg.my_option1` etc...
> >
> > This could certainly be done in different ways and I'd love to hear about
> > other ideas or obstacles to improvements in this area.
> >
>
> I think there are too many packages that would need changes under this
> scheme.
>
> A more easily achievable improvement would be to provide functions to
> support registration, validation and documentation, and leave it up to
> the package author to call those.  This wouldn't give you validation at
> the time a user set an option, but could make it easier to validate when
> the package retrieved the value:  specify rules in one place, then
> retrieve from multiple places, without needing to duplicate the rules.
>
> If those functions could be made simple enough and bulletproof and were
> widely adopted, maybe they'd be copied into one of the base packages,
> but really the only need for that would be to support validation on
> setting, rather than validation on retrieval.
>
> Duncan Murdoch
>

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