[R-pkg-devel] Handling Not-Always-Needed Dependencies?
Mark van der Loo
mark.vanderloo at gmail.com
Wed Aug 3 15:04:07 CEST 2016
>> Recommends: only gets installed, can be used via if(requireNamespace())
>> from the package and in pkg tests[1] [snip]
>> Build-Depends: gets installed before build, removed after.
>> Suggests: only installed when requested at install.packages() and only
>> used in examples/vignettes.
[snip]
> I'd much rather
> have a way of declaring explicitly the different aspects of dependence
> on a package rather than bundling them up into cute labels,
Agreed
> but it's too late for that now. However, we don't need to make things
worse.
Disagreed. We could follow the well-established practices of Debian (and
CRAN already does that, partially).
>> If 'tons of packages' are using if(requireNamespace) in their package
>> code there seems to be a need for something like this. [snip]
> I don't follow the argument here. What problem are you solving?
Basically I'm trying to address the idea suggested by Thomas, who started
this conversation, and make it a bit more explicit. I felt that the
discussion went a little off-track there.
Right now, when package code (not examples) uses a suggested package, part
of that package will by default not work - at least that's how people use
it now. I would like it to work by default. For examples/vignettes you
could be more forgiving since running an example is not core functionality
of a package.
>> Perhaps more controversially a 'Breaks' field could be considered. [snip]
> This isn't controversial, it's just a bad idea. Don't encourage people
> to break things.
Your reaction just proved my point about it being controversial. More
seriously, real progress is hardly ever possible without breaking things,
so I think at least people could have a serious discussion about it before
dismissing it simply as a bad idea. The Debian community obviously once
thought it was a good idea, so why not discuss it for R/CRAN? (discussions
are also an important way to progress even if no line of code is changed).
At the moment, I'm inclined against the idea, but I for one like to see me
proven wrong.
>> [1] actually, once we know a pkg is Recommended, the
>> 'if(requireNamespace)' could even be absorbed in the :: operator.
>I don't see how :: would be any different than it is now. If you don't
>have foo available, and you try to use foo::bar(), what would happen
>other than an error?
I think you're right there. <resets brain>.
Best,
Mark
Op wo 3 aug. 2016 om 13:41 schreef Duncan Murdoch <murdoch.duncan at gmail.com
>:
> On 03/08/2016 5:32 AM, Mark van der Loo wrote:
> >
> > After reading the link in Dirk's initial reply, how about adding fields
> > 'Recommends' and 'Build-Depends' to DESCRIPTION as in Debian?
> >
> > Recommends: only gets installed, can be used via if(requireNamespace())
> > from the package and in pkg tests[1]. [Debian: The Recommends field
> > should list packages that would be found together with this one in all
> > but unusual installations.]
> > Build-Depends: gets installed before build, removed after.
> > Suggests: only installed when requested at install.packages() and only
> > used in examples/vignettes.
>
> I think the distinction between Recommends and Suggests is too subtle
> here. I already think it's a bad thing that we are using these words in
> ways that don't really correspond to English usage. I'd much rather
> have a way of declaring explicitly the different aspects of dependence
> on a package rather than bundling them up into cute labels, but it's too
> late for that now. However, we don't need to make things worse.
>
> >
> > If 'tons of packages' are using if(requireNamespace) in their package
> > code there seems to be a need for something like this. Compliance to the
> > above can be checked automatically and a gradual implementation via
> > NOTE->WARNING->ERROR in R CMD check seems possible.
>
> I don't follow the argument here. What problem are you solving?
>
> > Perhaps more controversially a 'Breaks' field could be considered. There
> > are a few packages out there that have many, many, dependencies.
> > Implementing breaking updates currently depends on the willingness of
> > many authors to update their package or convincing the CRAN maintainers
> > to allow for (temporary) breakage.
>
> This isn't controversial, it's just a bad idea. Don't encourage people
> to break things.
>
> > The suggestion to have functions auto-install things is very
> > inconvenient for the good reasons pointed out by Thomas. Additionally,
> > it is often based on the wrong assumptions. Example: the RGtk2 package
> > has this habit of trying to install when libgtk2 is not on the path. But
> > in my case that is often exactly the case: it is just not on the path
> > (libgtk2 is on the network, the VM just doesn't know yet). So I'd rather
> > have a proper and accurate error message (which is good practice anyway).
> >
> >
> > Best,
> > Mark
> >
> > [1] actually, once we know a pkg is Recommended, the
> > 'if(requireNamespace)' could even be absorbed in the :: operator.
>
> I don't see how :: would be any different than it is now. If you don't
> have foo available, and you try to use foo::bar(), what would happen
> other than an error?
>
> Duncan Murdoch
>
> >
> >
> >
> >
> > Op wo 3 aug. 2016 om 01:46 schreef Duncan Murdoch
> > <murdoch.duncan at gmail.com <mailto:murdoch.duncan at gmail.com>>:
> >
> > On 02/08/2016 6:34 PM, Dirk Eddelbuettel wrote:
> > >
> > > On 2 August 2016 at 18:13, Duncan Murdoch wrote:
> > > | Okay, now I think I understand, but I agree with CRAN. It is not
> > > | feasible to tell if the test happened somewhere in the code
> > unless we
> > > | enforce a particular way of writing the test.
> > >
> > > Debian has well over 20k packages, and they are tested this way.
> > You just
> > > need to show the will of testing in an _empty_ environment to
> ensure
> > > _everything_ that is needed is loaded.
> > >
> > > | I would object if I had to write if (requireNamespace("foo"))
> > multiple
> > > | times just to satisfy CRAN's test, when any sane human could
> > tell that
> > > | the first test was sufficient.
> > > |
> > > | For example, if my package Suggests: foo, I should be able to
> write
> > > |
> > > | if (!requireNamespace("foo"))
> > > | stop("Package foo is needed for this example")
> > > |
> > > | and then merrily call foo::bar() as many times as I like.
> > > |
> > > | Or am I still misunderstanding you? What particular thing
> > should CRAN
> > > | change?
> > >
> > > You seem to misunderstand that both you and I want
> > >
> > > if (!requireNamespace("foo"))
> > > stop("Package foo is needed for this example")
> > >
> > > (or alternative per-call tests) and that CRAN does not enforce
> either.
> > >
> > > CRAN, like Hadley, just closes its eyes, swallows hard, and then
> > simply loads
> > > everything treating Suggests as if it were Depends.
> > >
> > > But it ain't. Suggests != Depends.
> > >
> > > Now clearer?
> >
> >
> > So really what you're suggesting is that CRAN should run tests with
> the
> > suggested packages absent. Presumably tests should also be run with
> > them present.
> >
> > But if they did that, the code that I want to write would call stop()
> > and fail. So we'd need some way to say "Let the user know they need
> > 'foo' to run this, but don't fail." And we'd need to phase this in
> > really gradually, because tons of packages are using code like my
> > example.
> >
> > You volunteered to help CRAN package checking. Why not put together
> > code to implement your idea, and see how big the problem would be to
> > phase it in, by seeing how many packages fail under it?
> >
> > Duncan Murdoch
> >
> > ______________________________________________
> > R-package-devel at r-project.org <mailto:R-package-devel at r-project.org>
> > mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-package-devel
> >
>
>
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