[Rd] Upgrading a package to which other packages are LinkingTo

[Duncan Murdoch]

I think there's one typo in your post which may confuse some readers; 
I've edited it inline below.  My comments on the suggestion are at the 
bottom of the message.


On 16/12/2016 5:35 AM, Kirill Müller wrote:
> Hi
>
>
> I'd like to suggest to make R more informative when a user updates a
> package A where there's at least one package B that has "LinkingTo: A"
> in its description.
>
> To illustrate the problem, assume package A is updated so that its C/C++
> header interface (in inst/include) is changed. For package B to pick up
> these changes, we need to reinstall package A.

This should be "reinstall package B", I think.

 > In extreme cases, if B
> also imports A and uses functions from A's shared library, failure to
> reinstall B may lead to all sorts of undefined behavior.
>
> I've stumbled over this recently for A = Rcpp 0.12.8 and B = dplyr 0.5.0
> [1], with a bug fix available in Rcpp 0.12.8.2. Simply upgrading Rcpp to
> 0.12.8.2 wasn't enough to propagate the bug fix to dplyr; we need to
> reinstall dplyr 0.5.0 too.
>
> I've prepared an example with R-devel r71799. The initial configuration
> [2] is Rcpp 0.12.8 and dplyr 0.5.0. There is no warning from R after
> upgrading Rcpp to 0.12.8.2 [3], and no warning when loading the (now
> "broken") dplyr 0.5.0 linked against Rcpp 0.12.8 but importing Rcpp
> 0.12.8.2 [4].
>
> As a remedy, I'd like to suggest that upgrading Rcpp gives a warning
> about installed packages that are LinkingTo it [3], and that loading
> dplyr gives a warning that it has been built against a different version
> of Rcpp [4], just like the warning when packages are built against a
> different version of R.

I'd call it a bug that we allow the situation to exist without some sort 
of warning or error.

Your suggestion is one remedy, but might lead to too many warnings (or 
too many unnecessary recompiles).

An argument could be made that it's a bug in package A that it has 
updated its interface in a way that breaks packages that use it.

Perhaps the solution is to recommend that packages which export their 
C-level entry points either guarantee them not to change or offer 
(require?) version checks by user code.  So dplyr should start out by 
saying "I'm using Rcpp interface 0.12.8".  If Rcpp has a new version 
with a compatible interface, it replies "that's fine".  If Rcpp has 
changed its interface, it says "Sorry, I don't support that any more."

Duncan Murdoch

>
> Thanks.
>
>
> Best regards
>
> Kirill
>
>
> [1] https://github.com/hadley/dplyr/issues/2308#issuecomment-267495075
> [2] https://travis-ci.org/krlmlr/pkg.upgrade.test#L589-L593
> [3] https://travis-ci.org/krlmlr/pkg.upgrade.test#L619-L645
> [4] https://travis-ci.org/krlmlr/pkg.upgrade.test#L671-L703
>
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