[R-pkg-devel] New test in R-devel causes existing packages to fail: "Error: connections left open"

[Gábor Csárdi]

Sorry, missed that these were examples, so, yeah, that's harder.  G.
On Sun, Aug 19, 2018 at 6:32 PM Gábor Csárdi <csardi.gabor using gmail.com> wrote:
>
> You could just create a function to close the connection and then
> people could call it at the end of their test suites.
>
> Gabor
> On Sun, Aug 19, 2018 at 6:22 PM David B. Dahl <dahl using stat.byu.edu> wrote:
> >
> > In preparing to submit an update of my package to CRAN, I found that
> > R-devel has a new test regarding "connects left open" that my packages
> > fail.  The new test appears to have been committed by Uwe Ligges in
> > revisions 74959 and 74964 on 2018-07-14 and 2018-07-15, respectively.
> > The commit message says, "check after each example whether open
> > connections exist, indicating e.g. file connections were left open or
> > parallel clusters still running."
> >
> > I am hoping for advice on how to pass "R CMD check --as-cran".  Or,
> > perhaps my situation will prompt a change to the test or, at least,
> > having it result in a warning instead of an error.
> >
> > Below I describe the situation.  My rscala package allows developers
> > to write R packages based on Scala (much like rJava and Rcpp for Java
> > and C++, respectively).  Scala runs as a separate process and
> > interprocess communication is implemented using socket connections.
> >
> > Suppose a package using rscala has functions that call Scala code.
> > (Such packages are 'bamboo', 'sdols', and 'shallot' on CRAN.)  The
> > first time a user executes an R function calling down into Scala, a
> > socket connect between Scala and R is established.  For the sake of
> > low latency, after the call to the function ends, the connection stays
> > open until the package is unloaded or the R session ends.  But, this
> > approach runs afoul of the new test mentioned above that appears to be
> > designed to catch connections that are *accidentally* left open.
> >
> > I definitely do not want to users of my packages 'bamboo', 'sdols',
> > and 'shallot' to have to think about managing connection between Scala
> > and R.  That's an implementation detail and uing the package should be
> > transparent for the user (who doesn't care about the implementation
> > details).
> >
> > On my end, I see two solutions:  1. I could try to reengineer my
> > approach --- establishing a new connection for every single call into
> > Scala --- although I am loath to do anything to increase the latency,
> > or 2. I could wrap all the examples in \donttest so that CRAN checks
> > are passed.
> >
> > Or, again, perhaps my situation will prompt a reevaluation of the
> > test.  Perhaps it could result in a warning (instead of an error) and
> > the CRAN maintainers would accept packages with such a warning.
> >
> > Any advise?  Thanks a lot!
> >
> > -- David
> >
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