Import packages, don't depend on them

[hadley]

Currently you have Depends: Rcpp (>= 0.11.0), utils, inline, methods, but these should all be moved into imports. It's bad practice (and not needed) to attach other packages to the search path when loading a package.

[bgoodri]

Thanks Hadley.

• I'm not sure how utils got in there so it probably shouldn't be
• For methods the manual ( https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Namespaces-with-S4-classes-and-methods ) said to put it in Depends but then footnote 53 suggests maybe it is not necessary any more now that we require R >= 3.0.2.
• Rcpp is needed in Depends because if Rcpp is not loaded the user's model will fail with the message Error in .Object$initialize(...) : could not find function "cpp_object_initializer" which is unexported by Rcpp
• I thought inline had a similar issue as Rcpp but now I think I'm wrong about that.

[hadley]

Are you using Rcpp modules? You shouldn't need to depend on Rcpp in most cases.

[bgoodri]

Yeah, it is this issue RcppCore/Rcpp#168

[hadley]

I'll try and find some time to look into this in more detail. Would be nice if we could get a fix into Rcpp. I bet me and @wch can work it out between us.

[lionel-]

a temporary solution would be to import and reexport cpp_object_initializer(), this way Rcpp can be moved to Imports.

[bgoodri]

I've made this change in d531b6e and it seems to work in every situation except compiling the vignette automatically when multiple cores are used, whereupon it says

Error: processing vignette 'rstan_vignette.Rnw' failed with diagnostics:
 chunk 5 (label = callstan) 
Error in unserialize(node$con) : error reading from connection
Execution halted

But that doesn't happen if cores = 1, or if I install the package without the vignettes and run a model manually with multiple cores, or even if I explicitly call tools::buildVignette(). Any ideas? I'm currently only using 1 core in the vignette.

[bgoodri]

This was largely fixed for rstan 2.9.0 or maybe 2.8.2, but I believe the "fix" entails that downstream packages of rstan that come with stanmodel objects have to put Rcpp in Depends. FYI, see the rstanarm package for how this can be done.