[R-pkg-devel] Checking package dependencies before loading namespace

[Duncan Murdoch]

People shouldn't be able to install your package unless the "hard" 
dependencies are available.

If EBImage isn't essential to your package, you should make it a "soft" 
dependency by listing it in Suggests and checking for it every time you 
use it.

Duncan Murdoch

On 31/08/2021 3:20 p.m., Tiago Olivoto wrote:
> Dear all,
> I have a package called pliman <https://CRAN.R-project.org/package=pliman>
> which depends on the Bioconductor package EBImage.
> 
> When running install.packages("pliman") I get the following warning
> 
> Warning in install.packages :  dependency ‘EBImage’ is not available
> 
> and thus when loading the package with library(pliman), the following error
> occurs
> 
> Erro: package or namespace load failed for ‘pliman’ in loadNamespace(i,
> c(lib.loc, .libPaths()), versionCheck = vI[[i]]):
>   there is no package called ‘EBImage’
> 
> I created a check function to check if EBImage is available and if not, ask
> users if they want to install it
> 
> ---
> check_ebi <- function(){
>    if(!requireNamespace("EBImage", quietly = TRUE)) {
>      inst <-
>      switch(menu(c("Yes", "No"), title = "Package {EBImage} required but not
> available.\nDo you want to install it now?"),
>             "yes", "no")
>      if(inst == "yes"){
>        if (!requireNamespace("BiocManager", quietly = TRUE)){
>          install.packages("BiocManager")
>        }
>        BiocManager::install("EBImage", ask = FALSE, update = FALSE)
>      } else{
>        message("To use {pliman}, first install {EBImage} with
> 'BiocManager::install(\"EBImage\")'.")
>      }
>    }
> }
> ---
> 
> Is there any way to run this function prior to namespace loading? I tried
> putting check_ebi() into .onLoad() but the same error occurs.
> 
> Thanks in advance for any suggestions.
> Tiago
> 
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