[R-pkg-devel] Avoid reprocessing Rmd vignette
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The idea exposed by Dirk is the same: requireNamespace will find the package on CRAN and will set eval=TRUE. What you want though is to avoid running a chunk on CRAN, even if the package is available. So you need to set eval=FALSE *unconditionally*.
Or conditional on the package version (as Dirk proposed regarding tests) or on an environment variable NOT_CRAN which you can set to true on the machine where you do want to run the code (as used by devtools). Johannes