available.packages function and UNC paths

FWIW, at least as far as R is concerned, you should be able to use a
file URI with a UNC path. For example, the following works for me:

repopath <- tempfile("minicran-")
dir.create(repopath)
repopath <- normalizePath(repopath, winslash = "/", mustWork = TRUE)
miniCRAN::makeRepo("renv", path = repopath)

uncpath <- paste0("file:////localhost/c$", substring(repopath, 3L))
options(repos = c(local = uncpath))
available.packages()
install.packages("renv", type = "source")

In this example, the call to available.packages() succeeds for me. I'm
not sure if miniCRAN itself supports such URIs consistently, though. I
agree that using a mapped letter drive is the simplest workaround.

Best,
Kevin

On Thu, Apr 21, 2022 at 6:26 AM Tomas Kalibera <tomas.kalibera at gmail.com> wrote:

On 4/6/22 18:07, mark.lee--- via R-devel wrote:

Hello,

I'm responsible for maintaining a mirrored internal CRAN repository for my organization. We have a script that uses the miniCRAN library to add and update packages within the repository and since the repository is stored on a network drive I have to use UNC paths when calling miniCRAN functions such as this:

updatePackages(path = '\\\\my-network-drive.net\\repos\\packages', ...)

updatePackages function in turns call pkgAvail, another miniCRAN function, which calls available.packages and then read.dcf function. However I discovered that this line in available.packages transforms the UNC path to a form that read.dcf can't use:

if (startsWith(repos, "file:///")) {tmpf <- paste0('/', substring(repos, 8L), "/PACKAGES")

This line transforms my UNC path to //\\\\my-network-drive.net\\repos\\packages, which read.dcf can't use. During debugging I found that pkgAvail transformed my UNC path to 'file:///\\\\ my-network-drive.net\\repos\\packages' and that is the path being passed to available.packages. To fix my issue I re-defined my own available.packages function and changed the line to:

if (startsWith(repos, "file:///")) {tmpf <- paste0('/', substring(repos, 10L), "/PACKAGES")

This way the UNC path being passed to read.dcf will be '/\\my-network-drive.net\\repos\\packages', which read.dcf can use. I'm wondering if similar changes can be made in the available.packages function for the next R release to automatically detect UNC paths and modify it so that it can work with UNC paths.

R does not support UNC paths, even though they work in some functions
(as stated at least in R-intro documentation). You can use e.g. a mapped
drive as a reliable work-around.

Transforming the file URIs is tricky enough even without UNC support,
and as UNC is only used on Windows, and there is an easy work-around,
support for it in update.packages would have very low priority. The cost
is not only implementing it, but also maintaining and testing. Still, to
increase the chances, you can submit a bug (wishlist) report to R
bugzilla, referring only to base R packages (so not e.g. miniCRAN) and
add a well-tested patch to be considered.

Best
Tomas

Thanks,

Mark






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