R devel - Apr 2022 - available.packages function and UNC paths

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.

Thanks,

Mark






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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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>
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