[Rd] Respecting custom repositories files in interactive/batch R sessions

[Gabriel Becker]

Hi all,

A company I work with mirrors CRAN internally behind its firewall for
security (and reproducibility/consistency/etc) reasons. In that case, we
would like all R processes (across all the R CMD *, as well as interactive
and batch sessions) to automatically hit our cran mirror instead of
prompting the user to select a mirror or failing to contact CRAN at all
(during check).

I recently found out about the ${R_HOME}/etc/repositories file (after
multiple years owning the R installations of a sizable corporate research
outfit in my previous job).

Contrary to my expectations, however, the CRAN entry found in the
repositories file is not respected in interactive or batch sessions.

With the value "https://fakeyfakeyfake" for the CRAN URL, I get this
behavior in an interactive session in Rdevel built from trunk:

R Under development (unstable) (2022-09-14 r82853) -- "Unsuffered
Consequences"


<snip>


> available.packages()

--- Please select a CRAN mirror for use in this session ---

Secure CRAN mirrors


 <snip>


Selection: 0

*Error in contrib.url(repos, type) : *

*  trying to use CRAN without setting a mirror*

> readLines(file.path(R.home(), "etc", "repositories"))

 <snip>

[11] "menu_name\tURL\tdefault\tsource\twin.binary\tmac.binary"


[12] "CRAN\tCRAN\t\*"https://fakeyfakeyfake
<https://fakeyfakeyfake>\"*\tTRUE\tTRUE\tTRUE\tTRUE"
  <snip>


R CMD check, on the other hand, *does* use it the entry in repositories out
of the box:


gabrielbecker$ Rdevel CMD check switchr_0.14.5.tar.gz

[1]
"/Users/gabrielbecker/local/Rdevelraw/R.framework/Versions/4.3/Resources/library"

* using log directory ‘/Users/gabrielbecker/gabe/checkedout/switchr.Rcheck’

* using R Under development (unstable) (2022-09-14 r82853)

* using platform: x86_64-apple-darwin21.5.0 (64-bit)

* using session charset: UTF-8

* checking for file ‘switchr/DESCRIPTION’ ... OK

* checking extension type ... Package

* this is package ‘switchr’ version ‘0.14.5’

* checking package namespace information ... OK

* checking package dependencies ...Warning: unable to access index for
repository https://fakeyfakeyfake/src/contrib:

  cannot open URL 'https://fakeyfakeyfake/src/contrib/PACKAGES'


This behavior is coming from the fact that the repos option is unilaterally
set to c(CRAN = "@CRAN@") in utils::.onLoad


I propose instead that this should be set to either a) the CRAN entry to
the repository file, or even better imho, b) the set of all repos marked as
default in the repositories file, with a caveat that its set to @CRAN@ in
the case there is no cran entry, though comments around the source code in
tools suggest other things will break in that case anyway.

The default value of the repositories file has @CRAN@ for the cran entry,
and cran is the only repo marked as default, so this preserves the existing
behavior in what I assume to be the overwhelming majority of cases where
the repositories file is either not custom, or is only appended to .

I have a patch which does option (b) (and can easily be adapted to option
(a)) that I will submit to bugzilla after any discussion here.

Also, as a separate issue, I strongly feel that the R administration manual
section about repositories be updated to more clearly describe behavior and
best practices around setting the repos R will look in. I will develop a
patch for that separately once I see whether one of the above changes is
likely to go in or not (as I don't want to write it twice).

For completeness, I know that we could put a setRepositories call in the
the site Rprofile, but I have to admit I don't really understand why this
should be necessary.

Thoughts?
~G

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