[Rd] as-cran issue ==> set _R_CHECK_LENGTH_1_* settings!

[Martin Maechler]

>>>>> Ben Bolker 
>>>>>     on Mon, 13 Jan 2020 11:49:09 -0500 writes:

    > From R NEWS (changes in 3.6.0)
    > Experimentally, setting environment variable _R_CHECK_LENGTH_1_LOGIC2_
    > will lead to warnings (or errors if the variable is set to a ‘true’
    > value) when && or || encounter and use arguments of length more than one.

Indeed,  thank you, Ben.

Note (Dirk) this is not just something 
  "by Henrik (..) as he tried to convince us all to use it more"

I've activated this (and the other
  _R_CHECK_LENGTH_1_CONDITION_ ! )
for years (maybe not many years, it just feels like it), and *EVERY TIME*
it triggers, it's been revealing a programmeR's thinko / bug / ..,
something where the code was clearly suboptimal and should've been improved.
(Unfortunately, the bug has often been in packages, and sometimes I had to
 disable the setting when I wanted that "buggy" package to work ..)

Occasionally being puristic, let me state this:
   __________________________________________________________________
  /------------------------------------------------------------------\
  |                                                                  | 
  | Every careful R programmer should use (something like "true",    | 
  | "verbose", or even package=... )                                 | 
  |                                                                  | 
  | export _R_CHECK_LENGTH_1_CONDITION_=true                         | 
  | export _R_CHECK_LENGTH_1_LOGIC2_=verbose                         | 
  |                                                                  | 
  | in her/his ~/.profile equivalent (*)                             | 
  \__________________________________________________________________/


*) well assuming a careful R programmer would never develop on
   Windows anyway (where you need different means to set such
   environment variables). 



    > On 2020-01-13 11:46 a.m., Therneau, Terry M., Ph.D. via R-devel wrote:
    >> Thanks for the feedback Dirk.   I sent my follow-up before I saw it.
    >> 
    >> Looking at the source code, it appears that there is no options() call
    >> to turn this on. Nor does "R --help" reveal a command line option.
    >> How then does a user turn this on outside of the R CMD check
    >> envirionment, so as to chase things like this down?
    >> 
    >> The fact that 1. renaming my function makes the error go away, 2. my
    >> function is just a wrapper to inherits(), and 3. its a new error in code
    >> that hasn't changed, all point me towards some oddity with the check
    >> function.
    >> 
    >> Terry
    >> 
    >> 
    >> On 1/13/20 10:22 AM, Dirk Eddelbuettel wrote:
    >>> 
    >>> On 13 January 2020 at 10:02, Therneau, Terry M., Ph.D. via R-devel wrote:
    >>> | Where can I find out (and replicate) what options as-cran turns on?
    >>> 
    >>> See the file src/library/tools/R/check.R in the R sources, and grep for
    >>> as_cran which is the internal variable controlled by the --as-cran option
    >>> 
    >>> [...]
    >>> 
    >>> | The check log contains multiple instances of the lines below:
    >>> |
    >>> | < Warning message:
    >>> | < In if (ismat(kmat)) { :
    >>> | <   the condition has length > 1 and only the first element will be
    >>> used
    >>> |
    >>> | I don't see how the error could arise, but if I know what as-cran is
    >>> doing perhaps I can
    >>> | replicate it.
    >>> 
    >>> This was widely discussed on this list and should also be in the NEWS
    >>> file.
    >>> 
    >>> The change is about what the message says: the if () tests a scalar
    >>> logical,
    >>> it appears that ismat(kmat) returns more than a scalar.
    >>> 
    >>> There has always been an opt-in for this to error -- cf many messages
    >>> by Henrik
    >>> over the years as he tried to convince us all to use it more.
    >>> 
    >>> 
    >>> Dirk
    >>> 
    >> 
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