From luke-tierney at uiowa.edu  Thu Sep 10 13:47:24 2015
From: luke-tierney at uiowa.edu (luke-tierney at uiowa.edu)
Date: Thu, 10 Sep 2015 06:47:24 -0500
Subject: [Rd] Using IDs to suppress specific messages and warnings
In-Reply-To: <CAPp_+=dnGknY1_SzsMw48q89LCBvavrceUZj4hyowWt8YAOseg@mail.gmail.com>
References: <CAPp_+=dnGknY1_SzsMw48q89LCBvavrceUZj4hyowWt8YAOseg@mail.gmail.com>
Message-ID: <alpine.DEB.2.10.1509100642530.2561@luke-Latitude>

Conditions have classes and the condition system is designed around
the idea that classes would be used for this sort of thing. That is
already how tryCatch and withCallingHandlers discriminate the
conditions to handle.

Designing and implementing a condition class hierarchy to support this
is indeed the hard/tedious part.

Best,

luke

On Thu, 10 Sep 2015, Richard Cotton wrote:

> The suppressMessages and suppressWarnings functions currently suppress
> all the message or warnings that are generated by the input
> expression.
>
> The ability to suppress only specific messages or warnings is
> sometimes useful, particularly for cases like file import where there
> are lots of things that can go wrong.
>
> Suppressing only messages that match a regular expression has rightly
> been rejected as problematic due to non-portability across locales.
> See, for example,
>
> https://stat.ethz.ch/pipermail/r-devel/2012-October/065089.html
>
> A better way of suppressing certain conditions would be to allow them
> to have an identifier.  (This is how MATLAB allows control over
> individual conditions.)
>
> The implementation ought to be fairly simple.
>
> simpleMessage, simpleWarning, and simpleError gain an id arg, which is
> stored in their structure.
>
> simpleMessage <- function (message, call = NULL, id = NULL)
> {
>  structure(
>    list(message = message, call = call, id = id),
>    class = c("simpleMessage", "message", "condition")
>  )
> }
>
> I envisage IDs being strings, for example, the "NaN produced" warning
> when you ask call, e.g., sqrt(-1) could have an ID of
> "base:sqrt:nan_produced".
>
> suppressMessage and suppressWarnings gain an ids arg, defaulting to
> NULL, which preserves existing behaviour.  If it takes a character
> vector, messages with the IDs provided get muffled.  Something like:
>
> suppressMessages <- function (expr, ids = NULL)
> {
>  withCallingHandlers(
>    expr,
>    message = function(c)
>    {
>       if(is.null(ids) || (inherits(c, "simpleMessage") && c$id %in%
> as.character(ids)))
>       {
>         invokeRestart("muffleMessage")
>       }
>    }
>  )
> }
>
> The hard part is providing IDs for all the existing messages in R and
> its packages.  It's certainly do-able, but I imagine would take quite
> a lot of time.
>
> Is there any enthusiasm for implementing this feature, or something like it?
>
>

-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney at uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu



[Rd] Using IDs to suppress specific messages and warnings
luke-tierney at uiowa.edu