attach "warning" is a message

Barry,

it is not a warning nor plain output, it is a message, so you can use
d = data.frame(x=1:10)
x=1
suppressMessages(attach(d))

Looking at the history, this used to be cat() but got changed to a message in R 3.2.0 (r65385, CCIng Martin in case he remembers the rationale for warning vs message). I don't know for sure why it is not a warning, but I can see that it is more in the line with informative messages (like package masking) as opposed to a warning - in fact the change suggest that the intention was to synchonize both. That said, I guess the two options are to clarify the documentation (also in library()) or change to a warning - not sure what the consequences of the latter would be.

Cheers,
Simon
On 10/08/2021, at 2:06 AM, Barry Rowlingson <b.rowlingson at lancaster.ac.uk> wrote:

If I mask something via `attach`:

d = data.frame(x=1:10)
x=1
attach(d)
The following object is masked _by_ .GlobalEnv:

   x

I get that message. The documentation for `attach` uses the phrase
"warnings", although the message isn't coming from `warning()`:

warn.conflicts: logical.  If ?TRUE?, warnings are printed about
         ?conflicts? from attaching the database, unless that database
         contains an object ?.conflicts.OK?.  A conflict is a function
         masking a function, or a non-function masking a non-function.

and so you can't trap them with options(warn=...) and so on. This sent me
briefly down the wrong track while trying to figure out why R was showing a
masking error in one context but not another - I wondered if I'd supressed
warning()s in the other context.

Personally I'd like these messages to be coming from warning() since that
seems the appropriate way to warn someone they've done something which
might have unwanted effects. But fixing the documentation to say "If
?TRUE?, *messages* are printed" is probably less likely to break existing
code.

Happy to add something to bugzilla if anyone thinks I'm not being overly
pedantic here.

Barry

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