Drew Adams <drew.adams@oracle.com> writes:

>> (toggle-truncate-lines t)
>> 
>> Prints the message "Truncate long lines enabled". When called from
>> elisp, this message should be ignored. If called interactively, the
>> message should be displayed.
>
> Yes.
>
> But the right fix is to add "&optional msg",
> use (interactive "P\np"), and test for non-nil
> MSG as the condition for showing the message.
>
> Lisp code for a command can use that toggle
> function, and when _that_ command is invoked
> interactively it too might make sense to show
> the message (that can depend on the command
> and when the toggling occurs as part of it).
>
> The same kind of fix is no doubt appropriate
> for some other existing commands that instead
> just test `called-interactively-p'.  Surely
> we shouldn't perpetuate such design by adding
> more such.

Sounds good to me.