[Rd] savePlot() no longer automatically adds an extension to the filename.

[Simon Urbanek]

On Jun 3, 2008, at 8:40 PM, Duncan Murdoch wrote:

> On 03/06/2008 2:35 PM, Mike Prager wrote:
>> "S Ellison" <S.Ellison at lgc.co.uk> wrote:
>>> Plaintive squeak: Why the change?
>>> Some OS's and desktops use the extension, so forgetting it causes
>>> trouble. The new default filename keeps a filetype (as before) but  
>>> the
>>> user now has to type a filetype twice (once as the type, once as
>>> extension) to get the same effect fo rtheir own filenames. And the
>>> extension isn't then checked for consistency with valid file  
>>> types, so
>>> it can be mistyped and saved with no warning. Hard to see the  
>>> advantage
>>> of doing away with it...
>> Just for the record. . .
>> This change broke a *lot* of my code, including code used by
>> others.  Windows depends on file extensions.  Fortunately, fixes
>> using getRversion are not too difficult.
>
> Then you'll be happy to hear that Steve put together a patch and  
> it's already committed, so it should make it into 2.7.1.  The patch  
> adds the extension if there's no dot in the name, leaves the  
> filename as-is if it sees one.  So this should be compatible with  
> the majority of uses, only messing up cases where people really  
> don't want an extension (now they'll have to add a dot at the end of  
> their filename), or where they want an automatic one, but have  
> another dot in the name.
>

AFAICS the savePlot() behavior is now (as of r45830) inconsistent  
across platforms due to the patch (r458229). The inconsistency is IMHO  
a bad thing - you shouldn't expect the same function to behave  
differently across platforms.

I'd strongly recommend against this change for several reasons: it  
changes the behavior of the function between 2.7.0 and 2.7.1, so that  
now you have to special-case three different versions (pre 2.7.0,  
2.7.0 and 2.7.1), there is now no way to specify a file without a dot  
(which is quite common in non-Windows world) and the behavior is  
incompatible with other similar functions.

I think the change of behavior in 2.7.0 was deliberate and in favor of  
consistency, because a filename specification should not be randomly  
mangled by the function (I have made that mistake myself before, so I  
know the pitfalls ;)). Extension is part of the filename, it's not a  
separate concept (also note that ".foo" is a valid  filename that  
doesn't have an extension). The argument about typos is moot since you  
can always define functions like
saveFoo <- function(prefix) savePlot(filename = paste(prefix, "foo",  
sep="."), type="foo")
At any rate I don't see how this can realistically be part of 2.7.1  
since it's not a bugfix and it changes the meaning of a function  
parameter. (And I usually don't mind disguising small features as  
bugfixes ;P)

Whether the change in 2.7.0 could be done differently (e.g. using  
another parameter for a full file name) is a different story, but I  
suspect that it should have been discussed before the 2.7.0 release...

Cheers,
Simon