Updating animation file writer to allow keywork arguments when using `with` construct

[jmc734]

Previously, in order to pass configurations to saving() and subsequently setup(), the caller had to provide positional arguments. There is nothing explicitly wrong with that approach though the saving() method is currently advertised as taking the same parameters as setup(). For example, if you wanted to disable temporary file clearing for a FileMovieWriter, you previously would not have been able to structure it like this:

with recorder.saving(fig, capFile, capDPI, tempPrefix, clear_temp = False):

Instead, you would have to know the order of the arguments and make the call like so:

with recorder.saving(fig, capFile, capDPI, tempPrefix, False):

This is a small change but I think it makes code easier to read and more tolerant to future API change.

[tacaswell]

can you remove both args and kwargs from this signature? We do not use either of them so having them will just mask errors.

[WeatherGod]

Wouldn't removing *args be a potential compatibility break? Admittedly, I am having a hard time imagining a scenario where one would have had extra arguments down to this point, but I just wanted to make sure we aren't doing something blindly. It would be nice if I could remember why we had *args there in the first place...

[jmc734]

It was added way back in 2012 in the original work-in-progress commit for animation file writers. Unfortunately, that commit has no further documentation other than the code changes themselves. I would venture a guess though that the reasoning was that saving() took arbitrary arguments and called setup() with them so, if for some reason an overriden setup() called the super setup() with the entire set of arbitrary arguments, it wouldn't break. If that is true then I think we should remove it as that case is unlikely and would be kind of dirty anyway.

[dopplershift]

Other than @tacaswell 's comment, it's a 👍 from me.

[tacaswell]

Thanks!

@jmc734 I think this is your first contribution to mpl. Congratulations and hopefully we will see you again 🎉 .

[efiring]

@tacaswell, may I backport this? I view it as fixing a rather frustrating bug, which I tripped over and reported in #7191.