Making grid arguments for divergence and vorticity keyword-only as forward-looking API change

[jthielen]

It occurred to me after the overhaul of advection in #1490 that a similar "quasi-overloading" approach may work well for vorticity and divergence to handle both their 2D and 3D cases with the same function (as discussed in #684, "We can defer designs on extending divergence to 3D and vorticity to other planes until we actually can see what we're doing with xarray.").

While we definitely don't have to have the 3D forms implemented immediately for v1.0, I think it would make sense to make the grid arguments keyword-only in anticipation of this change so that we don't have an API break when adding in the optional w term. Would this be a reasonable change? Also, while we're at it, what should the behavior be for these (now-optional-with-xarray) grid arguments in the rest of the kinematics calculations (right now they're just regular optional arguments)?

[dopplershift]

I think this would be a reasonable change to make. I'm not sure what you're asking about:

what should the behavior be for these (now-optional-with-xarray) grid arguments in the rest of the kinematics calculations

?

[jthielen]

[...] I'm not sure what you're asking about:

what should the behavior be for these (now-optional-with-xarray) grid arguments in the rest of the kinematics calculations

?

Sorry, that was really vague. It is really just asking if there are any other kinematics functions we should make the same change to as well...i.e.: With each function, should we leave the grid arguments as they are now (as regular optional arguments, that can be specified positionaly or with keywords), or are there other cases of kinematics calculations that may have analogous desired API changes, so that we should similarly enforce the grid arguments as keyword-only?

[dopplershift]

Nothing jumps to mind and I feel like we should avoid guessing. Need to avoid turning 1.0 into "get it perfect". Let's shoot for "not horribly broken".

Great project motto: "MetPy: Not horribly broken". Sadly, that's the bar for software in our field. 😉

[KCorb11]

Suggestion: Add absolute vorticity, so both vorticity and absolute vorticity have the same syntax with keyword arguments.

[dopplershift]

@KCorb11 Thanks for the suggestion. See #2102 for an even bigger list that we plan to change when we break API compatibility.