Array api extension support function

[purepani]

Right now, the dask library has a linalg attribute, but doesn't currently implement the entire linalg extension spec. The lack of full support is mentioned here: https://data-apis.org/array-api-compat/supported-array-libraries.html

This means that an array api library consumer can't do

if hasattr(xp, 'linalg'):
    xp.linalg.cross(x, y)

as recommended here,
and work with dask. I suppose this is hard to change for existing array libraries that have such an attribute already. I'm generally thinking that this is best added as part of the array api spec(see data-apis/array-api#950), but in the meantime, a supports_extension(xp, extension_name: str) in array_api_compat would be helpful, so that

from array_api_compat import supports_extension

if supports_extension(xp, 'linalg'):
    xp.linalg.cross(x, y)

is possible.

Alternatively(or additionally), returning a list might be a good idea:

from array_api_compat import get_supported_extensions

print(get_supported_extensions(xp)) # ['linalg', 'fft'], or [] for dask
if 'linalg' in get_supported_extensions(xp):
    xp.linalg.cross(x, y)

(discussed in magpylib/magpylib#844)

[rgommers]

Hi @purepani, I suggest to not discuss exactly the same question in two places. For now, data-apis/array-api#950 is the more appropriate place to discuss a supports_extension function.

The more idiomatic change in this library is to add a linalg.cross compat function for dask. That can then be used until it materializes upstream. I suggest closing this issue and opening a new one for implementing missing dask.linalg functions (is it only cross, or more?).

[purepani]

Sure I'll close this issue. I viewed these as 2 separate things, so I made 2 issues, but I think what you suggest makes more sense.

(As a note it's not only for cross, it was just an example. There's something like 10 or 15 missing functions).