Use chunks="auto" by default in xarray_open_kwargs

[dougiesquire]

Change Summary

Very small change to default to chunks="auto" rather than chunks={} when opening files with xarray. This is motivated by recent changes in xarray to the behaviour of chunks={}.

Related issue number

Closes #632

Checklist

• Tests pass on CI

[dougiesquire]

Ah, unfortunately auto rechunking does not work with object dtype. This is probably too common for it to make sense to use chunks="auto" by default. Some options:

• try to use chunks="auto" and revert to chunks={} if that fails;
• use chunks=-1, which gives the same behaviour as pre-v2023.09.0 chunks={} (prior to v2023.09.0, these did the same thing);
• ditch this and stick with chunks={}

Thoughts @mgrover1, @dcherian?

[mgrover1]

Ah, unfortunately auto rechunking does not work with object dtype. This is probably too common for it to make sense to use chunks="auto" by default. Some options:

• try to use chunks="auto" and revert to chunks={} if that fails;
• use chunks=-1, which gives the same behaviour as pre-v2023.09.0 chunks={} (prior to v2023.09.0, these did the same thing);
• ditch this and stick with chunks={}

Thoughts @mgrover1, @dcherian?

I think sticking with chunks={} by default makes the most sense here still... any thoughts here @dcherian or @andersy005 ?

[andersy005]

Ah, unfortunately auto rechunking does not work with object dtype. This is probably too common for it to make sense to use chunks="auto" by default. Some options:

• try to use chunks="auto" and revert to chunks={} if that fails;
• use chunks=-1, which gives the same behaviour as pre-v2023.09.0 chunks={} (prior to v2023.09.0, these did the same thing);
• ditch this and stick with chunks={}

Thoughts @mgrover1, @dcherian?

I think sticking with chunks={} by default makes the most sense here still... any thoughts here @dcherian or @andersy005 ?

i vote in favor of sticking with chunks={} unless implementing the work around above ( * try to use chunks="auto" and revert to chunks={} if that fails;) doesn't result in complicated code :(

[dougiesquire]

Thanks @mgrover1 and @andersy005. I agree with you both so I'll close this PR