compatibility with xr.DataTree

[mathause]

• Closes #xxx
• Tests added
• Fully documented, including CHANGELOG.rst

Adds compatibility with xr.DataTree. Works (at least locally) but is not finished and needs some ugly workarounds due to some design decisions in the new version... The new code path is only tested in upstream-dev ci.

I am not sure we should support both, datatree and xarray datatree, but this was actually the smaller part of the whole operation.

[codecov]

Codecov Report

Attention: Patch coverage is 81.66667% with 11 lines in your changes missing coverage. Please review.

Project coverage is 80.31%. Comparing base (bd011cf) to head (37d49e2).

Files with missing lines	Patch %	Lines
mesmer/core/_datatreecompat.py	42.10%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #607      +/-   ##
==========================================
- Coverage   80.42%   80.31%   -0.12%     
==========================================
  Files          49       50       +1     
  Lines        3076     3114      +38     
==========================================
+ Hits         2474     2501      +27     
- Misses        602      613      +11     

Flag	Coverage Δ
unittests	80.31% <81.66%> (-0.12%)	⬇️

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[mathause]

The upstream packages seem flaky

[veni-vidi-vici-dormivi]

Wow thanks, that is a lot of work! I think it's okay not to support xarray-datatree at all then, since it is not recommended to use it anyway.

[mathause]

Thanks. It was mostly annoying because 98 % I did not understand what is happening 🤷‍♂️

As long as we need to patch xr.map_over_datasets we can just as well support datatree (because we need to import from _datatreecompat anyway.

It's annoying that the new version has become so bothersome to work with 😒

[mathause]

This takes all the fun out of using xr.DataTree and cannot be expected from a user. The other 'issues' (missing methods) will probably be fixed in time but this seems to be a design decision. 👎

[veni-vidi-vici-dormivi]

Yes I agree.

[mathause]

I think what we have to do is write a helper function calc_anomaly(dt, ref_period) with this inside.

[mathause]

I have not yet updated the example scripts and we need to fix the pin for xarray (so it's not only tested in upstream-dev ci).

[mathause]

I opened pydata/xarray#10042 - there seems to be some willingness to enable skipping empty nodes. With this change we could avoid the skip_empty_nodes helper function and I'd say that's the moment we can "fully" support xr.DataTree.

But not super convinced this PR gets a fast turnaround 😒

[mathause]

Ah yes and after 507cd1c this definitely requires xarray main, i.e. we require

xarray >=2023.07, < 2024.10, > 2025.1

(thats probably not a valid specifier)