Support zarr v3

[Koncopd]

Please make sure these conditions are met

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of anndata.
• (optional) I have confirmed this bug exists on the master branch of anndata.

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[mbstadler]

We also noticed this issue (our package depends on anndata as well as zarr).
This guide was useful to update our own code to zarr v3: https://zarr.readthedocs.io/en/latest/user-guide/v3_migration.html#

[flying-sheep]

Huh, I thought we had a feature request for this already! OK, I’ll make this one into it.

Maybe we should have added a zarr extra that you can use to say “get the newest supported zarr version”, instead of just being able to see that we don’t support it yet from our test pin:

anndata/pyproject.toml

Line 91 in 21d191d

"zarr<3.0.0a0",

See

• (fix): upper bound zarr at runtime (and in docs + benchmark) #1819
• (feat): support for zarr-python>=3  #1726