Crash on /info: extract_zarr_variable_encoding() got unexpected region

[Anebrithien]

Description

When serving a dataset using ds.rest.serve() and accessing the /info endpoint, an internal server error occurs due to an unexpected keyword argument region passed to extract_zarr_variable_encoding(). This appears to be caused by an incompatibility with the latest xarray version (2025.7.1).

To Reproduce

import xarray as xr
import xpublish

ds = xr.tutorial.open_dataset(
    "air_temperature",
    chunks=dict(lat=5, lon=5),
)

ds.rest.serve()

Then, request:

GET /info

Expected behavior

The /info endpoint should return metadata about the dataset without error.

Actual behavior

The server responds with HTTP 500 and the traceback shows:

TypeError: extract_zarr_variable_encoding() got an unexpected keyword argument 'region'

Full traceback

...
  File "xpublish/utils/zarr.py", line 202, in create_zmetadata
    encoding = extract_zarr_variable_encoding(
        dvar,
        zarr_format=ZARR_FORMAT,
        region=tuple([SimpleNamespace(start=None, stop=None) for _ in da.shape]),
    )
TypeError: extract_zarr_variable_encoding() got an unexpected keyword argument 'region'

Environment

xpublish: 0.4.1

The response of /versions API

{
  "python": "3.13.5 | packaged by conda-forge | (main, Jun 16 2025, 08:27:50) [GCC 13.3.0]",
  "python-bits": 64,
  "OS": "Linux",
  "OS-release": "6.15.5-arch1-1",
  "Version": "#1 SMP PREEMPT_DYNAMIC Sun, 06 Jul 2025 11:14:36 +0000",
  "machine": "x86_64",
  "processor": "",
  "byteorder": "little",
  "LC_ALL": "None",
  "LANG": "en_US.UTF-8",
  "LOCALE": "en_US.UTF-8",
  "libhdf5": "1.14.6",
  "libnetcdf": "4.9.2",
  "xarray": "2025.7.1",
  "zarr": "3.0.10",
  "numcodecs": "0.16.1",
  "fastapi": "0.116.0",
  "starlette": "0.46.2",
  "pandas": "2.3.1",
  "numpy": "2.3.1",
  "dask": "2025.5.1",
  "uvicorn": "0.35.0"
}

Additional context

This appears to be a compatibility issue with newer versions of xarray, where extract_zarr_variable_encoding() no longer accepts a region parameter. Possibly related to upstream API changes in xarray.

When send request to /zarr/*, the same error.

[xaviernogueira]

Saw this issue myself, this behavior was changed in the xarray.backends.zarr module pretty recently on June 5, 2025 (SHA=15ed8e5256317e9ef8e81c8e074c8816d0e7fa1e). Version v2025.04.0 should work.

I presume we either support both behaviors depending on xarray version for now or just limit the xarray versions in the pyproj? I will make a quick PR for the later if that is the desired stop-gap approach. @Anebrithien

[Anebrithien]

I think supporting both behaviors depending on the xarray version would be a better long-term solution. It might also be helpful to include a version compatibility matrix in the documentation, so users can more easily manage environments with older dependencies.

[mpiannucci]

Thanks @xaviernogueira . I would prefer pinning a minimum xarray and supporting the current functionality because that region syntax was only there for a few versions and now it's gone again. There was a pr a while back I think that added it

Upstream Zarr 3 has changed a lot the last few releases and supporting older versions of Zarr 3 + xarray long term is more trouble than it is worth