release v2025.11.0

doc/whats-new.rst

@@ -6,122 +6,31 @@
 What's New
 ==========
 
-.. _whats-new.2025.10.2:
+.. _whats-new.2025.11.0:
 
-v2025.10.2 (unreleased)
------------------------
+v2025.11.0 (Nov 17, 2025)
+-------------------------
+This release changes the default for ``keep_attrs`` such that attributes are preserved by default, adds support for :py:class:`DataTree` in top-level functions, and contains several memory and performance improvements as well as a number of bug fixes.
+
+Thanks to the 21 contributors to this release:
+Aled Owen, Charles Turner, Christine P. Chai, David Huard, Deepak Cherian, Gregorio L. Trevisan, Ian Hunt-Isaak, Ilan Gold, Illviljan, Jan Meischner, Jemma Jeffree, Jonas Lundholm Bertelsen, Justus Magin, Kai Mühlbauer, Kristian Bodolai, Lukas Riedel, Max Jones, Maximilian Roos, Niclas Rieger, Stephan Hoyer and William Andrea
 
 New Features
 ~~~~~~~~~~~~
 
 - :py:func:`merge` and :py:func:`concat` now support :py:class:`DataTree`
   objects (:issue:`9790`, :issue:`9778`).
   By `Stephan Hoyer <https://github.com/shoyer>`_.
-- The ``h5netcdf`` engine has support for pseudo ``NETCDF4_CLASSIC`` files, meaning variables and attributes are cast to supported types. Note that the saved files won't be recognized as genuine ``NETCDF4_CLASSIC`` files until ``h5netcdf`` adds support with version 1.7.0. (:issue:`10676`, :pull:`10686`).
+- The ``h5netcdf`` engine has support for pseudo ``NETCDF4_CLASSIC`` files, meaning variables and attributes are cast to supported types. Note that the saved files won't be recognized as genuine ``NETCDF4_CLASSIC`` files until ``h5netcdf`` adds support with version 1.7.0 (:issue:`10676`, :pull:`10686`).
   By `David Huard <https://github.com/huard>`_.
 - Support comparing :py:class:`DataTree` objects with :py:func:`testing.assert_allclose` (:pull:`10887`).
   By `Justus Magin <https://github.com/keewis>`_.
+- Add support for ``chunks="auto"`` for cftime datasets (:issue:`9834`, :pull:`10527`).
+  By `Charles Turner <https://github.com/charles-turner-1>`_.
 
 Breaking Changes
 ~~~~~~~~~~~~~~~~
-
-
-Deprecations
-~~~~~~~~~~~~
-
-
-Bug Fixes
-~~~~~~~~~
-- Fix h5netcdf backend for format=None, use same rule as netcdf4 backend (:pull:`10859`).
-  By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_
-- ``netcdf4`` and ``pydap`` backends now use stricter URL detection to avoid incorrectly claiming
-  remote URLs. The ``pydap`` backend now only claims URLs with explicit DAP protocol indicators
-  (``dap2://`` or ``dap4://`` schemes, or ``/dap2/`` or ``/dap4/`` in the URL path). This prevents
-  both backends from claiming remote Zarr stores and other non-DAP URLs without an explicit
-  ``engine=`` argument. (:pull:`10804`). By `Ian Hunt-Isaak <https://github.com/ianhi>`_.
-- Fix indexing with empty arrays for scipy & h5netcdf backends which now resolves to empty slices (:issue:`10867`, :pull:`10870`).
-  By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_
-- Fix error handling issue in ``decode_cf_variables`` when decoding fails - the exception is now re-raised
-  correctly, with a note added about the variable name that caused the error (:issue:`10873`, :pull:`10886`).
-  By `Jonas L. Bertelsen <https://github.com/jonaslb>`_
-
-Performance
-~~~~~~~~~~~
-
-- Speedup and reduce memory usage of :py:func:`concat`. Magnitude of improvement scales
-  with size of the concatenation dimension. By `Deepak Cherian <https://github.com/dcherian>`_.
-  :issue:`10864` :pull:`10866`.
-- Speedup and reduce memory usage when coarsening along multiple dimensions.
-  By `Deepak Cherian <https://github.com/dcherian>`_. :pull:`10921`.
-
-Documentation
-~~~~~~~~~~~~~
-
-
-Internal Changes
-~~~~~~~~~~~~~~~~
-
-.. _whats-new.2025.10.1:
-
-v2025.10.1 (October 7, 2025)
-----------------------------
-
-This release reverts a breaking change to Xarray's preferred netCDF backend.
-
-Breaking changes
-~~~~~~~~~~~~~~~~
-
-- Xarray's default engine for reading/writing netCDF files has been reverted to
-  prefer netCDF4 over h5netcdf over scipy, which was the default before
-  v2025.09.1. This change had larger implications for the ecosystem than we
-  anticipated. We are still considering changing the default in the future, but
-  will be a bit more careful about the implications. See :issue:`10657` and
-  linked issues for discussion. The behavior can still be customized, e.g., with
-  ``xr.set_options(netcdf_engine_order=['h5netcdf', 'netcdf4', 'scipy'])``.
-  By `Stephan Hoyer <https://github.com/shoyer>`_.
-
-New features
-~~~~~~~~~~~~
-
-- Coordinates are ordered to match dims when displaying Xarray objects. (:pull:`10778`).
-  By `Julia Signell <https://github.com/jsignell>`_.
-
-Bug fixes
-~~~~~~~~~
-- Fix error raised when writing scalar variables to Zarr with ``region={}``
-  (:pull:`10796`).
-  By `Stephan Hoyer <https://github.com/shoyer>`_.
-
-
-
-.. _whats-new.2025.09.1:
-
-v2025.09.1 (September 29, 2025)
--------------------------------
-
-This release contains improvements to netCDF IO and the
-:py:func:`DataTree.from_dict` constructor, as well as a variety of bug fixes.
-In particular, the default netCDF backend has switched from netCDF4 to h5netcdf,
-which is typically faster.
-
-Thanks to the 17 contributors to this release:
-Claude, Deepak Cherian, Dimitri Papadopoulos Orfanos, Dylan H. Morris, Emmanuel Mathot, Ian Hunt-Isaak, Joren Hammudoglu, Julia Signell, Justus Magin, Maximilian Roos, Nick Hodgskin, Spencer Clark, Stephan Hoyer, Tom Nicholas, gronniger, joseph nowak and pierre-manchon
-
-New Features
-~~~~~~~~~~~~
-
-- :py:func:`DataTree.from_dict` now supports passing in ``DataArray`` and nested
-  dictionary values, and has a ``coords`` argument for specifying coordinates as
-  ``DataArray`` objects (:pull:`10658`).
-- ``engine='netcdf4'`` now supports reading and writing in-memory netCDF files.
-  All of Xarray's netCDF backends now support in-memory reads and writes
-  (:pull:`10624`).
-  By `Stephan Hoyer <https://github.com/shoyer>`_.
-
-Breaking changes
-~~~~~~~~~~~~~~~~
-
-- **All xarray operations now preserve attributes by default** (:issue:`3891`, :issue:`2582`).
+- All xarray operations now preserve attributes by default (:issue:`3891`, :issue:`2582`).
   Previously, operations would drop attributes unless explicitly told to preserve them via ``keep_attrs=True``.
   Additionally, when attributes are preserved in binary operations, they now combine attributes from both
   operands using ``drop_conflicts`` (keeping matching attributes, dropping conflicts), instead of keeping
@@ -131,7 +40,7 @@ Breaking changes
 
   .. code-block:: python
 
-      # Before (xarray <2025.09.1):
+      # Before (xarray <2025.11.0):
       data = xr.DataArray([1, 2, 3], attrs={"units": "meters", "long_name": "height"})
       result = data.mean()
       result.attrs  # {}  - Attributes lost!
@@ -166,7 +75,7 @@ Breaking changes
   - Transformations: ``map()``, ``pipe()``, ``assign()``, ``assign_coords()``
   - Shape operations: ``expand_dims()``, ``squeeze()``, ``transpose()``, ``stack()``, ``unstack()``
 
-  **Binary operations - combines attributes with ``drop_conflicts``:**
+  **Binary operations - combines attributes with** ``drop_conflicts``:
 
   .. code-block:: python
 
@@ -207,6 +116,96 @@ Breaking changes
 
   By `Maximilian Roos <https://github.com/max-sixty>`_.
 
+Bug Fixes
+~~~~~~~~~
+- Fix h5netcdf backend for format=None, use same rule as netcdf4 backend (:pull:`10859`).
+  By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_.
+- ``netcdf4`` and ``pydap`` backends now use stricter URL detection to avoid incorrectly claiming
+  remote URLs. The ``pydap`` backend now only claims URLs with explicit DAP protocol indicators
+  (``dap2://`` or ``dap4://`` schemes, or ``/dap2/`` or ``/dap4/`` in the URL path). This prevents
+  both backends from claiming remote Zarr stores and other non-DAP URLs without an explicit
+  ``engine=`` argument (:pull:`10804`).
+  By `Ian Hunt-Isaak <https://github.com/ianhi>`_.
+- Fix indexing with empty arrays for scipy & h5netcdf backends which now resolves to empty slices (:issue:`10867`, :pull:`10870`).
+  By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_
+- Fix error handling issue in ``decode_cf_variables`` when decoding fails - the exception is now re-raised
+  correctly, with a note added about the variable name that caused the error (:issue:`10873`, :pull:`10886`).
+  By `Jonas L. Bertelsen <https://github.com/jonaslb>`_.
+- Fix ``equivalent`` for numpy scalar nan comparison (:issue:`10833`, :pull:`10838`).
+  By `Maximilian Roos <https://github.com/max-sixty>`_.
+- Support non-``DataArray`` outputs in :py:meth:`Dataset.map` (:issue:`10835`, :pull:`10839`).
+  By `Maximilian Roos <https://github.com/max-sixty>`_.
+- Support ``drop_sel`` on ``MultiIndex`` objects (:issue:`10862`, :pull:`10863`).
+  By `Aled Owen <https://github.com/owena11>`_.
+
+Performance
+~~~~~~~~~~~
+
+- Speedup and reduce memory usage of :py:func:`concat`. Magnitude of improvement scales
+  with size of the concatenation dimension (:issue:`10864`, :pull:`10866`).
+  By `Deepak Cherian <https://github.com/dcherian>`_.
+- Speedup and reduce memory usage when coarsening along multiple dimensions (:pull:`10921`)
+  By `Deepak Cherian <https://github.com/dcherian>`_.
+
+.. _whats-new.2025.10.1:
+
+v2025.10.1 (Oct 7, 2025)
+------------------------
+
+This release reverts a breaking change to Xarray's preferred netCDF backend.
+
+Breaking changes
+~~~~~~~~~~~~~~~~
+
+- Xarray's default engine for reading/writing netCDF files has been reverted to
+  prefer netCDF4 over h5netcdf over scipy, which was the default before
+  v2025.09.1. This change had larger implications for the ecosystem than we
+  anticipated. We are still considering changing the default in the future, but
+  will be a bit more careful about the implications. See :issue:`10657` and
+  linked issues for discussion. The behavior can still be customized, e.g., with
+  ``xr.set_options(netcdf_engine_order=['h5netcdf', 'netcdf4', 'scipy'])``.
+  By `Stephan Hoyer <https://github.com/shoyer>`_.
+
+New features
+~~~~~~~~~~~~
+
+- Coordinates are ordered to match dims when displaying Xarray objects. (:pull:`10778`).
+  By `Julia Signell <https://github.com/jsignell>`_.
+
+Bug fixes
+~~~~~~~~~
+- Fix error raised when writing scalar variables to Zarr with ``region={}``
+  (:pull:`10796`).
+  By `Stephan Hoyer <https://github.com/shoyer>`_.
+
+
+.. _whats-new.2025.09.1:
+
+v2025.09.1 (Sep 29, 2025)
+-------------------------
+
+This release contains improvements to netCDF IO and the
+:py:func:`DataTree.from_dict` constructor, as well as a variety of bug fixes.
+In particular, the default netCDF backend has switched from netCDF4 to h5netcdf,
+which is typically faster.
+
+Thanks to the 17 contributors to this release:
+Claude, Deepak Cherian, Dimitri Papadopoulos Orfanos, Dylan H. Morris, Emmanuel Mathot, Ian Hunt-Isaak, Joren Hammudoglu, Julia Signell, Justus Magin, Maximilian Roos, Nick Hodgskin, Spencer Clark, Stephan Hoyer, Tom Nicholas, gronniger, joseph nowak and pierre-manchon
+
+New Features
+~~~~~~~~~~~~
+
+- :py:func:`DataTree.from_dict` now supports passing in ``DataArray`` and nested
+  dictionary values, and has a ``coords`` argument for specifying coordinates as
+  ``DataArray`` objects (:pull:`10658`).
+- ``engine='netcdf4'`` now supports reading and writing in-memory netCDF files.
+  All of Xarray's netCDF backends now support in-memory reads and writes
+  (:pull:`10624`).
+  By `Stephan Hoyer <https://github.com/shoyer>`_.
+
+Breaking changes
+~~~~~~~~~~~~~~~~
+
 - :py:meth:`Dataset.update` now returns ``None``, instead of the updated dataset. This
   completes the deprecation cycle started in version 0.17. The method still updates the
   dataset in-place. (:issue:`10167`)
@@ -288,8 +287,8 @@ Internal Changes
 
 .. _whats-new.2025.09.0:
 
-v2025.09.0 (September 2, 2025)
-------------------------------
+v2025.09.0 (Sep 2, 2025)
+------------------------
 
 This release brings a number of small improvements and fixes, especially related
 to writing DataTree objects and netCDF files to disk.
@@ -365,8 +364,8 @@ Internal Changes
 
 .. _whats-new.2025.08.0:
 
-v2025.08.0 (August 14, 2025)
-----------------------------
+v2025.08.0 (Aug 14, 2025)
+-------------------------
 
 This release brings the ability to load xarray objects asynchronously, write netCDF as bytes, fixes a number of bugs, and starts an important deprecation cycle for changing the default values of keyword arguments for various xarray combining functions.
 
@@ -442,8 +441,8 @@ Performance
 
 .. _whats-new.2025.07.1:
 
-v2025.07.1 (July 09, 2025)
---------------------------
+v2025.07.1 (Jul 09, 2025)
+-------------------------
 
 This release brings a lot of improvements to flexible indexes functionality, including new classes
 to ease building of new indexes with custom coordinate transforms (:py:class:`indexes.CoordinateTransformIndex`)