Squashed commit of the following:

commit 0a0f800
Merge: 33c8033 41d33f5
Author: Deepak Cherian <[email protected]>
Date:   Tue Jan 2 20:42:51 2024 -0700

    Merge branch 'main' into depr-groupby-squeeze-2

commit 33c8033
Author: Deepak Cherian <[email protected]>
Date:   Tue Jan 2 20:40:42 2024 -0700

    Don't skip for resampling

commit d7be352
Author: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date:   Wed Jan 3 03:24:13 2024 +0000

    [pre-commit.ci] auto fixes from pre-commit.com hooks

    for more information, see https://pre-commit.ci

commit d13fa0e
Author: Deepak Cherian <[email protected]>
Date:   Tue Jan 2 20:23:43 2024 -0700

    Apply suggestions from code review

    Co-authored-by: Michael Niklas  <[email protected]>

commit dd6ea53
Author: Deepak Cherian <[email protected]>
Date:   Thu Dec 21 19:29:40 2023 -0700

    Silence more warnings

commit 44e5a41
Author: Deepak Cherian <[email protected]>
Date:   Thu Dec 21 19:21:06 2023 -0700

    minimize test mods

commit 94c1c1f
Author: Deepak Cherian <[email protected]>
Date:   Thu Dec 21 18:55:46 2023 -0700

    Add tests for pydata#8263

commit 0ab4eb6
Author: Deepak Cherian <[email protected]>
Date:   Thu Dec 21 18:47:41 2023 -0700

    Fix typing

commit a064430
Merge: d6a3f2d 03ec3cb
Author: Deepak Cherian <[email protected]>
Date:   Thu Dec 21 18:47:04 2023 -0700

    Merge branch 'main' into depr-groupby-squeeze-2

    * main:
      Fix mypy type ignore (pydata#8564)
      Support for the new compression arguments. (pydata#7551)
      FIX: reverse index output of bottleneck move_argmax/move_argmin functions (pydata#8552)
      Adapt map_blocks to use new Coordinates API (pydata#8560)
      add xeofs to ecosystem.rst (pydata#8561)
      Offer a fixture for unifying DataArray & Dataset tests (pydata#8533)
      Generalize cumulative reduction (scan) to non-dask types (pydata#8019)

commit d6a3f2d
Author: Deepak Cherian <[email protected]>
Date:   Thu Dec 21 18:46:50 2023 -0700

    Fix generator for aggregations

commit 97f1695
Author: Deepak Cherian <[email protected]>
Date:   Tue Dec 19 10:58:11 2023 -0700

    Fix docs

commit 5b33b98
Author: Deepak Cherian <[email protected]>
Date:   Sun Dec 17 20:35:53 2023 -0700

    fix whats-new

commit 80b2b36
Author: Deepak Cherian <[email protected]>
Date:   Sun Dec 17 20:26:17 2023 -0700

    Reduce more warnings

commit 5f6f4ea
Merge: a57d4ae 2971994
Author: Deepak Cherian <[email protected]>
Date:   Sat Dec 16 20:33:13 2023 -0700

    Merge branch 'main' into depr-groupby-squeeze-2

    * main: (26 commits)
      Filter null values before plotting (pydata#8535)
      Update concat.py (pydata#8538)
      Add getitem to array protocol (pydata#8406)
      Added option to specify weights in xr.corr() and xr.cov() (pydata#8527)
      Filter out doctest warning (pydata#8539)
      Bump actions/setup-python from 4 to 5 (pydata#8540)
      Point users to where in their code they should make mods for Dataset.dims (pydata#8534)
      Add Cumulative aggregation (pydata#8512)
      dev whats-new
      Whats-new for 2023.12.0 (pydata#8532)
      explicitly skip using `__array_namespace__` for `numpy.ndarray` (pydata#8526)
      Add `eval` method to Dataset (pydata#7163)
      Deprecate ds.dims returning dict (pydata#8500)
      test and fix empty xindexes repr (pydata#8521)
      Remove PR labeler bot (pydata#8525)
      Hypothesis strategy for generating Variable objects (pydata#8404)
      Use numbagg for `rolling` methods (pydata#8493)
      Bump pypa/gh-action-pypi-publish from 1.8.10 to 1.8.11 (pydata#8514)
      fix RTD docs build (pydata#8519)
      Fix type of `.assign_coords` (pydata#8495)
      ...

commit a57d4ae
Author: Deepak Cherian <[email protected]>
Date:   Fri Dec 1 21:36:04 2023 -0700

    Test one more warning

commit bf8139d
Author: Deepak Cherian <[email protected]>
Date:   Fri Dec 1 21:33:45 2023 -0700

    Update xarray/tests/test_groupby.py

commit 4e9a063
Author: Deepak Cherian <[email protected]>
Date:   Fri Dec 1 21:10:14 2023 -0700

    Set squeeze=None for Dataset too

commit c2e576e
Author: Deepak Cherian <[email protected]>
Date:   Fri Dec 1 20:54:17 2023 -0700

    Fix first, last

commit 6d8e822
Author: Deepak Cherian <[email protected]>
Date:   Fri Dec 1 20:46:21 2023 -0700

    better warning

commit 62c334b
Author: Deepak Cherian <[email protected]>
Date:   Fri Dec 1 20:45:17 2023 -0700

    silence warnings

commit b7805a8
Author: dcherian <[email protected]>
Date:   Tue Aug 15 10:54:25 2023 -0600

    Deprecate `squeeze` in GroupBy.

    Closes pydata#2157

Author: dcherian

doc/user-guide/groupby.rst

@@ -177,28 +177,18 @@ This last line is roughly equivalent to the following::
         results.append(group - alt.sel(letters=label))
     xr.concat(results, dim='x')
 
-Squeezing
-~~~~~~~~~
+Iterating and Squeezing
+~~~~~~~~~~~~~~~~~~~~~~~
 
-When grouping over a dimension, you can control whether the dimension is
-squeezed out or if it should remain with length one on each group by using
-the ``squeeze`` parameter:
-
-.. ipython:: python
-
-    next(iter(arr.groupby("x")))
+Previously, Xarray defaulted to squeezing out dimensions of size one when iterating over
+a GroupBy object. This behaviour is being removed.
+You can always squeeze explicitly later with the Dataset or DataArray
+:py:meth:`~xarray.DataArray.squeeze` methods.
 
 .. ipython:: python
 
     next(iter(arr.groupby("x", squeeze=False)))
 
-Although xarray will attempt to automatically
-:py:attr:`~xarray.DataArray.transpose` dimensions back into their original order
-when you use apply, it is sometimes useful to set ``squeeze=False`` to
-guarantee that all original dimensions remain unchanged.
-
-You can always squeeze explicitly later with the Dataset or DataArray
-:py:meth:`~xarray.DataArray.squeeze` methods.
 
 .. _groupby.multidim:
 

doc/whats-new.rst

@@ -37,7 +37,8 @@ Breaking changes
 
 Deprecations
 ~~~~~~~~~~~~
-
+- The `squeeze` kwarg to GroupBy is now deprecated. (:issue:`2157`, :pull:`8507`)
+  By `Deepak Cherian <https://github.com/dcherian>`_.
 
 Bug fixes
 ~~~~~~~~~
@@ -116,7 +117,6 @@ Breaking changes
 
 Deprecations
 ~~~~~~~~~~~~
-
 - As part of an effort to standardize the API, we're renaming the ``dims``
   keyword arg to ``dim`` for the minority of functions which current use
   ``dims``. This started with :py:func:`xarray.dot` & :py:meth:`DataArray.dot`