Exclude dimensions used in faceting from squeeze (#8174)

* Exclude dimensions used in faceting from squeeze

* Add unit test for facetting singleton dim

* Add bug fix to changelog

* Move test to proper class

* Update doc/whats-new.rst

* Apply suggestions from code review

* Update doc/whats-new.rst

---------

Co-authored-by: Mathias Hauser <[email protected]>
Co-authored-by: Deepak Cherian <[email protected]>

Author: 3 people

doc/whats-new.rst

@@ -73,6 +73,9 @@ Bug fixes
   special case ``NaT`` handling in :py:meth:`~core.accessor_dt.DatetimeAccessor.isocalendar()`
   (:issue:`7928`, :pull:`8084`).
   By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_.
+- Calling plot with kwargs ``col``, ``row`` or ``hue`` no longer squeezes dimensions passed via these arguments
+  (:issue:`7552`, :pull:`8174`).
+  By `Wiktor Kraśnicki <https://github.com/wkrasnicki>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/plot/dataarray_plot.py

@@ -264,7 +264,9 @@ def plot(
     --------
     xarray.DataArray.squeeze
     """
-    darray = darray.squeeze().compute()
+    darray = darray.squeeze(
+        d for d, s in darray.sizes.items() if s == 1 and d not in (row, col, hue)
+    ).compute()
 
     plot_dims = set(darray.dims)
     plot_dims.discard(row)

xarray/tests/test_plot.py

@@ -729,6 +729,13 @@ def test_labels_with_units_with_interval(self, dim) -> None:
         expected = "dim_0_bins_center [m]"
         assert actual == expected
 
+    def test_multiplot_over_length_one_dim(self) -> None:
+        a = easy_array((3, 1, 1, 1))
+        d = DataArray(a, dims=("x", "col", "row", "hue"))
+        d.plot(col="col")
+        d.plot(row="row")
+        d.plot(hue="hue")
+
 
 class TestPlot1D(PlotTestCase):
     @pytest.fixture(autouse=True)