Undo the transpose change and add test to make sure transposition is right.

Author: dcherian

xarray/plot/plot.py

@@ -693,7 +693,7 @@ def newplotfunc(
             dims = yx_dims + tuple(d for d in darray.dims if d not in yx_dims)
             if dims != darray.dims:
                 darray = darray.transpose(*dims, transpose_coords=True)
-        elif xval.shape[-1] == darray.shape[0]:
+        elif darray[xlab].dims[-1] == darray.dims[0]:
             darray = darray.transpose(transpose_coords=True)
 
         # Pass the data as a masked ndarray too

xarray/tests/test_plot.py

@@ -2167,4 +2167,4 @@ def test_plot_transposed_nondim_coord(plotfunc):
 def test_plot_transposes_properly():
     da = xr.DataArray([np.sin(2 * np.pi / 10 * np.arange(10))] * 10, dims=("y", "x"))
     hdl = da.plot(x="x", y="y")
-    np.all(hdl.get_array() == da.to_masked_array().ravel())
+    assert np.all(hdl.get_array() == da.to_masked_array().ravel())