iris plot bug when certain aux and dim coords present

[cpelley]

import numpy as np

import iris
import iris.analysis.cartography as icart

import matplotlib.pyplot as plt
import iris.plot as iplt

cube = iris.load_cube(iris.sample_data_path('rotated_pole.nc'))

glon = cube.coord('grid_longitude')
rotated_lons = glon.points
glat = cube.coord('grid_latitude')
rotated_lats = glat.points
pole_lat = glat.coord_system.grid_north_pole_latitude
pole_lon = glat.coord_system.grid_north_pole_longitude

rotated_lats, rotated_lons = np.meshgrid(rotated_lons, rotated_lats)

lons, lats = icart.unrotate_pole(rotated_lons, rotated_lats, pole_lon, pole_lat)

lat = iris.coords.AuxCoord(lons, standard_name='longitude', units='degree_north')
lon = iris.coords.AuxCoord(lats, standard_name='latitude', units='degree_east')

cube.add_aux_coord(lat, [0, 1])
cube.add_aux_coord(lon, [0, 1])

iplt.contourf(cube)
plt.show()

Producing the following error:

Traceback (most recent call last):
  File "/net/home/h05/cpelley/Remedy/GITHUB/no_pass_coords.py", line 28, in <module>
    iplt.contourf(cube)
  File "/home/h05/cpelley/git/iris/lib/iris/plot.py", line 464, in contourf
    result = _draw_2d_from_points('contourf', None, cube, *args, **kwargs)
  File "/home/h05/cpelley/git/iris/lib/iris/plot.py", line 261, in _draw_2d_from_points
    *args, **kwargs)
  File "/home/h05/cpelley/git/iris/lib/iris/plot.py", line 373, in _map_common
    x, y = cartography.get_xy_grids(cube)
  File "/home/h05/cpelley/git/iris/lib/iris/analysis/cartography.py", line 190, in get_xy_grids
    x_coord, y_coord = cube.coord(axis="X"), cube.coord(axis="Y")
  File "/home/h05/cpelley/git/iris/lib/iris/cube.py", line 1041, in coord
    raise iris.exceptions.CoordinateNotFoundError(msg)
iris.exceptions.CoordinateNotFoundError: u'Expected to find exactly 1 coordinate, but found 2. They were: grid_longitude, longitude.'

Current workaround is to simply delete the dim coords or delete the aux coords.

[pelson]

How about:

iplt.contourf(cube, coords=['grid_longitude', 'grid_latitude'])

?

[cpelley]

No I'm afraid I already tried this, in fact there is a bug with the coords keyword argument not being passed through in some situations (which I was going to raise, once I clarify better the specific problem). That along with coords not being an argument but a keyword argument (contrary to documentation).

I'll raise the coords bug sometime today if I can and link from here.
(In any case I would have expected iris to have defaulted to use the dimension coordinates)

[esc24]

iplt.contourf(cube, coords=['grid_longitude', 'grid_latitude'])

Interestingly iplt.contourf(cube, coords=['grid_latitude', 'grid_longitude']) works (albeit not as a map type plot).