Fix reading of FITS files with SkyCoord columns

glue/core/data_factories/fits.py

@@ -2,7 +2,7 @@
 import warnings
 from os.path import basename
 from collections import OrderedDict
-
+from astropy.coordinates import SkyCoord
 from glue.core.coordinates import coordinates_from_header, WCSCoordinates
 from glue.core.data import Component, Data
 from glue.config import data_factory, cli_parser
@@ -151,9 +151,16 @@ def new_data(suffix=True):
                     if column.ndim != 1:
                         warnings.warn("Dropping column '{0}' since it is not 1-dimensional".format(column_name))
                         continue
-                    component = Component.autotyped(column, units=column.unit)
-                    data.add_component(component=component,
-                                       label=column_name)
+                    if isinstance(column, SkyCoord):
+                        for attribute_name in column.get_representation_component_names():
+                            values = getattr(column, attribute_name)
+                            component = Component.autotyped(values, units=values.unit)
+                            data.add_component(component=component,
+                                               label=f"{column_name}.{attribute_name}")
+                    else:
+                        component = Component.autotyped(column, units=column.unit)
+                        data.add_component(component=component,
+                                           label=column_name)
 
     if close_hdulist:
         hdulist.close()

glue/core/data_factories/tests/test_fits.py

@@ -6,6 +6,10 @@
 import numpy as np
 from numpy.testing import assert_array_equal
 
+from astropy.table import Table
+from astropy.coordinates import SkyCoord
+from astropy import units as u
+
 from glue.core import data_factories as df
 
 from glue.tests.helpers import requires_astropy, make_file
@@ -229,3 +233,31 @@ def test_coordinate_component_units():
     assert d.get_component(wid[2]).units == 'deg'
     assert wid[3].label == 'Right Ascension'
     assert d.get_component(wid[3]).units == 'deg'
+
+
+@requires_astropy
+def test_mixin_columns(tmp_path):
+
+    t = Table()
+    t['coords'] = SkyCoord([1, 2, 3] * u.deg, [4, 5, 6] * u.deg, frame='galactic')
+    t['coords_with_distance'] = SkyCoord([1, 2, 3] * u.deg, [4, 5, 6] * u.deg, [7, 8, 9] * u.kpc, frame='fk5')
+
+    t.write(tmp_path / 'table.fits', format='fits')
+
+    d = fits_reader(tmp_path / 'table.fits')[0]
+
+    assert len(d.main_components) == 6
+
+    assert_array_equal(d['coords.l'], [1, 2, 3])
+    assert d.get_component('coords.l').units == 'deg'
+    assert_array_equal(d['coords.b'], [4, 5, 6])
+    assert d.get_component('coords.b').units == 'deg'
+    assert_array_equal(d['coords.distance'], [1, 1, 1])
+    assert d.get_component('coords.distance').units == ''
+
+    assert_array_equal(d['coords_with_distance.ra'], [1, 2, 3])
+    assert d.get_component('coords_with_distance.ra').units == 'deg'
+    assert_array_equal(d['coords_with_distance.dec'], [4, 5, 6])
+    assert d.get_component('coords_with_distance.dec').units == 'deg'
+    assert_array_equal(d['coords_with_distance.distance'], [7, 8, 9])
+    assert d.get_component('coords_with_distance.distance').units == 'kpc'