consider masked case

Author: rcomer

lib/iris/coords.py

@@ -1950,7 +1950,7 @@ def collapsed(self, dims_to_collapse=None):
             # bounds as strings.
             def serialize(x, axis):
                 if axis is None:
-                    return "|".join(x.flatten())
+                    return "|".join(str(i) for i in x.flatten())
                 # np.apply_along_axis does not work with str.join, so we
                 # need to loop through the array directly. First move (possibly
                 # multiple) axis of interest to trailing dim(s), then make a 2D
@@ -1961,7 +1961,7 @@ def serialize(x, axis):
 
                 joined = []
                 for arr_slice in work_array:
-                    joined.append("|".join(arr_slice))
+                    joined.append(serialize(arr_slice, None))
 
                 return np.array(joined).reshape(out_shape)
 

lib/iris/tests/unit/coords/test_Coord.py

@@ -15,6 +15,7 @@
 
 import dask.array as da
 import numpy as np
+import numpy.ma as ma
 
 import iris
 from iris.coords import AuxCoord, Coord, DimCoord
@@ -483,6 +484,15 @@ def test_string_nd_first(self):
 
         self.assertArrayEqual(collapsed_coord.points, expected)
 
+    def test_string_masked(self):
+        points = ma.array(["foo", "bar", "bing"], mask=[0, 1, 0], dtype=str)
+        coord = AuxCoord(points)
+
+        collapsed_coord = coord.collapsed()
+
+        expected = "foo|--|bing"
+        self.assertEqual(collapsed_coord.points, expected)
+
     def test_string_nd_second(self):
         self.setupTestArrays((3, 4))
         coord = AuxCoord(self.pts_real.astype(str))