Fix attribute array comparison

docs/src/whatsnew/latest.rst

@@ -57,6 +57,9 @@ This document explains the changes made to Iris for this release
    attribute. Also made cell_method string parsing more lenient w.r.t.
    whitespace. (:pull:`6083`)
 
+#. `@ukmo-ccbunney`_ fixed comparison of cubes with array type attributes;
+   fixes :issue:`6027` (:pull:`6181`)
+
 💣 Incompatible Changes
 =======================
 

lib/iris/_merge.py

@@ -388,7 +388,9 @@ def _defn_msgs(self, other_defn):
                 diff_attrs = [
                     repr(key[1])
                     for key in attrs_1
-                    if np.all(attrs_1[key] != attrs_2[key])
+                    if not np.array_equal(
+                        np.array(attrs_1[key], ndmin=1), np.array(attrs_2[key], ndmin=1)
+                    )
                 ]
                 diff_attrs = ", ".join(sorted(diff_attrs))
                 msgs.append(

lib/iris/common/mixin.py

@@ -11,6 +11,7 @@
 from typing import Any
 
 import cf_units
+import numpy as np
 
 import iris.std_names
 
@@ -104,11 +105,9 @@ def __eq__(self, other):
         match = set(self.keys()) == set(other.keys())
         if match:
             for key, value in self.items():
-                match = value == other[key]
-                try:
-                    match = bool(match)
-                except ValueError:
-                    match = match.all()
+                match = np.array_equal(
+                    np.array(value, ndmin=1), np.array(other[key], ndmin=1)
+                )
                 if not match:
                     break
         return match

lib/iris/tests/unit/common/mixin/test_LimitedAttributeDict.py

@@ -42,12 +42,22 @@ def test___eq___numpy(self):
         right = LimitedAttributeDict(**values)
         self.assertEqual(left, right)
         self.assertEqual(left, values)
+
         values = dict(one=np.arange(1), two=np.arange(1), three=np.arange(1))
         left = LimitedAttributeDict(dict(one=0, two=0, three=0))
         right = LimitedAttributeDict(**values)
         self.assertEqual(left, right)
         self.assertEqual(left, values)
 
+        # Test inequality:
+        values = dict(one=np.arange(1), two=np.arange(2), three=np.arange(3))
+        left = LimitedAttributeDict(**values)
+        right = LimitedAttributeDict(
+            one=np.arange(3), two=np.arange(2), three=np.arange(1)
+        )
+        self.assertNotEqual(left, right)
+        self.assertNotEqual(values, right)
+
     def test___setitem__(self):
         for key in self.forbidden_keys:
             item = LimitedAttributeDict()