added eq and repr tests, and fixed shape of () not being valid

lib/iris/_data_manager.py

@@ -148,7 +148,7 @@ def _assert_axioms(self):
             if is_lazy and is_real:
                 msg = "Unexpected data state, got both lazy and real data."
                 raise ValueError(msg)
-            elif not self._shape:
+            elif self._shape is None:
                 msg = "Unexpected data state, got no lazy or real data, and no shape."
                 raise ValueError(msg)
 
@@ -300,7 +300,7 @@ def ndim(self):
     @property
     def shape(self):
         """The shape of the data being managed."""
-        return self._shape if self._shape else self.core_data().shape
+        return self._shape
 
     def is_dataless(self) -> bool:
         """Determine whether the cube has no data.

lib/iris/tests/unit/data_manager/test_DataManager.py

@@ -87,6 +87,16 @@ def test_lazy_with_lazy__dtype_failure(self):
         dm2 = DataManager(as_lazy_data(self.real_array).astype(int))
         self.assertFalse(dm1 == dm2)
 
+    def test_none(self):
+        dm1 = DataManager(data=None, shape=(1, ))
+        dm2 = DataManager(data=None, shape=(1, ))
+        self.assertTrue(dm1 == dm2)
+
+    def test_none_with_real(self):
+        dm1 = DataManager(data=None, shape=(1, ))
+        dm2 = DataManager(self.real_array)
+        self.assertFalse(dm1 == dm2)
+
     def test_non_DataManager_failure(self):
         dm = DataManager(np.array(0))
         self.assertFalse(dm == 0)
@@ -158,6 +168,13 @@ def test_lazy(self):
         expected = "{}({!r})".format(self.name, self.lazy_array)
         self.assertEqual(result, expected)
 
+    def test_dataless(self):
+        print(self.real_array.shape)
+        dm = DataManager(None, self.real_array.shape)
+        result = repr(dm)
+        expected = "{}({!r}), shape={}".format(self.name, None, self.real_array.shape)
+        self.assertEqual(result, expected)
+
 
 class Test__assert_axioms(tests.IrisTest):
     def setUp(self):