Add int_or_none adapter function

Add a function that allows a value to either be translated
to an int or left as None if the json value is null to account
for null values without throwing an error.

Change-Id: I03c76d01740cfb36648f09112611111a3b316467
Closes-bug: #1720443

sushy/resources/system/system.py

@@ -21,6 +21,7 @@ from sushy.resources import common
 from sushy.resources.system import constants as sys_cons
 from sushy.resources.system import mappings as sys_maps
 from sushy.resources.system import processor
+from sushy import utils
 
 
 LOG = logging.getLogger(__name__)
@@ -52,7 +53,7 @@ class MemorySummaryField(base.CompositeField):
     This signifies health state of memory along with its dependent resources.
     """
 
-    size_gib = base.Field('TotalSystemMemoryGiB', adapter=int)
+    size_gib = base.Field('TotalSystemMemoryGiB', adapter=utils.int_or_none)
     """The size of memory of the system in GiB.
 
     This signifies the total installed, operating system-accessible memory

sushy/tests/unit/resources/system/test_system.py

@@ -79,6 +79,11 @@ class SystemTestCase(base.TestCase):
             'attribute Actions/#ComputerSystem.Reset/target',
             self.sys_inst._parse_attributes)
 
+    def test__parse_attributes_null_memory_capacity(self):
+        self.sys_inst.json['MemorySummary']['TotalSystemMemoryGiB'] = None
+        self.sys_inst._parse_attributes()
+        self.assertIsNone(self.sys_inst.memory_summary.size_gib)
+
     def test_get__reset_action_element(self):
         value = self.sys_inst._get_reset_action_element()
         self.assertEqual("/redfish/v1/Systems/437XR1138R2/Actions/"

sushy/tests/unit/test_utils.py

@@ -35,3 +35,7 @@ class UtilsTestCase(base.TestCase):
         expected = ('/redfish/v1/Systems/FOO', '/redfish/v1/Systems/BAR')
         self.assertEqual(expected, utils.get_members_identities(members))
         self.assertEqual(1, log_mock.call_count)
+
+    def test_int_or_none(self):
+        self.assertEqual(1, utils.int_or_none('1'))
+        self.assertIsNone(None, utils.int_or_none(None))

sushy/utils.py

@@ -45,3 +45,15 @@ def get_members_identities(members):
         members_list.append(path.rstrip('/'))
 
     return tuple(members_list)
+
+
+def int_or_none(x):
+    """Given a value x it cast as int or None
+
+    :param x: The value to transform and return
+    :returns: Either None or x cast to an int
+
+    """
+    if x is None:
+        return None
+    return int(x)