Add FieldList class to resource base

Add a class capable of handling lists of fields in resource
body JSON. This is a general purpose class, and is being added
for use in the rsd-lib sushy extension as there are JSON responses
such as {"Initiator": [{"iSCSI": 1}, {"iSCSI": 2}]} that need to
be handled.

Change-Id: Ia5976d8646162e8558dc63584f89e4a3cabbf1f2

rsd_lib/resources/base.py

@@ -0,0 +1,48 @@
+# Copyright 2017 Intel, Inc.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import copy
+
+from sushy.resources import base
+
+
+class FieldList(base.CompositeField):
+    """Base class for fields consisting of a list of several sub-fields."""
+
+    def _load(self, body, resource, nested_in=None):
+        """Load the field list.
+
+        :param body: parent JSON body.
+        :param resource: parent resource.
+        :param nested_in: parent resource name (for error reporting only).
+        :returns: a new list object containing subfields.
+        """
+        nested_in = (nested_in or []) + self._path
+        values = base.Field._load(self, body, resource)
+        if values is None:
+            return None
+
+        # Initialize the list that will contain each field instance
+        instances = []
+        for value in values:
+            instance = copy.copy(self)
+            for attr, field in self._subfields.items():
+                # Hide the Field object behind the real value
+                setattr(instance, attr, field._load(value,
+                                                    resource,
+                                                    nested_in))
+            instances.append(instance)
+
+        return instances

rsd_lib/tests/unit/resources/test_base.py

@@ -0,0 +1,98 @@
+# Copyright 2017 Intel, Inc.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import copy
+import mock
+
+from sushy.resources import base as resource_base
+from sushy.tests.unit import base
+
+from rsd_lib.resources import base as rsd_resource_base
+
+TEST_JSON = {
+    'String': 'a string',
+    'Integer': '42',
+    'List': ['a string', 42],
+    'Nested': {
+        'String': 'another string',
+        'Integer': 0,
+        'Object': {
+            'Field': 'field value'
+        },
+        'Mapped': 'raw'
+    },
+    'FieldList': [
+        {
+            'String': 'a third string',
+            'Integer': 1
+        },
+        {
+            'String': 'a fourth string',
+            'Integer': 2
+        }
+    ]
+}
+
+
+MAPPING = {
+    'raw': 'real'
+}
+
+
+class NestedTestField(resource_base.CompositeField):
+    string = resource_base.Field('String', required=True)
+    integer = resource_base.Field('Integer', adapter=int)
+    nested_field = resource_base.Field(['Object', 'Field'], required=True)
+    mapped = resource_base.MappedField('Mapped', MAPPING)
+    non_existing = resource_base.Field('NonExisting', default=3.14)
+
+
+class TestFieldList(rsd_resource_base.FieldList):
+    string = resource_base.Field('String')
+    integer = resource_base.Field('Integer')
+
+
+class ComplexResource(resource_base.ResourceBase):
+    string = resource_base.Field('String', required=True)
+    integer = resource_base.Field('Integer', adapter=int)
+    nested = NestedTestField('Nested')
+    field_list = TestFieldList('FieldList')
+    non_existing_nested = NestedTestField('NonExistingNested')
+    non_existing_mapped = resource_base.MappedField('NonExistingMapped',
+                                                    MAPPING)
+
+
+class FieldTestCase(base.TestCase):
+    def setUp(self):
+        super(FieldTestCase, self).setUp()
+        self.conn = mock.Mock()
+        self.json = copy.deepcopy(TEST_JSON)
+        self.conn.get.return_value.json.return_value = self.json
+        self.test_resource = ComplexResource(self.conn,
+                                             redfish_version='1.0.x')
+
+    def test_ok(self):
+        self.assertEqual('a string', self.test_resource.string)
+        self.assertEqual(42, self.test_resource.integer)
+        self.assertEqual('another string', self.test_resource.nested.string)
+        self.assertEqual(0, self.test_resource.nested.integer)
+        self.assertEqual('field value', self.test_resource.nested.nested_field)
+        self.assertEqual('real', self.test_resource.nested.mapped)
+        self.assertEqual(3.14, self.test_resource.nested.non_existing)
+        self.assertEqual('a third string',
+                         self.test_resource.field_list[0].string)
+        self.assertEqual(2, self.test_resource.field_list[1].integer)
+        self.assertIsNone(self.test_resource.non_existing_nested)
+        self.assertIsNone(self.test_resource.non_existing_mapped)