Pre-check for missing dataset/table name when parsing resource.

Addresses:
#1045 (comment)

Author: tseaver

gcloud/bigquery/dataset.py

@@ -204,6 +204,10 @@ def from_api_repr(cls, resource, client):
         :rtype: :class:`gcloud.bigquery.dataset.Dataset`
         :returns: Dataset parsed from ``resource``.
         """
+        if ('datasetReference' not in resource or
+                'datasetId' not in resource['datasetReference']):
+            raise KeyError('Resource lacks required identity information:'
+                           '["datasetReference"]["datasetId"]')
         name = resource['datasetReference']['datasetId']
         dataset = cls(name, client=client)
         dataset._set_properties(resource)

gcloud/bigquery/table.py

@@ -311,6 +311,10 @@ def from_api_repr(cls, resource, dataset):
         :rtype: :class:`gcloud.bigquery.table.Table`
         :returns: Table parsed from ``resource``.
         """
+        if ('tableReference' not in resource or
+                'tableId' not in resource['tableReference']):
+            raise KeyError('Resource lacks required identity information:'
+                           '["tableReference"]["tableId"]')
         table_name = resource['tableReference']['tableId']
         table = cls(table_name, dataset=dataset)
         table._set_properties(resource)

gcloud/bigquery/test_dataset.py

@@ -143,6 +143,14 @@ def test_location_setter(self):
         dataset.location = 'LOCATION'
         self.assertEqual(dataset.location, 'LOCATION')
 
+    def test_from_api_repr_missing_identity(self):
+        self._setUpConstants()
+        client = _Client(self.PROJECT)
+        RESOURCE = {}
+        klass = self._getTargetClass()
+        with self.assertRaises(KeyError):
+            klass.from_api_repr(RESOURCE, client=client)
+
     def test_from_api_repr_bare(self):
         self._setUpConstants()
         client = _Client(self.PROJECT)

gcloud/bigquery/test_table.py

@@ -348,6 +348,15 @@ def test_view_query_deleter(self):
         del table.view_query
         self.assertEqual(table.view_query, None)
 
+    def test_from_api_repr_missing_identity(self):
+        self._setUpConstants()
+        client = _Client(self.PROJECT)
+        dataset = _Dataset(client)
+        RESOURCE = {}
+        klass = self._getTargetClass()
+        with self.assertRaises(KeyError):
+            klass.from_api_repr(RESOURCE, dataset)
+
     def test_from_api_repr_bare(self):
         self._setUpConstants()
         client = _Client(self.PROJECT)