Fix vision error when no results returned.

vision/google/cloud/vision/image.py

@@ -217,20 +217,22 @@ def detect_text(self, limit=10):
 
 def _entity_from_response_type(feature_type, results):
     """Convert a JSON result to an entity type based on the feature."""
-
-    detected_objects = []
     feature_key = _REVERSE_TYPES[feature_type]
+    annotations = results.get(feature_key, ())
+    if not annotations:
+        return []
 
+    detected_objects = []
     if feature_type == _FACE_DETECTION:
         detected_objects.extend(
-            Face.from_api_repr(face) for face in results[feature_key])
+            Face.from_api_repr(face) for face in annotations)
     elif feature_type == _IMAGE_PROPERTIES:
         detected_objects.append(
-            ImagePropertiesAnnotation.from_api_repr(results[feature_key]))
+            ImagePropertiesAnnotation.from_api_repr(annotations))
     elif feature_type == _SAFE_SEARCH_DETECTION:
-        result = results[feature_key]
-        detected_objects.append(SafeSearchAnnotation.from_api_repr(result))
+        detected_objects.append(
+            SafeSearchAnnotation.from_api_repr(annotations))
     else:
-        for result in results[feature_key]:
+        for result in annotations:
             detected_objects.append(EntityAnnotation.from_api_repr(result))
     return detected_objects

vision/unit_tests/test_client.py

@@ -116,6 +116,24 @@ def test_face_detection_from_content(self):
                          image_request['image']['content'])
         self.assertEqual(5, image_request['features'][0]['maxResults'])
 
+    def test_face_detection_from_content_no_results(self):
+        RETURNED = {
+            'responses': [{}]
+        }
+        credentials = _Credentials()
+        client = self._make_one(project=PROJECT, credentials=credentials)
+        client._connection = _Connection(RETURNED)
+
+        image = client.image(content=IMAGE_CONTENT)
+        faces = image.detect_faces(limit=5)
+        self.assertEqual(faces, [])
+        self.assertEqual(len(faces), 0)
+        image_request = client._connection._requested[0]['data']['requests'][0]
+
+        self.assertEqual(B64_IMAGE_CONTENT,
+                         image_request['image']['content'])
+        self.assertEqual(5, image_request['features'][0]['maxResults'])
+
     def test_label_detection_from_source(self):
         from google.cloud.vision.entity import EntityAnnotation
         from unit_tests._fixtures import (
@@ -138,6 +156,19 @@ def test_label_detection_from_source(self):
         self.assertEqual('/m/0k4j', labels[0].mid)
         self.assertEqual('/m/07yv9', labels[1].mid)
 
+    def test_label_detection_no_results(self):
+        RETURNED = {
+            'responses': [{}]
+        }
+        credentials = _Credentials()
+        client = self._make_one(project=PROJECT, credentials=credentials)
+        client._connection = _Connection(RETURNED)
+
+        image = client.image(content=IMAGE_CONTENT)
+        labels = image.detect_labels()
+        self.assertEqual(labels, [])
+        self.assertEqual(len(labels), 0)
+
     def test_landmark_detection_from_source(self):
         from google.cloud.vision.entity import EntityAnnotation
         from unit_tests._fixtures import (
@@ -178,6 +209,19 @@ def test_landmark_detection_from_content(self):
                          image_request['image']['content'])
         self.assertEqual(5, image_request['features'][0]['maxResults'])
 
+    def test_landmark_detection_no_results(self):
+        RETURNED = {
+            'responses': [{}]
+        }
+        credentials = _Credentials()
+        client = self._make_one(project=PROJECT, credentials=credentials)
+        client._connection = _Connection(RETURNED)
+
+        image = client.image(content=IMAGE_CONTENT)
+        landmarks = image.detect_landmarks()
+        self.assertEqual(landmarks, [])
+        self.assertEqual(len(landmarks), 0)
+
     def test_logo_detection_from_source(self):
         from google.cloud.vision.entity import EntityAnnotation
         from unit_tests._fixtures import LOGO_DETECTION_RESPONSE
@@ -254,6 +298,19 @@ def test_safe_search_detection_from_source(self):
         self.assertEqual('POSSIBLE', safe_search.medical)
         self.assertEqual('VERY_UNLIKELY', safe_search.violence)
 
+    def test_safe_search_no_results(self):
+        RETURNED = {
+            'responses': [{}]
+        }
+        credentials = _Credentials()
+        client = self._make_one(project=PROJECT, credentials=credentials)
+        client._connection = _Connection(RETURNED)
+
+        image = client.image(content=IMAGE_CONTENT)
+        safe_search = image.detect_safe_search()
+        self.assertEqual(safe_search, [])
+        self.assertEqual(len(safe_search), 0)
+
     def test_image_properties_detection_from_source(self):
         from google.cloud.vision.color import ImagePropertiesAnnotation
         from unit_tests._fixtures import IMAGE_PROPERTIES_RESPONSE
@@ -277,6 +334,19 @@ def test_image_properties_detection_from_source(self):
         self.assertEqual(65, image_properties.colors[0].color.blue)
         self.assertEqual(0.0, image_properties.colors[0].color.alpha)
 
+    def test_image_properties_no_results(self):
+        RETURNED = {
+            'responses': [{}]
+        }
+        credentials = _Credentials()
+        client = self._make_one(project=PROJECT, credentials=credentials)
+        client._connection = _Connection(RETURNED)
+
+        image = client.image(content=IMAGE_CONTENT)
+        image_properties = image.detect_properties()
+        self.assertEqual(image_properties, [])
+        self.assertEqual(len(image_properties), 0)
+
 
 class TestVisionRequest(unittest.TestCase):
     @staticmethod