[Datumaro] Fix COCO keypoint export bug (#1388)

CHANGELOG.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Merge is allowed for points, but clicks on points conflict with frame dragging logic
 - Removed objects are visible for search
 - Add missed task_id and job_id fields into exception logs for the new UI (https://github.com/opencv/cvat/pull/1372)
+- Fixed polygon exporting bug in COCO dataset (https://github.com/opencv/cvat/issues/1387)
 - Task creation from remote files (https://github.com/opencv/cvat/pull/1392)
 
 ### Security

datumaro/datumaro/plugins/coco_format/converter.py

@@ -1,5 +1,5 @@
 
-# Copyright (C) 2019 Intel Corporation
+# Copyright (C) 2020 Intel Corporation
 #
 # SPDX-License-Identifier: MIT
 
@@ -364,9 +364,9 @@ class _KeypointsConverter(_InstancesConverter):
         solitary_points = []
 
         for g_id, group in groupby(annotations, lambda a: a.group):
-            if g_id and not cls.find_instance_anns(group):
+            if not g_id or g_id and not cls.find_instance_anns(group):
                 group = [a for a in group if a.type == AnnotationType.points]
-            solitary_points.extend(group)
+                solitary_points.extend(group)
 
         return solitary_points
 

datumaro/tests/test_coco_format.py

@@ -560,6 +560,9 @@ class CocoConverterTest(TestCase):
                         annotations=[
                             # Solitary keypoints
                             Points([1, 2, 0, 2, 4, 1], label=5, id=3),
+
+                            # Some other solitary annotations (bug #1387)
+                            Polygon([0, 0, 4, 0, 4, 4], label=3, id=4),
                         ]),
 
                     DatasetItem(id=3, subset='val',