Add mypy tests to check static typing

sros2/package.xml

@@ -18,11 +18,12 @@
 
   <test_depend>ament_copyright</test_depend>
   <test_depend>ament_flake8</test_depend>
+  <test_depend>ament_mypy</test_depend>
   <test_depend>ament_pep257</test_depend>
   <test_depend>python3-pytest</test_depend>
   <test_depend>std_msgs</test_depend>
   <test_depend>std_srvs</test_depend>
-  
+
   <export>
     <build_type>ament_python</build_type>
   </export>

sros2/setup.py

@@ -12,11 +12,11 @@ def package_files(directory):
     return paths
 
 
-extra_files = []
-extra_files.extend(package_files('sros2/policy/defaults'))
-extra_files.extend(package_files('sros2/policy/schemas'))
-extra_files.extend(package_files('sros2/policy/templates'))
-
+extra_files = (
+    package_files('sros2/policy/defaults') +
+    package_files('sros2/policy/schemas') +
+    package_files('sros2/policy/templates')
+)
 
 setup(
     name='sros2',

sros2/test/test_mypy.py

@@ -0,0 +1,22 @@
+# Copyright 2019 Canonical Ltd
+#
+# 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.
+
+from ament_mypy.main import main
+import pytest
+
+
+@pytest.mark.mypy
+@pytest.mark.linter
+def test_mypy():
+    assert main(argv=[]) == 0, 'Found errors'