Sourcing overlay workspace's setup file isn't enough for python packages

[dhood]

If you follow this tutorial https://github.com/ros2/ros2/wiki/Ament-Tutorial the part where it says

If you are returning with a new terminal to your development and want to pick up developing on your overlay you can simply source ~/overlay_ws/setup.bash which will source all parent workspaces environments automatically.

works fine for ament_cmake packages but doesn't seem to apply to ament_python packages.

I understand this to be related to #109

(The following outputs are from a while ago, but ros2/ros2#312, which was opened today, is the same issue)

dhood@osrf-esteve:~/overlay_ws [overlay_ws]$ . install/setup.bash 
Warning: OSPL_URI was already set to [[file:///usr/etc/opensplice/config/ospl.xml]]. This will not override it to the default [[file:///home/dhood/ros2_ws1/install_isolated/opensplice_cmake_module/share/opensplice_cmake_module/config/ros_ospl.xml]]. Please make sure this is the config that you want.
dhood@osrf-esteve:~/overlay_ws [overlay_ws]$ talker_py 
Traceback (most recent call last):
File "/home/dhood/overlay_ws/install/bin/talker_py", line 9, in 
load_entry_point('rclpy-examples==0.0.0', 'console_scripts', 'talker_py')()
File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 542, in load_entry_point
return get_distribution(dist).load_entry_point(group, name)
File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2569, in load_entry_point
return ep.load()
File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2229, in load
return self.resolve()
File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 2235, in resolve
module = __import__(self.module_name, fromlist=['__name__'], level=0)
File "/home/dhood/overlay_ws/install/lib/python3.5/site-packages/topics/talker_py.py", line 18, in 
import rclpy
File "/home/dhood/ros2_ws1/install_isolated/rclpy/lib/python3.5/site-packages/rclpy/__init__.py", line 23, in 
from rclpy.impl import rmw_implementation_tools
File "/home/dhood/ros2_ws1/install_isolated/rclpy/lib/python3.5/site-packages/rclpy/impl/rmw_implementation_tools.py", line 18, in 
import ament_index_python
ImportError: No module named 'ament_index_python'
dhood@osrf-esteve:~/overlay_ws [overlay_ws]$ echo $PYTHONPATH 
/home/dhood/overlay_ws/install/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/tf2_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rclpy/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/sensor_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/ros1_bridge/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/nav_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/diagnostic_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/geometry_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/std_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_py/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rcl_interfaces/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/pendulum_msgs/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/example_interfaces/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/builtin_interfaces/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_opensplice_c/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_opensplice_cpp/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_introspection_cpp/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_introspection_c/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_connext_c/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_connext_cpp/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_dds_idl/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_cpp/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_c/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_cmake/lib/python3.5/site-packages:/home/dhood/ros2_ws1/install_isolated/rosidl_parser/lib/python3.5/site-packages
dhood@osrf-esteve:~/overlay_ws [overlay_ws]$ echo $PYTHONPATH | grep ament
dhood@osrf-esteve:~/overlay_ws [overlay_ws]$

dhood@osrf-esteve:~/overlay_ws [overlay_ws]$ echo $PATH
/home/dhood/overlay_ws/install/bin:/home/dhood/ros2_ws1/install_isolated/uncrustify/bin:/home/dhood/ros2_ws1/install_isolated/pendulum_control/bin:/home/dhood/ros2_ws1/install_isolated/tlsf_cpp/bin:/home/dhood/ros2_ws1/install_isolated/tlsf/bin:/home/dhood/ros2_ws1/install_isolated/tf2_ros/bin:/home/dhood/ros2_ws1/install_isolated/tf2_msgs/bin:/home/dhood/ros2_ws1/install_isolated/tf2/bin:/home/dhood/ros2_ws1/install_isolated/test_rclcpp/bin:/home/dhood/ros2_ws1/install_isolated/test_communication/bin:/home/dhood/ros2_ws1/install_isolated/rclpy/bin:/home/dhood/ros2_ws1/install_isolated/rclcpp_examples/bin:/home/dhood/ros2_ws1/install_isolated/intra_process_demo/bin:/home/dhood/ros2_ws1/install_isolated/image_tools/bin:/home/dhood/ros2_ws1/install_isolated/sensor_msgs/bin:/home/dhood/ros2_ws1/install_isolated/ros1_bridge/bin:/home/dhood/ros2_ws1/install_isolated/composition/bin:/home/dhood/ros2_ws1/install_isolated/rclcpp/bin:/home/dhood/ros2_ws1/install_isolated/rclc/bin:/home/dhood/ros2_ws1/install_isolated/rcl/bin:/home/dhood/ros2_ws1/install_isolated/nav_msgs/bin:/home/dhood/ros2_ws1/install_isolated/diagnostic_msgs/bin:/home/dhood/ros2_ws1/install_isolated/geometry_msgs/bin:/home/dhood/ros2_ws1/install_isolated/std_msgs/bin:/home/dhood/ros2_ws1/install_isolated/rttest/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_default_generators/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_py/bin:/home/dhood/ros2_ws1/install_isolated/rcl_interfaces/bin:/home/dhood/ros2_ws1/install_isolated/pendulum_msgs/bin:/home/dhood/ros2_ws1/install_isolated/example_interfaces/bin:/home/dhood/ros2_ws1/install_isolated/builtin_interfaces/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_default_runtime/bin:/home/dhood/ros2_ws1/install_isolated/rmw_implementation/bin:/home/dhood/ros2_ws1/install_isolated/rmw_opensplice_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_opensplice_c/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_opensplice_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rmw_fastrtps_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rmw_connext_dynamic_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_introspection_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_introspection_c/bin:/home/dhood/ros2_ws1/install_isolated/rmw_connext_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_connext_c/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_typesupport_connext_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_dds_idl/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_cpp/bin:/home/dhood/ros2_ws1/install_isolated/rmw/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_generator_c/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_cmake/bin:/home/dhood/ros2_ws1/install_isolated/rosidl_parser/bin:/home/dhood/ros2_ws1/install_isolated/rmw_implementation_cmake/bin:/home/dhood/ros2_ws1/install_isolated/rmw_connext_shared_cpp/bin:/home/dhood/ros2_ws1/install_isolated/python_cmake_module/bin:/home/dhood/ros2_ws1/install_isolated/class_loader/bin:/home/dhood/ros2_ws1/install_isolated/poco_vendor/bin:/home/dhood/ros2_ws1/install_isolated/opensplice_cmake_module/bin:/home/dhood/ros2_ws1/install_isolated/ament_index_cpp/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_gtest/bin:/home/dhood/ros2_ws1/install_isolated/gtest_vendor/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_gmock/bin:/home/dhood/ros2_ws1/install_isolated/gmock_vendor/bin:/home/dhood/ros2_ws1/install_isolated/fastrtps_cmake_module/bin:/home/dhood/ros2_ws1/install_isolated/fastrtps/bin:/home/dhood/ros2_ws1/install_isolated/fastcdr/bin:/home/dhood/ros2_ws1/install_isolated/console_bridge/bin:/home/dhood/ros2_ws1/install_isolated/connext_cmake_module/bin:/home/dhood/rti_connext_dds-5.2.3/lib/x64Linux3gcc4.8.2:/home/dhood/rti_connext_dds-5.2.3/bin:/home/dhood/ros2_ws1/install_isolated/ament_lint_common/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_uncrustify/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_pyflakes/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_pep8/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_pep257/bin:/home/dhood/ros2_ws1/install_isolated/ament_lint_auto/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_nose/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_cpplint/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_cppcheck/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_clang_format/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_copyright/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_lint_cmake/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_auto/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_test/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_target_dependencies/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_python/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_export_dependencies/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_libraries/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_include_directories/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_export_link_flags/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_export_libraries/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_export_interfaces/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_export_include_directories/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_export_definitions/bin:/home/dhood/ros2_ws1/install_isolated/ament_cmake_core/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

[wjwwood]

I've seen this too. If I build a workspace (non-isolated) on top of my full ros2 workspace (isolated) then I get a PYTHONPATH which does not contain several important paths (like launch).

[wjwwood]

It looks like the issue is that pure python packages are not put on the AMENT_PREFIX_PATH when the local_setup.*sh file is sourced, so later the second workspace never visits them to source their environment hooks.