how to call pyros_setup ?

[asmodehn]

We need to find a better way to use pyros_setup.

Currently the user is supposed to do :

try:
   import something
except ImportError:
   import pyros_setup
   pyros_setup.configurable_import().configure().activate()
   import something

The main drawback with this is that if an import trigger an error, which is not related with setting up ROS, it will be hidden by a further error, potentially related with pyros_setup...

[asmodehn]

Idea:
we could use one of these variables to check for ROS setup

alexv@AlexV-Linux:~$ source /opt/ros/indigo/setup.bash 
alexv@AlexV-Linux:~$ env | grep ROS
ROS_ROOT=/opt/ros/indigo/share/ros
ROS_PACKAGE_PATH=/opt/ros/indigo/share:/opt/ros/indigo/stacks
ROS_MASTER_URI=http://localhost:11311
ROSLISP_PACKAGE_DIRECTORIES=
ROS_DISTRO=indigo
ROS_ETC_DIR=/opt/ros/indigo/etc/ros

If the variable is set => we raise exception directly
Else => we attempt pyros_setup configure and activate before importing again.

Maybe that check should be in pyros_setup itself...

[asmodehn]

A better way to use pyros_setup could be :

try:
    import something
except ImportError:
    import pyros_setup
    if pyros_setup.activation_required:
        pyros_setup.configurable_import().configure().activate()
        import something
    else:
        raise

[asmodehn]

Another possibility would be to leverage the "next" pyros structure (with plugins - probably using pkg_resources).

This way we could so something along the lines of :

try:
    import pyros_rosplugin  # we use only one specific package that is ONLY in ROS
except ImportError:
    import pyros_setup
    if not pyros_setup.activated:  # that would be the list of distro + workspaces from configuration
        pyros_setup.configurable_import().configure().activate()
        import pyros_rosplugin
    else:
        raise

import <more random ros packages>

as a first step we could implement that "activated" member (or similar, maybe it s just in need of documenting...) and rely on rospy as a lowlevel package existing only in ros distro.

[asmodehn]

Note that if not pyros_setup.activated should rely on actual pyros activation, not ROS.

We could have ROS activated by a source, but catkin_pip wouldn't put the editable packages at the beginning of the pythonpath. However this is done by pyros-setup and required by ROS to work as expected with existing pythonpath mechanism and editable packages. (Does this mean we have a design flaw somewhere since we cannot use catkin_pip OR pyros-setup, but in some cases have to use both ? )

That being said, activating pyros-setup multiple times might be permitted or not, it depends on pyros-setup itself. So in the end it might be better if it wasn't checked at all here (but it might be inside pyros-setup configure or activate.)

However we still need a way to determine if we should raise the previous ImportError or not, without requiring pyros-setup to be needed on a pure ROS system.

[asmodehn]

Regarding previous comment, I think catkin_pip should not rely on pyros_setup, so that design problem should be fixed...

On another part, we should probably check if ROS itself is activated (to prevent import pyros_setup if it is the case -> we dont need it). We should probably use one of the ROS environment variables...

[asmodehn]

So it seems we are targeting something like :

if not 'ROS_DISTRO' in os.environ:
    import pyros_setup
    pyros_setup.configure().activate()

import rospy

This should attempt to import pyros_setup only when ROS is not loaded.
If rospy has an import problem we will except on rospy import, in both cases (with or without pyros_setup).