Add warnings for reserved Python keywords in interface members

[samiamlabs]

This is a temporary fix related to issue #95. Until a language-specific name mangling is implemented to avoid keywords as described in ros2/design#172, a warning would be nice.

I can add stderr prints for services and actions also if this pull request seems like a good idea.

Example build output from colcon:

Starting >>> dredgebot_msgs
Starting >>> rosidl_generator_py
Finished <<< rosidl_generator_py [7.05s]                                                               
[Processing: dredgebot_msgs]                             
--- stderr: dredgebot_msgs                                  
Member name "from" in the message "LatLonLineSegment" is a reserved keyword in Python and is not supported at the moment. Please use a different name.
---
Finished <<< dredgebot_msgs [39.4s]

Summary: 2 packages finished [39.5s]
  1 package had stderr output: dredgebot_msgs

[wjwwood]

@samiamlabs is this still a WIP?

[samiamlabs]

I have not added error-prints for services or actions yet. If you think this PR makes sense I can fix that before merging.

Alternatively, we could just merge this PR and I can make a new one for actions and services.

[wjwwood]

I'd advise you to fix it up to check in actions and services too before removing the WIP, but that's up to you. I do think this pr makes sense in general. @dirk-thomas do you think so too? My one concern is that this will warn on messages that already exist and cannot easily be changed, but maybe we already fixed that. I don't remember.

[wjwwood]

ping @dirk-thomas

Also, @samiamlabs do you think you'll have time to follow up on this? No pressure but it would help us triaging things to know.

[samiamlabs]

I will try to find some time to work on this at the start of next week :)

[samiamlabs]

Finally got around to do some more work on this.
Here is an example build output:

[Processing: rosidl_python_test_interfaces]                              
--- stderr: rosidl_python_test_interfaces                                  
Member name 'from' in the message 'ReservedKeywords' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
Member name 'yield' in the message 'ReservedKeywords' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
Member name 'is' in the service request 'ReservedKeywordsRequest' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
Member name 'lambda' in the service response 'ReservedKeywordsResponse' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
Member name 'nonlocal' in the action feedback 'ReservedKeywordsFeedback' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
Member name 'global' in the action goal 'ReservedKeywordsGoal' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
Member name 'pass' in the action result 'ReservedKeywordsResult' is a reserved keyword in Python and is not supported at the moment. Please use a different name.
---
Finished <<< rosidl_python_test_interfaces [30.7s]

I also set up a VSCode "Dev Container" for the nightly ROS2 docker image in case anyone is interested: https://github.com/samiamlabs/ros2-nightly-vscode/tree/reserved-keyword-warnings

[wjwwood]

lgtm, I'll run CI.

[wjwwood]

CI:

• Linux
• Linux-aarch64
• macOS
• Windows

[ivanpauno]

@wjwwood friendly ping. Is this ready? Does something have to be addressed?

[wjwwood]

There are unresolved linter failures, see: #96 (comment)

[samiamlabs]

I pushed a fix for the linter issues a while back @wjwwood
Would be great if you can run CI again to make sure the errors are gone :)

[ivanpauno]

CI (only fastrtps):

• Linux
• Linux-aarch64
• macOS
• Windows

[samiamlabs]

We noticed that using "from" in a message caused a runtime syntax error for python when importing the message.
Some of the reserved keywords can probably be accessed using getattr without issues like this.
See #95

[ivanpauno]

We noticed that using "from" in a message caused a runtime syntax error for python when importing the message.
Some of the reserved keywords can probably be accessed using getattr without issues like this.
See #95

IMO, that could be fixed if we use everywhere in the generated files getattr instead of dot syntax.
If the current generated files raise an error when importing, we should rather fail than log a warning (maybe it's a bad idea, because it can generate problems in existing messages). The other option is to fix the places that makes the imported message to fail (using getattr), and just log a warning indicating the usage of a python keyword.

[ivanpauno]

@samiamlabs Can you rebase? Most of the test failures are resolved in master.

[samiamlabs]

I pushed a rebase with upstream master just now. Hope that helps with CI :)

[ivanpauno]

I pushed a rebase with upstream master just now. Hope that helps with CI :)

Thanks! Another round of CI:

• Linux

[wjwwood]

lgtm, @ivanpauno should we merge this or run CI again (since the interactive markers issues have been fixed)?

[ivanpauno]

CI failure seems unrelated, merging!