Add conditional substitution

[nlamprian]

Closes #727

[clalancette]

This looks fantastic to me, thanks for a nice clean pull request. I'll run CI on it next.

[clalancette]

CI:

• Linux
• Linux-aarch64
• Windows

[clalancette]

@nlamprian It looks like flake8 is unhappy here, mostly about double quotes but also about some import order stuff. I don't know why the Rpr job didn't pick up on it, but if you setup your workspace locally it should show it to you. That will need to be fixed before we merge this, thanks.

[nlamprian]

Fixed, allegedly.
I did run the tests successfully last time. I am not able to reproduce the errors.
I am working on a fresh ros:rolling-ros-core container. I haven't identified what's different from the logs.

[clalancette]

Fixed, allegedly. I did run the tests successfully last time. I am not able to reproduce the errors. I am working on a fresh ros:rolling-ros-core container. I haven't identified what's different from the logs.

Out of curiosity, what does pip3 list | grep flake8 in the container show you?

[clalancette]

Locally I'm still seeing:

_________________________________ test_flake8 __________________________________
test/test_flake8.py:23: in test_flake8
    assert rc == 0, \
E   AssertionError: Found 1 code style errors / warnings:
E     ./launch/substitutions/if_else_substitution.py:27:1: I100 Import statements are in the wrong order. 'from .substitution_failure import SubstitutionFailure' should be before 'from ..utilities import perform_substitutions'
E   assert 1 == 0

[nlamprian]

root@nlamprian:~/ros_ws# pip3 list | grep flake8
ament-flake8                         0.15.2
flake8                               4.0.1

The last error is hopefully fixed (the message can be misinterpreted).

[clalancette]

root@nlamprian:~/ros_ws# pip3 list | grep flake8
ament-flake8                         0.15.2
flake8                               4.0.1

OK, yeah. You are missing a bunch of plugins, and flake8 is a bit annoying in that you can't specify which ones are required; it only runs the plugins you have installed. My list looks like this:

ament-flake8                         0.15.2
flake8                               4.0.1
flake8-blind-except                  0.2.0
flake8-builtins                      1.5.3
flake8-class-newline                 1.6.0
flake8-comprehensions                3.8.0
flake8-deprecated                    1.3
flake8-docstrings                    1.6.0
flake8-import-order                  0.18.1
flake8-quotes                        3.3.1

We have a long-term plan to fix this up by making those plugins hard requirements, but we aren't there today.

Anyway, this looks good to me now (verified locally), so I'll run CI on this again. Thanks for iterating.

[clalancette]

CI:

• Linux
• Linux-aarch64
• Windows

[federicociresola]

@nlamprian is it possible to include this feature also in the Humble branch?