Plugin integration with NRE fails to return values

While extending Nile with plugins works well with CLI, one issue I’ve stumbled upon is returning values in the NRE. For simplicity, consider this plugin example:

# plugins/do_something.py

@click.command()
def do_something():
    click.echo("AHHHHHHHH")
    return 5

And let’s say we have this script:

# scripts/do_something.py

def run(nre):
    x = nre.do_something()
    print(x)

Running the script will print AHHHHHHHH but the expected return value 5 is returned as None; therefore, the logic is being executed, but the values are not being returned.

[franalgaba]

Yes, definitely. It is possible to inject the parameter in the command call that happens underneath I think. It should be very straightforward. I will open a PR to handle this 😃

[franalgaba]

Hi @andrew-fleming !

Glad to see you are using plugins. I reproduced the error you are having and diving into the NRE and how the plugins work there does not seem to be anything wrong.

Then, I looked at how click works internally for handling commands and… that’s where the issue is. If you check the click documentation about Command Return Values you will see something like this:

When a Click script is invoked as command line application (through BaseCommand.main()) the return value is ignored unless the standalone_mode is disabled in which case it’s bubbled through.

So, how to solve the issue? When you are using the plugin in a programmatic way with the NRE you have to pass the standalone_mode argument like this in order to retrieve the return value from the click command:

# scripts/do_something.py

def run(nre):
    x = nre.do_something(standalone_mode=False)
    print(x)

Just tried it and it works as expected. Hope it helps 😃