Empty output is not truly empty

[T2L]

When there is no changes to the lock file, an empty composer_diff output is produced, but it's not truly empty.

See log of one oof my workflows:

##[debug]Evaluating: format('{0}
##[debug]', steps.composer_diff.outputs.composer_diff)
##[debug]Evaluating format:
##[debug]..Evaluating String:
##[debug]..=> '{0}
##[debug]'
##[debug]..Evaluating Index:
##[debug]....Evaluating Index:
##[debug]......Evaluating Index:
##[debug]........Evaluating steps:
##[debug]........=> Object
##[debug]........Evaluating String:
##[debug]........=> 'composer_diff'
##[debug]......=> Object
##[debug]......Evaluating String:
##[debug]......=> 'outputs'
##[debug]....=> Object
##[debug]....Evaluating String:
##[debug]....=> 'composer_diff'
##[debug]..=> ''
##[debug]=> '
##[debug]'
##[debug]Result: '
##[debug]'

then marocchino/sticky-pull-request-comment@v2 fails with Error: Either message or path input is required, but I cannot check if the output is an empty string like '' and skip the step, because it's not an empty string

[IonBazan]

@T2L thank you for the report. I've moved it to https://github.com/IonBazan/composer-diff-action because it is caused by the action itself and not the composer plugin. I will investigate this issue a bit more and I think it happened to me once too. Could you provide a repository where it actually happened?

[T2L]

it can be easily reproduced with this simple bash one-liner (make sure there are no update to the lock file, of course ) :

$ output=$(composer diff $*) && echo $output

You'll see that a newline is being printed. Calling a command directly does not produce one

Not sure what's the thing here, but it is related to how bash works ...

The easiest way of fixing is always call command with --strict parameter and then check if command result is 0, return an empty string ...