Add --exit-code (-x) flag to enable carrying error codes from task cmds

[BrunoDelor]

Hello,

I recently found the need to get the return code that was returned from a failed command from a task's cmds. After investigating quickly it appeared to me that the task tool would always return with status code 1 when an error occurred during a task.

This PR proposes an additional command flag (--carry), false by default, that will carry the error code, if any, over to the calling shell.

[ghostsquad]

Please add some tests to assert on this functionality.

[andreynering]

Hi @BrunoDelor, thanks for your PR!

Given this would be a pretty small breaking change, perhaps we could even get rid of the flag and always return the right exit code? Do you guys have an opinion on this?

Another question: does other tools like Make does this as well?

[mgbowman]

Always returning the right exit code seems logical to me.

Looks like make only uses 0, 1 or 2

$ man make

EXIT STATUS
       GNU make exits with a status of zero if all makefiles were successfully parsed and no targets that were built failed.
       A status of one will be returned if the -q flag was used and make determines that a target needs to be rebuilt.
       A status of two will be returned if any errors were encountered.

[BrunoDelor]

Thank you for your comments

@ghostsquad
As this is mainly about what happens in the main I'm not entirely sure how to go about unit-testing it specifically.

If that's would be enough I can add a test that will show that the error code can be exposed through the new func (err *TaskRunError) ExitCode() int after being returned from a task command.

@andreynering
I agree with your comment about not having the flag at all and always returning the right error code.

It appears the question about Make is already answered.
This is why I thought about making it optional. I find a use for it, as I use my error code for decisions afterward, but considering it's not really a standard behavior I preferred not to enforce the change on everyone by default.

[ghostsquad]

I think maybe this flag could be renamed too. I've seen it described as exit code pass thru.

Heroku uses --exit-code as the flag and describes it as allowing the exit code of the sub process to "pass thru" the main/parent process.

https://github.com/heroku/heroku-run

I'm trying to recall specifically where else I've seen this.

[BrunoDelor]

This sounds good to me, I'll push a change for -x --exit-code if this is agreed upon

[andreynering]

@BrunoDelor Thanks for contributing! ❤️