Returning an exit code from a task

[bluenote10]

Currently the task API doesn't seem to support exit codes. If a task encounters an error it can:

• return: this will abort, but the exit code of running nimble myTask will be 0.
• raise an exception: Sets a non-zero exit code, but the traceback is maybe not what we want to show to the user, after having printed an error message already.
• quit(exitCode): Sets a non-zero exit code, but for some reason Nimble seems to issue a warning "quit called". This warning doesn't make sense from a user perspective, because the task has already printed a meaningful error message and simply wants to abort. The "quit called" warning is out of place.

Maybe the task API could be extended so that it supports return <int> and Nimble forwards the code directly to quit without injecting a warning?

[Araq]

The "quit called" warning is out of place.

I like it and I think quit is what should be used. It's not out of place since otherwise debugging can be a nightmare. (How do I know? We used to lack this hint and the compiler would "die" and we didn't know why nor how nor where.)

[bluenote10]

Agreed logging quit calls in the compiler makes sense, but for NimScript / Nimble there are use cases to exit gracefully without a message:

• If the stdout of Nimble task is supposed to be pipeable into other command line utilities, the stdout must not be contaminated.
• The message simply does not make sense after you already present the user with a meaningful explanation why the task has failed.

Supporting return <int> for Nimble tasks would achieve silent exists without the need to explicitly kill the script.

[genotrance]

Given nimble now just calls nim e behind the scenes, quit(1) now behaves differently.

raise newException() =>

> nimble one --verbose
    Reading config file at ~/.config/nimble/nimble.ini
  Executing task one in ~/programming/a/a.nimble
stack trace: (most recent call last)
/tmp/nimblecache/nimscriptapi.nim(164, 16)
~/programming/a/a_15029.nims(21, 3) oneTask
~/programming/a/a_15029.nims(21, 3) Error: unhandled exception: Exception text
     Error: ~/programming/nimbledevel/src/nimble.nim(1145) nimble
        ... ~/programming/nimbledevel/src/nimble.nim(1129) doAction
        ... ~/programming/nimbledevel/src/nimblepkg/nimscriptexecutor.nim(46) execCustom
        ... ~/programming/nimbledevel/src/nimblepkg/nimscriptwrapper.nim(164) execTask
        ... ~/programming/nimbledevel/src/nimblepkg/nimscriptwrapper.nim(135) execScript
        ... Exception raised during nimble script execution

quit(1) =>

> nimble one --verbose
    Reading config file at ~/.config/nimble/nimble.ini
  Executing task one in ~/programming/a/a.nimble
     Error: ~/programming/nimbledevel/src/nimble.nim(1145) nimble
        ... ~/programming/nimbledevel/src/nimble.nim(1129) doAction
        ... ~/programming/nimbledevel/src/nimblepkg/nimscriptexecutor.nim(46) execCustom
        ... ~/programming/nimbledevel/src/nimblepkg/nimscriptwrapper.nim(164) execTask
        ... ~/programming/nimbledevel/src/nimbl

[dom96]

It seems quit(1) was broken, that sucks.

I actually disallow quit in Nimble's source code for the untraceability reason too and instead offer a NimbleQuit exception so you can always find which code wanted to quit. Personally I would like the same thing for the task API. What I really think we should do is create an RFC outlining precisely the API that the task API should have. I'm going to start the conversation in another issue.