On March 22, 2018 9:22 AM, Carsten Haitzler <[email protected]> wrote:
> On Thu, 22 Mar 2018 09:56:37 +0100 Jérémy Zurcher [email protected] said:
> > just trying to follow here and maybe clarify a bit.
> >
> > Of course everybody here knows about the conventions :
> >
> > - 0 is the success return code
> > - anything else is an (hopefully documented) error
> >
> > we all know about logical shell chaining :
> >
> > cmd1 && cmd2 && cmd3 || cmd4
> >
> > but what I think I understood here is that promises chaining should be a
> > different construction where the chaining is not dependent on the return
> > code
> > (success/failure) of any of the actions.
> >
> > { action 1 } then { action 2 } then { action 3 }
> >
> > it's a 'then' meaning 'after that', not an '&&' that means 'on action
> > success'
>
> actually then is on success. if the promise rejects (as a failure) it won't be
> a "then" chain that continues. that's key to promises. then here is then IF
> the
> promise succeeds without failure.
What are you talking about ??? There is only one callback and you get an
Eina_Value that will be an Eina_Error in case of a rejected promise and
something else if it was a success. The code inside the then has to decide what
to do in all case.
> see eio efl_io_managr.c - if stat fails on a file it rejects the promise with
> an error.
> it's doing that and that is apparently correct, but an exit error code is not
> correct
> doing the same thing.
Is an exit code a system failure ? Is an exit code something you can do
something with ? Which exit code value mean ENOENT ?
> > so with v beeing the value of the promise, you do
> >
> > { action 1 } then { if (v!=0) return action21 else return action22 } then
> > { if (v==0) action 3 }
> >
> > and with handy helpers (operator logic) like
> >
> > bypassOnFailure(if (v!=0) return v)
> > bypassOnSuccess(if (v==0) return v)
> >
> > you can do
> >
> > { action1 } then { bypassOnFailure(); action2 } then { bypassOnSuccess();
> >
> > action3 } then { byPassOnFailure; action4 }
> >
> > the chaining fails on "System errors" -> Exception on some languages
> > the logic is implemented in the futur
> >
> > hope I'm not in outer space.
>
> see efl_io_manager.c - if a stat() of a file fails (e.g. file doesn't exist),
> the promise rejects with a error. i simply did precisely the same thing with
> an
> exit code of non-zero. it's an error/failure (that was my point in indicating
> it is in shell examples). thus it should behave the same way. not doing so is
> inconsistent.
man 1 stat vs man 2 stat
Does the first one define any return value in case of error ? Does the second
one ? This are not the same things. They do not have the same documented
behavior. There is consistency between what you are comparing in the first
place.
Cedric
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