RE: [Problem] test_must_fail makes possibly questionable assumptions about exit_code.

["Randall S. Becker" <rsbecker@nexbridge.com>]

On February 28, 2018 2:49 AM, Peff wrote:
> On Wed, Feb 28, 2018 at 07:42:51AM +0000, Eric Wong wrote:
> 
> > > > >  a) We could override the meaning of die() in Git.pm.  This feels
> > > > >     ugly but if it works, it would be a very small patch.
> > > >
> > > > Unlikely to work since I think we use eval {} to trap exceptions
> > > > from die.
> > > >
> > > > >  b) We could forbid use of die() and use some git_die() instead (but
> > > > >     with a better name) for our own error handling.
> > > >
> > > > Call sites may be dual-use: "die" can either be caught by an eval
> > > > or used to show an error message to the user.
> >
> > <snip>
> >
> > > > >  d) We could wrap each command in an eval {...} block to convert the
> > > > >     result from die() to exit 128.
> > > >
> > > > I prefer option d)
> > >
> > > FWIW, I agree with all of that. You can do (d) without an enclosing
> > > eval block by just hooking the __DIE__ handler, like:
> > >
> > > $SIG{__DIE__} = sub {
> > >   print STDERR "fatal: @_\n";
> > >   exit 128;
> > > };
> >
> > Looks like it has the same problems I pointed out with a) and b).
> 
> You're right. I cut down my example too much and dropped the necessary
> eval magic. Try this:
> 
> -- >8 --
> SIG{__DIE__} = sub {
>   CORE::die @_ if $^S || !defined($^S);
>   print STDERR "fatal: @_";
>   exit 128;
> };
> 
> eval {
>   die "inside eval";
> };
> print "eval status: $@" if $@;
> 
> die "outside eval";
> -- 8< --
> 
> Running that should produce:
> 
> $ perl foo.pl; echo $?
> eval status: inside eval at foo.pl line 8.
> fatal: outside eval at foo.pl line 12.
> 128
> 
> It may be getting a little too black-magic, though. Embedding in an eval is at
> least straightforward, if a bit more invasive.

I like this solution. The $64K question for me is how (a.k.a. where) to instrument this broadly instead of in each perl fragment in the test suite.  The code:

$SIG{__DIE__} = sub {
  CORE::die @_ if $^S || !defined($^S);
  print STDERR "fatal: @_";
  exit 128;
};

eval {
  die "inside eval";
};

print "eval status: $@" if $@;

die "outside eval";

as tested above, in NonStop results in an exit code of 128 whether run from a script or from stdin (a good thing). I'm happy to do the heavy lifting on this, but  a bit more direction as to the implementation would help.

Cheers,
Randall