Re: git-svn: handling merge-base failures

[Eric Wong <normalperson@yhbt.net>]

Andrew Myrick <amyrick@apple.com> wrote:
> On Dec 23, 2009, at 12:09 PM, Eric Wong wrote:
> > Andrew Myrick <amyrick@apple.com> wrote:
> >> One of my projects is failing to clone because merge-base is failing
> >> on one of the revisions; the branch is a partial branch, so merge-base
> >> can't find a common ancestor with trunk.  I'd like to catch the
> >> exception that command_oneline should throw when merge-base fails, but
> >> my perl is very rusty and I'm struggling to get git-svn.perl to grok
> >> the Git::Error::Command class.  What is the appropriate way to import
> >> that class?  Or more generally, is there a better solution to handling
> >> this error case?
> > 
> > Hi Andrew,
> > 
> > Git::Error::Command should be imported with the rest of Git.pm
> > 
> > It's a special way of doing exceptions in Perl which I don't see much
> > point of...  Looking at git-send-email as an example, it does this:
> > 
> > 	use Error qw(:try);
> > 	use Git;
> > 
> > 	try {
> > 		# something that will throw
> > 	} catch Git::Error::Command with {
> > 		# error handling
> > 	}
> 
> I looked at git-send-email's example, but I wanted to do a bit more:
> 	
> 	try {
> 		# command_oneline(...);
> 	} catch Git::Error::Command with {
> 		$E = shift;
> 		if ($E->value() == 1) {
> 			# do something
> 		} else {
> 			# do something else
> 		}
> 	}
>  	
> This is used in perl/Git.pm, but when I tried it in git-svn.perl, it
> fails with the error "Can't locate object method 'value' via package
> 'Git::SVN'".

That's strange.  I'm at a bit of a loss here so I'll wait for somebody
with more Perl knowledge than myself.

What happens when you dump @_ in your catch block?

	use Data::Dumper;
	try {
	} catch Git::Error::Command with {
		print STDERR Dumper(\@_);
	}

> Presumably $@ contains the Git::Error::Command object, which leaves me
> in the same spot, unfortunately.
> 
> > But yes, it is Perl after all and TMTOWTDI :)
> 
> Is there ever :)

Yes I'm lost here, too, so in these cases I default to putting
print statements everywhere and Data::Dumper :)

-- 
Eric Wong