#dzil

1. motivation

There’s been a curious dump_config build error in my Dist::Zilla Travis-CI builds as of late. I’m using the [TravisYML] Dist::Zilla plugin to generate my .travis.yml file, and up until now it’s been working great. But, there seems to be some dependency conflict that I don’t have on my local machine - at some point, the travis build box can no longer run any dzil commands, as it bombs out with:

The method 'dump_config' was not found in the inheritance hierarchy for Dist::Zilla::App::CommandHelper::ChainSmoking at [...]

Which is then followed by a completely unhelpful (to me) Moose stacktrace.

2. debugging travis builds?

I wasn’t aware of a good method to debug travis builds - previously, I had been just committing minor changes, pushing ‘em to Github, and then waiting for the Travis build to kick off. That feedback loop could take up to 15 minutes, and wasn’t really conducive to any sort of debugging method.

I emailed support AT travis-ci.com inquiring about getting access to one of their build boxes, since the outdated vagrant box method was now obsolete and one of their support staff got back to me within minutes with a cloud box I could SSH into for 24 hours. Really pleased with their turnaround time and support, considering it’s a free service!

3. perlbrew on travis debug boxes

The box I got had a ~/perl5 folder with a bunch of perls already installed. But, it didn’t have the perlbrew binary in the path. I updated the path

$ export PATH=~/perl5/perlbrew/bin:$PATH

but the commands like perlbrew use and perlbrew switch weren’t having any impact on perl -v. It turns out I needed to

$ perlbrew init $ source ~/perl5/perlbrew/etc/bashrc

in order to get perl -v to recognize I didn’t want to use the system perl anymore. Had I been using more shells, I’d probably want to put all of that in the ~/.bash_profile, but I only needed the one, especially since perlbrew lib lets you manage completely separate local::libs.

So, I switched to 5.19 and spun up a new local::lib and started playing around with dependencies. If I got too far and broke everything again, a new local::lib can reset all the installed deps and get me into pristine condition.

$ perlbrew switch 5.19 $ perlbrew lib create debug_dist_zilla $ perlbrew use 5.19@debug_dist_zilla

4. getting to the heart of the issue

The generated .travis.yml file does a couple of things - it exports some global variables, configures a bit of necessary git settings, and then gets to the business of handling author and project dependencies.

$ cpanm --quiet --notest --skip-satisfied Dist::Zilla $ dzil authordeps | grep -vP '[^\\w:]' | \ xargs -n 5 -P 10 cpanm --quiet --notest --skip-satisfied" $ dzil listdeps | grep -vP '[^\\w:]' | cpanm --verbose --skip-satisfied"

The travis build boxes come with 5.006 installed, so the first line actually doesn’t do anything. As reported in the github issue, the dump_config bug occurs at the dzil listdeps step. So, one of the authordeps must be causing it … probably.

$ dzil authordeps --missing | head -n 1 | cpanm --skip-satisfied && dzil

It just steps through each of the author dependencies one at a time, installing it with cpanm, and then verifying that I can still dzil afterwards.

5. solutions?

In not-so stunning turn of events that seems incredibly obvious now, the problem seems to arise after installing Dist::Zilla::Plugin::TravisYML. In the generated travis script, the author deps are installed with cpanm --notest, so it’s not caught until the next time we attempt to dzil listdeps. Stepping through the tests one by one, the ::TravisCI install actually fails its own tests with the same dump_config error that we see in the travis logs after --notest installing it.