Friday, July 31, 2009

Fixing dependencies

Fixing other people code is not easy - but this is what we need to do if we want to clean our dependencies. In answer to John's invitation here is what I did.

I wanted to write some code using Catalyst::Authentication::Credential::OpenID unfortunately one of it's dependencies fails it's tests. Here I'll document how I analysed that and produced a patch, it's not yet approved by the author - but the tests pass.

Step first - checkout the ParanoidAged from it's repository (I had the repository address from an email to the Catalyst mailing list). If you don't have access to the repository of your failing dependency - then just download the source from CPAN unpack it and work from there. Then run the tests:

zby@zby:~/progs/pa$ perl -Ilib t/00-all.t
ok 27
5 second tarpit (tolerance 2)...
not ok 28
# Failed test at t/00-all.t line 180.
3 second tarpit (tolerance 4)...
ok 29
Killing child pid: 7669
# Looks like you failed 1 test of 29.

OK - the failing test is at line 180. Let's see what is there:

I changed that to:

ran the tests and save my debug output:
zby@zby:~/progs/pa$ perl t/00-all.t 2>debug.
What I got there is:

Now the info is there - but of course I did not spot it at once. I did a lot of more debugging and testing other hypothesis before I focused on: 'x-died' => 'read timeout at lib/LWPx/Protocol/ line 394.'. Yeah interesting - something died, but no error was reported. The line in question is:

To get some more evidence I changed that to:

Now the debug output changes to:

And again - it is there - but to spot it I had to play with the debugger first. I don't remember what exactly I did - but finally I sow it - there are two evals in this stack trace, the first one is in LWP::Protocol and the second in lib/LWPx/ line 313. I checked that second eval - and yeah - it tried to retrieve the error already catched by the first one. So when there was a timeout the agent was aborting the retrieval - but the error was being cleared and not reported. I wrote following patch:

and now all the tests pass. Finally I uploaded the patch to RT.

No comments: