TPF Devel::Cover grant report Week 1

From: Paul Johnson

Date: May 28, 2012 16:48

Subject: TPF Devel::Cover grant report Week 1

Message ID: 20120528234844.GB4807@pjcj.net

May 28, 2012 16:48TPF Devel::Cover grant report Week 1

What is this? You may recall that recently I submitted a grant proposal to The Perl Foundation to work on Devel::Cover. I'd like to thank everyone who thought that this might be a good idea, and I'm pleased to say that the proposal was accepted and I have started work. Modelled on the successful grants of Dave and Nick, one of the conditions of the grant is that I should produce weekly and monthly reports of my progress, and these reports will be sent to perl-qa@perl.org. If you are not interested in these reports, please set up a filter, or just ignore them. This is my first weekly report. In fact, this report covers a little more than my first week because I started mid-week and it didn't seem worthwhile reporting on a few hours of work. Other commitments meant that I couldn't start as early as I would have liked, but I was able to put in almost a full week of work, which I don't expect to be the case as often as I would like. I suppose there are two deliverables this week - Devel::Cover 0.87 and http://cpancover.com My plan is to work primarily on existing, relatively simple bugs and problems before getting down to the complicated bugs and the more interesting work of adding functionality, and most of my work so far has indeed fallen into that category. There have been a couple of deviations from that - one planned and one not. Much of the rest of my work was related to Moose and Mouse. I've had a report about Moo which I need to look at, but I've heard nothing about Mo so I'm not sure if there are any problems there. Very shortly after I started work perl-5.16.0 was released. So the second bug that I looked at was RT 75314 which concerned a regression on condition cover in 5.16. Unfortunately this problem went to the core of one of the most tricky parts of Devel::Cover and it took me quite some time to get to the bottom of it. The good news though, is that without this grant I would never have been able to solve this problem and so condition and branch coverage in 5.16 would have been broken. The bulk of the fix is found in f26ba32 and it relates to an optimisation from David Mitchell: http://perl5.git.perl.org/perl.git/blobdiff/0e1b3a4b35c4f6798b244c5b82edcf759e9e6806..db4d68cf2dda3f17:/op.c Nick's bisecting code in the perl core was very helpful in fingering this commit but, really, I should have remembered it. When Dave announced this optimisation, I suspected that it would affect Devel::Cover, but I had not fully followed up on that. The problem for Devel::Cover is that I was depending on that op ordering to properly calculate condition coverage. Devel::Cover has two ways of collecting condition coverage, depending on whether or not the condition is short circuited. If it is short circuited, then when we get to the condition all we have to do is look at the top of the stack to see whether the LHS is true or false. If not, we have to remember that we are interested in the value of the RHS when it has been evaluated. Devel::Cover does this by hijacking the op_next pointer to look at the value of the RHS and collect its coverage before moving on to the expected op. The optimisation meant that we never evaluated the RHS and so Devel::Cover didn't know its value. So Devel::Cover fell back to its default behaviour in such cases which is to assume that the RHS is false, as it is in cases when we never return a value from the RHS. This is somewhat simplified, but gives you the idea of what is going on. (Incidently, this is also the primary reason that Devel::Cover doesn't run under threads.) The solution to this involves grovelling around the optree a little more to find the conditional ops and, whilst it solves most of the problems, there is still a little work to be done in this area. (Where "a little" means that the problem is simple, but the solution may not be.) There's also a question here of whether Devel::Cover should be doing this sort of thing, or whether I should be adding some hooks into the core, for example. Hopefully, I will be able to look into such matters later. The other main area I looked at was getting cpancover up and running again. This is not completely altruistic, since I tend to think of CPAN as my extended test suite. I think cpancover could be quite useful, and the current version gets many hits. To this end, I was able to procure a machine from the nice folk at bigv.io and I bought the domain name cpancover.com, with the result that http://cpancover.com now points to an updated list of coverage for some CPAN modules, run against perl 5.16.0. If there are any modules you would like to see added here, please let me know, or just make your changes to utils/install_modules in https://github.com/pjcj/Devel--Cover and send me a pull request. So, the work I have completed in the time covered by this report is: Closed RT tickets: 75944 Warning about Moose clearers when processing Test::TempDir 75314 conditional testing broken in blead? 73452 Bleadperl v5.15.5-331-g4d8ac5c breaks PJCJ/Devel-Cover-0.79.tar.gz 69892 Tests busted on perl 5.15 57174 Devel::Cover 0.66 does not work with Moose+type constraints 68389 Moose's make_immutable call causes Devel::Cover to emit many warnings 77163 t/e2e/amoose_basic.t fails while installing Devel::Cover 0.86 37350 Missing whatis entry of Devel::Cover::Tutorial manual 71680 Devel::Cover spews error-messages when Moose is used 72819 0% branch coverage for methods defined in non-reported files 68353 perl 5.14.0 breaks D:C in t/e2e/ainc_sub.t 63090 conditionals where one element is data from a Moose attrib are not evaluated 63568 Devel::Cover can't handle Test::More's is() Closed Github tickets: 12 Devel::Cover 0.80 and up fails t/e2e/amoose_basic.t 9 Remove use Data::Dumper from Devel::Cover Merged pull requests: 14 -launch option opens report in appropriate viewer Fixed cpantesters reports: http://www.cpantesters.org/cpan/report/370c28c8-a3ef-11e1-b57c-2d415ba78cfe http://www.cpantesters.org/cpan/report/363db460-91a3-11e1-a1fe-d0960df65b4f http://www.cpantesters.org/cpan/report/e042a488-9109-11e1-bd3e-c0e207492f11 And many more covering the same problems in various guises. You can see the commits at https://github.com/pjcj/Devel--Cover/commits/master Hours worked: 17.05 0:35 18.05 4:25 19.05 5:50 21.05 3:20 22.05 11:00 23.05 7:30 24.05 8:05 25.05 3:25 Total 44:10 -- Paul Johnson - paul@pjcj.net http://www.pjcj.net

TPF Devel::Cover grant report Week 1 by Paul Johnson

by Paul Johnson Re: TPF Devel::Cover grant report Week 1 by James E Keenan



