How To Merge Devel::Cover databases

[DrWhy]

Dear brothers and sisters of the Monastery,

I need to merge a complex set of Devel::Cover databases in order to get global usage measures, and am having some difficulty. The core problem is that while results from usage of Perl module files (.pm) can be combined across multiple databases, results for multiple perl scripts (.pl) cannot. You can apparently merge databases by calling

cover database1 database2 database3 ...

In the combined results coming out of this, all the .pm files have reasonable looking coverage metrics, and one of the .pl files does as well, but all the other .pl files while they are lissted in the output table have all 'n/a' for their coverage metrics. Has anyone ever had to do this before and come up with a good solution?

Here's a little more about my situation. I have a large, highly parallel system that I'd like to compute test coverage for. This system consists of multiple perl scripts and modules. The modules are used by multiple scripts, and some scripts call other scripts as well. The scripts often run in parallel on a Condor system with several nodes (so that scripts may be running at the same time on different comptuters all sharing the same NFS filesystem). Devel::Cover seems to be the only game in town for Perl test coverage measurement tools so that's what we are using. Because different pieces of the system run in parallel and Devel::Cover is not multi-process safe -- attempting to have all processes use the same coverage database results in a corrupted database and crashing scripts -- I have to specify a separate database for every run of every script (some scripts are run multiple times during one execution of the system)

[DrWhy]

After staring at Devel::Cover code for most of a day I believe the crux of the problem is that the cover program merges only half of the databases. It merges that runs portion which contains basic count statistics but does not merge the structure portion which contains mappings of counts data to source code locations. The solution is pretty straigthforward, a function to copy missing structure files from the various source databases into the structures directory for the target database.

It has nothing to do with a difference between the handling of .pm and .pl files.

I'm at least 75% sure this is right :)

[gcmandrake]

Dear Dr. Why and other denizens and seekers of Perl wisdom,

I have encountered a similar issue and need to merge Devel::Cover databases. Did you (or anyone else) make any progress on this issue? Thanks.

An unworthy Physicist posing as a Perl programmer,

gcmandrake

[DrWhy]

In fact I did solve that problem along with a couple of other issues I ran into along the way. I've been meaning to send diffs to the module's maintainer for inclusion in a future release, but it seems my big bag of round tuits has holes in it and the tuits keep leaking out.

Maybe this will give me the excuse I need to move this forward.

[Anonymous Monk]

I did hack similar problem with few steps:
1. Check which of databases has the most files (let's say it is database3 in original example)
2. Put that database first in the command, i.e.

cover database3 database1 database2 ...

it seems to work for me - maybe will help somebody as well.