Re^2: Seeking thoughts on version numbers in modules

[xdg]

Great comments. #5 is intriguing and I poked around a little to investigate. It looks like CPAN (er., search.cpan.org anyway) maintains version numbers on all files, but only if they exist. And the version of individual files can bear little/no relation to the distribution version. Compare these:

• Excel-Template
• ExtUtils-MakeMaker

I wonder if the version number for the distribution that CPAN uses even comes from a file at all or simply from the distribution tar file numbering (or a META.yaml file, if it exists). If the latter is true, you could manually set your version in a Makefile.PL or Build.PL and have no VERSION in your files at all.

The only downside I see to this (and to leaving version numbers out of submodules) is that you lose version checking ability. If a distribution contains a "main" module and submodules that would never be directly used, then it won't really matter if you only have a VERSION in your main module file. On the other hand, if a distribution contained modules which could be used independently, then it does matter.

See Test-Simple for an example where this might be the case. (It's not, for reasons I'll explain, but bear with as an example.) Test::Builder's version is out of sync at 0.22 compared to 0.54 for distribution as a whole. In a Makefile.PL or Build.PL, if my list of pre-requisites had Test::Builder => 0.22, and Test::Builder's version number hadn't been updated in a while, I could pass the pre-req with an old version of Test::Builder, even though the distribution version number of the Test-Simple distribution had been updated. It turns out in this case, that Michael does actually increment Test::Builder's number when it changes, but only when it changes and not just because Test::More or Test::Simple or the distribution version number change.

This may suggest a general good practice of using the same module in a prerequisites statement as is being used to generate the version number for the distribution, just in case the distribution author isn't as diligent about maintaining all the version numbers.

[dragonchild]

It's funny you mention Excel::Template because I'm the author. I actually deliberately removed version numbers from the individual files because I wanted to have a version number for the release. The individual files don't matter as much as the functionality from the release itself.

I wonder if the version number for the distribution that CPAN even comes from a file at all or simply from the distribution tar file numbering (or a META.yaml file, if it exists).

In your Makefile.PL (or Build.PL, I suppose), there is an item called VERSION_FROM or VERSION. If you have a VERSION, CPAN uses that. If you have a VERSION_FROM, CPAN goes into that file and looks for the first $VERSION line. (It's a little more complicated than that, but you get the idea.) This is all documented in ExtUtils::MakeMaker (and, I'm sure, in Module::Build).

[PodMaster]

This is kind of a reply to both of you. CPAN has an item entitled "Finding packages and VERSION", in which it lists

...

perl -MExtUtils::MakeMaker -le \
        'print MM->parse_version(shift)' filename

If you are author of a package and wonder if your $VERSION can be parsed, please try the above method.

CPAN::DistnameInfo - Extract distribution name and version from a distribution filename.