Getting "specific" modules from a CPAN data file?

Question

Given the file with the CPAN mailing list (for example, Acme-Chef-1.01.tar.gz ), which algorithm determines which versions of the modules are “defined” (or presented) in the dist file?

For example, in the 02packages.details.txt file, 02packages.details.txt are four lines that correspond to this dist file:

 Acme::Chef 1.01 S/SM/SMUELLER/Acme-Chef-1.01.tar.gz Acme::Chef::Container 1.00 S/SM/SMUELLER/Acme-Chef-1.01.tar.gz Acme::Chef::Ingredient 1.00 S/SM/SMUELLER/Acme-Chef-1.01.tar.gz Acme::Chef::Recipe 1.00 S/SM/SMUELLER/Acme-Chef-1.01.tar.gz 

Basically I want to know how these lines are generated.

Is the procedure similar:

• find all .pm files in dist file
• download each of the .pm files and print ${ "${pkg}::VERSION"} , where $pkg is the package name corresponding to the name of the .pm file (i.e. if the file name is .pm Foo/Bar.pm , then $pkg Foo::Bar .)

Is there any code that performs this indexing procedure?

Do you really need to download the module to determine what version it is?

Answer 1

The actual code that does this for PAUSE is on GitHub here . Routines that parse package and version declarations are located in the lib / PAUSE / pmfile.pm folder ( packages_per_pmfile and parse_version ). This is authoritative as far as CPAN does, but it is not the code that you would ever want to use for yourself - PAUSE is almost 20 years old, and even after a recent cleanup it is still pretty rude.

Instead, check out Module :: Metadata . You give it a file, and it provides a fairly simple interface for detecting package names inside this file and their versions.

It is about as simple:

 my $mm = Module::Metadata->new_from_file("My/Module.pm"); for my $package ($mm->packages_inside) { print "$package: ", $mm->version($package), "\n"; } 

And really, this "one-line" works:

 find Acme-Chef-1.01 -name \*.pm \ | perl -MModule::Metadata -ln \ -e 'my $mm = Module::Metadata->new_from_file($_); ' \ -e 'print "$_: ", $mm->version($_) for $mm->packages_inside' \ | sort 

and outputs:

 Acme::Chef: 1.01 Acme::Chef::Container: 1.00 Acme::Chef::Ingredient: 1.00 Acme::Chef::Recipe: 1.00