Re: CPAN, recursive dependency problem

[saintmike]

You could break the cycle by downloading individual tarballs, e.g:

    cpan> get K/KW/KWILLIAMS/PathTools-3.03.tar.gz

hunt it down on disk (~/.cpan/sources/...), untar, build and install manually:

    tar zxfv PathTools-3.03.tar.gz
    cd PathTools-3.03
    perl Makefile.PL
    make install

[ecsd]

Where (or how) does CPAN's install figure that there is a dependency? I would like to be able to break stuff to lie to it,
and I'd as soon break the "idea" that there is a dependency loop.

Also, if this comes up with any frequency, I'd suggest enforcing some scheme to prevent such loops in the first place.
I haven't seen any reference to this issue in any other FAQs (CPAN, Perl) but it bites often enough.

Thanks for the information.
-ecsd

[ecsd]

It's worth pointing out that CPAN will also not allow a "get"
of a module in a dependency chain, so that has to be done manually also.

[saintmike]

It's worth pointing out that CPAN will also not allow a "get" of a module in a dependency chain ...

Not true.

Here's a quick way to verify dependencies (even circular ones): There's two modules on CPAN with the sole purpose of defining a circular dependency between each other: Acme::Prereq::A and Acme::Prereq::B.

Acme::Prereq::A depends on Acme::Prereq::B and vice versa, see Acme::Prereq::A's Makefile.PL:

    'PREREQ_PM'    => {
                         'Acme::Prereq::B' => 0,
                      }, # e.g., Module::Name => 1.1

Try it out, it works fine:

    perl -MCPAN -eshell
    cpan> get Acme::Prereq::B

The CPAN shell's get command will fetch the requested module's tarball without checking dependencies.

However, if you've run into a recursive dependency within a CPAN session, CPAN.pm will keep complaining, even if you switch to get. Restart the CPAN shell to get back to normal.