[Module-build-general] CPANPLUS support for Module::Build

[Dave R. <au...@ur...>]

I was happy to see this in the latest release, but out of curiosity I
started digging into the implementation code, and I found some problems.

In CPANPLUS::Internals::Make::_find_prereq_module_build, the code looks at
the _build/prereqs and then _parses_ the file.  This is not a good idea
for several reasons.  One, the file is perfectly good Perl code, and can
be eval'd.

But even more importantly, Module::Build supports a more complex version
number specification system.  For example:

  requires => {Foo::Module => '2.4',
               Bar::Module => 0,
               Ken::Module => '>= 1.2, != 1.5, < 2.0',
               perl => '5.6.0'},

Notice the third line, which says the version must be greater than or
equal to 1.2, not 1.5, and less than 2.0.

What CPANPLUS should do is _load_ Module::Build and then do something like
this:

  my $build = resume Module::Build (
    properties => {
      config_dir => '_build',
      build_script => 'Build',
    },
  );

  my $failures = $build->prereq_failures;

$failures will contain a hashref that details exactly what failed (or
it'll be empty if everything passed).

This A) lets there be just one piece of code to check prereqs, and B) lets
CPANPLUS take advantage of Module::Build's more sophisticated version
specs (plus the ability to list conflicts, etc.)


Another problem is that CPANPLUS might end up passing MakeMaker flags to
Module::Build (like TEST_VERBOSE=1 instead of verbose=1).  Ken, I'd
suggest just having Module::Build look for at least a commonly used
superset of the MM flags.


-dave

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