DBIx::Class::Schema::Loader::Optional::Dependencies(3p)

NAME
$class - Optional module dependency specifications (for module authors) EOC

#@@ #@@ SYNOPSIS HEADING #@@
  push @chunks, <<"EOC"; =head1 SYNOPSIS

Somewhere in your build-file (e.g. ExtUtils::MakeMaker's Makefile.PL):

  ...

  \$EUMM_ARGS{CONFIGURE_REQUIRES} = {
    \%{ \$EUMM_ARGS{CONFIGURE_REQUIRES} || {} },
    'DBIx::Class::Schema::Loader' => '$distver',
  };

  ...

  my %DBIC_CONFIG_AND_ORACLE_DEPS = %{ eval {
    require $class;
    $class->req_list_for([qw( dbicdump_config rdbms_oracle )]);
  } || {} };

  \$EUMM_ARGS{PREREQ_PM} = {
    \%DBIC_CONFIG_AND_ORACLE_DEPS,
    \%{ \$EUMM_ARGS{PREREQ_PM} || {} },
  };

  ...

  ExtUtils::MakeMaker::WriteMakefile(\%EUMM_ARGS);

Note: The "eval" protection within the example is due to support for requirements during the "configure" build phase not being available on a sufficient portion of production installations of Perl. Robust support for such dependency requirements is available in the CPAN installer only since version "1.94_56" first made available for production with perl version 5.12. It is the belief of the current maintainer that support for requirements during the "configure" build phase will not be sufficiently ubiquitous until the year 2020 at the earliest, hence the extra care demonstrated above. It should also be noted that some 3rd party installers (e.g. cpanminus) do the right thing with configure requirements independent from the versions of perl and CPAN available. EOC

#@@ #@@ DESCRIPTION HEADING #@@
  push @chunks, <<'EOC'; =head1 DESCRIPTION

Some of the less-frequently used features of DBIx::Class::Schema::Loader have external module dependencies on their own. In order not to burden the average user with modules they will never use, these optional dependencies are not included in the base Makefile.PL. Instead an exception with a descriptive message is thrown when a specific feature can't find one or several modules required for its operation. This module is the central holding place for the current list of such dependencies, for DBIx::Class::Schema::Loader core authors, and DBIx::Class::Schema::Loader extension authors alike.

Dependencies are organized in groups where each group can list one or more required modules, with an optional minimum version (or 0 for any version). In addition groups prefixed with "test_" can specify a set of environment variables, some (or all) of which are marked as required for the group to be considered by "req_list_for"

Each group name (or a combination thereof) can be used in the public methods as described below. EOC

#@@ #@@ REQUIREMENT GROUPLIST HEADING #@@
  push @chunks, '=head1 CURRENT REQUIREMENT GROUPS';

  my $standalone_info;

  for my $group (sort keys %$dbic_reqs) {

    my $info = $standalone_info->{$group} ||= $class->_groups_to_reqs($group);

    next unless (
      $info->{modreqs_fully_documented}
        and
      ( $info->{augments} or $info->{modreqs} )
    );

    my $p = $dbic_reqs->{$group}{pod};

    push @chunks, (
      "=head2 $p->{title}",
      "=head3 $group",
      $p->{desc},
      '=over',
    );

    if ( keys %{ $info->{modreqs}||{} } ) {
      push @chunks, map
        { "=item * $_" . ($info->{modreqs}{$_} ? " >= $info->{modreqs}{$_}" : '') }
        ( sort keys %{ $info->{modreqs} } )
      ;
    }
    else {
      push @chunks, '=item * No standalone requirements',
    }

    push @chunks, '=back';

    for my $ag ( sort keys %{ $info->{augments} || {} } ) {
      my $ag_info = $standalone_info->{$ag} ||= $class->_groups_to_reqs($ag);

      my $newreqs = $class->modreq_list_for([ $group, $ag ]);
      for (keys %$newreqs) {
        delete $newreqs->{$_} if (
          ( defined $info->{modreqs}{$_}    and $info->{modreqs}{$_}    == $newreqs->{$_} )
            or
          ( defined $ag_info->{modreqs}{$_} and $ag_info->{modreqs}{$_} == $newreqs->{$_} )
        );
      }

      if (keys %$newreqs) {
        push @chunks, (
          "Combined with L</$ag> additionally requires:",
          '=over',
          ( map
            { "=item * $_" . ($newreqs->{$_} ? " >= $newreqs->{$_}" : '') }
            ( sort keys %$newreqs )
          ),
          '=back',
        );
      }
    }
  }

#@@ #@@ API DOCUMENTATION HEADING #@@
  push @chunks, <<'EOC';

IMPORT-LIKE ACTIONS
Even though this module is not an Exporter, it recognizes several "actions" supplied to its "import" method.

  -skip_all_without

Arguments: @group_names

A convenience wrapper for use during testing: EOC

  push @chunks, " use $class -skip_all_without => qw(admin test_rdbms_mysql);";

  push @chunks, 'Roughly equivalent to the following code:';

  push @chunks, sprintf <<'EOS', ($class) x 2;

 BEGIN {
   require %s;
   if ( my $missing = %s->req_missing_for(\@group_names_) ) {
     print "1..0 # SKIP requirements not satisfied: $missing\n";
     exit 0;
   }
 }
EOS

  push @chunks, <<'EOC';

It also takes into account the "RELEASE_TESTING" environment variable and behaves like "-die_without" for any requirement groups marked as "release_testing_mandatory".

  -die_without

Arguments: @group_names

A convenience wrapper around "die_unless_req_ok_for": EOC

  push @chunks, " use $class -die_without => qw(deploy admin);";

  push @chunks, <<'EOC';

  -list_missing

Arguments: @group_names

A convenience wrapper around "modreq_missing_for":

 perl -Ilib -MDBIx::Class::Schema::Loader::Optional::Dependencies=-list_missing,dbicdump_config,rdbms_oracle | cpanm

METHODS

  req_group_list

Arguments: none
Return Value: \%list_of_requirement_groups

This method should be used by DBIx::Class::Schema::Loader packagers, to get a hashref of all dependencies keyed by dependency group. Each key (group name), or a combination thereof (as an arrayref) can be supplied to the methods below. The values of the returned hash are currently a set of options without a well defined structure. If you have use for any of the contents - contact the maintainers, instead of treating this as public (left alone stable) API.

  req_list_for

Arguments: $group_name | \@group_names
Return Value: \%set_of_module_version_pairs

This method should be used by DBIx::Class::Schema::Loader extension authors, to determine the version of modules a specific set of features requires for this version of DBIx::Class::Schema::Loader (regardless of their availability on the system). See the "SYNOPSIS" for a real-world example.

When handling "test_*" groups this method behaves differently from "modreq_list_for" below (and is the only such inconsistency among the "req_*" methods). If a particular group declares as requirements some "environment variables" and these requirements are not satisfied (the envvars are unset) - then the "module requirements" of this group are not included in the returned list.

  modreq_list_for

Arguments: $group_name | \@group_names
Return Value: \%set_of_module_version_pairs

Same as "req_list_for" but does not take into consideration any "environment variable requirements" - returns just the list of required modules.

  req_ok_for

Arguments: $group_name | \@group_names
Return Value: 1|0

Returns true or false depending on whether all modules/envvars required by the group(s) are loadable/set on the system.

  req_missing_for

Arguments: $group_name | \@group_names
Return Value: $error_message_string

Returns a single-line string suitable for inclusion in larger error messages. This method would normally be used by DBIx::Class::Schema::Loader core features, to indicate to the user that they need to install specific modules and/or set specific environment variables before being able to use a specific feature set.

For example if some of the requirements for "deploy" are not available, the returned string could look like: EOC

  push @chunks, qq{ "Moose~$moosever" (see $class documentation for details)};

  push @chunks, <<'EOC';
The author is expected to prepend the necessary text to this message before
returning the actual error seen by the user. See also L</modreq_missing_for>

  modreq_missing_for

Arguments: $group_name | \@group_names
Return Value: $error_message_string

Same as "req_missing_for" except that the error string is guaranteed to be either empty, or contain a set of module requirement specifications suitable for piping to e.g. cpanminus. The method explicitly does not attempt to validate the state of required environment variables (if any).

For instance if some of the requirements for "deploy" are not available, the returned string could look like: EOC

  push @chunks, qq{ "Moose~$moosever"};

  push @chunks, <<'EOC';

See also "-list_missing".

  skip_without

Arguments: $group_name | \@group_names

A convenience wrapper around skip. It does not take neither a reason (it is generated by "req_missing_for") nor an amount of skipped tests (it is always 1, thus mandating unconditional use of done_testing). Most useful in combination with ad hoc requirement specifications: EOC

  push @chunks, <<EOC;
  SKIP: {
    $class->skip_without([ deploy YAML>=0.90 ]);

    ...
  }
EOC

  push @chunks, <<'EOC';

  die_unless_req_ok_for

Arguments: $group_name | \@group_names

Checks if "req_ok_for" passes for the supplied group(s), and in case of failure throws an exception including the information from "req_missing_for". See also "-die_without".

  modreq_errorlist_for

Arguments: $group_name | \@group_names
Return Value: \%set_of_loaderrors_per_module

Returns a hashref containing the actual errors that occurred while attempting to load each module in the requirement group(s).

  req_errorlist_for
Deprecated method name, equivalent (via proxy) to "modreq_errorlist_for".

EOC

#@@ #@@ FOOTER #@@
  push @chunks, <<'EOC'; =head1 FURTHER QUESTIONS?

Check the list of additional DBIC resources.

COPYRIGHT AND LICENSE
This module is free software copyright by the DBIx::Class::Schema::Loader (DBICSL) authors. You can redistribute it and/or modify it under the same terms as the DBIx::Class::Schema::Loader library. EOC

  eval {
    open (my $fh, '>', $podfn) or die;
    print $fh join ("\n\n", @chunks) or die;
    print $fh "\n" or die;
    close ($fh) or die;
  } or croak( "Unable to write $podfn: " . ( $! || $@ || 'unknown error') );
}

1;