[pod-constants.git] / lib / Pod / Constants.pm

# Copyright (C) 2001, 2002, 2007 Sam Vilain.  All Rights Reserved.
# This module is free software. It may be used, redistributed and/or
# modified under the terms of the Perl Artistic License, version 2 or
# later, OR the terms of the GNU General Public License, v3 or later.

package Pod::Constants;

use 5.006002;
use strict;
use warnings;

use base qw(Pod::Parser Exporter);
use Carp;

our $VERSION = 0.17;

# An ugly hack to go from caller() to the relevant parser state
# variable
my %parsers;

sub end_input {
	#my ($parser, $command, $paragraph, $line_num) = (@_);
	my $parser = shift;

	return unless $parser->{active};

	print "Found end of $parser->{active}\n" if $parser->{DEBUG};
	my $whereto = $parser->{wanted_pod_tags}->{$parser->{active}};
	print "\$_ will be set to:\n---\n$parser->{paragraphs}\n---\n" if $parser->{DEBUG};

	$parser->{paragraphs} =~ s/^\s*|\s*$//gs if $parser->{trimmed_tags}->{$parser->{active}};

	if (ref $whereto eq "CODE") {
		print "calling sub\n" if $parser->{DEBUG};
		local ($_) = $parser->{paragraphs};
		$whereto->();
		print "done\n" if $parser->{DEBUG};
	} elsif (ref $whereto eq "SCALAR") {
		print "inserting into scalar\n" if $parser->{DEBUG};
		$$whereto = $parser->{paragraphs};
	} elsif (ref $whereto eq "ARRAY") {
		print "inserting into array\n" if $parser->{DEBUG};
		@$whereto = split /\n/, $parser->{paragraphs};
	} elsif (ref $whereto eq "HASH") {
		print "inserting into hash\n" if $parser->{DEBUG};
		# Oh, sorry, should I be in LISP101?
		%$whereto = (
			map { map { s/^\s*|\s*$//g; $_ } split /=>/, $_ } grep m/^
					 ( (?:[^=]|=[^>])+ )   # scan up to "=>"
					 =>
					 ( (?:[^=]|=[^>])+ =? )# don't allow more "=>"'s
					 $/x, split /\n/, $parser->{paragraphs});
	} else { die $whereto }
	$parser->{active} = undef;
}

# Pod::Parser overloaded command
sub command {
	my ($parser, $command, $paragraph, $line_num) = @_;

	$paragraph =~ s/(?:\r\n|\n\r)/\n/g;

	print "Got command =$command, value=$paragraph\n" if $parser->{DEBUG};

	$parser->end_input() if $parser->{active};

	my ($lookup);
	# first check for a catch-all for this command type
	if ( exists $parser->{wanted_pod_tags}->{"*$command"} ) {
		$parser->{paragraphs} = $paragraph;
		$parser->{active} = "*$command";
	} elsif ($command =~ m/^(head\d+|item|(for|begin))$/) {
		if ( $2 ) {
			# if it's a "for" or "begin" section, the title is the
			# first word only
			($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s*(\S*)\s*(.*)/s;
		} else {
			# otherwise, it's up to the end of the line
			($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s*(\S[^\n]*?)\s*\n(.*)$/s;
		}

		# Look for a match by name
		if (defined $lookup && exists $parser->{wanted_pod_tags}->{$lookup}) {
			print "Found $lookup\n" if ($parser->{DEBUG});
			$parser->{active} = $lookup;
		} elsif ($parser->{DEBUG}) {
			local $^W = 0;
			print "Ignoring =$command $paragraph (lookup = $lookup)\n"
		}

	} else {
		# nothing
		print "Ignoring =$command (not known)\n" if $parser->{DEBUG};
	}
}

# Pod::Parser overloaded verbatim
sub verbatim {
	my ($parser, $paragraph, $line_num) = @_;
	$paragraph =~ s/(?:\r\n|\n\r)/\n/g;

	my $status = $parser->{active} ? "using" : "ignoring";
	print "Got paragraph: $paragraph ($status)\n" if $parser->{DEBUG};

	$parser->{paragraphs} .= $paragraph if defined $parser->{active}
}

# Pod::Parser overloaded textblock
sub textblock { goto \&verbatim }

sub import {
	my $class = shift;

	# if no args, just return
	return unless (@_);

	# try to guess the source file of the caller
	my $source_file;
	if (caller ne "main") {
		(my $module = caller().".pm") =~ s|::|/|g;
		$source_file = $INC{$module};
	}
	$source_file ||= $0;

	croak "Cannot find source file (guessed $source_file) for package ".caller unless -f $source_file;

	# nasty tricks with the stack so we don't have to be silly with
	# caller()
	unshift @_, $source_file;
	goto \&import_from_file;
}

use IO::Handle;

sub import_from_file {
	my $filename = shift;

	my $parser = __PACKAGE__->new();

	$parser->{wanted_pod_tags} = {};
	$parser->{trimmed_tags} = {};
	$parser->{trim_next} = 0;
	$parser->{DEBUG} = 0;
	$parser->{active} = undef;
	$parsers{caller()} = $parser;

	$parser->add_hook(@_);

	print "Pod::Parser: DEBUG: Opening $filename for reading\n" if $parser->{DEBUG};
	my $fh = new IO::Handle;
	open $fh, "<$filename" or die "cannot open $filename for reading; $!";

	$parser->parse_from_filehandle($fh, \*STDOUT);

	close $fh;
}

sub add_hook {
	my $parser;
	if (UNIVERSAL::isa($_[0], __PACKAGE__)) {
		$parser = shift;
	} else {
		$parser = $parsers{caller()} or die "add_hook called, but don't know what for - caller = ".caller;
	}
	while (my ($pod_tag, $var) = splice @_, 0, 2) {
		#print "$pod_tag: $var\n";
		if (lc($pod_tag) eq "-trim") {
			$parser->{trim_next} = $var;
		} elsif ( lc($pod_tag) eq "-debug" ) {
			$parser->{DEBUG} = $var;
		} elsif (lc($pod_tag) eq "-usage") {
			# an idea for later - automatic "usage"
			#%wanted_pod_tags{@tags}
		} else {
			if ((ref $var) =~ /^(?:SCALAR|CODE|ARRAY|HASH)$/) {
				print "Will look for $pod_tag.\n" if $parser->{DEBUG};
				$parser->{wanted_pod_tags}->{$pod_tag} = $var;
				$parser->{trimmed_tags}->{$pod_tag} = 1 if $parser->{trim_next};
			} else {
				die "Sorry - need a reference to import POD sections into, not the scalar value $var"
			}
		}
	}
}

sub delete_hook {
	my $parser;
	if ( UNIVERSAL::isa($_[0], __PACKAGE__) ) {
		$parser = shift;
	} else {
		$parser = $parsers{caller()} or die "delete_hook called, but don't know what for - caller = ".caller;
	}
	while ( my $label = shift ) {
		delete $parser->{wanted_pod_tags}->{$label};
		delete $parser->{trimmed_tags}->{$label};
	}
}

1.4142;
__END__

=encoding utf-8

=head1 NAME

Pod::Constants - Include constants from POD

=head1 SYNOPSIS

 our ($myvar, $VERSION, @myarray, $html, %myhash);

 use Pod::Constants -trim => 1,
     'Pod Section Name' => \$myvar,
     'Version' => sub { eval },
     'Some list' => \@myarray,
     html => \$html,
     'Some hash' => \%myhash;

 =head2 Pod Section Name

 This string will be loaded into $myvar

 =head2 Version

 # This is an example of using a closure.  $_ is set to the
 # contents of the paragraph.  In this example, "eval" is
 # used to execute this code at run time.
 $VERSION = 0.17;

 =head2 Some list

 Each line from this section of the file
 will be placed into a separate array element.
 For example, this is $myarray[2].

 =head2 Some hash

 This text will not go into the hash, because
 it doesn't look like a definition list.
     key1 => Some value (this will go into the hash)
     var2 => Some Other value (so will this)
     wtf = This won't make it in.

 =head2 %myhash's value after the above:

    ( key1 => "Some value (this will go into the hash)",
      var2 => "Some Other value (so will this)"          )

 =begin html <p>This text will be in $html</p>

 =cut

=head1 DESCRIPTION

This module allows you to specify those constants that should be
documented in your POD, and pull them out a run time in a fairly
arbitrary fashion.

Pod::Constants uses Pod::Parser to do the parsing of the source file.
It has to open the source file it is called from, and does so directly
either by lookup in %INC or by assuming it is $0 if the caller is
"main" (or it can't find %INC{caller()})

=head2 ARBITARY DECISIONS

I have made this code only allow the "Pod Section Name" to match
`headN', `item', `for' and `begin' POD sections.  If you have a good
reason why you think it should match other POD sections, drop me a
line and if I'm convinced I'll put it in the standard version.

For `for' and `begin' sections, only the first word is counted as
being a part of the specifier, as opposed to `headN' and `item', where
the entire rest of the line counts.

=head1 FUNCTIONS

=head2 import(@args)

This function is called when we are "use"'d.  It determines the source
file by inspecting the value of caller() or $0.

The form of @args is HOOK => $where.

$where may be a scalar reference, in which case the contents of the
POD section called "HOOK" will be loaded into $where.

$where may be an array reference, in which case the contents of the
array will be the contents of the POD section called "HOOK", split
into lines.

$where may be a hash reference, in which case any lines with a "=>"
symbol present will have everything on the left have side of the =>
operator as keys and everything on the right as values.  You do not
need to quote either, nor have trailing commas at the end of the
lines.

$where may be a code reference (sub { }), in which case the sub is
called when the hook is encountered.  $_ is set to the value of the
POD paragraph.

You may also specify the behaviour of whitespace trimming; by default,
no trimming is done except on the HOOK names.  Setting "-trim => 1"
turns on a package "global" (until the next time import is called)
that will trim the $_ sent for processing by the hook processing
function (be it a given function, or the built-in array/hash
splitters) for leading and trailing whitespace.

The name of HOOK is matched against any "=head1", "=head2", "=item",
"=for", "=begin" value.  If you specify the special hooknames "*item",
"*head1", etc, then you will get a function that is run for every 

Note that the supplied functions for array and hash splitting are
exactly equivalent to fairly simple Perl blocks:

Array:

  HOOK => sub { @array = split /\n/, $_ }

Hash:

  HOOK => sub {
  %hash =
      (map { map { s/^\s+|\s+$//g; $_ } split /=>/, $_ }
        (grep m/^
            ( (?:[^=]|=[^>])+ )   # scan up to "=>"
            =>
            ( (?:[^=]|=[^>])+ =? )# don't allow more "=>"'s
            $/x, split /\n/, $_));
  }

Well, they're simple if you can grok map, a regular expression like
that and a functional programming style.  If you can't I'm sure it is
probably voodoo to you.

Here's the procedural equivalent:

  HOOK => sub {
     for my $line (split /\n/, $_) {
         my ($key, $value, $junk) = split /=>/, $line;
         next if $junk;
         $key =~ s/^\s+|\s+$//g
         $value =~ s/^\s+|\s+$//g
         $hash{$key} = $value;
     }
  },

=head2 import_from_file($filename, @args)

Very similar to straight "import", but you specify the source filename
explicitly.

=head2 add_hook(NAME => value)

This function adds another hook, it is useful for dynamic updating of
parsing through the document.

For an example, please see t/01-constants.t in the source
distribution.  More detailed examples will be added in a later
release.

=head2 delete_hook(@list)

Deletes the named hooks.  Companion function to add_hook

=head2 CLOSURES AS DESTINATIONS

If the given value is a ref CODE, then that function is called, with
$_ set to the value of the paragraph.  This can be very useful for
applying your own custom mutations to the POD to change it from human
readable text into something your program can use.

After I added this function, I just kept on thinking of cool uses for
it.  The nice, succinct code you can make with it is one of
Pod::Constant's strongest features.

Below are some examples.

=head1 EXAMPLES

=head2 Module Makefile.PL maintenance

Tired of keeping those module Makefile.PL's up to date?  Note: This
method seems to break dh-make-perl.

=head2 Example Makefile.PL

 eval "use Pod::Constants";
 ($Pod::Constants::VERSION >= 0.11)
     or die <<EOF
 ####
 ####  ERROR: This module requires Pod::Constants 0.11 or
 ####  higher to be installed.
 ####
 EOF

 my ($VERSION, $NAME, $PREREQ_PM, $ABSTRACT, $AUTHOR);
 Pod::Constants::import_from_file 
     (
      'MyTestModule.pm',
      'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+)/ },
      'DEPENDENCIES' => ($PREREQ_PM = { }),
       -trim => 1,
      'NAME' => sub { $ABSTRACT=$_; ($NAME) = m/(\S+)/ },
      'AUTHOR' => \$AUTHOR,
     );

 WriteMakefile
     (
      'NAME'        => $NAME,
      'PREREQ_PM'        => $PREREQ_PM,
      'VERSION'          => $VERSION,
      ($] >= 5.005 ?    ## Add these new keywords supported since 5.005
       (ABSTRACT         => $ABSTRACT,
        AUTHOR           => $AUTHOR) : ()),
     );

=head2 Corresponding Module

 =head1 NAME

 MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness

 =head2 MODULE RELEASE

 This is release 1.05 of this module.

 =head2 DEPENDENCIES

 The following modules are required to make this module:

    Some::Module => 0.02

 =head2 AUTHOR

 Ima Twat <ima@twat.name>

 =cut

 our $VERSION;
 use Pod::Constants -trim => 1,
     'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };

=head1 AUTHOR

Sam Vilain, <samv@cpan.org>

=head1 BUGS/TODO

I keep thinking it would be nice to be able to import an =item list
into an array or something, eg for a program argument list.  But I'm
not too sure how it would be all that useful in practice; you'd end up
putting the function names for callbacks in the pod or something
(perhaps not all that bad).

Would this be useful?

 Pod::Constants::import(Foo::SECTION => \$myvar);

Debug output is not very readable

=head1 PATCHES WELCOME

If you have any suggestions for enhancements, they are much more likely
to happen if you submit them as a patch to the distribution.

Source is kept at

  git://utsl.gen.nz/Pod-Constants 


=cut
Commit	Line	Data
f46dd377 MG	1	# Copyright (C) 2001, 2002, 2007 Sam Vilain. All Rights Reserved.
	2	# This module is free software. It may be used, redistributed and/or
	3	# modified under the terms of the Perl Artistic License, version 2 or
	4	# later, OR the terms of the GNU General Public License, v3 or later.
	5
	6	package Pod::Constants;
	7
222de36b	8	use 5.006002;
f46dd377	9	use strict;
222de36b	10	use warnings;
f46dd377 MG	11
f46dd377 MG	12	use base qw(Pod::Parser Exporter);
f46dd377 MG	13	use Carp;
f46dd377 MG	14
222de36b	15	our $VERSION = 0.17;
f46dd377 MG	16
	17	# An ugly hack to go from caller() to the relevant parser state
	18	# variable
	19	my %parsers;
	20
	21	sub end_input {
db966dd0 MG	22	#my ($parser, $command, $paragraph, $line_num) = (@_);
	23	my $parser = shift;
	24
	25	return unless $parser->{active};
	26
612aada2	27	print "Found end of $parser->{active}\n" if $parser->{DEBUG};
db966dd0	28	my $whereto = $parser->{wanted_pod_tags}->{$parser->{active}};
612aada2	29	print "\$_ will be set to:\n---\n$parser->{paragraphs}\n---\n" if $parser->{DEBUG};
db966dd0	30
612aada2	31	$parser->{paragraphs} =~ s/^\s\|\s$//gs if $parser->{trimmed_tags}->{$parser->{active}};
db966dd0 MG	32
	33	if (ref $whereto eq "CODE") {
	34	print "calling sub\n" if $parser->{DEBUG};
	35	local ($_) = $parser->{paragraphs};
	36	$whereto->();
	37	print "done\n" if $parser->{DEBUG};
	38	} elsif (ref $whereto eq "SCALAR") {
	39	print "inserting into scalar\n" if $parser->{DEBUG};
	40	$$whereto = $parser->{paragraphs};
	41	} elsif (ref $whereto eq "ARRAY") {
	42	print "inserting into array\n" if $parser->{DEBUG};
	43	@$whereto = split /\n/, $parser->{paragraphs};
	44	} elsif (ref $whereto eq "HASH") {
	45	print "inserting into hash\n" if $parser->{DEBUG};
	46	# Oh, sorry, should I be in LISP101?
612aada2 MG	47	%$whereto = (
	48	map { map { s/^\s\|\s$//g; $_ } split /=>/, $_ } grep m/^
	49	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
	50	=>
	51	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
	52	$/x, split /\n/, $parser->{paragraphs});
db966dd0 MG	53	} else { die $whereto }
db966dd0 MG	54	$parser->{active} = undef;
f46dd377 MG	55	}
	56
	57	# Pod::Parser overloaded command
	58	sub command {
db966dd0 MG	59	my ($parser, $command, $paragraph, $line_num) = @_;
	60
	61	$paragraph =~ s/(?:\r\n\|\n\r)/\n/g;
	62
612aada2	63	print "Got command =$command, value=$paragraph\n" if $parser->{DEBUG};
db966dd0 MG	64
	65	$parser->end_input() if $parser->{active};
	66
db966dd0 MG	67	my ($lookup);
	68	# first check for a catch-all for this command type
	69	if ( exists $parser->{wanted_pod_tags}->{"*$command"} ) {
	70	$parser->{paragraphs} = $paragraph;
	71	$parser->{active} = "*$command";
db966dd0 MG	72	} elsif ($command =~ m/^(head\d+\|item\|(for\|begin))$/) {
	73	if ( $2 ) {
	74	# if it's a "for" or "begin" section, the title is the
	75	# first word only
612aada2	76	($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s(\S)\s(.)/s;
db966dd0 MG	77	} else {
db966dd0 MG	78	# otherwise, it's up to the end of the line
612aada2	79	($lookup, $parser->{paragraphs}) = $paragraph =~ m/^\s(\S[^\n]?)\s\n(.)$/s;
db966dd0 MG	80	}
	81
	82	# Look for a match by name
612aada2	83	if (defined $lookup && exists $parser->{wanted_pod_tags}->{$lookup}) {
db966dd0 MG	84	print "Found $lookup\n" if ($parser->{DEBUG});
db966dd0 MG	85	$parser->{active} = $lookup;
612aada2 MG	86	} elsif ($parser->{DEBUG}) {
	87	local $^W = 0;
	88	print "Ignoring =$command $paragraph (lookup = $lookup)\n"
db966dd0	89	}
f46dd377	90
f46dd377	91	} else {
db966dd0 MG	92	# nothing
db966dd0 MG	93	print "Ignoring =$command (not known)\n" if $parser->{DEBUG};
f46dd377	94	}
f46dd377 MG	95	}
	96
	97	# Pod::Parser overloaded verbatim
	98	sub verbatim {
db966dd0 MG	99	my ($parser, $paragraph, $line_num) = @_;
db966dd0 MG	100	$paragraph =~ s/(?:\r\n\|\n\r)/\n/g;
f46dd377	101
612aada2 MG	102	my $status = $parser->{active} ? "using" : "ignoring";
612aada2 MG	103	print "Got paragraph: $paragraph ($status)\n" if $parser->{DEBUG};
f46dd377	104
612aada2	105	$parser->{paragraphs} .= $paragraph if defined $parser->{active}
f46dd377 MG	106	}
	107
	108	# Pod::Parser overloaded textblock
	109	sub textblock { goto \&verbatim }
	110
f46dd377	111	sub import {
db966dd0 MG	112	my $class = shift;
	113
	114	# if no args, just return
	115	return unless (@_);
	116
	117	# try to guess the source file of the caller
	118	my $source_file;
	119	if (caller ne "main") {
	120	(my $module = caller().".pm") =~ s\|::\|/\|g;
	121	$source_file = $INC{$module};
	122	}
	123	$source_file \|\|= $0;
	124
612aada2	125	croak "Cannot find source file (guessed $source_file) for package ".caller unless -f $source_file;
db966dd0 MG	126
	127	# nasty tricks with the stack so we don't have to be silly with
	128	# caller()
	129	unshift @_, $source_file;
	130	goto \&import_from_file;
f46dd377 MG	131	}
f46dd377 MG	132
f46dd377 MG	133	use IO::Handle;
	134
	135	sub import_from_file {
db966dd0	136	my $filename = shift;
f46dd377	137
db966dd0	138	my $parser = __PACKAGE__->new();
f46dd377	139
db966dd0 MG	140	$parser->{wanted_pod_tags} = {};
	141	$parser->{trimmed_tags} = {};
	142	$parser->{trim_next} = 0;
	143	$parser->{DEBUG} = 0;
	144	$parser->{active} = undef;
	145	$parsers{caller()} = $parser;
f46dd377	146
db966dd0	147	$parser->add_hook(@_);
f46dd377	148
612aada2	149	print "Pod::Parser: DEBUG: Opening $filename for reading\n" if $parser->{DEBUG};
db966dd0	150	my $fh = new IO::Handle;
612aada2	151	open $fh, "<$filename" or die "cannot open $filename for reading; $!";
f46dd377	152
db966dd0	153	$parser->parse_from_filehandle($fh, \*STDOUT);
f46dd377	154
db966dd0	155	close $fh;
f46dd377 MG	156	}
f46dd377 MG	157
f46dd377	158	sub add_hook {
db966dd0	159	my $parser;
612aada2	160	if (UNIVERSAL::isa($_[0], __PACKAGE__)) {
db966dd0	161	$parser = shift;
f46dd377	162	} else {
612aada2	163	$parser = $parsers{caller()} or die "add_hook called, but don't know what for - caller = ".caller;
db966dd0 MG	164	}
	165	while (my ($pod_tag, $var) = splice @_, 0, 2) {
	166	#print "$pod_tag: $var\n";
	167	if (lc($pod_tag) eq "-trim") {
	168	$parser->{trim_next} = $var;
	169	} elsif ( lc($pod_tag) eq "-debug" ) {
	170	$parser->{DEBUG} = $var;
	171	} elsif (lc($pod_tag) eq "-usage") {
	172	# an idea for later - automatic "usage"
	173	#%wanted_pod_tags{@tags}
	174	} else {
	175	if ((ref $var) =~ /^(?:SCALAR\|CODE\|ARRAY\|HASH)$/) {
612aada2	176	print "Will look for $pod_tag.\n" if $parser->{DEBUG};
db966dd0	177	$parser->{wanted_pod_tags}->{$pod_tag} = $var;
612aada2	178	$parser->{trimmed_tags}->{$pod_tag} = 1 if $parser->{trim_next};
db966dd0	179	} else {
612aada2	180	die "Sorry - need a reference to import POD sections into, not the scalar value $var"
db966dd0 MG	181	}
db966dd0 MG	182	}
f46dd377	183	}
f46dd377 MG	184	}
f46dd377 MG	185
f46dd377	186	sub delete_hook {
db966dd0 MG	187	my $parser;
	188	if ( UNIVERSAL::isa($_[0], __PACKAGE__) ) {
	189	$parser = shift;
	190	} else {
612aada2	191	$parser = $parsers{caller()} or die "delete_hook called, but don't know what for - caller = ".caller;
db966dd0 MG	192	}
	193	while ( my $label = shift ) {
	194	delete $parser->{wanted_pod_tags}->{$label};
	195	delete $parser->{trimmed_tags}->{$label};
	196	}
f46dd377 MG	197	}
f46dd377 MG	198
49655cb6 MG	199	1.4142;
	200	__END__
	201
	202	=encoding utf-8
	203
	204	=head1 NAME
	205
	206	Pod::Constants - Include constants from POD
	207
	208	=head1 SYNOPSIS
	209
612aada2	210	our ($myvar, $VERSION, @myarray, $html, %myhash);
49655cb6 MG	211
	212	use Pod::Constants -trim => 1,
	213	'Pod Section Name' => \$myvar,
	214	'Version' => sub { eval },
	215	'Some list' => \@myarray,
	216	html => \$html,
	217	'Some hash' => \%myhash;
	218
	219	=head2 Pod Section Name
	220
	221	This string will be loaded into $myvar
	222
	223	=head2 Version
	224
	225	# This is an example of using a closure. $_ is set to the
	226	# contents of the paragraph. In this example, "eval" is
	227	# used to execute this code at run time.
	228	$VERSION = 0.17;
	229
	230	=head2 Some list
	231
	232	Each line from this section of the file
	233	will be placed into a separate array element.
	234	For example, this is $myarray[2].
	235
	236	=head2 Some hash
	237
	238	This text will not go into the hash, because
	239	it doesn't look like a definition list.
	240	key1 => Some value (this will go into the hash)
	241	var2 => Some Other value (so will this)
	242	wtf = This won't make it in.
	243
	244	=head2 %myhash's value after the above:
	245
	246	( key1 => "Some value (this will go into the hash)",
	247	var2 => "Some Other value (so will this)" )
	248
	249	=begin html <p>This text will be in $html</p>
	250
	251	=cut
	252
	253	=head1 DESCRIPTION
	254
	255	This module allows you to specify those constants that should be
	256	documented in your POD, and pull them out a run time in a fairly
	257	arbitrary fashion.
	258
	259	Pod::Constants uses Pod::Parser to do the parsing of the source file.
	260	It has to open the source file it is called from, and does so directly
	261	either by lookup in %INC or by assuming it is $0 if the caller is
	262	"main" (or it can't find %INC{caller()})
	263
	264	=head2 ARBITARY DECISIONS
	265
	266	I have made this code only allow the "Pod Section Name" to match
	267	`headN', `item', `for' and `begin' POD sections. If you have a good
	268	reason why you think it should match other POD sections, drop me a
	269	line and if I'm convinced I'll put it in the standard version.
	270
	271	For `for' and `begin' sections, only the first word is counted as
	272	being a part of the specifier, as opposed to `headN' and `item', where
	273	the entire rest of the line counts.
	274
275	=head1 FUNCTIONS
276
277	=head2 import(@args)
278
279	This function is called when we are "use"'d. It determines the source
280	file by inspecting the value of caller() or $0.
281
282	The form of @args is HOOK => $where.
283
284	$where may be a scalar reference, in which case the contents of the
285	POD section called "HOOK" will be loaded into $where.
286
287	$where may be an array reference, in which case the contents of the
288	array will be the contents of the POD section called "HOOK", split
289	into lines.
290
291	$where may be a hash reference, in which case any lines with a "=>"
292	symbol present will have everything on the left have side of the =>
293	operator as keys and everything on the right as values. You do not
294	need to quote either, nor have trailing commas at the end of the
295	lines.
296
297	$where may be a code reference (sub { }), in which case the sub is
298	called when the hook is encountered. $_ is set to the value of the
299	POD paragraph.
300
301	You may also specify the behaviour of whitespace trimming; by default,
302	no trimming is done except on the HOOK names. Setting "-trim => 1"
303	turns on a package "global" (until the next time import is called)
304	that will trim the $_ sent for processing by the hook processing
305	function (be it a given function, or the built-in array/hash
306	splitters) for leading and trailing whitespace.
307
308	The name of HOOK is matched against any "=head1", "=head2", "=item",
309	"=for", "=begin" value. If you specify the special hooknames "*item",
310	"*head1", etc, then you will get a function that is run for every
311
312	Note that the supplied functions for array and hash splitting are
313	exactly equivalent to fairly simple Perl blocks:
314
315	Array:
316
317	HOOK => sub { @array = split /\n/, $_ }
318
319	Hash:
320
321	HOOK => sub {
322	%hash =
323	(map { map { s/^\s+\|\s+$//g; $_ } split /=>/, $_ }
324	(grep m/^
325	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
326	=>
327	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
328	$/x, split /\n/, $_));
329	}
330
331	Well, they're simple if you can grok map, a regular expression like
332	that and a functional programming style. If you can't I'm sure it is
333	probably voodoo to you.
334
335	Here's the procedural equivalent:
336
337	HOOK => sub {
338	for my $line (split /\n/, $_) {
339	my ($key, $value, $junk) = split /=>/, $line;
340	next if $junk;
341	$key =~ s/^\s+\|\s+$//g
342	$value =~ s/^\s+\|\s+$//g
343	$hash{$key} = $value;
344	}
345	},
346
347	=head2 import_from_file($filename, @args)
348
349	Very similar to straight "import", but you specify the source filename
350	explicitly.
351
352	=head2 add_hook(NAME => value)
353
354	This function adds another hook, it is useful for dynamic updating of
355	parsing through the document.
356
357	For an example, please see t/01-constants.t in the source
358	distribution. More detailed examples will be added in a later
359	release.
360
361	=head2 delete_hook(@list)
362
363	Deletes the named hooks. Companion function to add_hook
364
f46dd377 MG	365	=head2 CLOSURES AS DESTINATIONS
	366
	367	If the given value is a ref CODE, then that function is called, with
	368	$_ set to the value of the paragraph. This can be very useful for
	369	applying your own custom mutations to the POD to change it from human
	370	readable text into something your program can use.
	371
	372	After I added this function, I just kept on thinking of cool uses for
	373	it. The nice, succinct code you can make with it is one of
	374	Pod::Constant's strongest features.
	375
	376	Below are some examples.
	377
	378	=head1 EXAMPLES
	379
	380	=head2 Module Makefile.PL maintenance
	381
	382	Tired of keeping those module Makefile.PL's up to date? Note: This
	383	method seems to break dh-make-perl.
	384
	385	=head2 Example Makefile.PL
	386
	387	eval "use Pod::Constants";
	388	($Pod::Constants::VERSION >= 0.11)
	389	or die <<EOF
	390	####
	391	#### ERROR: This module requires Pod::Constants 0.11 or
	392	#### higher to be installed.
	393	####
	394	EOF
	395
	396	my ($VERSION, $NAME, $PREREQ_PM, $ABSTRACT, $AUTHOR);
	397	Pod::Constants::import_from_file
	398	(
	399	'MyTestModule.pm',
	400	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+)/ },
e18addae	401	'DEPENDENCIES' => ($PREREQ_PM = { }),
f46dd377 MG	402	-trim => 1,
	403	'NAME' => sub { $ABSTRACT=$_; ($NAME) = m/(\S+)/ },
	404	'AUTHOR' => \$AUTHOR,
	405	);
	406
	407	WriteMakefile
	408	(
db966dd0	409	'NAME' => $NAME,
f46dd377 MG	410	'PREREQ_PM' => $PREREQ_PM,
	411	'VERSION' => $VERSION,
	412	($] >= 5.005 ? ## Add these new keywords supported since 5.005
	413	(ABSTRACT => $ABSTRACT,
	414	AUTHOR => $AUTHOR) : ()),
	415	);
	416
	417	=head2 Corresponding Module
	418
	419	=head1 NAME
	420
	421	MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness
	422
	423	=head2 MODULE RELEASE
	424
	425	This is release 1.05 of this module.
	426
e18addae	427	=head2 DEPENDENCIES
f46dd377 MG	428
	429	The following modules are required to make this module:
	430
	431	Some::Module => 0.02
	432
	433	=head2 AUTHOR
	434
	435	Ima Twat <ima@twat.name>
	436
	437	=cut
	438
222de36b	439	our $VERSION;
f46dd377 MG	440	use Pod::Constants -trim => 1,
	441	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };
	442
	443	=head1 AUTHOR
	444
	445	Sam Vilain, <samv@cpan.org>
	446
	447	=head1 BUGS/TODO
	448
	449	I keep thinking it would be nice to be able to import an =item list
	450	into an array or something, eg for a program argument list. But I'm
	451	not too sure how it would be all that useful in practice; you'd end up
	452	putting the function names for callbacks in the pod or something
	453	(perhaps not all that bad).
	454
	455	Would this be useful?
	456
	457	Pod::Constants::import(Foo::SECTION => \$myvar);
	458
	459	Debug output is not very readable
	460
	461	=head1 PATCHES WELCOME
	462
	463	If you have any suggestions for enhancements, they are much more likely
	464	to happen if you submit them as a patch to the distribution.
	465
	466	Source is kept at
	467
	468	git://utsl.gen.nz/Pod-Constants
	469
f46dd377	470
49655cb6	471	=cut