[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 Data::Dumper;
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 $does_she_want_it_sir;

	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";
		$does_she_want_it_sir = "oohw";

	} 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
			  and exists $parser->{wanted_pod_tags}->{$lookup}) {
			print "Found $lookup\n" if ($parser->{DEBUG});
			$parser->{active} = $lookup;
			$does_she_want_it_sir = "suits you sir";
		}

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

	{
		local $^W = 0;
		print "Ignoring =$command $paragraph (lookup = $lookup)\n"
		  if (!$does_she_want_it_sir and $parser->{DEBUG})
	  }
}

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

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

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

# 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;

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

	# 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"
					   ." importing $pod_tag into ".caller());
			}
		}
	}
}

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
	12	use base qw(Pod::Parser Exporter);
	13	use Data::Dumper;
	14	use Carp;
	15
222de36b	16	our $VERSION = 0.17;
f46dd377 MG	17
	18	# An ugly hack to go from caller() to the relevant parser state
	19	# variable
	20	my %parsers;
	21
	22	sub end_input {
db966dd0 MG	23	#my ($parser, $command, $paragraph, $line_num) = (@_);
	24	my $parser = shift;
	25
	26	return unless $parser->{active};
	27
	28	print "Found end of $parser->{active}\n" if ($parser->{DEBUG});
	29	my $whereto = $parser->{wanted_pod_tags}->{$parser->{active}};
	30	print "\$_ will be set to:\n---\n$parser->{paragraphs}\n---\n"
	31	if ($parser->{DEBUG});
	32
	33	$parser->{paragraphs} =~ s/^\s\|\s$//gs
	34	if $parser->{trimmed_tags}->{$parser->{active}};
	35
	36	if (ref $whereto eq "CODE") {
	37	print "calling sub\n" if $parser->{DEBUG};
	38	local ($_) = $parser->{paragraphs};
	39	$whereto->();
	40	print "done\n" if $parser->{DEBUG};
	41	} elsif (ref $whereto eq "SCALAR") {
	42	print "inserting into scalar\n" if $parser->{DEBUG};
	43	$$whereto = $parser->{paragraphs};
	44	} elsif (ref $whereto eq "ARRAY") {
	45	print "inserting into array\n" if $parser->{DEBUG};
	46	@$whereto = split /\n/, $parser->{paragraphs};
	47	} elsif (ref $whereto eq "HASH") {
	48	print "inserting into hash\n" if $parser->{DEBUG};
	49	# Oh, sorry, should I be in LISP101?
	50	%$whereto = (map { map { s/^\s\|\s$//g; $_ }
	51	split /=>/, $_ }
	52	grep m/^
	53	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
	54	=>
	55	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
	56	$/x,
	57	split /\n/, $parser->{paragraphs});
	58	} else { die $whereto }
	59	$parser->{active} = undef;
f46dd377 MG	60	}
	61
	62	# Pod::Parser overloaded command
	63	sub command {
db966dd0 MG	64	my ($parser, $command, $paragraph, $line_num) = @_;
	65
	66	$paragraph =~ s/(?:\r\n\|\n\r)/\n/g;
	67
	68	print "Got command =$command, value=$paragraph\n"
	69	if $parser->{DEBUG};
	70
	71	$parser->end_input() if $parser->{active};
	72
	73	my $does_she_want_it_sir;
	74
	75	my ($lookup);
	76	# first check for a catch-all for this command type
	77	if ( exists $parser->{wanted_pod_tags}->{"*$command"} ) {
	78	$parser->{paragraphs} = $paragraph;
	79	$parser->{active} = "*$command";
	80	$does_she_want_it_sir = "oohw";
	81
	82	} elsif ($command =~ m/^(head\d+\|item\|(for\|begin))$/) {
	83	if ( $2 ) {
	84	# if it's a "for" or "begin" section, the title is the
	85	# first word only
	86	($lookup, $parser->{paragraphs}) =
	87	($paragraph =~ m/^\s(\S)\s(.)/s);
	88	} else {
	89	# otherwise, it's up to the end of the line
	90	($lookup, $parser->{paragraphs})
	91	= ($paragraph =~ m/^\s(\S[^\n]?)\s\n(.)$/s);
	92	}
	93
	94	# Look for a match by name
	95	if (defined $lookup
	96	and exists $parser->{wanted_pod_tags}->{$lookup}) {
	97	print "Found $lookup\n" if ($parser->{DEBUG});
	98	$parser->{active} = $lookup;
	99	$does_she_want_it_sir = "suits you sir";
	100	}
f46dd377	101
f46dd377	102	} else {
db966dd0 MG	103	# nothing
db966dd0 MG	104	print "Ignoring =$command (not known)\n" if $parser->{DEBUG};
f46dd377 MG	105	}
f46dd377 MG	106
db966dd0 MG	107	{
	108	local $^W = 0;
	109	print "Ignoring =$command $paragraph (lookup = $lookup)\n"
	110	if (!$does_she_want_it_sir and $parser->{DEBUG})
	111	}
f46dd377 MG	112	}
	113
	114	# Pod::Parser overloaded verbatim
	115	sub verbatim {
db966dd0 MG	116	my ($parser, $paragraph, $line_num) = @_;
db966dd0 MG	117	$paragraph =~ s/(?:\r\n\|\n\r)/\n/g;
f46dd377	118
db966dd0 MG	119	print("Got paragraph: $paragraph ("
	120	.($parser->{active}?"using":"ignoring").")\n")
	121	if $parser->{DEBUG};
f46dd377	122
db966dd0 MG	123	if (defined $parser->{active}) {
	124	$parser->{paragraphs} .= $paragraph;
	125	}
f46dd377 MG	126	}
	127
	128	# Pod::Parser overloaded textblock
	129	sub textblock { goto \&verbatim }
	130
f46dd377	131	sub import {
db966dd0 MG	132	my $class = shift;
	133
	134	# if no args, just return
	135	return unless (@_);
	136
	137	# try to guess the source file of the caller
	138	my $source_file;
	139	if (caller ne "main") {
	140	(my $module = caller().".pm") =~ s\|::\|/\|g;
	141	$source_file = $INC{$module};
	142	}
	143	$source_file \|\|= $0;
	144
	145	( -f $source_file )
	146	or croak ("Cannot find source file (guessed $source_file) for"
	147	." package ".caller());
	148
	149	# nasty tricks with the stack so we don't have to be silly with
	150	# caller()
	151	unshift @_, $source_file;
	152	goto \&import_from_file;
f46dd377 MG	153	}
f46dd377 MG	154
f46dd377 MG	155	use IO::Handle;
	156
	157	sub import_from_file {
db966dd0	158	my $filename = shift;
f46dd377	159
db966dd0	160	my $parser = __PACKAGE__->new();
f46dd377	161
db966dd0 MG	162	$parser->{wanted_pod_tags} = {};
	163	$parser->{trimmed_tags} = {};
	164	$parser->{trim_next} = 0;
	165	$parser->{DEBUG} = 0;
	166	$parser->{active} = undef;
	167	$parsers{caller()} = $parser;
f46dd377	168
db966dd0	169	$parser->add_hook(@_);
f46dd377	170
db966dd0 MG	171	print "Pod::Parser: DEBUG: Opening $filename for reading\n"
	172	if $parser->{DEBUG};
	173	my $fh = new IO::Handle;
	174	open $fh, "<$filename"
	175	or die ("cannot open $filename for reading; $!");
f46dd377	176
db966dd0	177	$parser->parse_from_filehandle($fh, \*STDOUT);
f46dd377	178
db966dd0	179	close $fh;
f46dd377 MG	180	}
f46dd377 MG	181
f46dd377	182	sub add_hook {
db966dd0 MG	183	my $parser;
	184	if ( UNIVERSAL::isa($_[0], __PACKAGE__) ) {
	185	$parser = shift;
f46dd377	186	} else {
db966dd0 MG	187	$parser = $parsers{caller()}
	188	or die("add_hook called, but don't know what for - "
	189	."caller = ".caller());
	190	}
	191	while (my ($pod_tag, $var) = splice @_, 0, 2) {
	192	#print "$pod_tag: $var\n";
	193	if (lc($pod_tag) eq "-trim") {
	194	$parser->{trim_next} = $var;
	195	} elsif ( lc($pod_tag) eq "-debug" ) {
	196	$parser->{DEBUG} = $var;
	197	} elsif (lc($pod_tag) eq "-usage") {
	198	# an idea for later - automatic "usage"
	199	#%wanted_pod_tags{@tags}
	200	} else {
	201	if ((ref $var) =~ /^(?:SCALAR\|CODE\|ARRAY\|HASH)$/) {
	202	print "Will look for $pod_tag.\n"
	203	if ($parser->{DEBUG});
	204	$parser->{wanted_pod_tags}->{$pod_tag} = $var;
	205	$parser->{trimmed_tags}->{$pod_tag} = 1
	206	if $parser->{trim_next};
	207	} else {
	208	die ("Sorry - need a reference to import POD "
	209	."sections into, not the scalar value $var"
	210	." importing $pod_tag into ".caller());
	211	}
	212	}
f46dd377	213	}
f46dd377 MG	214	}
f46dd377 MG	215
f46dd377	216	sub delete_hook {
db966dd0 MG	217	my $parser;
	218	if ( UNIVERSAL::isa($_[0], __PACKAGE__) ) {
	219	$parser = shift;
	220	} else {
	221	$parser = $parsers{caller()}
	222	or die("delete_hook called, but don't know what for - "
	223	."caller = ".caller());
	224	}
	225	while ( my $label = shift ) {
	226	delete $parser->{wanted_pod_tags}->{$label};
	227	delete $parser->{trimmed_tags}->{$label};
	228	}
f46dd377 MG	229	}
f46dd377 MG	230
49655cb6 MG	231	1.4142;
	232	__END__
	233
	234	=encoding utf-8
	235
	236	=head1 NAME
	237
	238	Pod::Constants - Include constants from POD
	239
	240	=head1 SYNOPSIS
	241
222de36b	242	our ($myvar $VERSION @myarray $html %myhash);
49655cb6 MG	243
	244	use Pod::Constants -trim => 1,
	245	'Pod Section Name' => \$myvar,
	246	'Version' => sub { eval },
	247	'Some list' => \@myarray,
	248	html => \$html,
	249	'Some hash' => \%myhash;
	250
	251	=head2 Pod Section Name
	252
	253	This string will be loaded into $myvar
	254
	255	=head2 Version
	256
	257	# This is an example of using a closure. $_ is set to the
	258	# contents of the paragraph. In this example, "eval" is
	259	# used to execute this code at run time.
	260	$VERSION = 0.17;
	261
	262	=head2 Some list
	263
	264	Each line from this section of the file
	265	will be placed into a separate array element.
	266	For example, this is $myarray[2].
	267
	268	=head2 Some hash
	269
	270	This text will not go into the hash, because
	271	it doesn't look like a definition list.
	272	key1 => Some value (this will go into the hash)
	273	var2 => Some Other value (so will this)
	274	wtf = This won't make it in.
	275
	276	=head2 %myhash's value after the above:
	277
	278	( key1 => "Some value (this will go into the hash)",
	279	var2 => "Some Other value (so will this)" )
	280
	281	=begin html <p>This text will be in $html</p>
	282
	283	=cut
	284
	285	=head1 DESCRIPTION
	286
	287	This module allows you to specify those constants that should be
	288	documented in your POD, and pull them out a run time in a fairly
	289	arbitrary fashion.
	290
	291	Pod::Constants uses Pod::Parser to do the parsing of the source file.
	292	It has to open the source file it is called from, and does so directly
	293	either by lookup in %INC or by assuming it is $0 if the caller is
	294	"main" (or it can't find %INC{caller()})
	295
	296	=head2 ARBITARY DECISIONS
	297
	298	I have made this code only allow the "Pod Section Name" to match
	299	`headN', `item', `for' and `begin' POD sections. If you have a good
	300	reason why you think it should match other POD sections, drop me a
	301	line and if I'm convinced I'll put it in the standard version.
	302
	303	For `for' and `begin' sections, only the first word is counted as
	304	being a part of the specifier, as opposed to `headN' and `item', where
	305	the entire rest of the line counts.
	306
307	=head1 FUNCTIONS
308
309	=head2 import(@args)
310
311	This function is called when we are "use"'d. It determines the source
312	file by inspecting the value of caller() or $0.
313
314	The form of @args is HOOK => $where.
315
316	$where may be a scalar reference, in which case the contents of the
317	POD section called "HOOK" will be loaded into $where.
318
319	$where may be an array reference, in which case the contents of the
320	array will be the contents of the POD section called "HOOK", split
321	into lines.
322
323	$where may be a hash reference, in which case any lines with a "=>"
324	symbol present will have everything on the left have side of the =>
325	operator as keys and everything on the right as values. You do not
326	need to quote either, nor have trailing commas at the end of the
327	lines.
328
329	$where may be a code reference (sub { }), in which case the sub is
330	called when the hook is encountered. $_ is set to the value of the
331	POD paragraph.
332
333	You may also specify the behaviour of whitespace trimming; by default,
334	no trimming is done except on the HOOK names. Setting "-trim => 1"
335	turns on a package "global" (until the next time import is called)
336	that will trim the $_ sent for processing by the hook processing
337	function (be it a given function, or the built-in array/hash
338	splitters) for leading and trailing whitespace.
339
340	The name of HOOK is matched against any "=head1", "=head2", "=item",
341	"=for", "=begin" value. If you specify the special hooknames "*item",
342	"*head1", etc, then you will get a function that is run for every
343
344	Note that the supplied functions for array and hash splitting are
345	exactly equivalent to fairly simple Perl blocks:
346
347	Array:
348
349	HOOK => sub { @array = split /\n/, $_ }
350
351	Hash:
352
353	HOOK => sub {
354	%hash =
355	(map { map { s/^\s+\|\s+$//g; $_ } split /=>/, $_ }
356	(grep m/^
357	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
358	=>
359	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
360	$/x, split /\n/, $_));
361	}
362
363	Well, they're simple if you can grok map, a regular expression like
364	that and a functional programming style. If you can't I'm sure it is
365	probably voodoo to you.
366
367	Here's the procedural equivalent:
368
369	HOOK => sub {
370	for my $line (split /\n/, $_) {
371	my ($key, $value, $junk) = split /=>/, $line;
372	next if $junk;
373	$key =~ s/^\s+\|\s+$//g
374	$value =~ s/^\s+\|\s+$//g
375	$hash{$key} = $value;
376	}
377	},
378
379	=head2 import_from_file($filename, @args)
380
381	Very similar to straight "import", but you specify the source filename
382	explicitly.
383
384	=head2 add_hook(NAME => value)
385
386	This function adds another hook, it is useful for dynamic updating of
387	parsing through the document.
388
389	For an example, please see t/01-constants.t in the source
390	distribution. More detailed examples will be added in a later
391	release.
392
393	=head2 delete_hook(@list)
394
395	Deletes the named hooks. Companion function to add_hook
396
f46dd377 MG	397	=head2 CLOSURES AS DESTINATIONS
	398
	399	If the given value is a ref CODE, then that function is called, with
	400	$_ set to the value of the paragraph. This can be very useful for
	401	applying your own custom mutations to the POD to change it from human
	402	readable text into something your program can use.
	403
	404	After I added this function, I just kept on thinking of cool uses for
	405	it. The nice, succinct code you can make with it is one of
	406	Pod::Constant's strongest features.
	407
	408	Below are some examples.
	409
	410	=head1 EXAMPLES
	411
	412	=head2 Module Makefile.PL maintenance
	413
	414	Tired of keeping those module Makefile.PL's up to date? Note: This
	415	method seems to break dh-make-perl.
	416
	417	=head2 Example Makefile.PL
	418
	419	eval "use Pod::Constants";
	420	($Pod::Constants::VERSION >= 0.11)
	421	or die <<EOF
	422	####
	423	#### ERROR: This module requires Pod::Constants 0.11 or
	424	#### higher to be installed.
	425	####
	426	EOF
	427
	428	my ($VERSION, $NAME, $PREREQ_PM, $ABSTRACT, $AUTHOR);
	429	Pod::Constants::import_from_file
	430	(
	431	'MyTestModule.pm',
	432	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+)/ },
e18addae	433	'DEPENDENCIES' => ($PREREQ_PM = { }),
f46dd377 MG	434	-trim => 1,
	435	'NAME' => sub { $ABSTRACT=$_; ($NAME) = m/(\S+)/ },
	436	'AUTHOR' => \$AUTHOR,
	437	);
	438
	439	WriteMakefile
	440	(
db966dd0	441	'NAME' => $NAME,
f46dd377 MG	442	'PREREQ_PM' => $PREREQ_PM,
	443	'VERSION' => $VERSION,
	444	($] >= 5.005 ? ## Add these new keywords supported since 5.005
	445	(ABSTRACT => $ABSTRACT,
	446	AUTHOR => $AUTHOR) : ()),
	447	);
	448
	449	=head2 Corresponding Module
	450
	451	=head1 NAME
	452
	453	MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness
	454
	455	=head2 MODULE RELEASE
	456
	457	This is release 1.05 of this module.
	458
e18addae	459	=head2 DEPENDENCIES
f46dd377 MG	460
	461	The following modules are required to make this module:
	462
	463	Some::Module => 0.02
	464
	465	=head2 AUTHOR
	466
	467	Ima Twat <ima@twat.name>
	468
	469	=cut
	470
222de36b	471	our $VERSION;
f46dd377 MG	472	use Pod::Constants -trim => 1,
	473	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };
	474
	475	=head1 AUTHOR
	476
	477	Sam Vilain, <samv@cpan.org>
	478
	479	=head1 BUGS/TODO
	480
	481	I keep thinking it would be nice to be able to import an =item list
	482	into an array or something, eg for a program argument list. But I'm
	483	not too sure how it would be all that useful in practice; you'd end up
	484	putting the function names for callbacks in the pod or something
	485	(perhaps not all that bad).
	486
	487	Would this be useful?
	488
	489	Pod::Constants::import(Foo::SECTION => \$myvar);
	490
	491	Debug output is not very readable
	492
	493	=head1 PATCHES WELCOME
	494
	495	If you have any suggestions for enhancements, they are much more likely
	496	to happen if you submit them as a patch to the distribution.
	497
	498	Source is kept at
	499
	500	git://utsl.gen.nz/Pod-Constants
	501
f46dd377	502
49655cb6	503	=cut