[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 5.004;
use strict;

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

use vars qw($VERSION);
$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};
	}
}

BEGIN {
	Pod::Constants->import
		(
			SYNOPSIS => sub {
				eval pop @{[ grep /^\s*\$VERSION/, split /\n/, $_ ]}
			}
		)
};

1.4142;
__END__

=encoding utf-8

=head1 NAME

Pod::Constants - Include constants from POD

=head1 SYNOPSIS

 use vars qw($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

 use vars qw($VERSION);
 use Pod::Constants -trim => 1,
     'MODULE RELEASE' => sub { ($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
f46dd377 MG	8	use 5.004;
	9	use strict;
	10
	11	use base qw(Pod::Parser Exporter);
	12	use Data::Dumper;
	13	use Carp;
	14
	15	use vars qw($VERSION);
	16	$VERSION = 0.17;
	17
	18	# An ugly hack to go from caller() to the relevant parser state
	19	# variable
	20	my %parsers;
	21
	22	sub end_input {
db966dd0 MG	23	#my ($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	BEGIN {
	232	Pod::Constants->import
	233	(
	234	SYNOPSIS => sub {
	235	eval pop @{[ grep /^\s*\$VERSION/, split /\n/, $_ ]}
	236	}
	237	)
	238	};
	239
	240	1.4142;
	241	__END__
	242
	243	=encoding utf-8
	244
	245	=head1 NAME
	246
	247	Pod::Constants - Include constants from POD
	248
	249	=head1 SYNOPSIS
	250
	251	use vars qw($myvar $VERSION @myarray $html %myhash);
	252
	253	use Pod::Constants -trim => 1,
	254	'Pod Section Name' => \$myvar,
	255	'Version' => sub { eval },
	256	'Some list' => \@myarray,
	257	html => \$html,
	258	'Some hash' => \%myhash;
	259
	260	=head2 Pod Section Name
	261
	262	This string will be loaded into $myvar
	263
	264	=head2 Version
	265
	266	# This is an example of using a closure. $_ is set to the
	267	# contents of the paragraph. In this example, "eval" is
	268	# used to execute this code at run time.
	269	$VERSION = 0.17;
	270
	271	=head2 Some list
	272
	273	Each line from this section of the file
	274	will be placed into a separate array element.
	275	For example, this is $myarray[2].
	276
	277	=head2 Some hash
	278
	279	This text will not go into the hash, because
	280	it doesn't look like a definition list.
	281	key1 => Some value (this will go into the hash)
	282	var2 => Some Other value (so will this)
	283	wtf = This won't make it in.
	284
	285	=head2 %myhash's value after the above:
	286
	287	( key1 => "Some value (this will go into the hash)",
	288	var2 => "Some Other value (so will this)" )
	289
	290	=begin html <p>This text will be in $html</p>
	291
	292	=cut
	293
	294	=head1 DESCRIPTION
295
296	This module allows you to specify those constants that should be
297	documented in your POD, and pull them out a run time in a fairly
298	arbitrary fashion.
299
300	Pod::Constants uses Pod::Parser to do the parsing of the source file.
301	It has to open the source file it is called from, and does so directly
302	either by lookup in %INC or by assuming it is $0 if the caller is
303	"main" (or it can't find %INC{caller()})
304
305	=head2 ARBITARY DECISIONS
306
307	I have made this code only allow the "Pod Section Name" to match
308	`headN', `item', `for' and `begin' POD sections. If you have a good
309	reason why you think it should match other POD sections, drop me a
310	line and if I'm convinced I'll put it in the standard version.
311
312	For `for' and `begin' sections, only the first word is counted as
313	being a part of the specifier, as opposed to `headN' and `item', where
314	the entire rest of the line counts.
315
316	=head1 FUNCTIONS
317
318	=head2 import(@args)
319
320	This function is called when we are "use"'d. It determines the source
321	file by inspecting the value of caller() or $0.
322
323	The form of @args is HOOK => $where.
324
325	$where may be a scalar reference, in which case the contents of the
326	POD section called "HOOK" will be loaded into $where.
327
328	$where may be an array reference, in which case the contents of the
329	array will be the contents of the POD section called "HOOK", split
330	into lines.
331
332	$where may be a hash reference, in which case any lines with a "=>"
333	symbol present will have everything on the left have side of the =>
334	operator as keys and everything on the right as values. You do not
335	need to quote either, nor have trailing commas at the end of the
336	lines.
337
338	$where may be a code reference (sub { }), in which case the sub is
339	called when the hook is encountered. $_ is set to the value of the
340	POD paragraph.
341
342	You may also specify the behaviour of whitespace trimming; by default,
343	no trimming is done except on the HOOK names. Setting "-trim => 1"
344	turns on a package "global" (until the next time import is called)
345	that will trim the $_ sent for processing by the hook processing
346	function (be it a given function, or the built-in array/hash
347	splitters) for leading and trailing whitespace.
348
349	The name of HOOK is matched against any "=head1", "=head2", "=item",
350	"=for", "=begin" value. If you specify the special hooknames "*item",
351	"*head1", etc, then you will get a function that is run for every
352
353	Note that the supplied functions for array and hash splitting are
354	exactly equivalent to fairly simple Perl blocks:
355
356	Array:
357
358	HOOK => sub { @array = split /\n/, $_ }
359
360	Hash:
361
362	HOOK => sub {
363	%hash =
364	(map { map { s/^\s+\|\s+$//g; $_ } split /=>/, $_ }
365	(grep m/^
366	( (?:[^=]\|=[^>])+ ) # scan up to "=>"
367	=>
368	( (?:[^=]\|=[^>])+ =? )# don't allow more "=>"'s
369	$/x, split /\n/, $_));
370	}
371
372	Well, they're simple if you can grok map, a regular expression like
373	that and a functional programming style. If you can't I'm sure it is
374	probably voodoo to you.
375
376	Here's the procedural equivalent:
377
378	HOOK => sub {
379	for my $line (split /\n/, $_) {
380	my ($key, $value, $junk) = split /=>/, $line;
381	next if $junk;
382	$key =~ s/^\s+\|\s+$//g
383	$value =~ s/^\s+\|\s+$//g
384	$hash{$key} = $value;
385	}
386	},
387
388	=head2 import_from_file($filename, @args)
389
390	Very similar to straight "import", but you specify the source filename
391	explicitly.
392
393	=head2 add_hook(NAME => value)
394
395	This function adds another hook, it is useful for dynamic updating of
396	parsing through the document.
397
398	For an example, please see t/01-constants.t in the source
399	distribution. More detailed examples will be added in a later
400	release.
401
402	=head2 delete_hook(@list)
403
404	Deletes the named hooks. Companion function to add_hook
405
f46dd377 MG	406	=head2 CLOSURES AS DESTINATIONS
	407
	408	If the given value is a ref CODE, then that function is called, with
	409	$_ set to the value of the paragraph. This can be very useful for
	410	applying your own custom mutations to the POD to change it from human
	411	readable text into something your program can use.
	412
	413	After I added this function, I just kept on thinking of cool uses for
	414	it. The nice, succinct code you can make with it is one of
	415	Pod::Constant's strongest features.
	416
	417	Below are some examples.
	418
	419	=head1 EXAMPLES
	420
	421	=head2 Module Makefile.PL maintenance
	422
	423	Tired of keeping those module Makefile.PL's up to date? Note: This
	424	method seems to break dh-make-perl.
	425
	426	=head2 Example Makefile.PL
	427
	428	eval "use Pod::Constants";
	429	($Pod::Constants::VERSION >= 0.11)
	430	or die <<EOF
	431	####
	432	#### ERROR: This module requires Pod::Constants 0.11 or
	433	#### higher to be installed.
	434	####
	435	EOF
	436
	437	my ($VERSION, $NAME, $PREREQ_PM, $ABSTRACT, $AUTHOR);
	438	Pod::Constants::import_from_file
	439	(
	440	'MyTestModule.pm',
	441	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+)/ },
e18addae	442	'DEPENDENCIES' => ($PREREQ_PM = { }),
f46dd377 MG	443	-trim => 1,
	444	'NAME' => sub { $ABSTRACT=$_; ($NAME) = m/(\S+)/ },
	445	'AUTHOR' => \$AUTHOR,
	446	);
	447
	448	WriteMakefile
	449	(
db966dd0	450	'NAME' => $NAME,
f46dd377 MG	451	'PREREQ_PM' => $PREREQ_PM,
	452	'VERSION' => $VERSION,
	453	($] >= 5.005 ? ## Add these new keywords supported since 5.005
	454	(ABSTRACT => $ABSTRACT,
	455	AUTHOR => $AUTHOR) : ()),
	456	);
	457
	458	=head2 Corresponding Module
	459
	460	=head1 NAME
	461
	462	MyTestModule - Demonstrate Pod::Constant's Makefile.PL usefulness
	463
	464	=head2 MODULE RELEASE
	465
	466	This is release 1.05 of this module.
	467
e18addae	468	=head2 DEPENDENCIES
f46dd377 MG	469
	470	The following modules are required to make this module:
	471
	472	Some::Module => 0.02
	473
	474	=head2 AUTHOR
	475
	476	Ima Twat <ima@twat.name>
	477
	478	=cut
	479
	480	use vars qw($VERSION);
	481	use Pod::Constants -trim => 1,
	482	'MODULE RELEASE' => sub { ($VERSION) = m/(\d+\.\d+) or die };
	483
	484	=head1 AUTHOR
	485
	486	Sam Vilain, <samv@cpan.org>
	487
	488	=head1 BUGS/TODO
	489
	490	I keep thinking it would be nice to be able to import an =item list
	491	into an array or something, eg for a program argument list. But I'm
	492	not too sure how it would be all that useful in practice; you'd end up
	493	putting the function names for callbacks in the pod or something
	494	(perhaps not all that bad).
	495
	496	Would this be useful?
	497
	498	Pod::Constants::import(Foo::SECTION => \$myvar);
	499
	500	Debug output is not very readable
	501
	502	=head1 PATCHES WELCOME
	503
	504	If you have any suggestions for enhancements, they are much more likely
	505	to happen if you submit them as a patch to the distribution.
	506
	507	Source is kept at
	508
	509	git://utsl.gen.nz/Pod-Constants
	510
f46dd377	511
49655cb6	512	=cut