xref: /openbsd-src/gnu/usr.bin/perl/cpan/podlators/lib/Pod/Text.pm (revision a0747c9f67a4ae71ccb71e62a28d1ea19e06a63c)

# Convert POD data to formatted text.
#
# This module converts POD to formatted text.  It replaces the old Pod::Text
# module that came with versions of Perl prior to 5.6.0 and attempts to match
# its output except for some specific circumstances where other decisions
# seemed to produce better output.  It uses Pod::Parser and is designed to be
# very easy to subclass.
#
# SPDX-License-Identifier: GPL-1.0-or-later OR Artistic-1.0-Perl

##############################################################################
# Modules and declarations
##############################################################################

package Pod::Text;

use 5.008;
use strict;
use warnings;

use vars qw(@ISA @EXPORT %ESCAPES $VERSION);

use Carp qw(carp croak);
use Encode qw(encode);
use Exporter ();
use Pod::Simple ();

@ISA = qw(Pod::Simple Exporter);

# We have to export pod2text for backward compatibility.
@EXPORT = qw(pod2text);

$VERSION = '4.14';

# Ensure that $Pod::Simple::nbsp and $Pod::Simple::shy are available.  Code
# taken from Pod::Simple 3.32, but was only added in 3.30.
my ($NBSP, $SHY);
if ($Pod::Simple::VERSION ge 3.30) {
    $NBSP = $Pod::Simple::nbsp;
    $SHY  = $Pod::Simple::shy;
} else {
    $NBSP = chr utf8::unicode_to_native(0xA0);
    $SHY  = chr utf8::unicode_to_native(0xAD);
}

##############################################################################
# Initialization
##############################################################################

# This function handles code blocks.  It's registered as a callback to
# Pod::Simple and therefore doesn't work as a regular method call, but all it
# does is call output_code with the line.
sub handle_code {
    my ($line, $number, $parser) = @_;
    $parser->output_code ($line . "\n");
}

# Initialize the object and set various Pod::Simple options that we need.
# Here, we also process any additional options passed to the constructor or
# set up defaults if none were given.  Note that all internal object keys are
# in all-caps, reserving all lower-case object keys for Pod::Simple and user
# arguments.
sub new {
    my $class = shift;
    my $self = $class->SUPER::new;

    # Tell Pod::Simple to handle S<> by automatically inserting &nbsp;.
    $self->nbsp_for_S (1);

    # Tell Pod::Simple to keep whitespace whenever possible.
    if ($self->can ('preserve_whitespace')) {
        $self->preserve_whitespace (1);
    } else {
        $self->fullstop_space_harden (1);
    }

    # The =for and =begin targets that we accept.
    $self->accept_targets (qw/text TEXT/);

    # Ensure that contiguous blocks of code are merged together.  Otherwise,
    # some of the guesswork heuristics don't work right.
    $self->merge_text (1);

    # Pod::Simple doesn't do anything useful with our arguments, but we want
    # to put them in our object as hash keys and values.  This could cause
    # problems if we ever clash with Pod::Simple's own internal class
    # variables.
    my %opts = @_;
    my @opts = map { ("opt_$_", $opts{$_}) } keys %opts;
    %$self = (%$self, @opts);

    # Send errors to stderr if requested.
    if ($$self{opt_stderr} and not $$self{opt_errors}) {
        $$self{opt_errors} = 'stderr';
    }
    delete $$self{opt_stderr};

    # Validate the errors parameter and act on it.
    if (not defined $$self{opt_errors}) {
        $$self{opt_errors} = 'pod';
    }
    if ($$self{opt_errors} eq 'stderr' || $$self{opt_errors} eq 'die') {
        $self->no_errata_section (1);
        $self->complain_stderr (1);
        if ($$self{opt_errors} eq 'die') {
            $$self{complain_die} = 1;
        }
    } elsif ($$self{opt_errors} eq 'pod') {
        $self->no_errata_section (0);
        $self->complain_stderr (0);
    } elsif ($$self{opt_errors} eq 'none') {
        $self->no_errata_section (1);
        $self->no_whining (1);
    } else {
        croak (qq(Invalid errors setting: "$$self{errors}"));
    }
    delete $$self{errors};

    # Initialize various things from our parameters.
    $$self{opt_alt}      = 0  unless defined $$self{opt_alt};
    $$self{opt_indent}   = 4  unless defined $$self{opt_indent};
    $$self{opt_margin}   = 0  unless defined $$self{opt_margin};
    $$self{opt_loose}    = 0  unless defined $$self{opt_loose};
    $$self{opt_sentence} = 0  unless defined $$self{opt_sentence};
    $$self{opt_width}    = 76 unless defined $$self{opt_width};

    # Figure out what quotes we'll be using for C<> text.
    $$self{opt_quotes} ||= '"';
    if ($$self{opt_quotes} eq 'none') {
        $$self{LQUOTE} = $$self{RQUOTE} = '';
    } elsif (length ($$self{opt_quotes}) == 1) {
        $$self{LQUOTE} = $$self{RQUOTE} = $$self{opt_quotes};
    } elsif (length ($$self{opt_quotes}) % 2 == 0) {
        my $length = length ($$self{opt_quotes}) / 2;
        $$self{LQUOTE} = substr ($$self{opt_quotes}, 0, $length);
        $$self{RQUOTE} = substr ($$self{opt_quotes}, $length);
    } else {
        croak qq(Invalid quote specification "$$self{opt_quotes}");
    }

    # If requested, do something with the non-POD text.
    $self->code_handler (\&handle_code) if $$self{opt_code};

    # Return the created object.
    return $self;
}

##############################################################################
# Core parsing
##############################################################################

# This is the glue that connects the code below with Pod::Simple itself.  The
# goal is to convert the event stream coming from the POD parser into method
# calls to handlers once the complete content of a tag has been seen.  Each
# paragraph or POD command will have textual content associated with it, and
# as soon as all of a paragraph or POD command has been seen, that content
# will be passed in to the corresponding method for handling that type of
# object.  The exceptions are handlers for lists, which have opening tag
# handlers and closing tag handlers that will be called right away.
#
# The internal hash key PENDING is used to store the contents of a tag until
# all of it has been seen.  It holds a stack of open tags, each one
# represented by a tuple of the attributes hash for the tag and the contents
# of the tag.

# Add a block of text to the contents of the current node, formatting it
# according to the current formatting instructions as we do.
sub _handle_text {
    my ($self, $text) = @_;
    my $tag = $$self{PENDING}[-1];
    $$tag[1] .= $text;
}

# Given an element name, get the corresponding method name.
sub method_for_element {
    my ($self, $element) = @_;
    $element =~ tr/-/_/;
    $element =~ tr/A-Z/a-z/;
    $element =~ tr/_a-z0-9//cd;
    return $element;
}

# Handle the start of a new element.  If cmd_element is defined, assume that
# we need to collect the entire tree for this element before passing it to the
# element method, and create a new tree into which we'll collect blocks of
# text and nested elements.  Otherwise, if start_element is defined, call it.
sub _handle_element_start {
    my ($self, $element, $attrs) = @_;
    my $method = $self->method_for_element ($element);

    # If we have a command handler, we need to accumulate the contents of the
    # tag before calling it.
    if ($self->can ("cmd_$method")) {
        push (@{ $$self{PENDING} }, [ $attrs, '' ]);
    } elsif ($self->can ("start_$method")) {
        my $method = 'start_' . $method;
        $self->$method ($attrs, '');
    }
}

# Handle the end of an element.  If we had a cmd_ method for this element,
# this is where we pass along the text that we've accumulated.  Otherwise, if
# we have an end_ method for the element, call that.
sub _handle_element_end {
    my ($self, $element) = @_;
    my $method = $self->method_for_element ($element);

    # If we have a command handler, pull off the pending text and pass it to
    # the handler along with the saved attribute hash.
    if ($self->can ("cmd_$method")) {
        my $tag = pop @{ $$self{PENDING} };
        my $method = 'cmd_' . $method;
        my $text = $self->$method (@$tag);
        if (defined $text) {
            if (@{ $$self{PENDING} } > 1) {
                $$self{PENDING}[-1][1] .= $text;
            } else {
                $self->output ($text);
            }
        }
    } elsif ($self->can ("end_$method")) {
        my $method = 'end_' . $method;
        $self->$method ();
    }
}

##############################################################################
# Output formatting
##############################################################################

# Wrap a line, indenting by the current left margin.  We can't use Text::Wrap
# because it plays games with tabs.  We can't use formline, even though we'd
# really like to, because it screws up non-printing characters.  So we have to
# do the wrapping ourselves.
sub wrap {
    my $self = shift;
    local $_ = shift;
    my $output = '';
    my $spaces = ' ' x $$self{MARGIN};
    my $width = $$self{opt_width} - $$self{MARGIN};
    while (length > $width) {
        if (s/^([^\n]{0,$width})[ \t\n]+// || s/^([^\n]{$width})//) {
            $output .= $spaces . $1 . "\n";
        } else {
            last;
        }
    }
    $output .= $spaces . $_;
    $output =~ s/\s+$/\n\n/;
    return $output;
}

# Reformat a paragraph of text for the current margin.  Takes the text to
# reformat and returns the formatted text.
sub reformat {
    my $self = shift;
    local $_ = shift;

    # If we're trying to preserve two spaces after sentences, do some munging
    # to support that.  Otherwise, smash all repeated whitespace.  Be careful
    # not to use \s here, which in Unicode input may match non-breaking spaces
    # that we don't want to smash.
    if ($$self{opt_sentence}) {
        s/ +$//mg;
        s/\.\n/. \n/g;
        s/\n/ /g;
        s/   +/  /g;
    } else {
        s/[ \t\n]+/ /g;
    }
    return $self->wrap ($_);
}

# Output text to the output device.  Replace non-breaking spaces with spaces
# and soft hyphens with nothing, and then try to fix the output encoding if
# necessary to match the input encoding unless UTF-8 output is forced.  This
# preserves the traditional pass-through behavior of Pod::Text.
sub output {
    my ($self, @text) = @_;
    my $text = join ('', @text);
    if ($NBSP) {
        $text =~ s/$NBSP/ /g;
    }
    if ($SHY) {
        $text =~ s/$SHY//g;
    }
    unless ($$self{opt_utf8}) {
        my $encoding = $$self{encoding} || '';
        if ($encoding && $encoding ne $$self{ENCODING}) {
            $$self{ENCODING} = $encoding;
            eval { binmode ($$self{output_fh}, ":encoding($encoding)") };
        }
    }
    if ($$self{ENCODE}) {
        print { $$self{output_fh} } encode ('UTF-8', $text);
    } else {
        print { $$self{output_fh} } $text;
    }
}

# Output a block of code (something that isn't part of the POD text).  Called
# by preprocess_paragraph only if we were given the code option.  Exists here
# only so that it can be overridden by subclasses.
sub output_code { $_[0]->output ($_[1]) }

##############################################################################
# Document initialization
##############################################################################

# Set up various things that have to be initialized on a per-document basis.
sub start_document {
    my ($self, $attrs) = @_;
    if ($$attrs{contentless} && !$$self{ALWAYS_EMIT_SOMETHING}) {
        $$self{CONTENTLESS} = 1;
    } else {
        delete $$self{CONTENTLESS};
    }
    my $margin = $$self{opt_indent} + $$self{opt_margin};

    # Initialize a few per-document variables.
    $$self{INDENTS} = [];       # Stack of indentations.
    $$self{MARGIN}  = $margin;  # Default left margin.
    $$self{PENDING} = [[]];     # Pending output.

    # We have to redo encoding handling for each document.
    $$self{ENCODING} = '';

    # When UTF-8 output is set, check whether our output file handle already
    # has a PerlIO encoding layer set.  If it does not, we'll need to encode
    # our output before printing it (handled in the output() sub).
    $$self{ENCODE} = 0;
    if ($$self{opt_utf8}) {
        $$self{ENCODE} = 1;
        eval {
            my @options = (output => 1, details => 1);
            my $flag = (PerlIO::get_layers ($$self{output_fh}, @options))[-1];
            if ($flag && ($flag & PerlIO::F_UTF8 ())) {
                $$self{ENCODE} = 0;
                $$self{ENCODING} = 'UTF-8';
            }
        };
    }

    return '';
}

# Handle the end of the document.  The only thing we do is handle dying on POD
# errors, since Pod::Parser currently doesn't.
sub end_document {
    my ($self) = @_;
    if ($$self{complain_die} && $self->errors_seen) {
        croak ("POD document had syntax errors");
    }
}

##############################################################################
# Text blocks
##############################################################################

# Intended for subclasses to override, this method returns text with any
# non-printing formatting codes stripped out so that length() correctly
# returns the length of the text.  For basic Pod::Text, it does nothing.
sub strip_format {
    my ($self, $string) = @_;
    return $string;
}

# This method is called whenever an =item command is complete (in other words,
# we've seen its associated paragraph or know for certain that it doesn't have
# one).  It gets the paragraph associated with the item as an argument.  If
# that argument is empty, just output the item tag; if it contains a newline,
# output the item tag followed by the newline.  Otherwise, see if there's
# enough room for us to output the item tag in the margin of the text or if we
# have to put it on a separate line.
sub item {
    my ($self, $text) = @_;
    my $tag = $$self{ITEM};
    unless (defined $tag) {
        carp "Item called without tag";
        return;
    }
    undef $$self{ITEM};

    # Calculate the indentation and margin.  $fits is set to true if the tag
    # will fit into the margin of the paragraph given our indentation level.
    my $indent = $$self{INDENTS}[-1];
    $indent = $$self{opt_indent} unless defined $indent;
    my $margin = ' ' x $$self{opt_margin};
    my $tag_length = length ($self->strip_format ($tag));
    my $fits = ($$self{MARGIN} - $indent >= $tag_length + 1);

    # If the tag doesn't fit, or if we have no associated text, print out the
    # tag separately.  Otherwise, put the tag in the margin of the paragraph.
    if (!$text || $text =~ /^\s+$/ || !$fits) {
        my $realindent = $$self{MARGIN};
        $$self{MARGIN} = $indent;
        my $output = $self->reformat ($tag);
        $output =~ s/^$margin /$margin:/ if ($$self{opt_alt} && $indent > 0);
        $output =~ s/\n*$/\n/;

        # If the text is just whitespace, we have an empty item paragraph;
        # this can result from =over/=item/=back without any intermixed
        # paragraphs.  Insert some whitespace to keep the =item from merging
        # into the next paragraph.
        $output .= "\n" if $text && $text =~ /^\s*$/;

        $self->output ($output);
        $$self{MARGIN} = $realindent;
        $self->output ($self->reformat ($text)) if ($text && $text =~ /\S/);
    } else {
        my $space = ' ' x $indent;
        $space =~ s/^$margin /$margin:/ if $$self{opt_alt};
        $text = $self->reformat ($text);
        $text =~ s/^$margin /$margin:/ if ($$self{opt_alt} && $indent > 0);
        my $tagspace = ' ' x $tag_length;
        $text =~ s/^($space)$tagspace/$1$tag/ or warn "Bizarre space in item";
        $self->output ($text);
    }
}

# Handle a basic block of text.  The only tricky thing here is that if there
# is a pending item tag, we need to format this as an item paragraph.
sub cmd_para {
    my ($self, $attrs, $text) = @_;
    $text =~ s/\s+$/\n/;
    if (defined $$self{ITEM}) {
        $self->item ($text . "\n");
    } else {
        $self->output ($self->reformat ($text . "\n"));
    }
    return '';
}

# Handle a verbatim paragraph.  Just print it out, but indent it according to
# our margin.
sub cmd_verbatim {
    my ($self, $attrs, $text) = @_;
    $self->item if defined $$self{ITEM};
    return if $text =~ /^\s*$/;
    $text =~ s/^(\n*)([ \t]*\S+)/$1 . (' ' x $$self{MARGIN}) . $2/gme;
    $text =~ s/\s*$/\n\n/;
    $self->output ($text);
    return '';
}

# Handle literal text (produced by =for and similar constructs).  Just output
# it with the minimum of changes.
sub cmd_data {
    my ($self, $attrs, $text) = @_;
    $text =~ s/^\n+//;
    $text =~ s/\n{0,2}$/\n/;
    $self->output ($text);
    return '';
}

##############################################################################
# Headings
##############################################################################

# The common code for handling all headers.  Takes the header text, the
# indentation, and the surrounding marker for the alt formatting method.
sub heading {
    my ($self, $text, $indent, $marker) = @_;
    $self->item ("\n\n") if defined $$self{ITEM};
    $text =~ s/\s+$//;
    if ($$self{opt_alt}) {
        my $closemark = reverse (split (//, $marker));
        my $margin = ' ' x $$self{opt_margin};
        $self->output ("\n" . "$margin$marker $text $closemark" . "\n\n");
    } else {
        $text .= "\n" if $$self{opt_loose};
        my $margin = ' ' x ($$self{opt_margin} + $indent);
        $self->output ($margin . $text . "\n");
    }
    return '';
}

# First level heading.
sub cmd_head1 {
    my ($self, $attrs, $text) = @_;
    $self->heading ($text, 0, '====');
}

# Second level heading.
sub cmd_head2 {
    my ($self, $attrs, $text) = @_;
    $self->heading ($text, $$self{opt_indent} / 2, '==  ');
}

# Third level heading.
sub cmd_head3 {
    my ($self, $attrs, $text) = @_;
    $self->heading ($text, $$self{opt_indent} * 2 / 3 + 0.5, '=   ');
}

# Fourth level heading.
sub cmd_head4 {
    my ($self, $attrs, $text) = @_;
    $self->heading ($text, $$self{opt_indent} * 3 / 4 + 0.5, '-   ');
}

##############################################################################
# List handling
##############################################################################

# Handle the beginning of an =over block.  Takes the type of the block as the
# first argument, and then the attr hash.  This is called by the handlers for
# the four different types of lists (bullet, number, text, and block).
sub over_common_start {
    my ($self, $attrs) = @_;
    $self->item ("\n\n") if defined $$self{ITEM};

    # Find the indentation level.
    my $indent = $$attrs{indent};
    unless (defined ($indent) && $indent =~ /^\s*[-+]?\d{1,4}\s*$/) {
        $indent = $$self{opt_indent};
    }

    # Add this to our stack of indents and increase our current margin.
    push (@{ $$self{INDENTS} }, $$self{MARGIN});
    $$self{MARGIN} += ($indent + 0);
    return '';
}

# End an =over block.  Takes no options other than the class pointer.  Output
# any pending items and then pop one level of indentation.
sub over_common_end {
    my ($self) = @_;
    $self->item ("\n\n") if defined $$self{ITEM};
    $$self{MARGIN} = pop @{ $$self{INDENTS} };
    return '';
}

# Dispatch the start and end calls as appropriate.
sub start_over_bullet { $_[0]->over_common_start ($_[1]) }
sub start_over_number { $_[0]->over_common_start ($_[1]) }
sub start_over_text   { $_[0]->over_common_start ($_[1]) }
sub start_over_block  { $_[0]->over_common_start ($_[1]) }
sub end_over_bullet { $_[0]->over_common_end }
sub end_over_number { $_[0]->over_common_end }
sub end_over_text   { $_[0]->over_common_end }
sub end_over_block  { $_[0]->over_common_end }

# The common handler for all item commands.  Takes the type of the item, the
# attributes, and then the text of the item.
sub item_common {
    my ($self, $type, $attrs, $text) = @_;
    $self->item if defined $$self{ITEM};

    # Clean up the text.  We want to end up with two variables, one ($text)
    # which contains any body text after taking out the item portion, and
    # another ($item) which contains the actual item text.  Note the use of
    # the internal Pod::Simple attribute here; that's a potential land mine.
    $text =~ s/\s+$//;
    my ($item, $index);
    if ($type eq 'bullet') {
        $item = '*';
    } elsif ($type eq 'number') {
        $item = $$attrs{'~orig_content'};
    } else {
        $item = $text;
        $item =~ s/\s*\n\s*/ /g;
        $text = '';
    }
    $$self{ITEM} = $item;

    # If body text for this item was included, go ahead and output that now.
    if ($text) {
        $text =~ s/\s*$/\n/;
        $self->item ($text);
    }
    return '';
}

# Dispatch the item commands to the appropriate place.
sub cmd_item_bullet { my $self = shift; $self->item_common ('bullet', @_) }
sub cmd_item_number { my $self = shift; $self->item_common ('number', @_) }
sub cmd_item_text   { my $self = shift; $self->item_common ('text',   @_) }
sub cmd_item_block  { my $self = shift; $self->item_common ('block',  @_) }

##############################################################################
# Formatting codes
##############################################################################

# The simple ones.
sub cmd_b { return $_[0]{alt} ? "``$_[2]''" : $_[2] }
sub cmd_f { return $_[0]{alt} ? "\"$_[2]\"" : $_[2] }
sub cmd_i { return '*' . $_[2] . '*' }
sub cmd_x { return '' }

# Apply a whole bunch of messy heuristics to not quote things that don't
# benefit from being quoted.  These originally come from Barrie Slaymaker and
# largely duplicate code in Pod::Man.
sub cmd_c {
    my ($self, $attrs, $text) = @_;

    # A regex that matches the portion of a variable reference that's the
    # array or hash index, separated out just because we want to use it in
    # several places in the following regex.
    my $index = '(?: \[.*\] | \{.*\} )?';

    # Check for things that we don't want to quote, and if we find any of
    # them, return the string with just a font change and no quoting.
    $text =~ m{
      ^\s*
      (?:
         ( [\'\`\"] ) .* \1                             # already quoted
       | \` .* \'                                       # `quoted'
       | \$+ [\#^]? \S $index                           # special ($^Foo, $")
       | [\$\@%&*]+ \#? [:\'\w]+ $index                 # plain var or func
       | [\$\@%&*]* [:\'\w]+ (?: -> )? \(\s*[^\s,]\s*\) # 0/1-arg func call
       | [+-]? ( \d[\d.]* | \.\d+ ) (?: [eE][+-]?\d+ )? # a number
       | 0x [a-fA-F\d]+                                 # a hex constant
      )
      \s*\z
     }xo && return $text;

    # If we didn't return, go ahead and quote the text.
    return $$self{opt_alt}
        ? "``$text''"
        : "$$self{LQUOTE}$text$$self{RQUOTE}";
}

# Links reduce to the text that we're given, wrapped in angle brackets if it's
# a URL.
sub cmd_l {
    my ($self, $attrs, $text) = @_;
    if ($$attrs{type} eq 'url') {
        if (not defined($$attrs{to}) or $$attrs{to} eq $text) {
            return "<$text>";
        } elsif ($$self{opt_nourls}) {
            return $text;
        } else {
            return "$text <$$attrs{to}>";
        }
    } else {
        return $text;
    }
}

##############################################################################
# Backwards compatibility
##############################################################################

# The old Pod::Text module did everything in a pod2text() function.  This
# tries to provide the same interface for legacy applications.
sub pod2text {
    my @args;

    # This is really ugly; I hate doing option parsing in the middle of a
    # module.  But the old Pod::Text module supported passing flags to its
    # entry function, so handle -a and -<number>.
    while ($_[0] =~ /^-/) {
        my $flag = shift;
        if    ($flag eq '-a')       { push (@args, alt => 1)    }
        elsif ($flag =~ /^-(\d+)$/) { push (@args, width => $1) }
        else {
            unshift (@_, $flag);
            last;
        }
    }

    # Now that we know what arguments we're using, create the parser.
    my $parser = Pod::Text->new (@args);

    # If two arguments were given, the second argument is going to be a file
    # handle.  That means we want to call parse_from_filehandle(), which means
    # we need to turn the first argument into a file handle.  Magic open will
    # handle the <&STDIN case automagically.
    if (defined $_[1]) {
        my @fhs = @_;
        local *IN;
        unless (open (IN, $fhs[0])) {
            croak ("Can't open $fhs[0] for reading: $!\n");
            return;
        }
        $fhs[0] = \*IN;
        $parser->output_fh ($fhs[1]);
        my $retval = $parser->parse_file ($fhs[0]);
        my $fh = $parser->output_fh ();
        close $fh;
        return $retval;
    } else {
        $parser->output_fh (\*STDOUT);
        return $parser->parse_file (@_);
    }
}

# Reset the underlying Pod::Simple object between calls to parse_from_file so
# that the same object can be reused to convert multiple pages.
sub parse_from_file {
    my $self = shift;
    $self->reinit;

    # Fake the old cutting option to Pod::Parser.  This fiddles with internal
    # Pod::Simple state and is quite ugly; we need a better approach.
    if (ref ($_[0]) eq 'HASH') {
        my $opts = shift @_;
        if (defined ($$opts{-cutting}) && !$$opts{-cutting}) {
            $$self{in_pod} = 1;
            $$self{last_was_blank} = 1;
        }
    }

    # Do the work.
    my $retval = $self->Pod::Simple::parse_from_file (@_);

    # Flush output, since Pod::Simple doesn't do this.  Ideally we should also
    # close the file descriptor if we had to open one, but we can't easily
    # figure this out.
    my $fh = $self->output_fh ();
    my $oldfh = select $fh;
    my $oldflush = $|;
    $| = 1;
    print $fh '';
    $| = $oldflush;
    select $oldfh;
    return $retval;
}

# Pod::Simple failed to provide this backward compatibility function, so
# implement it ourselves.  File handles are one of the inputs that
# parse_from_file supports.
sub parse_from_filehandle {
    my $self = shift;
    $self->parse_from_file (@_);
}

# Pod::Simple's parse_file doesn't set output_fh.  Wrap the call and do so
# ourself unless it was already set by the caller, since our documentation has
# always said that this should work.
sub parse_file {
    my ($self, $in) = @_;
    unless (defined $$self{output_fh}) {
        $self->output_fh (\*STDOUT);
    }
    return $self->SUPER::parse_file ($in);
}

# Do the same for parse_lines, just to be polite.  Pod::Simple's man page
# implies that the caller is responsible for setting this, but I don't see any
# reason not to set a default.
sub parse_lines {
    my ($self, @lines) = @_;
    unless (defined $$self{output_fh}) {
        $self->output_fh (\*STDOUT);
    }
    return $self->SUPER::parse_lines (@lines);
}

# Likewise for parse_string_document.
sub parse_string_document {
    my ($self, $doc) = @_;
    unless (defined $$self{output_fh}) {
        $self->output_fh (\*STDOUT);
    }
    return $self->SUPER::parse_string_document ($doc);
}

##############################################################################
# Module return value and documentation
##############################################################################

1;
__END__

=for stopwords
alt stderr Allbery Sean Burke's Christiansen UTF-8 pre-Unicode utf8 nourls
parsers

=head1 NAME

Pod::Text - Convert POD data to formatted text

=head1 SYNOPSIS

    use Pod::Text;
    my $parser = Pod::Text->new (sentence => 1, width => 78);

    # Read POD from STDIN and write to STDOUT.
    $parser->parse_from_filehandle;

    # Read POD from file.pod and write to file.txt.
    $parser->parse_from_file ('file.pod', 'file.txt');

=head1 DESCRIPTION

Pod::Text is a module that can convert documentation in the POD format
(the preferred language for documenting Perl) into formatted text.  It
uses no special formatting controls or codes whatsoever, and its output is
therefore suitable for nearly any device.

As a derived class from Pod::Simple, Pod::Text supports the same methods and
interfaces.  See L<Pod::Simple> for all the details; briefly, one creates a
new parser with C<< Pod::Text->new() >> and then normally calls parse_file().

new() can take options, in the form of key/value pairs, that control the
behavior of the parser.  The currently recognized options are:

=over 4

=item alt

If set to a true value, selects an alternate output format that, among other
things, uses a different heading style and marks C<=item> entries with a
colon in the left margin.  Defaults to false.

=item code

If set to a true value, the non-POD parts of the input file will be included
in the output.  Useful for viewing code documented with POD blocks with the
POD rendered and the code left intact.

=item errors

How to report errors.  C<die> says to throw an exception on any POD
formatting error.  C<stderr> says to report errors on standard error, but
not to throw an exception.  C<pod> says to include a POD ERRORS section
in the resulting documentation summarizing the errors.  C<none> ignores
POD errors entirely, as much as possible.

The default is C<pod>.

=item indent

The number of spaces to indent regular text, and the default indentation for
C<=over> blocks.  Defaults to 4.

=item loose

If set to a true value, a blank line is printed after a C<=head1> heading.
If set to false (the default), no blank line is printed after C<=head1>,
although one is still printed after C<=head2>.  This is the default because
it's the expected formatting for manual pages; if you're formatting
arbitrary text documents, setting this to true may result in more pleasing
output.

=item margin

The width of the left margin in spaces.  Defaults to 0.  This is the margin
for all text, including headings, not the amount by which regular text is
indented; for the latter, see the I<indent> option.  To set the right
margin, see the I<width> option.

=item nourls

Normally, LZ<><> formatting codes with a URL but anchor text are formatted
to show both the anchor text and the URL.  In other words:

    L<foo|http://example.com/>

is formatted as:

    foo <http://example.com/>

This option, if set to a true value, suppresses the URL when anchor text
is given, so this example would be formatted as just C<foo>.  This can
produce less cluttered output in cases where the URLs are not particularly
important.

=item quotes

Sets the quote marks used to surround CE<lt>> text.  If the value is a
single character, it is used as both the left and right quote.  Otherwise,
it is split in half, and the first half of the string is used as the left
quote and the second is used as the right quote.

This may also be set to the special value C<none>, in which case no quote
marks are added around CE<lt>> text.

=item sentence

If set to a true value, Pod::Text will assume that each sentence ends in two
spaces, and will try to preserve that spacing.  If set to false, all
consecutive whitespace in non-verbatim paragraphs is compressed into a
single space.  Defaults to false.

=item stderr

Send error messages about invalid POD to standard error instead of
appending a POD ERRORS section to the generated output.  This is
equivalent to setting C<errors> to C<stderr> if C<errors> is not already
set.  It is supported for backward compatibility.

=item utf8

By default, Pod::Text uses the same output encoding as the input encoding
of the POD source (provided that Perl was built with PerlIO; otherwise, it
doesn't encode its output).  If this option is given, the output encoding
is forced to UTF-8.

Be aware that, when using this option, the input encoding of your POD
source should be properly declared unless it's US-ASCII.  Pod::Simple will
attempt to guess the encoding and may be successful if it's Latin-1 or
UTF-8, but it will produce warnings.  Use the C<=encoding> command to
declare the encoding.  See L<perlpod(1)> for more information.

=item width

The column at which to wrap text on the right-hand side.  Defaults to 76.

=back

The standard Pod::Simple method parse_file() takes one argument naming the
POD file to read from.  By default, the output is sent to C<STDOUT>, but
this can be changed with the output_fh() method.

The standard Pod::Simple method parse_from_file() takes up to two
arguments, the first being the input file to read POD from and the second
being the file to write the formatted output to.

You can also call parse_lines() to parse an array of lines or
parse_string_document() to parse a document already in memory.  As with
parse_file(), parse_lines() and parse_string_document() default to sending
their output to C<STDOUT> unless changed with the output_fh() method.  Be
aware that parse_lines() and parse_string_document() both expect raw bytes,
not decoded characters.

To put the output from any parse method into a string instead of a file
handle, call the output_string() method instead of output_fh().

See L<Pod::Simple> for more specific details on the methods available to
all derived parsers.

=head1 DIAGNOSTICS

=over 4

=item Bizarre space in item

=item Item called without tag

(W) Something has gone wrong in internal C<=item> processing.  These
messages indicate a bug in Pod::Text; you should never see them.

=item Can't open %s for reading: %s

(F) Pod::Text was invoked via the compatibility mode pod2text() interface
and the input file it was given could not be opened.

=item Invalid errors setting "%s"

(F) The C<errors> parameter to the constructor was set to an unknown value.

=item Invalid quote specification "%s"

(F) The quote specification given (the C<quotes> option to the
constructor) was invalid.  A quote specification must be either one
character long or an even number (greater than one) characters long.

=item POD document had syntax errors

(F) The POD document being formatted had syntax errors and the C<errors>
option was set to C<die>.

=back

=head1 BUGS

Encoding handling assumes that PerlIO is available and does not work
properly if it isn't.  The C<utf8> option is therefore not supported
unless Perl is built with PerlIO support.

=head1 CAVEATS

If Pod::Text is given the C<utf8> option, the encoding of its output file
handle will be forced to UTF-8 if possible, overriding any existing
encoding.  This will be done even if the file handle is not created by
Pod::Text and was passed in from outside.  This maintains consistency
regardless of PERL_UNICODE and other settings.

If the C<utf8> option is not given, the encoding of its output file handle
will be forced to the detected encoding of the input POD, which preserves
whatever the input text is.  This ensures backward compatibility with
earlier, pre-Unicode versions of this module, without large numbers of
Perl warnings.

This is not ideal, but it seems to be the best compromise.  If it doesn't
work for you, please let me know the details of how it broke.

=head1 NOTES

This is a replacement for an earlier Pod::Text module written by Tom
Christiansen.  It has a revamped interface, since it now uses Pod::Simple,
but an interface roughly compatible with the old Pod::Text::pod2text()
function is still available.  Please change to the new calling convention,
though.

The original Pod::Text contained code to do formatting via termcap
sequences, although it wasn't turned on by default and it was problematic to
get it to work at all.  This rewrite doesn't even try to do that, but a
subclass of it does.  Look for L<Pod::Text::Termcap>.

=head1 AUTHOR

Russ Allbery <rra@cpan.org>, based I<very> heavily on the original
Pod::Text by Tom Christiansen <tchrist@mox.perl.com> and its conversion to
Pod::Parser by Brad Appleton <bradapp@enteract.com>.  Sean Burke's initial
conversion of Pod::Man to use Pod::Simple provided much-needed guidance on
how to use Pod::Simple.

=head1 COPYRIGHT AND LICENSE

Copyright 1999-2002, 2004, 2006, 2008-2009, 2012-2016, 2018-2019 Russ Allbery
<rra@cpan.org>

This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.

=head1 SEE ALSO

L<Pod::Simple>, L<Pod::Text::Termcap>, L<perlpod(1)>, L<pod2text(1)>

The current version of this module is always available from its web site at
L<https://www.eyrie.org/~eagle/software/podlators/>.  It is also part of the
Perl core distribution as of 5.6.0.

=cut

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