NAME
HTML::HTML5::Parser - parse HTML reliably
SYNOPSIS
use HTML::HTML5::Parser;
my $parser = HTML::HTML5::Parser->new;
my $doc = $parser->parse_string(<<'EOT');
<!doctype html>
<title>Foo</title>
<p><b><i>Foo</b> bar</i>.
<p>Baz</br>Quux.
EOT
my $fdoc = $parser->parse_file( $html_file_name );
my $fhdoc = $parser->parse_fh( $html_file_handle );
DESCRIPTION
This library is substantially the same as the non-CPAN module
Whatpm::HTML. Changes include:
* Provides an XML::LibXML-like DOM interface. If you usually use
XML::LibXML's DOM parser, this should be a drop-in solution for
tag soup HTML.
* Constructs an XML::LibXML::Document as the result of parsing.
* Via bundling and modifications, removed external dependencies on
non-CPAN packages.
Constructor
"new"
$parser = HTML::HTML5::Parser->new;
# or
$parser = HTML::HTML5::Parser->new(no_cache => 1);
The constructor does nothing interesting besides take one flag
argument, "no_cache => 1", to disable the global element
metadata cache. Disabling the cache is handy for conserving
memory if you parse a large number of documents, however, class
methods such as "/source_line" will not work, and must be run
from an instance of this parser.
XML::LibXML-Compatible Methods
"parse_file", "parse_html_file"
$doc = $parser->parse_file( $html_file_name [,\%opts] );
This function parses an HTML document from a file or network;
$html_file_name can be either a filename or an URL.
Options include 'encoding' to indicate file encoding (e.g. 'utf-8')
and 'user_agent' which should be a blessed "LWP::UserAgent" (or
HTTP::Tiny) object to be used when retrieving URLs.
If requesting a URL and the response Content-Type header indicates
an XML-based media type (such as XHTML), XML::LibXML::Parser will be
used automatically (instead of the tag soup parser). The XML parser
can be told to use a DTD catalogue by setting the option
'xml_catalogue' to the filename of the catalogue.
HTML (tag soup) parsing can be forced using the option 'force_html',
even when an XML media type is returned. If an options hashref was
passed, parse_file will set $options->{'parser_used'} to the name of
the class used to parse the URL, to allow the calling code to
double-check which parser was used afterwards.
If an options hashref was passed, parse_file will set
$options->{'response'} to the HTTP::Response object obtained by
retrieving the URI.
"parse_fh", "parse_html_fh"
$doc = $parser->parse_fh( $io_fh [,\%opts] );
"parse_fh()" parses a IOREF or a subclass of "IO::Handle".
Options include 'encoding' to indicate file encoding (e.g. 'utf-8').
"parse_string", "parse_html_string"
$doc = $parser->parse_string( $html_string [,\%opts] );
This function is similar to "parse_fh()", but it parses an HTML
document that is available as a single string in memory.
Options include 'encoding' to indicate file encoding (e.g. 'utf-8').
"load_xml", "load_html"
Wrappers for the parse_* functions. These should be roughly
compatible with the equivalently named functions in XML::LibXML.
Note that "load_xml" first attempts to parse as real XML, falling
back to HTML5 parsing; "load_html" just goes straight for HTML5.
"parse_balanced_chunk"
$fragment = $parser->parse_balanced_chunk( $string [,\%opts] );
This method is roughly equivalent to XML::LibXML's method of the
same name, but unlike XML::LibXML, and despite its name it does not
require the chunk to be "balanced". This method is somewhat black
magic, but should work, and do the proper thing in most cases. Of
course, the proper thing might not be what you'd expect! I'll try to
keep this explanation as brief as possible...
Consider the following string:
<b>Hello</b></td></tr> <i>World</i>
What is the proper way to parse that? If it were found in a document
like this:
<html>
<head><title>X</title></head>
<body>
<div>
<b>Hello</b></td></tr> <i>World</i>
</div>
</body>
</html>
Then the document would end up equivalent to the following XHTML:
<html>
<head><title>X</title></head>
<body>
<div>
<b>Hello</b> <i>World</i>
</div>
</body>
</html>
The superfluous "</td></tr>" is simply ignored. However, if it were
found in a document like this:
<html>
<head><title>X</title></head>
<body>
<table><tbody><tr><td>
<b>Hello</b></td></tr> <i>World</i>
</td></tr></tbody></table>
</body>
</html>
Then the result would be:
<html>
<head><title>X</title></head>
<body>
<i>World</i>
<table><tbody><tr><td>
<b>Hello</b></td></tr>
</tbody></table>
</body>
</html>
Yes, "<i>World</i>" gets hoisted up before the "<table>". This is
weird, I know, but it's how browsers do it in real life.
So what should:
$string = q{<b>Hello</b></td></tr> <i>World</i>};
$fragment = $parser->parse_balanced_chunk($string);
actually return? Well, you can choose...
$string = q{<b>Hello</b></td></tr> <i>World</i>};
$frag1 = $parser->parse_balanced_chunk($string, {within=>'div'});
say $frag1->toString; # <b>Hello</b> <i>World</i>
$frag2 = $parser->parse_balanced_chunk($string, {within=>'td'});
say $frag2->toString; # <i>World</i><b>Hello</b>
If you don't pass a "within" option, then the chunk is parsed as if
it were within a "<div>" element. This is often the most sensible
option. If you pass something like "{ within => "foobar" }" where
"foobar" is not a real HTML element name (as found in the HTML5
spec), then this method will croak; if you pass the name of a void
element (e.g. "br" or "meta") then this method will croak; there are
a handful of other unsupported elements which will croak (namely:
"noscript", "noembed", "noframes").
Note that the second time around, although we parsed the string "as
if it were within a "<td>" element", the "<i>Hello</i>" bit did not
strictly end up within the "<td>" element (not even within the
"<table>" element!) yet it still gets returned. We'll call things
such as this "outliers". There is a "force_within" option which
tells parse_balanced_chunk to ignore outliers:
$frag3 = $parser->parse_balanced_chunk($string,
{force_within=>'td'});
say $frag3->toString; # <b>Hello</b>
There is a boolean option "mark_outliers" which marks each outlier
with an attribute ("data-perl-html-html5-parser-outlier") to
indicate its outlier status. Clearly, this is ignored when you use
"force_within" because no outliers are returned. Some outliers may
be XML::LibXML::Text elements; text nodes don't have attributes, so
these will not be marked with an attribute.
A last note is to mention what gets returned by this method.
Normally it's an XML::LibXML::DocumentFragment object, but if you
call the method in list context, a list of the individual node
elements is returned. Alternatively you can request the data to be
returned as an XML::LibXML::NodeList object:
# Get an XML::LibXML::NodeList
my $list = $parser->parse_balanced_chunk($str, {as=>'list'});
The exact implementation of this method may change from version to
version, but the long-term goal will be to approach how common
desktop browsers parse HTML fragments when implementing the setter
for DOM's "innerHTML" attribute.
The push parser and SAX-based parser are not supported. Trying to change
an option (such as recover_silently) will make HTML::HTML5::Parser carp
a warning. (But you can inspect the options.)
Error Handling
Error handling is obviously different to XML::LibXML, as errors are
(bugs notwithstanding) non-fatal.
"error_handler"
Get/set an error handling function. Must be set to a coderef or
undef.
The error handling function will be called with a single parameter,
a HTML::HTML5::Parser::Error object.
"errors"
Returns a list of errors that occurred during the last parse.
See HTML::HTML5::Parser::Error.
Additional Methods
The module provides a few methods to obtain additional, non-DOM data
from DOM nodes.
"dtd_public_id"
$pubid = $parser->dtd_public_id( $doc );
For an XML::LibXML::Document which has been returned by
HTML::HTML5::Parser, using this method will tell you the Public
Identifier of the DTD used (if any).
"dtd_system_id"
$sysid = $parser->dtd_system_id( $doc );
For an XML::LibXML::Document which has been returned by
HTML::HTML5::Parser, using this method will tell you the System
Identifier of the DTD used (if any).
"dtd_element"
$element = $parser->dtd_element( $doc );
For an XML::LibXML::Document which has been returned by
HTML::HTML5::Parser, using this method will tell you the root
element declared in the DTD used (if any). That is, if the document
has this doctype:
<!doctype html>
... it will return "html".
This may return the empty string if a DTD was present but did not
contain a root element; or undef if no DTD was present.
"compat_mode"
$mode = $parser->compat_mode( $doc );
Returns 'quirks', 'limited quirks' or undef (standards mode).
"charset"
$charset = $parser->charset( $doc );
The character set apparently used by the document.
"source_line"
($line, $col) = $parser->source_line( $node );
$line = $parser->source_line( $node );
In scalar context, "source_line" returns the line number of the
source code that started a particular node (element, attribute or
comment).
In list context, returns a tuple: $line, $column, $implicitness. Tab
characters count as one column, not eight.
$implicitness indicates that the node was not explicitly marked up
in the source code, but its existence was inferred by the parser.
For example, in the following markup, the HTML, TITLE and P elements
are explicit, but the HEAD and BODY elements are implicit.
<html>
<title>I have an implicit head</title>
<p>And an implicit body too!</p>
</html>
(Note that implicit elements do still have a line number and column
number.) The implictness indicator is a new feature, and I'd
appreciate any bug reports where it gets things wrong.
XML::LibXML::Node has a "line_number" method. In general this will
always return 0 and HTML::HTML5::Parser has no way of influencing
it. However, if you install XML::LibXML::Devel::SetLineNumber on
your system, the "line_number" method will start working (at least
for elements).
SEE ALSO
<http://suika.fam.cx/www/markup/html/whatpm/Whatpm/HTML.html>.
HTML::HTML5::Writer, HTML::HTML5::Builder, XML::LibXML,
XML::LibXML::PrettyPrint, XML::LibXML::Devel::SetLineNumber.
AUTHOR
Toby Inkster, <tobyink@cpan.org>
COPYRIGHT AND LICENCE
Copyright (C) 2007-2011 by Wakaba
Copyright (C) 2009-2012 by Toby Inkster
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
DISCLAIMER OF WARRANTIES
THIS PACKAGE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.