=head1 NAME

XML::LibXML::Error - Structured Errors

=head1 SYNOPSIS



  eval { ... };
          if (ref($@)) {
            # handle a structured error (XML::LibXML::Error object)
          } elsif ($@) {
            # error, but not an XML::LibXML::Error object
          } else {
            # no error
          }

  $XML::LibXML::Error::WARNINGS=1;
  $message = $@->as_string();
  print $@->dump();
  $error_domain = $@->domain();
  $error_code = $@->code();
  $error_message = $@->message();
  $error_level = $@->level();
  $filename = $@->file();
  $line = $@->line();
  $nodename = $@->nodename();
  $error_str1 = $@->str1();
  $error_str2 = $@->str2();
  $error_str3 = $@->str3();
  $error_num1 = $@->num1();
  $error_num2 = $@->num2();
  $string = $@->context();
  $offset = $@->column();
  $previous_error = $@->_prev();

=head1 DESCRIPTION

The XML::LibXML::Error class is a tiny frontend to I<<<<<< libxml2 >>>>>>'s structured error support. If XML::LibXML is compied with structured error
support, all errors reported by libxml2 are transformed to XML::LibXML:Error
objects. These objects automatically serialize to the corresponding error
messages when printed or used in a string operation, but as objects, can also
be used to get a detailed and structured information about the error that
occurred. 

Unlike most other XML::LibXML objects, XML::LibXML::Error doesn't wrap an
underlying I<<<<<< libxml2 >>>>>> structure directly, but rather transforms it to a blessed Perl hash reference
containing the individual fields of the structured error information as hash
key-value pairs. Individual items (fields) of a structured error can either be
obtained directly as $@->{field}, or using autoloaded methods such as as
$@->field() (where field is the field name). XML::LibXML::Error objects have
the following fields: domain, code, level, file, line, nodename, message, str1,
str2, str3, num1, num2, and _prev (some of them may be undefined). 

=over 4

=item $XML::LibXML::Error::WARNINGS

  $XML::LibXML::Error::WARNINGS=1;

Traditionally, XML::LibXML was supressing parser warnings by setting libxml2's
global variable xmlGetWarningsDefaultValue to 0. Since 1.70 we do not change
libxml2's global variables anymore; for backward compatibility, XML::LibXML
suppresses warnings. This variable can be set to 1 to enable reporting of these
warnings via Perl C<<<<<< warn >>>>>> and to 2 to report hem via C<<<<<< die >>>>>>. 

  $message = $@->as_string();

This functions takes serializes a XML::LibXML::Error object to a string
containing the full error message close to the message produced by I<<<<<< libxml2 >>>>>> default error handlers and tools like xmllint. This method is also used to
overload "" operator on XML::LibXML::Error, so it is automatically called
whenever XML::LibXML::Error object is treated as a string (e.g. in print $@). 


=item dump

  print $@->dump();

This function serializes a XML::LibXML::Error to a string displaying all fields
of the error structure individually on separate lines of the form 'name' =>
'value'. 


=item domain

  $error_domain = $@->domain();

Returns string containing information about what part of the library raised the
error. Can be one of: "parser", "tree", "namespace", "validity", "HTML parser",
"memory", "output", "I/O", "ftp", "http", "XInclude", "XPath", "xpointer",
"regexp", "Schemas datatype", "Schemas parser", "Schemas validity", "Relax-NG
parser", "Relax-NG validity", "Catalog", "C14N", "XSLT", "validity". 


=item code

  $error_code = $@->code();

Returns the actual libxml2 error code. The XML::LibXML::ErrNo module defines
constants for individual error codes. Currently libxml2 uses over 480 different
error codes. 


=item message

  $error_message = $@->message();

Returns a human-readable informative error message.


=item level

  $error_level = $@->level();

Returns an integer value describing how consequent is the error.
XML::LibXML::Error defines the following constants: 


=over 4

=item *

XML_ERR_NONE = 0



=item *

XML_ERR_WARNING = 1 : A simple warning.



=item *

XML_ERR_ERROR = 2 : A recoverable error.



=item *

XML_ERR_FATAL = 3 : A fatal error.



=back


=item file

  $filename = $@->file();

Returns the filename of the file being processed while the error occurred. 


=item line

  $line = $@->line();

The line number, if available.


=item nodename

  $nodename = $@->nodename();

Name of the node where error occurred, if available. When this field is
non-empty, libxml2 actually returned a physical pointer to the specified node.
Due to memory management issues, it is very difficult to implement a way to
expose the pointer to the Perl level as a XML::LibXML::Node. For this reason,
XML::LibXML::Error currently only exposes the name the node. 


=item str1

  $error_str1 = $@->str1();

Error specific. Extra string information.


=item str2

  $error_str2 = $@->str2();

Error specific. Extra string information.


=item str3

  $error_str3 = $@->str3();

Error specific. Extra string information.


=item num1

  $error_num1 = $@->num1();

Error specific. Extra numeric information.


=item num2

  $error_num2 = $@->num2();

In recent libxml2 versions, this value contains a column number of the error or
0 if N/A.


=item context

  $string = $@->context();

For parsing errors, this field contains about 80 characters of the XML near the
place where the error occurred. The field C<<<<<< $@->column() >>>>>> contains the corresponding offset. Where N/A, the field is undefined. 


=item column

  $offset = $@->column();

See C<<<<<< $@->column() >>>>>> above. 


=item _prev

  $previous_error = $@->_prev();

This field can possibly hold a reference to another XML::LibXML::Error object
representing an error which occurred just before this error.



=back

=head1 AUTHORS

Matt Sergeant, 
Christian Glahn, 
Petr Pajas


=head1 VERSION

1.70

=head1 COPYRIGHT

2001-2007, AxKit.com Ltd.

2002-2006, Christian Glahn.

2006-2009, Petr Pajas.

=cut
