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# Error.pm | |
# | |
# Copyright (c) 1997-8 Graham Barr <[email protected]>. All rights reserved. | |
# This program is free software; you can redistribute it and/or | |
# modify it under the same terms as Perl itself. | |
# | |
# Based on my original Error.pm, and Exceptions.pm by Peter Seibel | |
# <[email protected]> and adapted by Jesse Glick <[email protected]>. | |
# | |
# but modified ***significantly*** | |
package Error; | |
use strict; | |
use warnings $ENV{GIT_PERL_FATAL_WARNINGS} ? qw(FATAL all) : (); | |
use vars qw($VERSION); | |
use 5.004; | |
$VERSION = "0.17025"; | |
use overload ( | |
'""' => 'stringify', | |
'0+' => 'value', | |
'bool' => sub { return 1; }, | |
'fallback' => 1 | |
); | |
$Error::Depth = 0; # Depth to pass to caller() | |
$Error::Debug = 0; # Generate verbose stack traces | |
@Error::STACK = (); # Clause stack for try | |
$Error::THROWN = undef; # last error thrown, a workaround until die $ref works | |
my $LAST; # Last error created | |
my %ERROR; # Last error associated with package | |
sub _throw_Error_Simple | |
{ | |
my $args = shift; | |
return Error::Simple->new($args->{'text'}); | |
} | |
$Error::ObjectifyCallback = \&_throw_Error_Simple; | |
# Exported subs are defined in Error::subs | |
use Scalar::Util (); | |
sub import { | |
shift; | |
my @tags = @_; | |
local $Exporter::ExportLevel = $Exporter::ExportLevel + 1; | |
@tags = grep { | |
if( $_ eq ':warndie' ) { | |
Error::WarnDie->import(); | |
0; | |
} | |
else { | |
1; | |
} | |
} @tags; | |
Error::subs->import(@tags); | |
} | |
# I really want to use last for the name of this method, but it is a keyword | |
# which prevent the syntax last Error | |
sub prior { | |
shift; # ignore | |
return $LAST unless @_; | |
my $pkg = shift; | |
return exists $ERROR{$pkg} ? $ERROR{$pkg} : undef | |
unless ref($pkg); | |
my $obj = $pkg; | |
my $err = undef; | |
if($obj->isa('HASH')) { | |
$err = $obj->{'__Error__'} | |
if exists $obj->{'__Error__'}; | |
} | |
elsif($obj->isa('GLOB')) { | |
$err = ${*$obj}{'__Error__'} | |
if exists ${*$obj}{'__Error__'}; | |
} | |
$err; | |
} | |
sub flush { | |
shift; #ignore | |
unless (@_) { | |
$LAST = undef; | |
return; | |
} | |
my $pkg = shift; | |
return unless ref($pkg); | |
undef $ERROR{$pkg} if defined $ERROR{$pkg}; | |
} | |
# Return as much information as possible about where the error | |
# happened. The -stacktrace element only exists if $Error::DEBUG | |
# was set when the error was created | |
sub stacktrace { | |
my $self = shift; | |
return $self->{'-stacktrace'} | |
if exists $self->{'-stacktrace'}; | |
my $text = exists $self->{'-text'} ? $self->{'-text'} : "Died"; | |
$text .= sprintf(" at %s line %d.\n", $self->file, $self->line) | |
unless($text =~ /\n$/s); | |
$text; | |
} | |
sub associate { | |
my $err = shift; | |
my $obj = shift; | |
return unless ref($obj); | |
if($obj->isa('HASH')) { | |
$obj->{'__Error__'} = $err; | |
} | |
elsif($obj->isa('GLOB')) { | |
${*$obj}{'__Error__'} = $err; | |
} | |
$obj = ref($obj); | |
$ERROR{ ref($obj) } = $err; | |
return; | |
} | |
sub new { | |
my $self = shift; | |
my($pkg,$file,$line) = caller($Error::Depth); | |
my $err = bless { | |
'-package' => $pkg, | |
'-file' => $file, | |
'-line' => $line, | |
@_ | |
}, $self; | |
$err->associate($err->{'-object'}) | |
if(exists $err->{'-object'}); | |
# To always create a stacktrace would be very inefficient, so | |
# we only do it if $Error::Debug is set | |
if($Error::Debug) { | |
require Carp; | |
local $Carp::CarpLevel = $Error::Depth; | |
my $text = defined($err->{'-text'}) ? $err->{'-text'} : "Error"; | |
my $trace = Carp::longmess($text); | |
# Remove try calls from the trace | |
$trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog; | |
$trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::run_clauses[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog; | |
$err->{'-stacktrace'} = $trace | |
} | |
$@ = $LAST = $ERROR{$pkg} = $err; | |
} | |
# Throw an error. this contains some very gory code. | |
sub throw { | |
my $self = shift; | |
local $Error::Depth = $Error::Depth + 1; | |
# if we are not rethrow-ing then create the object to throw | |
$self = $self->new(@_) unless ref($self); | |
die $Error::THROWN = $self; | |
} | |
# syntactic sugar for | |
# | |
# die with Error( ... ); | |
sub with { | |
my $self = shift; | |
local $Error::Depth = $Error::Depth + 1; | |
$self->new(@_); | |
} | |
# syntactic sugar for | |
# | |
# record Error( ... ) and return; | |
sub record { | |
my $self = shift; | |
local $Error::Depth = $Error::Depth + 1; | |
$self->new(@_); | |
} | |
# catch clause for | |
# | |
# try { ... } catch CLASS with { ... } | |
sub catch { | |
my $pkg = shift; | |
my $code = shift; | |
my $clauses = shift || {}; | |
my $catch = $clauses->{'catch'} ||= []; | |
unshift @$catch, $pkg, $code; | |
$clauses; | |
} | |
# Object query methods | |
sub object { | |
my $self = shift; | |
exists $self->{'-object'} ? $self->{'-object'} : undef; | |
} | |
sub file { | |
my $self = shift; | |
exists $self->{'-file'} ? $self->{'-file'} : undef; | |
} | |
sub line { | |
my $self = shift; | |
exists $self->{'-line'} ? $self->{'-line'} : undef; | |
} | |
sub text { | |
my $self = shift; | |
exists $self->{'-text'} ? $self->{'-text'} : undef; | |
} | |
# overload methods | |
sub stringify { | |
my $self = shift; | |
defined $self->{'-text'} ? $self->{'-text'} : "Died"; | |
} | |
sub value { | |
my $self = shift; | |
exists $self->{'-value'} ? $self->{'-value'} : undef; | |
} | |
package Error::Simple; | |
use vars qw($VERSION); | |
$VERSION = "0.17025"; | |
@Error::Simple::ISA = qw(Error); | |
sub new { | |
my $self = shift; | |
my $text = "" . shift; | |
my $value = shift; | |
my(@args) = (); | |
local $Error::Depth = $Error::Depth + 1; | |
@args = ( -file => $1, -line => $2) | |
if($text =~ s/\s+at\s+(\S+)\s+line\s+(\d+)(?:,\s*<[^>]*>\s+line\s+\d+)?\.?\n?$//s); | |
push(@args, '-value', 0 + $value) | |
if defined($value); | |
$self->SUPER::new(-text => $text, @args); | |
} | |
sub stringify { | |
my $self = shift; | |
my $text = $self->SUPER::stringify; | |
$text .= sprintf(" at %s line %d.\n", $self->file, $self->line) | |
unless($text =~ /\n$/s); | |
$text; | |
} | |
########################################################################## | |
########################################################################## | |
# Inspired by code from Jesse Glick <[email protected]> and | |
# Peter Seibel <[email protected]> | |
package Error::subs; | |
use Exporter (); | |
use vars qw(@EXPORT_OK @ISA %EXPORT_TAGS); | |
@EXPORT_OK = qw(try with finally except otherwise); | |
%EXPORT_TAGS = (try => \@EXPORT_OK); | |
@ISA = qw(Exporter); | |
sub run_clauses ($$$\@) { | |
my($clauses,$err,$wantarray,$result) = @_; | |
my $code = undef; | |
$err = $Error::ObjectifyCallback->({'text' =>$err}) unless ref($err); | |
CATCH: { | |
# catch | |
my $catch; | |
if(defined($catch = $clauses->{'catch'})) { | |
my $i = 0; | |
CATCHLOOP: | |
for( ; $i < @$catch ; $i += 2) { | |
my $pkg = $catch->[$i]; | |
unless(defined $pkg) { | |
#except | |
splice(@$catch,$i,2,$catch->[$i+1]->($err)); | |
$i -= 2; | |
next CATCHLOOP; | |
} | |
elsif(Scalar::Util::blessed($err) && $err->isa($pkg)) { | |
$code = $catch->[$i+1]; | |
while(1) { | |
my $more = 0; | |
local($Error::THROWN, $@); | |
my $ok = eval { | |
$@ = $err; | |
if($wantarray) { | |
@{$result} = $code->($err,\$more); | |
} | |
elsif(defined($wantarray)) { | |
@{$result} = (); | |
$result->[0] = $code->($err,\$more); | |
} | |
else { | |
$code->($err,\$more); | |
} | |
1; | |
}; | |
if( $ok ) { | |
next CATCHLOOP if $more; | |
undef $err; | |
} | |
else { | |
$err = $@ || $Error::THROWN; | |
$err = $Error::ObjectifyCallback->({'text' =>$err}) | |
unless ref($err); | |
} | |
last CATCH; | |
}; | |
} | |
} | |
} | |
# otherwise | |
my $owise; | |
if(defined($owise = $clauses->{'otherwise'})) { | |
my $code = $clauses->{'otherwise'}; | |
my $more = 0; | |
local($Error::THROWN, $@); | |
my $ok = eval { | |
$@ = $err; | |
if($wantarray) { | |
@{$result} = $code->($err,\$more); | |
} | |
elsif(defined($wantarray)) { | |
@{$result} = (); | |
$result->[0] = $code->($err,\$more); | |
} | |
else { | |
$code->($err,\$more); | |
} | |
1; | |
}; | |
if( $ok ) { | |
undef $err; | |
} | |
else { | |
$err = $@ || $Error::THROWN; | |
$err = $Error::ObjectifyCallback->({'text' =>$err}) | |
unless ref($err); | |
} | |
} | |
} | |
$err; | |
} | |
sub try (&;$) { | |
my $try = shift; | |
my $clauses = @_ ? shift : {}; | |
my $ok = 0; | |
my $err = undef; | |
my @result = (); | |
unshift @Error::STACK, $clauses; | |
my $wantarray = wantarray(); | |
do { | |
local $Error::THROWN = undef; | |
local $@ = undef; | |
$ok = eval { | |
if($wantarray) { | |
@result = $try->(); | |
} | |
elsif(defined $wantarray) { | |
$result[0] = $try->(); | |
} | |
else { | |
$try->(); | |
} | |
1; | |
}; | |
$err = $@ || $Error::THROWN | |
unless $ok; | |
}; | |
shift @Error::STACK; | |
$err = run_clauses($clauses,$err,wantarray,@result) | |
unless($ok); | |
$clauses->{'finally'}->() | |
if(defined($clauses->{'finally'})); | |
if (defined($err)) | |
{ | |
if (Scalar::Util::blessed($err) && $err->can('throw')) | |
{ | |
throw $err; | |
} | |
else | |
{ | |
die $err; | |
} | |
} | |
wantarray ? @result : $result[0]; | |
} | |
# Each clause adds a sub to the list of clauses. The finally clause is | |
# always the last, and the otherwise clause is always added just before | |
# the finally clause. | |
# | |
# All clauses, except the finally clause, add a sub which takes one argument | |
# this argument will be the error being thrown. The sub will return a code ref | |
# if that clause can handle that error, otherwise undef is returned. | |
# | |
# The otherwise clause adds a sub which unconditionally returns the users | |
# code reference, this is why it is forced to be last. | |
# | |
# The catch clause is defined in Error.pm, as the syntax causes it to | |
# be called as a method | |
sub with (&;$) { | |
@_ | |
} | |
sub finally (&) { | |
my $code = shift; | |
my $clauses = { 'finally' => $code }; | |
$clauses; | |
} | |
# The except clause is a block which returns a hashref or a list of | |
# key-value pairs, where the keys are the classes and the values are subs. | |
sub except (&;$) { | |
my $code = shift; | |
my $clauses = shift || {}; | |
my $catch = $clauses->{'catch'} ||= []; | |
my $sub = sub { | |
my $ref; | |
my(@array) = $code->($_[0]); | |
if(@array == 1 && ref($array[0])) { | |
$ref = $array[0]; | |
$ref = [ %$ref ] | |
if(UNIVERSAL::isa($ref,'HASH')); | |
} | |
else { | |
$ref = \@array; | |
} | |
@$ref | |
}; | |
unshift @{$catch}, undef, $sub; | |
$clauses; | |
} | |
sub otherwise (&;$) { | |
my $code = shift; | |
my $clauses = shift || {}; | |
if(exists $clauses->{'otherwise'}) { | |
require Carp; | |
Carp::croak("Multiple otherwise clauses"); | |
} | |
$clauses->{'otherwise'} = $code; | |
$clauses; | |
} | |
1; | |
package Error::WarnDie; | |
sub gen_callstack($) | |
{ | |
my ( $start ) = @_; | |
require Carp; | |
local $Carp::CarpLevel = $start; | |
my $trace = Carp::longmess(""); | |
# Remove try calls from the trace | |
$trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog; | |
$trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::run_clauses[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog; | |
my @callstack = split( m/\n/, $trace ); | |
return @callstack; | |
} | |
my $old_DIE; | |
my $old_WARN; | |
sub DEATH | |
{ | |
my ( $e ) = @_; | |
local $SIG{__DIE__} = $old_DIE if( defined $old_DIE ); | |
die @_ if $^S; | |
my ( $etype, $message, $location, @callstack ); | |
if ( ref($e) && $e->isa( "Error" ) ) { | |
$etype = "exception of type " . ref( $e ); | |
$message = $e->text; | |
$location = $e->file . ":" . $e->line; | |
@callstack = split( m/\n/, $e->stacktrace ); | |
} | |
else { | |
# Don't apply subsequent layer of message formatting | |
die $e if( $e =~ m/^\nUnhandled perl error caught at toplevel:\n\n/ ); | |
$etype = "perl error"; | |
my $stackdepth = 0; | |
while( caller( $stackdepth ) =~ m/^Error(?:$|::)/ ) { | |
$stackdepth++ | |
} | |
@callstack = gen_callstack( $stackdepth + 1 ); | |
$message = "$e"; | |
chomp $message; | |
if ( $message =~ s/ at (.*?) line (\d+)\.$// ) { | |
$location = $1 . ":" . $2; | |
} | |
else { | |
my @caller = caller( $stackdepth ); | |
$location = $caller[1] . ":" . $caller[2]; | |
} | |
} | |
shift @callstack; | |
# Do it this way in case there are no elements; we don't print a spurious \n | |
my $callstack = join( "", map { "$_\n"} @callstack ); | |
die "\nUnhandled $etype caught at toplevel:\n\n $message\n\nThrown from: $location\n\nFull stack trace:\n\n$callstack\n"; | |
} | |
sub TAXES | |
{ | |
my ( $message ) = @_; | |
local $SIG{__WARN__} = $old_WARN if( defined $old_WARN ); | |
$message =~ s/ at .*? line \d+\.$//; | |
chomp $message; | |
my @callstack = gen_callstack( 1 ); | |
my $location = shift @callstack; | |
# $location already starts in a leading space | |
$message .= $location; | |
# Do it this way in case there are no elements; we don't print a spurious \n | |
my $callstack = join( "", map { "$_\n"} @callstack ); | |
warn "$message:\n$callstack"; | |
} | |
sub import | |
{ | |
$old_DIE = $SIG{__DIE__}; | |
$old_WARN = $SIG{__WARN__}; | |
$SIG{__DIE__} = \&DEATH; | |
$SIG{__WARN__} = \&TAXES; | |
} | |
1; | |
__END__ | |
=head1 NAME | |
Error - Error/exception handling in an OO-ish way | |
=head1 WARNING | |
Using the "Error" module is B<no longer recommended> due to the black-magical | |
nature of its syntactic sugar, which often tends to break. Its maintainers | |
have stopped actively writing code that uses it, and discourage people | |
from doing so. See the "SEE ALSO" section below for better recommendations. | |
=head1 SYNOPSIS | |
use Error qw(:try); | |
throw Error::Simple( "A simple error"); | |
sub xyz { | |
... | |
record Error::Simple("A simple error") | |
and return; | |
} | |
unlink($file) or throw Error::Simple("$file: $!",$!); | |
try { | |
do_some_stuff(); | |
die "error!" if $condition; | |
throw Error::Simple "Oops!" if $other_condition; | |
} | |
catch Error::IO with { | |
my $E = shift; | |
print STDERR "File ", $E->{'-file'}, " had a problem\n"; | |
} | |
except { | |
my $E = shift; | |
my $general_handler=sub {send_message $E->{-description}}; | |
return { | |
UserException1 => $general_handler, | |
UserException2 => $general_handler | |
}; | |
} | |
otherwise { | |
print STDERR "Well I don't know what to say\n"; | |
} | |
finally { | |
close_the_garage_door_already(); # Should be reliable | |
}; # Don't forget the trailing ; or you might be surprised | |
=head1 DESCRIPTION | |
The C<Error> package provides two interfaces. Firstly C<Error> provides | |
a procedural interface to exception handling. Secondly C<Error> is a | |
base class for errors/exceptions that can either be thrown, for | |
subsequent catch, or can simply be recorded. | |
Errors in the class C<Error> should not be thrown directly, but the | |
user should throw errors from a sub-class of C<Error>. | |
=head1 PROCEDURAL INTERFACE | |
C<Error> exports subroutines to perform exception handling. These will | |
be exported if the C<:try> tag is used in the C<use> line. | |
=over 4 | |
=item try BLOCK CLAUSES | |
C<try> is the main subroutine called by the user. All other subroutines | |
exported are clauses to the try subroutine. | |
The BLOCK will be evaluated and, if no error is throw, try will return | |
the result of the block. | |
C<CLAUSES> are the subroutines below, which describe what to do in the | |
event of an error being thrown within BLOCK. | |
=item catch CLASS with BLOCK | |
This clauses will cause all errors that satisfy C<$err-E<gt>isa(CLASS)> | |
to be caught and handled by evaluating C<BLOCK>. | |
C<BLOCK> will be passed two arguments. The first will be the error | |
being thrown. The second is a reference to a scalar variable. If this | |
variable is set by the catch block then, on return from the catch | |
block, try will continue processing as if the catch block was never | |
found. The error will also be available in C<$@>. | |
To propagate the error the catch block may call C<$err-E<gt>throw> | |
If the scalar reference by the second argument is not set, and the | |
error is not thrown. Then the current try block will return with the | |
result from the catch block. | |
=item except BLOCK | |
When C<try> is looking for a handler, if an except clause is found | |
C<BLOCK> is evaluated. The return value from this block should be a | |
HASHREF or a list of key-value pairs, where the keys are class names | |
and the values are CODE references for the handler of errors of that | |
type. | |
=item otherwise BLOCK | |
Catch any error by executing the code in C<BLOCK> | |
When evaluated C<BLOCK> will be passed one argument, which will be the | |
error being processed. The error will also be available in C<$@>. | |
Only one otherwise block may be specified per try block | |
=item finally BLOCK | |
Execute the code in C<BLOCK> either after the code in the try block has | |
successfully completed, or if the try block throws an error then | |
C<BLOCK> will be executed after the handler has completed. | |
If the handler throws an error then the error will be caught, the | |
finally block will be executed and the error will be re-thrown. | |
Only one finally block may be specified per try block | |
=back | |
=head1 COMPATIBILITY | |
L<Moose> exports a keyword called C<with> which clashes with Error's. This | |
example returns a prototype mismatch error: | |
package MyTest; | |
use warnings; | |
use Moose; | |
use Error qw(:try); | |
(Thanks to C<[email protected]> for the report.). | |
=head1 CLASS INTERFACE | |
=head2 CONSTRUCTORS | |
The C<Error> object is implemented as a HASH. This HASH is initialized | |
with the arguments that are passed to it's constructor. The elements | |
that are used by, or are retrievable by the C<Error> class are listed | |
below, other classes may add to these. | |
-file | |
-line | |
-text | |
-value | |
-object | |
If C<-file> or C<-line> are not specified in the constructor arguments | |
then these will be initialized with the file name and line number where | |
the constructor was called from. | |
If the error is associated with an object then the object should be | |
passed as the C<-object> argument. This will allow the C<Error> package | |
to associate the error with the object. | |
The C<Error> package remembers the last error created, and also the | |
last error associated with a package. This could either be the last | |
error created by a sub in that package, or the last error which passed | |
an object blessed into that package as the C<-object> argument. | |
=over 4 | |
=item Error->new() | |
See the Error::Simple documentation. | |
=item throw ( [ ARGS ] ) | |
Create a new C<Error> object and throw an error, which will be caught | |
by a surrounding C<try> block, if there is one. Otherwise it will cause | |
the program to exit. | |
C<throw> may also be called on an existing error to re-throw it. | |
=item with ( [ ARGS ] ) | |
Create a new C<Error> object and returns it. This is defined for | |
syntactic sugar, eg | |
die with Some::Error ( ... ); | |
=item record ( [ ARGS ] ) | |
Create a new C<Error> object and returns it. This is defined for | |
syntactic sugar, eg | |
record Some::Error ( ... ) | |
and return; | |
=back | |
=head2 STATIC METHODS | |
=over 4 | |
=item prior ( [ PACKAGE ] ) | |
Return the last error created, or the last error associated with | |
C<PACKAGE> | |
=item flush ( [ PACKAGE ] ) | |
Flush the last error created, or the last error associated with | |
C<PACKAGE>.It is necessary to clear the error stack before exiting the | |
package or uncaught errors generated using C<record> will be reported. | |
$Error->flush; | |
=cut | |
=back | |
=head2 OBJECT METHODS | |
=over 4 | |
=item stacktrace | |
If the variable C<$Error::Debug> was non-zero when the error was | |
created, then C<stacktrace> returns a string created by calling | |
C<Carp::longmess>. If the variable was zero the C<stacktrace> returns | |
the text of the error appended with the filename and line number of | |
where the error was created, providing the text does not end with a | |
newline. | |
=item object | |
The object this error was associated with | |
=item file | |
The file where the constructor of this error was called from | |
=item line | |
The line where the constructor of this error was called from | |
=item text | |
The text of the error | |
=item $err->associate($obj) | |
Associates an error with an object to allow error propagation. I.e: | |
$ber->encode(...) or | |
return Error->prior($ber)->associate($ldap); | |
=back | |
=head2 OVERLOAD METHODS | |
=over 4 | |
=item stringify | |
A method that converts the object into a string. This method may simply | |
return the same as the C<text> method, or it may append more | |
information. For example the file name and line number. | |
By default this method returns the C<-text> argument that was passed to | |
the constructor, or the string C<"Died"> if none was given. | |
=item value | |
A method that will return a value that can be associated with the | |
error. For example if an error was created due to the failure of a | |
system call, then this may return the numeric value of C<$!> at the | |
time. | |
By default this method returns the C<-value> argument that was passed | |
to the constructor. | |
=back | |
=head1 PRE-DEFINED ERROR CLASSES | |
=head2 Error::Simple | |
This class can be used to hold simple error strings and values. It's | |
constructor takes two arguments. The first is a text value, the second | |
is a numeric value. These values are what will be returned by the | |
overload methods. | |
If the text value ends with C<at file line 1> as $@ strings do, then | |
this information will be used to set the C<-file> and C<-line> arguments | |
of the error object. | |
This class is used internally if an eval'd block die's with an error | |
that is a plain string. (Unless C<$Error::ObjectifyCallback> is modified) | |
=head1 $Error::ObjectifyCallback | |
This variable holds a reference to a subroutine that converts errors that | |
are plain strings to objects. It is used by Error.pm to convert textual | |
errors to objects, and can be overridden by the user. | |
It accepts a single argument which is a hash reference to named parameters. | |
Currently the only named parameter passed is C<'text'> which is the text | |
of the error, but others may be available in the future. | |
For example the following code will cause Error.pm to throw objects of the | |
class MyError::Bar by default: | |
sub throw_MyError_Bar | |
{ | |
my $args = shift; | |
my $err = MyError::Bar->new(); | |
$err->{'MyBarText'} = $args->{'text'}; | |
return $err; | |
} | |
{ | |
local $Error::ObjectifyCallback = \&throw_MyError_Bar; | |
# Error handling here. | |
} | |
=cut | |
=head1 MESSAGE HANDLERS | |
C<Error> also provides handlers to extend the output of the C<warn()> perl | |
function, and to handle the printing of a thrown C<Error> that is not caught | |
or otherwise handled. These are not installed by default, but are requested | |
using the C<:warndie> tag in the C<use> line. | |
use Error qw( :warndie ); | |
These new error handlers are installed in C<$SIG{__WARN__}> and | |
C<$SIG{__DIE__}>. If these handlers are already defined when the tag is | |
imported, the old values are stored, and used during the new code. Thus, to | |
arrange for custom handling of warnings and errors, you will need to perform | |
something like the following: | |
BEGIN { | |
$SIG{__WARN__} = sub { | |
print STDERR "My special warning handler: $_[0]" | |
}; | |
} | |
use Error qw( :warndie ); | |
Note that setting C<$SIG{__WARN__}> after the C<:warndie> tag has been | |
imported will overwrite the handler that C<Error> provides. If this cannot be | |
avoided, then the tag can be explicitly C<import>ed later | |
use Error; | |
$SIG{__WARN__} = ...; | |
import Error qw( :warndie ); | |
=head2 EXAMPLE | |
The C<__DIE__> handler turns messages such as | |
Can't call method "foo" on an undefined value at examples/warndie.pl line 16. | |
into | |
Unhandled perl error caught at toplevel: | |
Can't call method "foo" on an undefined value | |
Thrown from: examples/warndie.pl:16 | |
Full stack trace: | |
main::inner('undef') called at examples/warndie.pl line 20 | |
main::outer('undef') called at examples/warndie.pl line 23 | |
=cut | |
=head1 SEE ALSO | |
See L<Exception::Class> for a different module providing Object-Oriented | |
exception handling, along with a convenient syntax for declaring hierarchies | |
for them. It doesn't provide Error's syntactic sugar of C<try { ... }>, | |
C<catch { ... }>, etc. which may be a good thing or a bad thing based | |
on what you want. (Because Error's syntactic sugar tends to break.) | |
L<Error::Exception> aims to combine L<Error> and L<Exception::Class> | |
"with correct stringification". | |
L<TryCatch> and L<Try::Tiny> are similar in concept to Error.pm only providing | |
a syntax that hopefully breaks less. | |
=head1 KNOWN BUGS | |
None, but that does not mean there are not any. | |
=head1 AUTHORS | |
Graham Barr <[email protected]> | |
The code that inspired me to write this was originally written by | |
Peter Seibel <[email protected]> and adapted by Jesse Glick | |
<[email protected]>. | |
C<:warndie> handlers added by Paul Evans <[email protected]> | |
=head1 MAINTAINER | |
Shlomi Fish, L<http://www.shlomifish.org/> . | |
=head1 PAST MAINTAINERS | |
Arun Kumar U <[email protected]> | |
=head1 COPYRIGHT | |
Copyright (c) 1997-8 Graham Barr. All rights reserved. | |
This program is free software; you can redistribute it and/or modify it | |
under the same terms as Perl itself. | |
=cut | |