1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
|
# Error.pm
#
# Copyright (c) 1997-8 Graham Barr <gbarr@ti.com>. 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
# <peter@weblogic.com> and adapted by Jesse Glick <jglick@sig.bsh.com>.
#
# but modified ***significantly***
package Error;
use strict;
use warnings;
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 <jglick@sig.bsh.com> and
# Peter Seibel <peter@weblogic.com>
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<maik.hentsche@amd.com> 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 <gbarr@pobox.com>
The code that inspired me to write this was originally written by
Peter Seibel <peter@weblogic.com> and adapted by Jesse Glick
<jglick@sig.bsh.com>.
C<:warndie> handlers added by Paul Evans <leonerd@leonerd.org.uk>
=head1 MAINTAINER
Shlomi Fish, L<http://www.shlomifish.org/> .
=head1 PAST MAINTAINERS
Arun Kumar U <u_arunkumar@yahoo.com>
=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
|