| 1 | # Error.pm |
| 2 | # |
| 3 | # Copyright (c) 1997-8 Graham Barr <gbarr@ti.com>. All rights reserved. |
| 4 | # This program is free software; you can redistribute it and/or |
| 5 | # modify it under the same terms as Perl itself. |
| 6 | # |
| 7 | # Based on my original Error.pm, and Exceptions.pm by Peter Seibel |
| 8 | # <peter@weblogic.com> and adapted by Jesse Glick <jglick@sig.bsh.com>. |
| 9 | # |
| 10 | # but modified ***significantly*** |
| 11 | |
| 12 | package Error; |
| 13 | |
| 14 | use strict; |
| 15 | use warnings $ENV{GIT_PERL_FATAL_WARNINGS} ? qw(FATAL all) : (); |
| 16 | |
| 17 | use vars qw($VERSION); |
| 18 | use 5.004; |
| 19 | |
| 20 | $VERSION = "0.17025"; |
| 21 | |
| 22 | use overload ( |
| 23 | '""' => 'stringify', |
| 24 | '0+' => 'value', |
| 25 | 'bool' => sub { return 1; }, |
| 26 | 'fallback' => 1 |
| 27 | ); |
| 28 | |
| 29 | $Error::Depth = 0; # Depth to pass to caller() |
| 30 | $Error::Debug = 0; # Generate verbose stack traces |
| 31 | @Error::STACK = (); # Clause stack for try |
| 32 | $Error::THROWN = undef; # last error thrown, a workaround until die $ref works |
| 33 | |
| 34 | my $LAST; # Last error created |
| 35 | my %ERROR; # Last error associated with package |
| 36 | |
| 37 | sub _throw_Error_Simple |
| 38 | { |
| 39 | my $args = shift; |
| 40 | return Error::Simple->new($args->{'text'}); |
| 41 | } |
| 42 | |
| 43 | $Error::ObjectifyCallback = \&_throw_Error_Simple; |
| 44 | |
| 45 | |
| 46 | # Exported subs are defined in Error::subs |
| 47 | |
| 48 | use Scalar::Util (); |
| 49 | |
| 50 | sub import { |
| 51 | shift; |
| 52 | my @tags = @_; |
| 53 | local $Exporter::ExportLevel = $Exporter::ExportLevel + 1; |
| 54 | |
| 55 | @tags = grep { |
| 56 | if( $_ eq ':warndie' ) { |
| 57 | Error::WarnDie->import(); |
| 58 | 0; |
| 59 | } |
| 60 | else { |
| 61 | 1; |
| 62 | } |
| 63 | } @tags; |
| 64 | |
| 65 | Error::subs->import(@tags); |
| 66 | } |
| 67 | |
| 68 | # I really want to use last for the name of this method, but it is a keyword |
| 69 | # which prevent the syntax last Error |
| 70 | |
| 71 | sub prior { |
| 72 | shift; # ignore |
| 73 | |
| 74 | return $LAST unless @_; |
| 75 | |
| 76 | my $pkg = shift; |
| 77 | return exists $ERROR{$pkg} ? $ERROR{$pkg} : undef |
| 78 | unless ref($pkg); |
| 79 | |
| 80 | my $obj = $pkg; |
| 81 | my $err = undef; |
| 82 | if($obj->isa('HASH')) { |
| 83 | $err = $obj->{'__Error__'} |
| 84 | if exists $obj->{'__Error__'}; |
| 85 | } |
| 86 | elsif($obj->isa('GLOB')) { |
| 87 | $err = ${*$obj}{'__Error__'} |
| 88 | if exists ${*$obj}{'__Error__'}; |
| 89 | } |
| 90 | |
| 91 | $err; |
| 92 | } |
| 93 | |
| 94 | sub flush { |
| 95 | shift; #ignore |
| 96 | |
| 97 | unless (@_) { |
| 98 | $LAST = undef; |
| 99 | return; |
| 100 | } |
| 101 | |
| 102 | my $pkg = shift; |
| 103 | return unless ref($pkg); |
| 104 | |
| 105 | undef $ERROR{$pkg} if defined $ERROR{$pkg}; |
| 106 | } |
| 107 | |
| 108 | # Return as much information as possible about where the error |
| 109 | # happened. The -stacktrace element only exists if $Error::DEBUG |
| 110 | # was set when the error was created |
| 111 | |
| 112 | sub stacktrace { |
| 113 | my $self = shift; |
| 114 | |
| 115 | return $self->{'-stacktrace'} |
| 116 | if exists $self->{'-stacktrace'}; |
| 117 | |
| 118 | my $text = exists $self->{'-text'} ? $self->{'-text'} : "Died"; |
| 119 | |
| 120 | $text .= sprintf(" at %s line %d.\n", $self->file, $self->line) |
| 121 | unless($text =~ /\n$/s); |
| 122 | |
| 123 | $text; |
| 124 | } |
| 125 | |
| 126 | |
| 127 | sub associate { |
| 128 | my $err = shift; |
| 129 | my $obj = shift; |
| 130 | |
| 131 | return unless ref($obj); |
| 132 | |
| 133 | if($obj->isa('HASH')) { |
| 134 | $obj->{'__Error__'} = $err; |
| 135 | } |
| 136 | elsif($obj->isa('GLOB')) { |
| 137 | ${*$obj}{'__Error__'} = $err; |
| 138 | } |
| 139 | $obj = ref($obj); |
| 140 | $ERROR{ ref($obj) } = $err; |
| 141 | |
| 142 | return; |
| 143 | } |
| 144 | |
| 145 | |
| 146 | sub new { |
| 147 | my $self = shift; |
| 148 | my($pkg,$file,$line) = caller($Error::Depth); |
| 149 | |
| 150 | my $err = bless { |
| 151 | '-package' => $pkg, |
| 152 | '-file' => $file, |
| 153 | '-line' => $line, |
| 154 | @_ |
| 155 | }, $self; |
| 156 | |
| 157 | $err->associate($err->{'-object'}) |
| 158 | if(exists $err->{'-object'}); |
| 159 | |
| 160 | # To always create a stacktrace would be very inefficient, so |
| 161 | # we only do it if $Error::Debug is set |
| 162 | |
| 163 | if($Error::Debug) { |
| 164 | require Carp; |
| 165 | local $Carp::CarpLevel = $Error::Depth; |
| 166 | my $text = defined($err->{'-text'}) ? $err->{'-text'} : "Error"; |
| 167 | my $trace = Carp::longmess($text); |
| 168 | # Remove try calls from the trace |
| 169 | $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog; |
| 170 | $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; |
| 171 | $err->{'-stacktrace'} = $trace |
| 172 | } |
| 173 | |
| 174 | $@ = $LAST = $ERROR{$pkg} = $err; |
| 175 | } |
| 176 | |
| 177 | # Throw an error. this contains some very gory code. |
| 178 | |
| 179 | sub throw { |
| 180 | my $self = shift; |
| 181 | local $Error::Depth = $Error::Depth + 1; |
| 182 | |
| 183 | # if we are not rethrow-ing then create the object to throw |
| 184 | $self = $self->new(@_) unless ref($self); |
| 185 | |
| 186 | die $Error::THROWN = $self; |
| 187 | } |
| 188 | |
| 189 | # syntactic sugar for |
| 190 | # |
| 191 | # die with Error( ... ); |
| 192 | |
| 193 | sub with { |
| 194 | my $self = shift; |
| 195 | local $Error::Depth = $Error::Depth + 1; |
| 196 | |
| 197 | $self->new(@_); |
| 198 | } |
| 199 | |
| 200 | # syntactic sugar for |
| 201 | # |
| 202 | # record Error( ... ) and return; |
| 203 | |
| 204 | sub record { |
| 205 | my $self = shift; |
| 206 | local $Error::Depth = $Error::Depth + 1; |
| 207 | |
| 208 | $self->new(@_); |
| 209 | } |
| 210 | |
| 211 | # catch clause for |
| 212 | # |
| 213 | # try { ... } catch CLASS with { ... } |
| 214 | |
| 215 | sub catch { |
| 216 | my $pkg = shift; |
| 217 | my $code = shift; |
| 218 | my $clauses = shift || {}; |
| 219 | my $catch = $clauses->{'catch'} ||= []; |
| 220 | |
| 221 | unshift @$catch, $pkg, $code; |
| 222 | |
| 223 | $clauses; |
| 224 | } |
| 225 | |
| 226 | # Object query methods |
| 227 | |
| 228 | sub object { |
| 229 | my $self = shift; |
| 230 | exists $self->{'-object'} ? $self->{'-object'} : undef; |
| 231 | } |
| 232 | |
| 233 | sub file { |
| 234 | my $self = shift; |
| 235 | exists $self->{'-file'} ? $self->{'-file'} : undef; |
| 236 | } |
| 237 | |
| 238 | sub line { |
| 239 | my $self = shift; |
| 240 | exists $self->{'-line'} ? $self->{'-line'} : undef; |
| 241 | } |
| 242 | |
| 243 | sub text { |
| 244 | my $self = shift; |
| 245 | exists $self->{'-text'} ? $self->{'-text'} : undef; |
| 246 | } |
| 247 | |
| 248 | # overload methods |
| 249 | |
| 250 | sub stringify { |
| 251 | my $self = shift; |
| 252 | defined $self->{'-text'} ? $self->{'-text'} : "Died"; |
| 253 | } |
| 254 | |
| 255 | sub value { |
| 256 | my $self = shift; |
| 257 | exists $self->{'-value'} ? $self->{'-value'} : undef; |
| 258 | } |
| 259 | |
| 260 | package Error::Simple; |
| 261 | |
| 262 | use vars qw($VERSION); |
| 263 | |
| 264 | $VERSION = "0.17025"; |
| 265 | |
| 266 | @Error::Simple::ISA = qw(Error); |
| 267 | |
| 268 | sub new { |
| 269 | my $self = shift; |
| 270 | my $text = "" . shift; |
| 271 | my $value = shift; |
| 272 | my(@args) = (); |
| 273 | |
| 274 | local $Error::Depth = $Error::Depth + 1; |
| 275 | |
| 276 | @args = ( -file => $1, -line => $2) |
| 277 | if($text =~ s/\s+at\s+(\S+)\s+line\s+(\d+)(?:,\s*<[^>]*>\s+line\s+\d+)?\.?\n?$//s); |
| 278 | push(@args, '-value', 0 + $value) |
| 279 | if defined($value); |
| 280 | |
| 281 | $self->SUPER::new(-text => $text, @args); |
| 282 | } |
| 283 | |
| 284 | sub stringify { |
| 285 | my $self = shift; |
| 286 | my $text = $self->SUPER::stringify; |
| 287 | $text .= sprintf(" at %s line %d.\n", $self->file, $self->line) |
| 288 | unless($text =~ /\n$/s); |
| 289 | $text; |
| 290 | } |
| 291 | |
| 292 | ########################################################################## |
| 293 | ########################################################################## |
| 294 | |
| 295 | # Inspired by code from Jesse Glick <jglick@sig.bsh.com> and |
| 296 | # Peter Seibel <peter@weblogic.com> |
| 297 | |
| 298 | package Error::subs; |
| 299 | |
| 300 | use Exporter (); |
| 301 | use vars qw(@EXPORT_OK @ISA %EXPORT_TAGS); |
| 302 | |
| 303 | @EXPORT_OK = qw(try with finally except otherwise); |
| 304 | %EXPORT_TAGS = (try => \@EXPORT_OK); |
| 305 | |
| 306 | @ISA = qw(Exporter); |
| 307 | |
| 308 | sub run_clauses ($$$\@) { |
| 309 | my($clauses,$err,$wantarray,$result) = @_; |
| 310 | my $code = undef; |
| 311 | |
| 312 | $err = $Error::ObjectifyCallback->({'text' =>$err}) unless ref($err); |
| 313 | |
| 314 | CATCH: { |
| 315 | |
| 316 | # catch |
| 317 | my $catch; |
| 318 | if(defined($catch = $clauses->{'catch'})) { |
| 319 | my $i = 0; |
| 320 | |
| 321 | CATCHLOOP: |
| 322 | for( ; $i < @$catch ; $i += 2) { |
| 323 | my $pkg = $catch->[$i]; |
| 324 | unless(defined $pkg) { |
| 325 | #except |
| 326 | splice(@$catch,$i,2,$catch->[$i+1]->($err)); |
| 327 | $i -= 2; |
| 328 | next CATCHLOOP; |
| 329 | } |
| 330 | elsif(Scalar::Util::blessed($err) && $err->isa($pkg)) { |
| 331 | $code = $catch->[$i+1]; |
| 332 | while(1) { |
| 333 | my $more = 0; |
| 334 | local($Error::THROWN, $@); |
| 335 | my $ok = eval { |
| 336 | $@ = $err; |
| 337 | if($wantarray) { |
| 338 | @{$result} = $code->($err,\$more); |
| 339 | } |
| 340 | elsif(defined($wantarray)) { |
| 341 | @{$result} = (); |
| 342 | $result->[0] = $code->($err,\$more); |
| 343 | } |
| 344 | else { |
| 345 | $code->($err,\$more); |
| 346 | } |
| 347 | 1; |
| 348 | }; |
| 349 | if( $ok ) { |
| 350 | next CATCHLOOP if $more; |
| 351 | undef $err; |
| 352 | } |
| 353 | else { |
| 354 | $err = $@ || $Error::THROWN; |
| 355 | $err = $Error::ObjectifyCallback->({'text' =>$err}) |
| 356 | unless ref($err); |
| 357 | } |
| 358 | last CATCH; |
| 359 | }; |
| 360 | } |
| 361 | } |
| 362 | } |
| 363 | |
| 364 | # otherwise |
| 365 | my $owise; |
| 366 | if(defined($owise = $clauses->{'otherwise'})) { |
| 367 | my $code = $clauses->{'otherwise'}; |
| 368 | my $more = 0; |
| 369 | local($Error::THROWN, $@); |
| 370 | my $ok = eval { |
| 371 | $@ = $err; |
| 372 | if($wantarray) { |
| 373 | @{$result} = $code->($err,\$more); |
| 374 | } |
| 375 | elsif(defined($wantarray)) { |
| 376 | @{$result} = (); |
| 377 | $result->[0] = $code->($err,\$more); |
| 378 | } |
| 379 | else { |
| 380 | $code->($err,\$more); |
| 381 | } |
| 382 | 1; |
| 383 | }; |
| 384 | if( $ok ) { |
| 385 | undef $err; |
| 386 | } |
| 387 | else { |
| 388 | $err = $@ || $Error::THROWN; |
| 389 | |
| 390 | $err = $Error::ObjectifyCallback->({'text' =>$err}) |
| 391 | unless ref($err); |
| 392 | } |
| 393 | } |
| 394 | } |
| 395 | $err; |
| 396 | } |
| 397 | |
| 398 | sub try (&;$) { |
| 399 | my $try = shift; |
| 400 | my $clauses = @_ ? shift : {}; |
| 401 | my $ok = 0; |
| 402 | my $err = undef; |
| 403 | my @result = (); |
| 404 | |
| 405 | unshift @Error::STACK, $clauses; |
| 406 | |
| 407 | my $wantarray = wantarray(); |
| 408 | |
| 409 | do { |
| 410 | local $Error::THROWN = undef; |
| 411 | local $@ = undef; |
| 412 | |
| 413 | $ok = eval { |
| 414 | if($wantarray) { |
| 415 | @result = $try->(); |
| 416 | } |
| 417 | elsif(defined $wantarray) { |
| 418 | $result[0] = $try->(); |
| 419 | } |
| 420 | else { |
| 421 | $try->(); |
| 422 | } |
| 423 | 1; |
| 424 | }; |
| 425 | |
| 426 | $err = $@ || $Error::THROWN |
| 427 | unless $ok; |
| 428 | }; |
| 429 | |
| 430 | shift @Error::STACK; |
| 431 | |
| 432 | $err = run_clauses($clauses,$err,wantarray,@result) |
| 433 | unless($ok); |
| 434 | |
| 435 | $clauses->{'finally'}->() |
| 436 | if(defined($clauses->{'finally'})); |
| 437 | |
| 438 | if (defined($err)) |
| 439 | { |
| 440 | if (Scalar::Util::blessed($err) && $err->can('throw')) |
| 441 | { |
| 442 | throw $err; |
| 443 | } |
| 444 | else |
| 445 | { |
| 446 | die $err; |
| 447 | } |
| 448 | } |
| 449 | |
| 450 | wantarray ? @result : $result[0]; |
| 451 | } |
| 452 | |
| 453 | # Each clause adds a sub to the list of clauses. The finally clause is |
| 454 | # always the last, and the otherwise clause is always added just before |
| 455 | # the finally clause. |
| 456 | # |
| 457 | # All clauses, except the finally clause, add a sub which takes one argument |
| 458 | # this argument will be the error being thrown. The sub will return a code ref |
| 459 | # if that clause can handle that error, otherwise undef is returned. |
| 460 | # |
| 461 | # The otherwise clause adds a sub which unconditionally returns the users |
| 462 | # code reference, this is why it is forced to be last. |
| 463 | # |
| 464 | # The catch clause is defined in Error.pm, as the syntax causes it to |
| 465 | # be called as a method |
| 466 | |
| 467 | sub with (&;$) { |
| 468 | @_ |
| 469 | } |
| 470 | |
| 471 | sub finally (&) { |
| 472 | my $code = shift; |
| 473 | my $clauses = { 'finally' => $code }; |
| 474 | $clauses; |
| 475 | } |
| 476 | |
| 477 | # The except clause is a block which returns a hashref or a list of |
| 478 | # key-value pairs, where the keys are the classes and the values are subs. |
| 479 | |
| 480 | sub except (&;$) { |
| 481 | my $code = shift; |
| 482 | my $clauses = shift || {}; |
| 483 | my $catch = $clauses->{'catch'} ||= []; |
| 484 | |
| 485 | my $sub = sub { |
| 486 | my $ref; |
| 487 | my(@array) = $code->($_[0]); |
| 488 | if(@array == 1 && ref($array[0])) { |
| 489 | $ref = $array[0]; |
| 490 | $ref = [ %$ref ] |
| 491 | if(UNIVERSAL::isa($ref,'HASH')); |
| 492 | } |
| 493 | else { |
| 494 | $ref = \@array; |
| 495 | } |
| 496 | @$ref |
| 497 | }; |
| 498 | |
| 499 | unshift @{$catch}, undef, $sub; |
| 500 | |
| 501 | $clauses; |
| 502 | } |
| 503 | |
| 504 | sub otherwise (&;$) { |
| 505 | my $code = shift; |
| 506 | my $clauses = shift || {}; |
| 507 | |
| 508 | if(exists $clauses->{'otherwise'}) { |
| 509 | require Carp; |
| 510 | Carp::croak("Multiple otherwise clauses"); |
| 511 | } |
| 512 | |
| 513 | $clauses->{'otherwise'} = $code; |
| 514 | |
| 515 | $clauses; |
| 516 | } |
| 517 | |
| 518 | 1; |
| 519 | |
| 520 | package Error::WarnDie; |
| 521 | |
| 522 | sub gen_callstack($) |
| 523 | { |
| 524 | my ( $start ) = @_; |
| 525 | |
| 526 | require Carp; |
| 527 | local $Carp::CarpLevel = $start; |
| 528 | my $trace = Carp::longmess(""); |
| 529 | # Remove try calls from the trace |
| 530 | $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog; |
| 531 | $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; |
| 532 | my @callstack = split( m/\n/, $trace ); |
| 533 | return @callstack; |
| 534 | } |
| 535 | |
| 536 | my $old_DIE; |
| 537 | my $old_WARN; |
| 538 | |
| 539 | sub DEATH |
| 540 | { |
| 541 | my ( $e ) = @_; |
| 542 | |
| 543 | local $SIG{__DIE__} = $old_DIE if( defined $old_DIE ); |
| 544 | |
| 545 | die @_ if $^S; |
| 546 | |
| 547 | my ( $etype, $message, $location, @callstack ); |
| 548 | if ( ref($e) && $e->isa( "Error" ) ) { |
| 549 | $etype = "exception of type " . ref( $e ); |
| 550 | $message = $e->text; |
| 551 | $location = $e->file . ":" . $e->line; |
| 552 | @callstack = split( m/\n/, $e->stacktrace ); |
| 553 | } |
| 554 | else { |
| 555 | # Don't apply subsequent layer of message formatting |
| 556 | die $e if( $e =~ m/^\nUnhandled perl error caught at toplevel:\n\n/ ); |
| 557 | $etype = "perl error"; |
| 558 | my $stackdepth = 0; |
| 559 | while( caller( $stackdepth ) =~ m/^Error(?:$|::)/ ) { |
| 560 | $stackdepth++ |
| 561 | } |
| 562 | |
| 563 | @callstack = gen_callstack( $stackdepth + 1 ); |
| 564 | |
| 565 | $message = "$e"; |
| 566 | chomp $message; |
| 567 | |
| 568 | if ( $message =~ s/ at (.*?) line (\d+)\.$// ) { |
| 569 | $location = $1 . ":" . $2; |
| 570 | } |
| 571 | else { |
| 572 | my @caller = caller( $stackdepth ); |
| 573 | $location = $caller[1] . ":" . $caller[2]; |
| 574 | } |
| 575 | } |
| 576 | |
| 577 | shift @callstack; |
| 578 | # Do it this way in case there are no elements; we don't print a spurious \n |
| 579 | my $callstack = join( "", map { "$_\n"} @callstack ); |
| 580 | |
| 581 | die "\nUnhandled $etype caught at toplevel:\n\n $message\n\nThrown from: $location\n\nFull stack trace:\n\n$callstack\n"; |
| 582 | } |
| 583 | |
| 584 | sub TAXES |
| 585 | { |
| 586 | my ( $message ) = @_; |
| 587 | |
| 588 | local $SIG{__WARN__} = $old_WARN if( defined $old_WARN ); |
| 589 | |
| 590 | $message =~ s/ at .*? line \d+\.$//; |
| 591 | chomp $message; |
| 592 | |
| 593 | my @callstack = gen_callstack( 1 ); |
| 594 | my $location = shift @callstack; |
| 595 | |
| 596 | # $location already starts in a leading space |
| 597 | $message .= $location; |
| 598 | |
| 599 | # Do it this way in case there are no elements; we don't print a spurious \n |
| 600 | my $callstack = join( "", map { "$_\n"} @callstack ); |
| 601 | |
| 602 | warn "$message:\n$callstack"; |
| 603 | } |
| 604 | |
| 605 | sub import |
| 606 | { |
| 607 | $old_DIE = $SIG{__DIE__}; |
| 608 | $old_WARN = $SIG{__WARN__}; |
| 609 | |
| 610 | $SIG{__DIE__} = \&DEATH; |
| 611 | $SIG{__WARN__} = \&TAXES; |
| 612 | } |
| 613 | |
| 614 | 1; |
| 615 | |
| 616 | __END__ |
| 617 | |
| 618 | =head1 NAME |
| 619 | |
| 620 | Error - Error/exception handling in an OO-ish way |
| 621 | |
| 622 | =head1 WARNING |
| 623 | |
| 624 | Using the "Error" module is B<no longer recommended> due to the black-magical |
| 625 | nature of its syntactic sugar, which often tends to break. Its maintainers |
| 626 | have stopped actively writing code that uses it, and discourage people |
| 627 | from doing so. See the "SEE ALSO" section below for better recommendations. |
| 628 | |
| 629 | =head1 SYNOPSIS |
| 630 | |
| 631 | use Error qw(:try); |
| 632 | |
| 633 | throw Error::Simple( "A simple error"); |
| 634 | |
| 635 | sub xyz { |
| 636 | ... |
| 637 | record Error::Simple("A simple error") |
| 638 | and return; |
| 639 | } |
| 640 | |
| 641 | unlink($file) or throw Error::Simple("$file: $!",$!); |
| 642 | |
| 643 | try { |
| 644 | do_some_stuff(); |
| 645 | die "error!" if $condition; |
| 646 | throw Error::Simple "Oops!" if $other_condition; |
| 647 | } |
| 648 | catch Error::IO with { |
| 649 | my $E = shift; |
| 650 | print STDERR "File ", $E->{'-file'}, " had a problem\n"; |
| 651 | } |
| 652 | except { |
| 653 | my $E = shift; |
| 654 | my $general_handler=sub {send_message $E->{-description}}; |
| 655 | return { |
| 656 | UserException1 => $general_handler, |
| 657 | UserException2 => $general_handler |
| 658 | }; |
| 659 | } |
| 660 | otherwise { |
| 661 | print STDERR "Well I don't know what to say\n"; |
| 662 | } |
| 663 | finally { |
| 664 | close_the_garage_door_already(); # Should be reliable |
| 665 | }; # Don't forget the trailing ; or you might be surprised |
| 666 | |
| 667 | =head1 DESCRIPTION |
| 668 | |
| 669 | The C<Error> package provides two interfaces. Firstly C<Error> provides |
| 670 | a procedural interface to exception handling. Secondly C<Error> is a |
| 671 | base class for errors/exceptions that can either be thrown, for |
| 672 | subsequent catch, or can simply be recorded. |
| 673 | |
| 674 | Errors in the class C<Error> should not be thrown directly, but the |
| 675 | user should throw errors from a sub-class of C<Error>. |
| 676 | |
| 677 | =head1 PROCEDURAL INTERFACE |
| 678 | |
| 679 | C<Error> exports subroutines to perform exception handling. These will |
| 680 | be exported if the C<:try> tag is used in the C<use> line. |
| 681 | |
| 682 | =over 4 |
| 683 | |
| 684 | =item try BLOCK CLAUSES |
| 685 | |
| 686 | C<try> is the main subroutine called by the user. All other subroutines |
| 687 | exported are clauses to the try subroutine. |
| 688 | |
| 689 | The BLOCK will be evaluated and, if no error is throw, try will return |
| 690 | the result of the block. |
| 691 | |
| 692 | C<CLAUSES> are the subroutines below, which describe what to do in the |
| 693 | event of an error being thrown within BLOCK. |
| 694 | |
| 695 | =item catch CLASS with BLOCK |
| 696 | |
| 697 | This clauses will cause all errors that satisfy C<$err-E<gt>isa(CLASS)> |
| 698 | to be caught and handled by evaluating C<BLOCK>. |
| 699 | |
| 700 | C<BLOCK> will be passed two arguments. The first will be the error |
| 701 | being thrown. The second is a reference to a scalar variable. If this |
| 702 | variable is set by the catch block then, on return from the catch |
| 703 | block, try will continue processing as if the catch block was never |
| 704 | found. The error will also be available in C<$@>. |
| 705 | |
| 706 | To propagate the error the catch block may call C<$err-E<gt>throw> |
| 707 | |
| 708 | If the scalar reference by the second argument is not set, and the |
| 709 | error is not thrown. Then the current try block will return with the |
| 710 | result from the catch block. |
| 711 | |
| 712 | =item except BLOCK |
| 713 | |
| 714 | When C<try> is looking for a handler, if an except clause is found |
| 715 | C<BLOCK> is evaluated. The return value from this block should be a |
| 716 | HASHREF or a list of key-value pairs, where the keys are class names |
| 717 | and the values are CODE references for the handler of errors of that |
| 718 | type. |
| 719 | |
| 720 | =item otherwise BLOCK |
| 721 | |
| 722 | Catch any error by executing the code in C<BLOCK> |
| 723 | |
| 724 | When evaluated C<BLOCK> will be passed one argument, which will be the |
| 725 | error being processed. The error will also be available in C<$@>. |
| 726 | |
| 727 | Only one otherwise block may be specified per try block |
| 728 | |
| 729 | =item finally BLOCK |
| 730 | |
| 731 | Execute the code in C<BLOCK> either after the code in the try block has |
| 732 | successfully completed, or if the try block throws an error then |
| 733 | C<BLOCK> will be executed after the handler has completed. |
| 734 | |
| 735 | If the handler throws an error then the error will be caught, the |
| 736 | finally block will be executed and the error will be re-thrown. |
| 737 | |
| 738 | Only one finally block may be specified per try block |
| 739 | |
| 740 | =back |
| 741 | |
| 742 | =head1 COMPATIBILITY |
| 743 | |
| 744 | L<Moose> exports a keyword called C<with> which clashes with Error's. This |
| 745 | example returns a prototype mismatch error: |
| 746 | |
| 747 | package MyTest; |
| 748 | |
| 749 | use warnings; |
| 750 | use Moose; |
| 751 | use Error qw(:try); |
| 752 | |
| 753 | (Thanks to C<maik.hentsche@amd.com> for the report.). |
| 754 | |
| 755 | =head1 CLASS INTERFACE |
| 756 | |
| 757 | =head2 CONSTRUCTORS |
| 758 | |
| 759 | The C<Error> object is implemented as a HASH. This HASH is initialized |
| 760 | with the arguments that are passed to it's constructor. The elements |
| 761 | that are used by, or are retrievable by the C<Error> class are listed |
| 762 | below, other classes may add to these. |
| 763 | |
| 764 | -file |
| 765 | -line |
| 766 | -text |
| 767 | -value |
| 768 | -object |
| 769 | |
| 770 | If C<-file> or C<-line> are not specified in the constructor arguments |
| 771 | then these will be initialized with the file name and line number where |
| 772 | the constructor was called from. |
| 773 | |
| 774 | If the error is associated with an object then the object should be |
| 775 | passed as the C<-object> argument. This will allow the C<Error> package |
| 776 | to associate the error with the object. |
| 777 | |
| 778 | The C<Error> package remembers the last error created, and also the |
| 779 | last error associated with a package. This could either be the last |
| 780 | error created by a sub in that package, or the last error which passed |
| 781 | an object blessed into that package as the C<-object> argument. |
| 782 | |
| 783 | =over 4 |
| 784 | |
| 785 | =item Error->new() |
| 786 | |
| 787 | See the Error::Simple documentation. |
| 788 | |
| 789 | =item throw ( [ ARGS ] ) |
| 790 | |
| 791 | Create a new C<Error> object and throw an error, which will be caught |
| 792 | by a surrounding C<try> block, if there is one. Otherwise it will cause |
| 793 | the program to exit. |
| 794 | |
| 795 | C<throw> may also be called on an existing error to re-throw it. |
| 796 | |
| 797 | =item with ( [ ARGS ] ) |
| 798 | |
| 799 | Create a new C<Error> object and returns it. This is defined for |
| 800 | syntactic sugar, eg |
| 801 | |
| 802 | die with Some::Error ( ... ); |
| 803 | |
| 804 | =item record ( [ ARGS ] ) |
| 805 | |
| 806 | Create a new C<Error> object and returns it. This is defined for |
| 807 | syntactic sugar, eg |
| 808 | |
| 809 | record Some::Error ( ... ) |
| 810 | and return; |
| 811 | |
| 812 | =back |
| 813 | |
| 814 | =head2 STATIC METHODS |
| 815 | |
| 816 | =over 4 |
| 817 | |
| 818 | =item prior ( [ PACKAGE ] ) |
| 819 | |
| 820 | Return the last error created, or the last error associated with |
| 821 | C<PACKAGE> |
| 822 | |
| 823 | =item flush ( [ PACKAGE ] ) |
| 824 | |
| 825 | Flush the last error created, or the last error associated with |
| 826 | C<PACKAGE>.It is necessary to clear the error stack before exiting the |
| 827 | package or uncaught errors generated using C<record> will be reported. |
| 828 | |
| 829 | $Error->flush; |
| 830 | |
| 831 | =cut |
| 832 | |
| 833 | =back |
| 834 | |
| 835 | =head2 OBJECT METHODS |
| 836 | |
| 837 | =over 4 |
| 838 | |
| 839 | =item stacktrace |
| 840 | |
| 841 | If the variable C<$Error::Debug> was non-zero when the error was |
| 842 | created, then C<stacktrace> returns a string created by calling |
| 843 | C<Carp::longmess>. If the variable was zero the C<stacktrace> returns |
| 844 | the text of the error appended with the filename and line number of |
| 845 | where the error was created, providing the text does not end with a |
| 846 | newline. |
| 847 | |
| 848 | =item object |
| 849 | |
| 850 | The object this error was associated with |
| 851 | |
| 852 | =item file |
| 853 | |
| 854 | The file where the constructor of this error was called from |
| 855 | |
| 856 | =item line |
| 857 | |
| 858 | The line where the constructor of this error was called from |
| 859 | |
| 860 | =item text |
| 861 | |
| 862 | The text of the error |
| 863 | |
| 864 | =item $err->associate($obj) |
| 865 | |
| 866 | Associates an error with an object to allow error propagation. I.e: |
| 867 | |
| 868 | $ber->encode(...) or |
| 869 | return Error->prior($ber)->associate($ldap); |
| 870 | |
| 871 | =back |
| 872 | |
| 873 | =head2 OVERLOAD METHODS |
| 874 | |
| 875 | =over 4 |
| 876 | |
| 877 | =item stringify |
| 878 | |
| 879 | A method that converts the object into a string. This method may simply |
| 880 | return the same as the C<text> method, or it may append more |
| 881 | information. For example the file name and line number. |
| 882 | |
| 883 | By default this method returns the C<-text> argument that was passed to |
| 884 | the constructor, or the string C<"Died"> if none was given. |
| 885 | |
| 886 | =item value |
| 887 | |
| 888 | A method that will return a value that can be associated with the |
| 889 | error. For example if an error was created due to the failure of a |
| 890 | system call, then this may return the numeric value of C<$!> at the |
| 891 | time. |
| 892 | |
| 893 | By default this method returns the C<-value> argument that was passed |
| 894 | to the constructor. |
| 895 | |
| 896 | =back |
| 897 | |
| 898 | =head1 PRE-DEFINED ERROR CLASSES |
| 899 | |
| 900 | =head2 Error::Simple |
| 901 | |
| 902 | This class can be used to hold simple error strings and values. It's |
| 903 | constructor takes two arguments. The first is a text value, the second |
| 904 | is a numeric value. These values are what will be returned by the |
| 905 | overload methods. |
| 906 | |
| 907 | If the text value ends with C<at file line 1> as $@ strings do, then |
| 908 | this information will be used to set the C<-file> and C<-line> arguments |
| 909 | of the error object. |
| 910 | |
| 911 | This class is used internally if an eval'd block die's with an error |
| 912 | that is a plain string. (Unless C<$Error::ObjectifyCallback> is modified) |
| 913 | |
| 914 | |
| 915 | =head1 $Error::ObjectifyCallback |
| 916 | |
| 917 | This variable holds a reference to a subroutine that converts errors that |
| 918 | are plain strings to objects. It is used by Error.pm to convert textual |
| 919 | errors to objects, and can be overridden by the user. |
| 920 | |
| 921 | It accepts a single argument which is a hash reference to named parameters. |
| 922 | Currently the only named parameter passed is C<'text'> which is the text |
| 923 | of the error, but others may be available in the future. |
| 924 | |
| 925 | For example the following code will cause Error.pm to throw objects of the |
| 926 | class MyError::Bar by default: |
| 927 | |
| 928 | sub throw_MyError_Bar |
| 929 | { |
| 930 | my $args = shift; |
| 931 | my $err = MyError::Bar->new(); |
| 932 | $err->{'MyBarText'} = $args->{'text'}; |
| 933 | return $err; |
| 934 | } |
| 935 | |
| 936 | { |
| 937 | local $Error::ObjectifyCallback = \&throw_MyError_Bar; |
| 938 | |
| 939 | # Error handling here. |
| 940 | } |
| 941 | |
| 942 | =cut |
| 943 | |
| 944 | =head1 MESSAGE HANDLERS |
| 945 | |
| 946 | C<Error> also provides handlers to extend the output of the C<warn()> perl |
| 947 | function, and to handle the printing of a thrown C<Error> that is not caught |
| 948 | or otherwise handled. These are not installed by default, but are requested |
| 949 | using the C<:warndie> tag in the C<use> line. |
| 950 | |
| 951 | use Error qw( :warndie ); |
| 952 | |
| 953 | These new error handlers are installed in C<$SIG{__WARN__}> and |
| 954 | C<$SIG{__DIE__}>. If these handlers are already defined when the tag is |
| 955 | imported, the old values are stored, and used during the new code. Thus, to |
| 956 | arrange for custom handling of warnings and errors, you will need to perform |
| 957 | something like the following: |
| 958 | |
| 959 | BEGIN { |
| 960 | $SIG{__WARN__} = sub { |
| 961 | print STDERR "My special warning handler: $_[0]" |
| 962 | }; |
| 963 | } |
| 964 | |
| 965 | use Error qw( :warndie ); |
| 966 | |
| 967 | Note that setting C<$SIG{__WARN__}> after the C<:warndie> tag has been |
| 968 | imported will overwrite the handler that C<Error> provides. If this cannot be |
| 969 | avoided, then the tag can be explicitly C<import>ed later |
| 970 | |
| 971 | use Error; |
| 972 | |
| 973 | $SIG{__WARN__} = ...; |
| 974 | |
| 975 | import Error qw( :warndie ); |
| 976 | |
| 977 | =head2 EXAMPLE |
| 978 | |
| 979 | The C<__DIE__> handler turns messages such as |
| 980 | |
| 981 | Can't call method "foo" on an undefined value at examples/warndie.pl line 16. |
| 982 | |
| 983 | into |
| 984 | |
| 985 | Unhandled perl error caught at toplevel: |
| 986 | |
| 987 | Can't call method "foo" on an undefined value |
| 988 | |
| 989 | Thrown from: examples/warndie.pl:16 |
| 990 | |
| 991 | Full stack trace: |
| 992 | |
| 993 | main::inner('undef') called at examples/warndie.pl line 20 |
| 994 | main::outer('undef') called at examples/warndie.pl line 23 |
| 995 | |
| 996 | =cut |
| 997 | |
| 998 | =head1 SEE ALSO |
| 999 | |
| 1000 | See L<Exception::Class> for a different module providing Object-Oriented |
| 1001 | exception handling, along with a convenient syntax for declaring hierarchies |
| 1002 | for them. It doesn't provide Error's syntactic sugar of C<try { ... }>, |
| 1003 | C<catch { ... }>, etc. which may be a good thing or a bad thing based |
| 1004 | on what you want. (Because Error's syntactic sugar tends to break.) |
| 1005 | |
| 1006 | L<Error::Exception> aims to combine L<Error> and L<Exception::Class> |
| 1007 | "with correct stringification". |
| 1008 | |
| 1009 | L<TryCatch> and L<Try::Tiny> are similar in concept to Error.pm only providing |
| 1010 | a syntax that hopefully breaks less. |
| 1011 | |
| 1012 | =head1 KNOWN BUGS |
| 1013 | |
| 1014 | None, but that does not mean there are not any. |
| 1015 | |
| 1016 | =head1 AUTHORS |
| 1017 | |
| 1018 | Graham Barr <gbarr@pobox.com> |
| 1019 | |
| 1020 | The code that inspired me to write this was originally written by |
| 1021 | Peter Seibel <peter@weblogic.com> and adapted by Jesse Glick |
| 1022 | <jglick@sig.bsh.com>. |
| 1023 | |
| 1024 | C<:warndie> handlers added by Paul Evans <leonerd@leonerd.org.uk> |
| 1025 | |
| 1026 | =head1 MAINTAINER |
| 1027 | |
| 1028 | Shlomi Fish, L<https://www.shlomifish.org/> . |
| 1029 | |
| 1030 | =head1 PAST MAINTAINERS |
| 1031 | |
| 1032 | Arun Kumar U <u_arunkumar@yahoo.com> |
| 1033 | |
| 1034 | =head1 COPYRIGHT |
| 1035 | |
| 1036 | Copyright (c) 1997-8 Graham Barr. All rights reserved. |
| 1037 | This program is free software; you can redistribute it and/or modify it |
| 1038 | under the same terms as Perl itself. |
| 1039 | |
| 1040 | =cut |