10 indirect - Lexically warn about using the indirect object syntax.
27 my $x = new Apple 1, 2, 3; # warns
30 my $y = new Pear; # ok
32 no indirect hook => sub { die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]" };
33 my $z = new Pineapple 'fresh'; # croaks 'You really wanted Pineapple->new at blurp.pm:13'
38 no indirect ':fatal'; # or 'FATAL', or ':Fatal' ...
39 if (defied $foo) { ... } # croaks, note the typo
41 # From the command-line
42 perl -M-indirect -e 'my $x = new Banana;' # warns
44 # Or each time perl is ran
45 export PERL5OPT="-M-indirect"
46 perl -e 'my $y = new Coconut;' # warns
50 When enabled (or disabled as some may prefer to say, since you actually turn it on by calling C<no indirect>), this pragma warns about indirect object syntax constructs that may have slipped into your code.
52 This syntax is now considered harmful, since its parsing has many quirks and its use is error prone (when C<swoosh> is not defined, C<swoosh $x> actually compiles to C<< $x->swoosh >>).
53 In L<http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal>, Matt S. Trout gives an example of an indirect construct that can cause a particularly bewildering error.
55 It currently does not warn for core functions (C<print>, C<say>, C<exec> or C<system>).
56 This may change in the future, or may be added as optional features that would be enabled by passing options to C<unimport>.
58 This module is B<not> a source filter.
63 if ($ENV{PERL_INDIRECT_PM_DISABLE}) {
64 *_tag = sub ($) { 1 };
65 *I_THREADSAFE = sub () { 1 };
66 *I_FORKSAFE = sub () { 1 };
69 XSLoader::load(__PACKAGE__, $VERSION);
75 =head2 C<< unimport [ hook => $hook | ':fatal', 'FATAL', ... ] >>
77 Magically called when C<no indirect @opts> is encountered.
79 The policy to apply depends on what is first found in C<@opts> :
85 If it is a string that matches C</^:?fatal$/i>, the compilation will croak on the first indirect syntax met.
89 If the key/value pair C<< hook => $hook >> comes first, C<$hook> will be called for each error with a string representation of the object as C<$_[0]>, the method name as C<$_[1]>, the current file as C<$_[2]> and the line number as C<$_[3]>.
90 If and only if the object is actually a block, C<$_[0]> is assured to start by C<'{'>.
94 Otherwise, a warning will be emitted for each indirect construct.
106 if ($arg eq 'hook') {
108 } elsif ($arg =~ /^:?fatal$/i) {
109 $hook = sub { die msg(@_) };
113 $hook = sub { warn msg(@_) } unless defined $hook;
116 $^H{+(__PACKAGE__)} = _tag($hook);
123 Magically called at each C<use indirect>. Turns the module off.
128 $^H{+(__PACKAGE__)} = undef;
134 =head2 C<msg $object, $method, $file, $line>
136 Returns the default error message generated by C<indirect> when an invalid construct is reported.
143 join ' ', "Indirect call of method \"$_[1]\" on",
144 ($obj =~ /^\s*\{/ ? "a block" : "object \"$obj\""),
145 "at $_[2] line $_[3].\n";
150 =head2 C<I_THREADSAFE>
152 True iff the module could have been built with thread-safety features enabled.
156 True iff this module could have been built with fork-safety features enabled.
157 This will always be true except on Windows where it's false for perl 5.10.0 and below .
161 =head2 C<Indirect call of method "%s" on object "%s" at %s line %d.>
163 The default warning/exception message thrown when an indirect call on an object is found.
165 =head2 C<Indirect call of method "%s" on a block at %s line %d.>
167 The default warning/exception message thrown when an indirect call on a block is found.
171 =head2 C<PERL_INDIRECT_PM_DISABLE>
173 If this environment variable is set to true when the pragma is used for the first time, the XS code won't be loaded and, although the C<'indirect'> lexical hint will be set to true in the scope of use, the pragma itself won't do anything.
174 In this case, the pragma will always be considered to be thread-safe, and as such L</I_THREADSAFE> will be true.
175 This is useful for disabling C<indirect> in production environments.
177 Note that clearing this variable after C<indirect> was loaded has no effect.
178 If you want to re-enable the pragma later, you also need to reload it by deleting the C<'indirect.pm'> entry from C<%INC>.
182 The implementation was tweaked to work around several limitations of vanilla C<perl> pragmas : it's thread safe, and does not suffer from a C<perl 5.8.x-5.10.0> bug that causes all pragmas to propagate into C<require>d scopes.
184 C<meth $obj> (no semicolon) at the end of a file won't be seen as an indirect object syntax, although it will as soon as there is another token before the end (as in C<meth $obj;> or C<meth $obj 1>).
186 With 5.8 perls, the pragma does not propagate into C<eval STRING>.
187 This is due to a shortcoming in the way perl handles the hints hash, which is addressed in perl 5.10.
189 The search for indirect method calls happens before constant folding.
190 Hence C<my $x = new Class if 0> will be caught.
196 L<XSLoader> (standard since perl 5.006).
200 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
202 You can contact me by mail or on C<irc.perl.org> (vincent).
206 Please report any bugs or feature requests to C<bug-indirect at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=indirect>.
207 I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
211 You can find documentation for this module with the perldoc command.
215 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/indirect>.
217 =head1 ACKNOWLEDGEMENTS
219 Bram, for motivation and advices.
221 Andrew Main and Florian Ragwitz, for testing on real-life code and reporting issues.
223 =head1 COPYRIGHT & LICENSE
225 Copyright 2008,2009,2010 Vincent Pit, all rights reserved.
227 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.