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 {
33 die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]"
35 # croaks 'You really wanted Pineapple->new at blurp.pm:13'
36 my $z = new Pineapple 'fresh';
41 no indirect ':fatal'; # or 'FATAL', or ':Fatal' ...
42 if (defied $foo) { ... } # croaks, note the typo
44 # Globally enabled from the command-line
45 perl -M-indirect=global -e 'my $x = new Banana;' # warns
47 # Or globally enabled each time perl is executed
48 export PERL5OPT="-M-indirect=global"
49 perl -e 'my $y = new Coconut;' # warns
53 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.
55 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<< $x->swoosh >>).
56 In L<http://www.shadowcat.co.uk/blog/matt-s-trout/indirect-but-still-fatal>, Matt S. Trout gives an example of an indirect construct that can cause a particularly bewildering error.
58 It currently does not warn for core functions (C<print>, C<say>, C<exec> or C<system>).
59 This may change in the future, or may be added as optional features that would be enabled by passing options to C<unimport>.
61 This module is B<not> a source filter.
66 if ($ENV{PERL_INDIRECT_PM_DISABLE}) {
67 *_tag = sub ($) { 1 };
68 *I_THREADSAFE = sub () { 1 };
69 *I_FORKSAFE = sub () { 1 };
72 XSLoader::load(__PACKAGE__, $VERSION);
78 =head2 C<< unimport [ 'global', hook => $hook | 'fatal' ] >>
80 Magically called when C<no indirect @opts> is encountered.
82 The policy to apply depends on what is first found in C<@opts> :
88 If it is a string that matches C</^:?fatal$/i>, the compilation will croak on the first indirect syntax met.
92 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]>.
93 If and only if the object is actually a block, C<$_[0]> is assured to start by C<'{'>.
97 If none of C<fatal> and C<hook> are specified, a warning will be emitted for each indirect construct.
101 If C<@opts> contains a string that matches C</^:?global$/i>, the pragma will be globally enabled for B<all> code compiled after the current C<no indirect> statement, except for code that is in the lexical scope of C<use indirect>.
102 This option may come indifferently before or after the C<fatal> or C<hook> options, in the case they are also passed to L</unimport>.
104 The global policy applied is the one resulting of the C<fatal> or C<hook> options, thus defaults to a warning when none of those are specified :
106 no indirect 'global'; # warn for any indirect call
107 no indirect qw<global fatal>; # die on any indirect call
108 no indirect 'global', hook => \&hook # custom global action
110 Note that if another policy is installed by a C<no indirect> statement further in the code, it will overrule the global policy :
112 no indirect 'global'; # warn globally
114 no indirect 'fatal'; # throw exceptions for this lexical scope
116 require Some::Module; # the global policy will apply for the
117 # compilation phase of this module
131 if ($arg eq 'hook') {
134 } elsif ($arg =~ /^:?fatal$/i) {
136 $hook = sub { die msg(@_) };
137 } elsif ($arg =~ /^:?global$/i) {
141 $hook = sub { warn msg(@_) } unless defined $hook;
145 delete $^H{+(__PACKAGE__)};
148 $^H{+(__PACKAGE__)} = _tag($hook);
156 Magically called at each C<use indirect>. Turns the module off.
158 As explained in L</unimport>'s description, an C<use indirect> statement will lexically override a global policy previously installed by C<no indirect 'global', ...> (if there's one).
164 $^H{+(__PACKAGE__)} = _tag(undef);
171 =head2 C<msg $object, $method, $file, $line>
173 Returns the default error message generated by C<indirect> when an invalid construct is reported.
180 join ' ', "Indirect call of method \"$_[1]\" on",
181 ($obj =~ /^\s*\{/ ? "a block" : "object \"$obj\""),
182 "at $_[2] line $_[3].\n";
187 =head2 C<I_THREADSAFE>
189 True iff the module could have been built with thread-safety features enabled.
193 True iff this module could have been built with fork-safety features enabled.
194 This will always be true except on Windows where it's false for perl 5.10.0 and below .
198 =head2 C<Indirect call of method "%s" on object "%s" at %s line %d.>
200 The default warning/exception message thrown when an indirect call on an object is found.
202 =head2 C<Indirect call of method "%s" on a block at %s line %d.>
204 The default warning/exception message thrown when an indirect call on a block is found.
208 =head2 C<PERL_INDIRECT_PM_DISABLE>
210 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.
211 In this case, the pragma will always be considered to be thread-safe, and as such L</I_THREADSAFE> will be true.
212 This is useful for disabling C<indirect> in production environments.
214 Note that clearing this variable after C<indirect> was loaded has no effect.
215 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>.
219 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.
221 Before C<perl> 5.12, C<meth $obj> (no semicolon) at the end of a file is not seen as an indirect object syntax, although it is as soon as there is another token before the end (as in C<meth $obj;> or C<meth $obj 1>).
222 If you use C<perl> 5.12 or greater, those constructs are correctly reported.
224 With 5.8 perls, the pragma does not propagate into C<eval STRING>.
225 This is due to a shortcoming in the way perl handles the hints hash, which is addressed in perl 5.10.
227 The search for indirect method calls happens before constant folding.
228 Hence C<my $x = new Class if 0> will be caught.
235 This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
237 L<XSLoader> (standard since perl 5.006).
241 Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
243 You can contact me by mail or on C<irc.perl.org> (vincent).
247 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>.
248 I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
252 You can find documentation for this module with the perldoc command.
256 Tests code coverage report is available at L<http://www.profvince.com/perl/cover/indirect>.
258 =head1 ACKNOWLEDGEMENTS
260 Bram, for motivation and advices.
262 Andrew Main and Florian Ragwitz, for testing on real-life code and reporting issues.
264 =head1 COPYRIGHT & LICENSE
266 Copyright 2008,2009,2010,2011 Vincent Pit, all rights reserved.
268 This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.