indirect - Lexically warn about using the indirect object syntax.

Version 0.23

    # In a script
    no indirect;
    my $x = new Apple 1, 2, 3; # warns
    {
     use indirect;
     my $y = new Pear; # ok
     {
      no indirect hook => sub { die "You really wanted $_[0]\->$_[1] at $_[2]:$_[3]" };
      my $z = new Pineapple 'fresh'; # croaks 'You really wanted Pineapple->new at blurp.pm:13'
     }
    }
    try { ... }; # warns

    no indirect ':fatal';    # or 'FATAL', or ':Fatal' ...
    if (defied $foo) { ... } # croaks, note the typo

    # From the command-line
    perl -M-indirect -e 'my $x = new Banana;' # warns

    # Or each time perl is ran
    export PERL5OPT="-M-indirect"
    perl -e 'my $y = new Coconut;' # warns

When enabled (or disabled as some may prefer to say, since you actually turn it on by calling no indirect), this pragma warns about indirect object syntax constructs that may have slipped into your code.

This syntax is now considered harmful, since its parsing has many quirks and its use is error prone (when swoosh is not defined, swoosh $x actually compiles to $x->swoosh). In 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.

It currently does not warn for core functions (print, say, exec or system). This may change in the future, or may be added as optional features that would be enabled by passing options to unimport.

This module is not a source filter.

Magically called when no indirect @opts is encountered. Turns the module on. The policy to apply depends on what is first found in @opts :

• If it is a string that matches /^:?fatal$/i, the compilation will croak on the first indirect syntax met.
• If the key/value pair hook => $hook comes first, $hook will be called for each error with a string representation of the object as $_[0], the method name as $_[1], the current file as $_[2] and the line number as $_[3]. If and only if the object is actually a block, $_[0] is assured to start by '{'.
• Otherwise, a warning will be emitted for each indirect construct.

Magically called at each use indirect. Turns the module off.

Returns the default error message generated by indirect when an invalid construct is reported.

True iff the module could have been built with thread-safety features enabled.

True iff this module could have been built with fork-safety features enabled. This will always be true except on Windows where it's false for perl 5.10.0 and below .

The default warning/exception message thrown when an indirect call on an object is found.

The default warning/exception message thrown when an indirect call on a block is found.

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 'indirect' lexical hint will be set to true in the scope of use, the pragma itself won't do anything. In this case, the pragma will always be considered to be thread-safe, and as such I_THREADSAFE will be true. This is useful for disabling indirect in production environments.

Note that clearing this variable after indirect was loaded has no effect. If you want to re-enable the pragma later, you also need to reload it by deleting the 'indirect.pm' entry from %INC.

The implementation was tweaked to work around several limitations of vanilla perl pragmas : it's thread safe, and does not suffer from a perl 5.8.x-5.10.0 bug that causes all pragmas to propagate into required scopes.

Before perl 5.12, 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 meth $obj; or meth $obj 1). If you use perl 5.12 or greater, those constructs are correctly reported.

With 5.8 perls, the pragma does not propagate into eval STRING. This is due to a shortcoming in the way perl handles the hints hash, which is addressed in perl 5.10.

The search for indirect method calls happens before constant folding. Hence my $x = new Class if 0 will be caught.

perl 5.8.1.

XSLoader (standard since perl 5.006).

Vincent Pit, <perl at profvince.com>, http://www.profvince.com.

You can contact me by mail or on irc.perl.org (vincent).

Please report any bugs or feature requests to bug-indirect at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=indirect. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

You can find documentation for this module with the perldoc command.

    perldoc indirect

Tests code coverage report is available at http://www.profvince.com/perl/cover/indirect.

Bram, for motivation and advices.

Andrew Main and Florian Ragwitz, for testing on real-life code and reporting issues.

Copyright 2008,2009,2010 Vincent Pit, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.