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indirect-0.23
River stage two • 60 direct dependents • 74 total dependents
9 ++
/ indirect

NAME

indirect - Lexically warn about using the indirect object syntax.

VERSION

Version 0.23

SYNOPSIS

    # 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

DESCRIPTION

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.

METHODS

unimport [ hook => $hook | ':fatal', 'FATAL', ... ]

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.

import

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

FUNCTIONS

msg $object, $method, $file, $line

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

CONSTANTS

I_THREADSAFE

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

I_FORKSAFE

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 .

DIAGNOSTICS

Indirect call of method "%s" on object "%s" at %s line %d.

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

Indirect call of method "%s" on a block at %s line %d.

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

ENVIRONMENT

PERL_INDIRECT_PM_DISABLE

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.

CAVEATS

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.

DEPENDENCIES

perl 5.8.1.

XSLoader (standard since perl 5.006).

AUTHOR

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

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

BUGS

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.

SUPPORT

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.

ACKNOWLEDGEMENTS

Bram, for motivation and advices.

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

COPYRIGHT & LICENSE

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.