indirect - README

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 "require"d 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.

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