Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls.3pm

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Version: 2010-09-08 (fedora - 01/12/10)

Section: 3 (Bibliothèques de fonctions)

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NAME

Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls - Write "if($condition){ do_something() }" instead of "do_something() if $condition".

AFFILIATION

This Policy is part of the core Perl::Critic distribution.

DESCRIPTION

Conway discourages using postfix control structures ("if", "for", "unless", "until", "while") because they hide control flow. The "unless" and "until" controls are particularly evil because they lead to double-negatives that are hard to comprehend. The only tolerable usage of a postfix "if" is when it follows a loop break such as "last", "next", "redo", or "continue". 
     do_something() if $condition;         #not ok
     if($condition){ do_something() }      #ok
 
     do_something() while $condition;      #not ok
     while($condition){ do_something() }   #ok
 
     do_something() unless $condition;     #not ok
     do_something() unless ! $condition;   #really bad
     if(! $condition){ do_something() }    #ok
 
     do_something() until $condition;      #not ok
     do_something() until ! $condition;    #really bad
     while(! $condition){ do_something() } #ok
 
     do_something($_) for @list;           #not ok
 
     LOOP:
     for my $n (0..100){
         next if $condition;               #ok
         last LOOP if $other_condition;    #also ok
     }

CONFIGURATION

A set of constructs to be ignored by this policy can specified by giving a value for 'allow' of a string of space-delimited keywords: "if", "for", "unless", "until", and/or "while". An example of specifying allowed flow-control structures in a .perlcriticrc file: 
     [ControlStructures::ProhibitPostfixControls]
     allow = for if until

By default, all postfix control keywords are prohibited.

The set of flow-control functions that are exempt from the restriction can also be configured with the 'flowcontrol' directive in your .perlcriticrc file:

     [ControlStructures::ProhibitPostfixControls]
     flowcontrol = warn die carp croak cluck confess goto exit

This is useful if you're using additional modules that add things like "assert" or "throw".

NOTES

The "die", "croak", and "confess" functions are frequently used as flow-controls just like "next" or "last". So this Policy does permit you to use a postfix "if" when the statement begins with one of those functions. It is also pretty common to use "warn", "carp", and "cluck" with a postfix "if", so those are allowed too.

BUGS

Look for the "do {} while" case and change the explanation to point to page 123 when it is found. RT #37905.

AUTHOR

Jeffrey Ryan Thalhammer <thaljef@cpan.org> Copyright (c) 2005-2009 Jeffrey Ryan Thalhammer. All rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module.