noble (3) Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls.3pm.gz

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", "when", "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"/"when"
       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

               next when m< 0 \z >xms;             # fine too
           }

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", "when", 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.

       The "when" keyword was added to the language after Perl Best Practices was written.  This policy treats
       "when" the same way it does "if", i.e. it's allowed after flow-control constructs.  Thanks to brian d foy
       for the inspiration <http://www.effectiveperlprogramming.com/blog/543>.

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 <jeff@imaginative-software.com>

COPYRIGHT

       Copyright (c) 2005-2011 Imaginative Software Systems.  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.

perl v5.36.0                               Perl::Critic::Policy::ControlStructures::ProhibitPostfixControls(3pm)