Incorporating some of Chris' suggestions.

[gknop/Perl-Critic.git] / lib / Perl / Critic.pm

##############################################################################
#      $URL$
#     $Date$
#   $Author$
# $Revision$
##############################################################################

package Perl::Critic;

use 5.006001;
use strict;
use warnings;

use English qw(-no_match_vars);
use Readonly;

use base qw(Exporter);

use File::Spec;
use Scalar::Util qw(blessed);

use PPI::Document;
use PPI::Document::File;

use Perl::Critic::Exception::Configuration::Generic;
use Perl::Critic::Exception::Parse qw{ throw_parse };
use Perl::Critic::Config;
use Perl::Critic::Violation;
use Perl::Critic::Document;
use Perl::Critic::Statistics;
use Perl::Critic::Utils qw{ :characters hashify };

#-----------------------------------------------------------------------------

our $VERSION = '1.093_01';

Readonly::Array our @EXPORT_OK => qw(critique);

#-----------------------------------------------------------------------------

sub new {
    my ( $class, %args ) = @_;
    my $self = bless {}, $class;
    $self->{_config} = $args{-config} || Perl::Critic::Config->new( %args );
    $self->{_stats} = Perl::Critic::Statistics->new();
    return $self;
}

#-----------------------------------------------------------------------------

sub config {
    my $self = shift;
    return $self->{_config};
}

#-----------------------------------------------------------------------------

sub add_policy {
    my ( $self, @args ) = @_;
    #Delegate to Perl::Critic::Config
    return $self->config()->add_policy( @args );
}

#-----------------------------------------------------------------------------

sub policies {
    my $self = shift;

    #Delegate to Perl::Critic::Config
    return $self->config()->policies();
}

#-----------------------------------------------------------------------------

sub statistics {
    my $self = shift;
    return $self->{_stats};
}

#-----------------------------------------------------------------------------

sub critique {  ## no critic (ArgUnpacking)

    #-------------------------------------------------------------------
    # This subroutine can be called as an object method or as a static
    # function.  In the latter case, the first argument can be a
    # hashref of configuration parameters that shall be used to create
    # an object behind the scenes.  Note that this object does not
    # persist.  In other words, it is not a singleton.  Here are some
    # of the ways this subroutine might get called:
    #
    # #Object style...
    # $critic->critique( $code );
    #
    # #Functional style...
    # critique( $code );
    # critique( {}, $code );
    # critique( {-foo => bar}, $code );
    #------------------------------------------------------------------

    my ( $self, $source_code ) = @_ >= 2 ? @_ : ( {}, $_[0] );
    $self = ref $self eq 'HASH' ? __PACKAGE__->new(%{ $self }) : $self;
    return if not defined $source_code;  # If no code, then nothing to do.

    my $doc = $self->_create_perl_critic_document($source_code);

    if ( 0 == $self->policies() ) {
        Perl::Critic::Exception::Configuration::Generic->throw(
            message => 'There are no enabled policies.',
        )
    }

    return $self->_gather_violations($doc);
}

#=============================================================================
# PRIVATE functions

sub _create_perl_critic_document {
    my ($self, $source_code) = @_;

    # $source_code can be a file name, or a reference to a
    # PPI::Document, or a reference to a scalar containing source
    # code.  In the last case, PPI handles the translation for us.

    my $doc = _is_ppi_doc( $source_code ) ? $source_code
              : ref $source_code ? PPI::Document->new($source_code)
              : PPI::Document::File->new($source_code);

    # Bail on error
    if ( not defined $doc ) {
        my $errstr   = PPI::Document::errstr();
        my $file     = ref $source_code ? undef : $source_code;
        throw_parse
            message     => qq<Can't parse code: $errstr>,
            file_name   => $file;
    }

    # Pre-index location of each node (for speed)
    $doc->index_locations();

    # Wrap the doc in a caching layer
    return Perl::Critic::Document->new($doc);
}

#-----------------------------------------------------------------------------

sub _gather_violations {
    my ($self, $doc) = @_;

    # Disable exempt code lines, if desired
    if ( not $self->config->force() ) {
        my @site_policies = $self->config->site_policy_names();
        $doc->mark_disabled_lines(@site_policies);
    }

    # Evaluate each policy
    my @policies = $self->config->policies();
    my @violations = map { _critique($_, $doc) } @policies;

    # Accumulate statistics
    $self->statistics->accumulate( $doc, \@violations );

    # If requested, rank violations by their severity and return the top N.
    if ( @violations && (my $top = $self->config->top()) ) {
        my $limit = @violations < $top ? $#violations : $top-1;
        @violations = Perl::Critic::Violation::sort_by_severity(@violations);
        @violations = ( reverse @violations )[ 0 .. $limit ];  #Slicing...
    }

    # Always return violations sorted by location
    return Perl::Critic::Violation->sort_by_location(@violations);
}

#-----------------------------------------------------------------------------

sub _is_ppi_doc {
    my ($ref) = @_;
    return blessed($ref) && $ref->isa('PPI::Document');
}

#-----------------------------------------------------------------------------

sub _critique {
    my ($policy, $doc) = @_;

    return if not $policy->prepare_to_scan_document($doc);

    my $maximum_violations = $policy->get_maximum_violations_per_document();
    return if defined $maximum_violations && $maximum_violations == 0;

    my @violations = ();
    my $policy_name = $policy->get_long_name();
    my %policies_that_cannot_be_disabled = hashify(_policies_that_cannot_be_disabled());

  TYPE:
    for my $type ( $policy->applies_to() ) {

      ELEMENT:
        for my $element ( @{ $doc->find($type) || [] } ) {

            # Evaluate the policy on this $element.  A policy may
            # return zero or more violations.  We only want the
            # violations that occur on lines that have not been
            # disabled.

          VIOLATION:
            for my $violation ( $policy->violates( $element, $doc ) ) {
                my $line = $violation->location()->[0];
                next VIOLATION if $doc->is_line_disabled($line, $policy_name)
                    and not exists $policies_that_cannot_be_disabled{$policy_name};

                push @violations, $violation;
                if (
                        defined $maximum_violations
                    and @violations >= $maximum_violations
                ) {
                    last TYPE;
                }
            }
        }
    }

    return @violations;
}

#-----------------------------------------------------------------------------

sub _policies_that_cannot_be_disabled {
    # This is a special list of policies that cannot
    # be disabled by the "no critic" pseudo-pragma.

    return qw(
        Perl::Critic::Policy::Miscellanea::ProhibitUnrestrictedNoCritic
    );
}

#-----------------------------------------------------------------------------

1;



__END__

=pod

=for stopwords DGR INI-style API -params pbp refactored ActivePerl
ben Jore Dolan's

=head1 NAME

Perl::Critic - Critique Perl source code for best-practices.


=head1 SYNOPSIS

  use Perl::Critic;
  my $file = shift;
  my $critic = Perl::Critic->new();
  my @violations = $critic->critique($file);
  print @violations;


=head1 DESCRIPTION

Perl::Critic is an extensible framework for creating and applying
coding standards to Perl source code.  Essentially, it is a static
source code analysis engine.  Perl::Critic is distributed with a
number of L<Perl::Critic::Policy|Perl::Critic::Policy> modules that
attempt to enforce various coding guidelines.  Most Policy modules are
based on Damian Conway's book B<Perl Best Practices>.  However,
Perl::Critic is B<not> limited to PBP and will even support Policies
that contradict Conway.  You can enable, disable, and customize those
Polices through the Perl::Critic interface.  You can also create new
Policy modules that suit your own tastes.

For a command-line interface to Perl::Critic, see the documentation
for L<perlcritic|perlcritic>.  If you want to integrate Perl::Critic
with your build process, L<Test::Perl::Critic|Test::Perl::Critic>
provides an interface that is suitable for test scripts.  Also,
L<Test::Perl::Critic::Progressive|Test::Perl::Critic::Progressive> is
useful for gradually applying coding standards to legacy code.  For
the ultimate convenience (at the expense of some flexibility) see the
L<criticism|criticism> pragma.

Win32 and ActivePerl users can find PPM distributions of Perl::Critic
at L<http://theoryx5.uwinnipeg.ca/ppms/>.

If you'd like to try L<Perl::Critic|Perl::Critic> without installing
anything, there is a web-service available at
L<http://perlcritic.com>.  The web-service does not yet support all
the configuration features that are available in the native
Perl::Critic API, but it should give you a good idea of what it does.
You can also invoke the perlcritic web-service from the command-line
by doing an HTTP-post, such as one of these:

   $> POST http://perlcritic.com/perl/critic.pl < MyModule.pm
   $> lwp-request -m POST http://perlcritic.com/perl/critic.pl < MyModule.pm
   $> wget -q -O - --post-file=MyModule.pm http://perlcritic.com/perl/critic.pl

Please note that the perlcritic web-service is still alpha code.  The
URL and interface to the service are subject to change.


=head1 CONSTRUCTOR

=over

=item C<< new( [ -profile => $FILE, -severity => $N, -theme => $string, -include => \@PATTERNS, -exclude => \@PATTERNS, -top => $N, -only => $B, -profile-strictness => $PROFILE_STRICTNESS_{WARN|FATAL|QUIET}, -force => $B, -verbose => $N ], -color => $B, -pager => $string, -criticism-fatal => $B) >>

=item C<< new() >>

Returns a reference to a new Perl::Critic object.  Most arguments are
just passed directly into
L<Perl::Critic::Config|Perl::Critic::Config>, but I have described
them here as well.  The default value for all arguments can be defined
in your F<.perlcriticrc> file.  See the L<"CONFIGURATION"> section for
more information about that.  All arguments are optional key-value
pairs as follows:

B<-profile> is a path to a configuration file. If C<$FILE> is not
defined, Perl::Critic::Config attempts to find a F<.perlcriticrc>
configuration file in the current directory, and then in your home
directory.  Alternatively, you can set the C<PERLCRITIC> environment
variable to point to a file in another location.  If a configuration
file can't be found, or if C<$FILE> is an empty string, then all
Policies will be loaded with their default configuration.  See
L<"CONFIGURATION"> for more information.

B<-severity> is the minimum severity level.  Only Policy modules that
have a severity greater than C<$N> will be applied.  Severity values
are integers ranging from 1 (least severe) to 5 (most severe).  The
default is 5.  For a given C<-profile>, decreasing the C<-severity>
will usually reveal more Policy violations.  You can set the default
value for this option in your F<.perlcriticrc> file.  Users can
redefine the severity level for any Policy in their F<.perlcriticrc>
file.  See L<"CONFIGURATION"> for more information.

If it is difficult for you to remember whether severity "5" is the
most or least restrictive level, then you can use one of these named
values:

    SEVERITY NAME   ...is equivalent to...   SEVERITY NUMBER
    --------------------------------------------------------
    -severity => 'gentle'                     -severity => 5
    -severity => 'stern'                      -severity => 4
    -severity => 'harsh'                      -severity => 3
    -severity => 'cruel'                      -severity => 2
    -severity => 'brutal'                     -severity => 1

B<-theme> is special expression that determines which Policies to
apply based on their respective themes.  For example, the following
would load only Policies that have a 'bugs' AND 'pbp' theme:

  my $critic = Perl::Critic->new( -theme => 'bugs && pbp' );

Unless the C<-severity> option is explicitly given, setting C<-theme>
silently causes the C<-severity> to be set to 1.  You can set the
default value for this option in your F<.perlcriticrc> file.  See the
L<"POLICY THEMES"> section for more information about themes.


B<-include> is a reference to a list of string C<@PATTERNS>.  Policy
modules that match at least one C<m/$PATTERN/ixms> will always be
loaded, irrespective of all other settings.  For example:

  my $critic = Perl::Critic->new(-include => ['layout'] -severity => 4);

This would cause Perl::Critic to apply all the C<CodeLayout::*> Policy
modules even though they have a severity level that is less than 4.
You can set the default value for this option in your F<.perlcriticrc>
file.  You can also use C<-include> in conjunction with the
C<-exclude> option.  Note that C<-exclude> takes precedence over
C<-include> when a Policy matches both patterns.

B<-exclude> is a reference to a list of string C<@PATTERNS>.  Policy
modules that match at least one C<m/$PATTERN/ixms> will not be loaded,
irrespective of all other settings.  For example:

  my $critic = Perl::Critic->new(-exclude => ['strict'] -severity => 1);

This would cause Perl::Critic to not apply the C<RequireUseStrict> and
C<ProhibitNoStrict> Policy modules even though they have a severity
level that is greater than 1.  You can set the default value for this
option in your F<.perlcriticrc> file.  You can also use C<-exclude> in
conjunction with the C<-include> option.  Note that C<-exclude> takes
precedence over C<-include> when a Policy matches both patterns.

B<-single-policy> is a string C<PATTERN>.  Only one policy that
matches C<m/$PATTERN/ixms> will be used.  Policies that do not match
will be excluded.  This option has precedence over the C<-severity>,
C<-theme>, C<-include>, C<-exclude>, and C<-only> options.  You can
set the default value for this option in your F<.perlcriticrc> file.

B<-top> is the maximum number of Violations to return when ranked by
their severity levels.  This must be a positive integer.  Violations
are still returned in the order that they occur within the file.
Unless the C<-severity> option is explicitly given, setting C<-top>
silently causes the C<-severity> to be set to 1.  You can set the
default value for this option in your F<.perlcriticrc> file.

B<-only> is a boolean value.  If set to a true value, Perl::Critic
will only choose from Policies that are mentioned in the user's
profile.  If set to a false value (which is the default), then
Perl::Critic chooses from all the Policies that it finds at your site.
You can set the default value for this option in your F<.perlcriticrc>
file.

B<-profile-strictness> is an enumerated value, one of
L<Perl::Critic::Utils::Constants/"$PROFILE_STRICTNESS_WARN"> (the
default),
L<Perl::Critic::Utils::Constants/"$PROFILE_STRICTNESS_FATAL">, and
L<Perl::Critic::Utils::Constants/"$PROFILE_STRICTNESS_QUIET">.  If set
to L<Perl::Critic::Utils::Constants/"$PROFILE_STRICTNESS_FATAL">,
Perl::Critic will make certain warnings about problems found in a
F<.perlcriticrc> or file specified via the B<-profile> option fatal.
For example, Perl::Critic normally only C<warn>s about profiles
referring to non-existent Policies, but this value makes this
situation fatal.  Correspondingly,
L<Perl::Critic::Utils::Constants/"$PROFILE_STRICTNESS_QUIET"> makes
Perl::Critic shut up about these things.

B<-force> is a boolean value that controls whether Perl::Critic
observes the magical C<"## no critic"> pseudo-pragmas in your code.
If set to a true value, Perl::Critic will analyze all code.  If set to
a false value (which is the default) Perl::Critic will ignore code
that is tagged with these comments.  See L<"BENDING THE RULES"> for
more information.  You can set the default value for this option in
your F<.perlcriticrc> file.

B<-verbose> can be a positive integer (from 1 to 11), or a literal
format specification.  See
L<Perl::Critic::Violation|Perl::Critic::Violation> for an explanation
of format specifications.  You can set the default value for this
option in your F<.perlcriticrc> file.

B<-color> and B<-pager> are not used by Perl::Critic but is provided for the benefit
of L<perlcritic|perlcritic>.

B<-criticism-fatal> is not used by Perl::Critic but is provided for
the benefit of L<criticism|criticism>.

=back


=head1 METHODS

=over

=item C<critique( $source_code )>

Runs the C<$source_code> through the Perl::Critic engine using all the
Policies that have been loaded into this engine.  If C<$source_code>
is a scalar reference, then it is treated as a string of actual Perl
code.  If C<$source_code> is a reference to an instance of
L<PPI::Document|PPI::Document>, then that instance is used directly.
Otherwise, it is treated as a path to a local file containing Perl
code.  This method returns a list of
L<Perl::Critic::Violation|Perl::Critic::Violation> objects for each
violation of the loaded Policies.  The list is sorted in the order
that the Violations appear in the code.  If there are no violations,
this method returns an empty list.

=item C<< add_policy( -policy => $policy_name, -params => \%param_hash ) >>

Creates a Policy object and loads it into this Critic.  If the object
cannot be instantiated, it will throw a fatal exception.  Otherwise,
it returns a reference to this Critic.

B<-policy> is the name of a
L<Perl::Critic::Policy|Perl::Critic::Policy> subclass module.  The
C<'Perl::Critic::Policy'> portion of the name can be omitted for
brevity.  This argument is required.

B<-params> is an optional reference to a hash of Policy parameters.
The contents of this hash reference will be passed into to the
constructor of the Policy module.  See the documentation in the
relevant Policy module for a description of the arguments it supports.

=item C< policies() >

Returns a list containing references to all the Policy objects that
have been loaded into this engine.  Objects will be in the order that
they were loaded.

=item C< config() >

Returns the L<Perl::Critic::Config|Perl::Critic::Config> object that
was created for or given to this Critic.

=item C< statistics() >

Returns the L<Perl::Critic::Statistics|Perl::Critic::Statistics>
object that was created for this Critic.  The Statistics object
accumulates data for all files that are analyzed by this Critic.

=back


=head1 FUNCTIONAL INTERFACE

For those folks who prefer to have a functional interface, The
C<critique> method can be exported on request and called as a static
function.  If the first argument is a hashref, its contents are used
to construct a new Perl::Critic object internally.  The keys of that
hash should be the same as those supported by the C<Perl::Critic::new>
method.  Here are some examples:

  use Perl::Critic qw(critique);

  # Use default parameters...
  @violations = critique( $some_file );

  # Use custom parameters...
  @violations = critique( {-severity => 2}, $some_file );

  # As a one-liner
  %> perl -MPerl::Critic=critique -e 'print critique(shift)' some_file.pm

None of the other object-methods are currently supported as static
functions.  Sorry.


=head1 CONFIGURATION

Most of the settings for Perl::Critic and each of the Policy modules
can be controlled by a configuration file.  The default configuration
file is called F<.perlcriticrc>.  Perl::Critic will look for this file
in the current directory first, and then in your home directory.
Alternatively, you can set the C<PERLCRITIC> environment variable to
explicitly point to a different file in another location.  If none of
these files exist, and the C<-profile> option is not given to the
constructor, then all the modules that are found in the
Perl::Critic::Policy namespace will be loaded with their default
configuration.

The format of the configuration file is a series of INI-style blocks
that contain key-value pairs separated by '='. Comments should start
with '#' and can be placed on a separate line or after the name-value
pairs if you desire.

Default settings for Perl::Critic itself can be set B<before the first
named block.> For example, putting any or all of these at the top of
your configuration file will set the default value for the
corresponding constructor argument.

    severity  = 3                                     #Integer or named level
    only      = 1                                     #Zero or One
    force     = 0                                     #Zero or One
    verbose   = 4                                     #Integer or format spec
    top       = 50                                    #A positive integer
    theme     = (pbp || security) && bugs             #A theme expression
    include   = NamingConventions ClassHierarchies    #Space-delimited list
    exclude   = Variables  Modules::RequirePackage    #Space-delimited list
    criticism-fatal = 1                               #Zero or One
    color     = 1                                     #Zero or One
    pager     = less                                  #pager to pipe output to

The remainder of the configuration file is a series of blocks like
this:

    [Perl::Critic::Policy::Category::PolicyName]
    severity = 1
    set_themes = foo bar
    add_themes = baz
    maximum_violations_per_document = 57
    arg1 = value1
    arg2 = value2

C<Perl::Critic::Policy::Category::PolicyName> is the full name of a
module that implements the policy.  The Policy modules distributed
with Perl::Critic have been grouped into categories according to the
table of contents in Damian Conway's book B<Perl Best Practices>. For
brevity, you can omit the C<'Perl::Critic::Policy'> part of the module
name.

C<severity> is the level of importance you wish to assign to the
Policy.  All Policy modules are defined with a default severity value
ranging from 1 (least severe) to 5 (most severe).  However, you may
disagree with the default severity and choose to give it a higher or
lower severity, based on your own coding philosophy.  You can set the
C<severity> to an integer from 1 to 5, or use one of the equivalent
names:

    SEVERITY NAME ...is equivalent to... SEVERITY NUMBER
    ----------------------------------------------------
    gentle                                             5
    stern                                              4
    harsh                                              3
    cruel                                              2
    brutal                                             1

C<set_themes> sets the theme for the Policy and overrides its default
theme.  The argument is a string of one or more whitespace-delimited
alphanumeric words.  Themes are case-insensitive.  See L<"POLICY
THEMES"> for more information.

C<add_themes> appends to the default themes for this Policy.  The
argument is a string of one or more whitespace-delimited words.
Themes are case-insensitive.  See L<"POLICY THEMES"> for more
information.

C<maximum_violations_per_document> limits the number of Violations the
Policy will return for a given document.  Some Policies have a default
limit; see the documentation for the individual Policies to see
whether there is one.  To force a Policy to not have a limit, specify
"no_limit" or the empty string for the value of this parameter.

The remaining key-value pairs are configuration parameters that will
be passed into the constructor for that Policy.  The constructors for
most Policy objects do not support arguments, and those that do should
have reasonable defaults.  See the documentation on the appropriate
Policy module for more details.

Instead of redefining the severity for a given Policy, you can
completely disable a Policy by prepending a '-' to the name of the
module in your configuration file.  In this manner, the Policy will
never be loaded, regardless of the C<-severity> given to the
Perl::Critic constructor.

A simple configuration might look like this:

    #--------------------------------------------------------------
    # I think these are really important, so always load them

    [TestingAndDebugging::RequireUseStrict]
    severity = 5

    [TestingAndDebugging::RequireUseWarnings]
    severity = 5

    #--------------------------------------------------------------
    # I think these are less important, so only load when asked

    [Variables::ProhibitPackageVars]
    severity = 2

    [ControlStructures::ProhibitPostfixControls]
    allow = if unless  # My custom configuration
    severity = cruel   # Same as "severity = 2"

    #--------------------------------------------------------------
    # Give these policies a custom theme.  I can activate just
    # these policies by saying `perlcritic -theme larry`

    [Modules::RequireFilenameMatchesPackage]
    add_themes = larry

    [TestingAndDebugging::RequireTestLables]
    add_themes = larry curly moe

    #--------------------------------------------------------------
    # I do not agree with these at all, so never load them

    [-NamingConventions::ProhibitMixedCaseVars]
    [-NamingConventions::ProhibitMixedCaseSubs]

    #--------------------------------------------------------------
    # For all other Policies, I accept the default severity,
    # so no additional configuration is required for them.

For additional configuration examples, see the F<perlcriticrc> file
that is included in this F<examples> directory of this distribution.

Damian Conway's own Perl::Critic configuration is also included in
this distribution as F<examples/perlcriticrc-conway>.


=head1 THE POLICIES

A large number of Policy modules are distributed with Perl::Critic.
They are described briefly in the companion document
L<Perl::Critic::PolicySummary|Perl::Critic::PolicySummary> and in more
detail in the individual modules themselves.  Say C<"perlcritic -doc
PATTERN"> to see the perldoc for all Policy modules that match the
regex C<m/PATTERN/ixms>

There are a number of distributions of additional policies on CPAN.
If L<Perl::Critic|Perl::Critic> doesn't contain a policy that you
want, some one may have already written it.  See the L</"SEE ALSO">
section below for a list of some of these distributions.


=head1 POLICY THEMES

Each Policy is defined with one or more "themes".  Themes can be used
to create arbitrary groups of Policies.  They are intended to provide
an alternative mechanism for selecting your preferred set of Policies.
For example, you may wish disable a certain subset of Policies when
analyzing test scripts.  Conversely, you may wish to enable only a
specific subset of Policies when analyzing modules.

The Policies that ship with Perl::Critic are have been broken into the
following themes.  This is just our attempt to provide some basic
logical groupings.  You are free to invent new themes that suit your
needs.

    THEME             DESCRIPTION
    --------------------------------------------------------------------------
    core              All policies that ship with Perl::Critic
    pbp               Policies that come directly from "Perl Best Practices"
    bugs              Policies that that prevent or reveal bugs
    maintenance       Policies that affect the long-term health of the code
    cosmetic          Policies that only have a superficial effect
    complexity        Policies that specificaly relate to code complexity
    security          Policies that relate to security issues
    tests             Policies that are specific to test scripts


Any Policy may fit into multiple themes.  Say C<"perlcritic -list"> to
get a listing of all available Policies and the themes that are
associated with each one.  You can also change the theme for any
Policy in your F<.perlcriticrc> file.  See the L<"CONFIGURATION">
section for more information about that.

Using the C<-theme> option, you can create an arbitrarily complex rule
that determines which Policies will be loaded.  Precedence is the same
as regular Perl code, and you can use parentheses to enforce
precedence as well.  Supported operators are:

   Operator    Altertative    Example
   ----------------------------------------------------------------------------
   &&          and            'pbp && core'
   ||          or             'pbp || (bugs && security)'
   !           not            'pbp && ! (portability || complexity)'

Theme names are case-insensitive.  If the C<-theme> is set to an empty
string, then it evaluates as true all Policies.


=head1 BENDING THE RULES

Perl::Critic takes a hard-line approach to your code: either you
comply or you don't.  In the real world, it is not always practical
(nor even possible) to fully comply with coding standards.  In such
cases, it is wise to show that you are knowingly violating the
standards and that you have a Damn Good Reason (DGR) for doing so.

To help with those situations, you can direct Perl::Critic to ignore
certain lines or blocks of code by using pseudo-pragmas:

    require 'LegacyLibaray1.pl';  ## no critic
    require 'LegacyLibrary2.pl';  ## no critic

    for my $element (@list) {

        ## no critic

        $foo = "";               #Violates 'ProhibitEmptyQuotes'
        $barf = bar() if $foo;   #Violates 'ProhibitPostfixControls'
        #Some more evil code...

        ## use critic

        #Some good code...
        do_something($_);
    }

The C<"## no critic"> comments direct Perl::Critic to ignore the
remaining lines of code until the end of the current block, or until a
C<"## use critic"> comment is found (whichever comes first).  If the
C<"## no critic"> comment is on the same line as a code statement,
then only that line of code is overlooked.  To direct perlcritic to
ignore the C<"## no critic"> comments, use the C<-force> option.

A bare C<"## no critic"> comment disables all the active Policies.  If
you wish to disable only specific Policies, add a list of Policy names
as arguments, just as you would for the C<"no strict"> or C<"no
warnings"> pragmas.  For example, this would disable the
C<ProhibitEmptyQuotes> and C<ProhibitPostfixControls> policies until
the end of the block or until the next C<"## use critic"> comment
(whichever comes first):

  ## no critic (EmptyQuotes, PostfixControls)

  # Now exempt from ValuesAndExpressions::ProhibitEmptyQuotes
  $foo = "";

  # Now exempt ControlStructures::ProhibitPostfixControls
  $barf = bar() if $foo;

  # Still subjected to ValuesAndExpression::RequireNumberSeparators
  $long_int = 10000000000;

Since the Policy names are matched against the C<"## no critic">
arguments as regular expressions, you can abbreviate the Policy names
or disable an entire family of Policies in one shot like this:

  ## no critic (NamingConventions)

  # Now exempt from NamingConventions::ProhibitMixedCaseVars
  my $camelHumpVar = 'foo';

  # Now exempt from NamingConventions::ProhibitMixedCaseSubs
  sub camelHumpSub {}

The argument list must be enclosed in parentheses and must contain one
or more comma-separated barewords (e.g. don't use quotes).  The
C<"## no critic"> pragmas can be nested, and Policies named by an
inner pragma will be disabled along with those already disabled an
outer pragma.

Some Policies like C<Subroutines::ProhibitExcessComplexity> apply to
an entire block of code.  In those cases, C<"## no critic"> must
appear on the line where the violation is reported.  For example:

  sub complicated_function {  ## no critic (ProhibitExcessComplexity)
      # Your code here...
  }

Policies such as C<Documentation::RequirePodSections> apply to the
entire document, in which case violations are reported at line 1.

Use this feature wisely.  C<"## no critic"> should be used in the
smallest possible scope, or only on individual lines of code. And you
should always be as specific as possible about which policies you want
to disable (i.e. never use a bare C<"## no critic">).  If Perl::Critic
complains about your code, try and find a compliant solution before
resorting to this feature.


=head1 THE L<Perl::Critic|Perl::Critic> PHILOSOPHY

Coding standards are deeply personal and highly subjective.  The goal
of Perl::Critic is to help you write code that conforms with a set of
best practices.  Our primary goal is not to dictate what those
practices are, but rather, to implement the practices discovered by
others.  Ultimately, you make the rules -- Perl::Critic is merely a
tool for encouraging consistency.  If there is a policy that you think
is important or that we have overlooked, we would be very grateful for
contributions, or you can simply load your own private set of policies
into Perl::Critic.


=head1 EXTENDING THE CRITIC

The modular design of Perl::Critic is intended to facilitate the
addition of new Policies.  You'll need to have some understanding of
L<PPI|PPI>, but most Policy modules are pretty straightforward and
only require about 20 lines of code.  Please see the
L<Perl::Critic::DEVELOPER|Perl::Critic::DEVELOPER> file included in
this distribution for a step-by-step demonstration of how to create
new Policy modules.

If you develop any new Policy modules, feel free to send them to C<<
<thaljef@cpan.org> >> and I'll be happy to put them into the
Perl::Critic distribution.  Or if you would like to work on the
Perl::Critic project directly, check out our repository at
L<http://perlcritic.tigris.org>.  To subscribe to our mailing list,
send a message to C<< <dev-subscribe@perlcritic.tigris.org> >>.

The Perl::Critic team is also available for hire.  If your
organization has its own coding standards, we can create custom
Policies to enforce your local guidelines.  Or if your code base is
prone to a particular defect pattern, we can design Policies that will
help you catch those costly defects B<before> they go into production.
To discuss your needs with the Perl::Critic team, just contact C<<
<thaljef@cpan.org> >>.


=head1 PREREQUISITES

Perl::Critic requires the following modules:

L<B::Keywords|B::Keywords>

L<Config::Tiny|Config::Tiny>

L<Exception::Class|Exception::Class>

L<File::Spec|File::Spec>

L<File::Spec::Unix|File::Spec::Unix>

L<IO::String|IO::String>

L<List::MoreUtils|List::MoreUtils>

L<List::Util|List::Util>

L<Module::Pluggable|Module::Pluggable>

L<PPI|PPI>

L<Pod::PlainText|Pod::PlainText>

L<Pod::Usage|Pod::Usage>

L<Readonly|Readonly>

L<Scalar::Util|Scalar::Util>

L<String::Format|String::Format>

L<version|version>


The following modules are optional, but recommended for complete
testing:

L<File::HomeDir|File::HomeDir>

L<File::Which|File::Which>

L<IO::String|IO::String>

L<IPC::Open2|IPC::Open2>

L<Perl::Tidy|Perl::Tidy>

L<Pod::Spell|Pod::Spell>

L<Test::Pod|Test::Pod>

L<Test::Pod::Coverage|Test::Pod::Coverage>

L<Text::ParseWords|Text::ParseWords>


=head1 CONTACTING THE DEVELOPMENT TEAM

You are encouraged to subscribe to the mailing list; send a message to
C<< <users-subscribe@perlcritic.tigris.org> >>.  See also
L<the archives|http://perlcritic.tigris.org/servlets/SummarizeList?listName=users>.
You can also contact the author at C<< <thaljef@cpan.org> >>.

At least one member of the development team has started hanging around
in L<irc://irc.perl.org/#perlcritic>.


=head1 SEE ALSO

There are a number of distributions of additional Policies available.
A few are listed here:

L<Perl::Critic::More|Perl::Critic::More>

L<Perl::Critic::Bangs|Perl::Critic::Bangs>

L<Perl::Critic::Lax|Perl::Critic::Lax>

L<Perl::Critic::StricterSubs|Perl::Critic::StricterSubs>

L<Perl::Critic::Swift|Perl::Critic::Swift>

L<Perl::Critic::Tics|Perl::Critic::Tics>

These distributions enable you to use Perl::Critic in your unit tests:

L<Test::Perl::Critic|Test::Perl::Critic>

L<Test::Perl::Critic::Progressive|Test::Perl::Critic::Progressive>

There are also a couple of distributions that will install all the
Perl::Critic related modules known to the development team:

L<Bundle::Perl::Critic|Bundle::Perl::Critic>

L<Task::Perl::Critic|Task::Perl::Critic>

If you want to make sure you have absolutely everything, you can use
these:

L<Bundle::Perl::Critic::IncludingOptionalDependencies|Bundle::Perl::Critic::IncludingOptionalDependencies>

L<Task::Perl::Critic::IncludingOptionalDependencies|Task::Perl::Critic::IncludingOptionalDependencies>


=head1 BUGS

Scrutinizing Perl code is hard for humans, let alone machines.  If you
find any bugs, particularly false-positives or false-negatives from a
Perl::Critic::Policy, please submit them to
L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Perl-Critic>.  Thanks.

Most policies will produce false-negatives if they cannot understand a
particular block of code.


=head1 CREDITS

Adam Kennedy - For creating L<PPI|PPI>, the heart and soul of
L<Perl::Critic|Perl::Critic>.

Damian Conway - For writing B<Perl Best Practices>, finally :)

Chris Dolan - For contributing the best features and Policy modules.

Andy Lester - Wise sage and master of all-things-testing.

Elliot Shank - The self-proclaimed quality freak.

Giuseppe Maxia - For all the great ideas and positive encouragement.

and Sharon, my wife - For putting up with my all-night code sessions.

Thanks also to the Perl Foundation for providing a grant to support
Chris Dolan's project to implement twenty PBP policies.
L<http://www.perlfoundation.org/april_1_2007_new_grant_awards>


=head1 AUTHOR

Jeffrey Ryan Thalhammer <thaljef@cpan.org>


=head1 COPYRIGHT

Copyright (c) 2005-2008 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.

=cut

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