NAME

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

SYNOPSIS

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

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 Perl::Critic::Policy modules that attempt to enforce various coding guidelines. Most Policy modules are based on Damian Conway's book Perl Best Practices. However, Perl::Critic is 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 convenient command-line interface to Perl::Critic, see the documentation for perlcritic. If you want to integrate Perl::Critic with your build process, Test::Perl::Critic provides an interface that is suitable for test scripts. For the ultimate convenience (at the expense of some flexibility) see the criticism pragma.

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

CONSTRUCTOR

new( -profile => $FILE, -severity => $N, -include => \@PATTERNS, -exclude => \@PATTERNS, -top = N, -force => 1 )> Returns a reference to a new Perl::Critic object. Most arguments are just passed directly into Perl::Critic::Config, but I have described them here as well. All arguments are optional key-value pairs as follows: -profile is a path to a configuration file. If $FILE is not defined, Perl::Critic::Config attempts to find a .perlcriticrc configuration file in the current directory, and then in your home directory. Alternatively, you can set the PERLCRITIC environment variable to point to a file in another location. If a configuration file can't be found, or if $FILE is an empty string, then all Policies will be loaded with their default configuration. See "CONFIGURATION" for more information. -severity is the minimum severity level. Only Policy modules that have a severity greater than $N will be loaded. Severity values are integers ranging from 1 (least severe) to 5 (most severe). The default is 5. For a given -profile , decreasing the -severity will usually result in more Policy violations. Users can redefine the severity level for any Policy in their .perlcriticrc file. See "CONFIGURATION" for more information. -include is a reference to a list of string @PATTERNS . Policy modules that match at least one m/$PATTERN/imx will always be loaded, irrespective of the severity settings. For example: my $critic = Perl::Critic->new(-include => ['layout'] -severity => 4); This would cause Perl::Critic to load all the CodeLayout::* Policy modules even though they have a severity level that is less than 4. You can use -include in conjunction with the -exclude option. Note that -exclude takes precedence over -include when a Policy matches both patterns. -exclude is a reference to a list of string @PATTERNS . Policy modules that match at least one m/$PATTERN/imx will not be loaded, irrespective of the severity settings. For example: my $critic = Perl::Critic->new(-exclude => ['strict'] -severity => 1); This would cause Perl::Critic to not load the RequireUseStrict and ProhibitNoStrict Policy modules even though they have a severity level that is greater than 1. You can use -exclude in conjunction with the -include option. Note that -exclude takes precedence over -include when a Policy matches both patterns. -top is the maximum number of Violations to return when ranked by their severity levels. Violations are still returned in the order that they occur within the file. This must be a positive integer -force controls whether Perl::Critic observes the magical "## 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 "BENDING THE RULES" for more information. -config is a reference to a Perl::Critic::Config object. If you have created your own Config object for some reason, you can pass it in here instead of having Perl::Critic create one for you. Using the -config option causes all the other options to be silently ignored.

METHODS

critique( $source_code ) Runs the $source_code through the Perl::Critic engine using all the Policies that have been loaded into this engine. If $source_code is a scalar reference, then it is treated as string of actual Perl code. If $source_code is a reference to an instance of 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 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. add_policy( -policy => $policy_name, -config => \%config_hash ) Creates a Policy object and loads it into this Critic. If the object cannot be instantiated, it will throw a warning and return a false value. Otherwise, it returns a reference to this Critic. -policy is the name of a Perl::Critic::Policy subclass module. The 'Perl::Critic::Policy' portion of the name can be omitted for brevity. This argument is required. -config is an optional reference to a hash of Policy configuration parameters. Note that this is not the same thing as a Perl::Critic::Config object. 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. 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. config() Returns the Perl::Critic::Config object that was created for or given to this Critic.

FUNCTIONAL INTERFACE

For those folks who prefer to have a functional interface, The 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 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 );

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

CONFIGURATION

The default configuration file is called .perlcriticrc. Perl::Critic will look for this file in the current directory first, and then in your home directory. Alternatively, you can set the PERLCRITIC environment variable to explicitly point to a different file in another location. If none of these files exist, and the -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 sections 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. The general recipe is a series of blocks like this:

[Perl::Critic::Policy::Category::PolicyName] severity = 1 arg1 = value1 arg2 = value2

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 Perl Best Practices. For brevity, you can omit the 'Perl::Critic::Policy' part of the module name.

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.

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 -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 = 2 #-------------------------------------------------------------- # 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.

A few sample configuration files are included in this distribution under the t/samples directory. The perlcriticrc.none file demonstrates how to disable Policy modules. The perlcriticrc.levels file demonstrates how to redefine the severity level for any given Policy module. The perlcriticrc.pbp file configures Perl::Critic to load only Policies described in Damian Conway's book "Perl Best Practice."

THE POLICIES

A large number of Policy modules are distributed with Perl::Critic. They are described briefly in the companion document Perl::Critic::PolicySummary and in more detail in the individual modules themselves.

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 (or 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 "## no critic" comments direct Perl::Critic to ignore the remaining lines of code until the end of the current block, or until a "## use critic" comment is found (whichever comes first). If the "## 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 "## no critic" comments, use the -force option.

A bare "## 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 "no strict" or "no warnings" pragmas. For example, this would disable the ProhibitEmptyQuotes and ProhibitPostfixControls policies until the end of the block or until the next "## use critic" comment (whichever comes first):

## no critic (EmptyQuotes, PostfixControls) $foo = ""; #Now exempt from ValuesAndExpressions::ProhibitEmptyQuotes $barf = bar() if $foo; #Now exempt ControlStructures::ProhibitPostfixControls $long_int = 10000000000; #Still subjected to ValuesAndExpression::RequireNumberSeparators

Since the Policy names are matched against the 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) my $camelHumpVar = 'foo'; #Now exempt from NamingConventions::ProhibitMixedCaseVars sub camelHumpSub {} #Now exempt from NamingConventions::ProhibitMixedCaseSubs

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

Use this feature wisely. "## 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 "## no critic" ). If Perl::Critic complains about your code, try and find a compliant solution before resorting to this feature.

IMPORTANT CHANGES

Perl-Critic is evolving rapidly. As such, some of the interfaces have changed in ways that are not backward-compatible. If you have been using an older version of Perl-Critic and/or you have been developing custom Policy modules, please read this section carefully.

VERSION 0.16

Starting in version 0.16, you can add a list Policy names as arguments to the "## no critic" pseudo-pragma. This feature allows you to disable specific policies. So if you have been in the habit of adding additional words after "no critic" , then those words might cause unexpected results. If you want to append other stuff to the "## no critic" comment, then terminate the pseudo-pragma with a semi-colon, and then start another comment. For example:

#This may not work as expected. $email = 'foo@bar.com'; ## no critic for literal '@' #This will work. $email = 'foo@bar.com'; ## no critic; #for literal '@' #This is even better. $email = 'foo@bar.com'; ## no critic (RequireInterpolation);

VERSION 0.14

Starting in version 0.14, the interface to Perl::Critic::Violation changed. This will also break any custom Policy modules that you might have written for earlier modules. See DEVELOPER.pod for an up-to-date guide on creating Policy modules.

The notion of "priority" was also replaced with "severity" in version 0.14. Consequently, the default behavior of Perl::Critic is to only load the most "severe" Policy modules, rather than loading all of them. This decision was based on user-feedback suggesting that Perl-Critic should be less "critical" for new users, and should steer them toward gradually increasing the strictness as they adopt better coding practices.

VERSION 0.11

Starting in version 0.11, the internal mechanics of Perl-Critic were rewritten so that only one traversal of the PPI document tree is required. Unfortunately, this will break any custom Policy modules that you might have written for earlier versions. Converting your policies to work with the new version is pretty easy and actually results in cleaner code. See DEVELOPER.pod for an up-to-date guide on creating Policy modules.

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.

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 PPI, but most Policy modules are pretty straightforward and only require about 20 lines of code. Please see the 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 <thaljef@cpan.org> and I'll be happy to put them into the Perl::Critic distribution. Or if you'd like to work on the Perl::Critic project directly, check out our repository at http://perlcritic.tigris.org. To subscribe to our mailing list, send a message to dev-subscribe@perlcritic.tigris.org .

PREREQUISITES

Perl::Critic requires the following modules:

Config::Tiny

File::Spec

IO::String

List::Util

List::MoreUtils

Module::Pluggable

PPI

Pod::Usage

Pod::PlainText

Scalar::Util

String::Format

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

Test::Pod

Test::Pod::Coverage

Test::Perl::Critic

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 http://rt.cpan.org/NoAuth/Bugs.html?Dist=Perl-Critic. Thanks.

CREDITS

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

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

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

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

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

AUTHOR

Jeffrey Ryan Thalhammer <thaljef@cpan.org>

COPYRIGHT

Copyright (c) 2005-2006 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.