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 . If you'd like to try Perl::Critic without installing anything, there is a web-service available at . 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. CONSTRUCTOR "new( [ -profile => $FILE, -severity => $N, -theme => $string, -include => \@PATTERNS, -exclude => \@PATTERNS, -top => $N, -only => $B, -force => $B, -verbose => $N ] )" "new( [ -config => Perl::Critic::Config->new() ]" "new()" 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. The default value for all arguments can be defined in your .perlcriticrc file. See the "CONFIGURATION" section for more information about that. 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. -theme is special string that defines a set of Policies based on their respective themes. If "-theme" is given, only policies that are members of that set will be loaded. For example, the following would load only Policies that have a 'danger' and 'pbp' theme: my $critic = Perl::Critic->new(-theme => 'danger * pbp'); See the "POLICY THEMES" section for more information about themes. Unless the "-severity" option is explicitly given, setting "-theme" silently causes the "-severity" to be set to 1. -include is a reference to a list of string @PATTERNS. Policy modules that match at least one "m/$PATTERN/imx" will always be loaded, irrespective of all other 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 all other 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. This must be a positive integer. Violations are still returned in the order that they occur within the file. Unless the "-severity" option is explicitly given, setting "-top" silently causes the "-severity" to be set to 1. -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. -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. -verbose can be a positive integer (from 1 to 10), or a literal format specification. See Perl::Critic::Violations for an explanation of format specifications. -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, -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. -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. -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. " 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 ); # 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. 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 .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 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 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 command-line argument. severity = 3 #Integer from 1 to 5 only = 1 #Zero or One force = 0 #Zero or One verbose = 4 #Integer or format spec top = 50 #A positive integer theme = risky + (pbp * security) - cosmetic #A theme expression include = NamingConventions ClassHierarchies #Space-delimited list exclude = Variables Modules::RequirePackage #Space-delimited list The remainder of the configuration file is a series of blocks like this: [Perl::Critic::Policy::Category::PolicyName] severity = 1 set_theme = foo bar add_theme = baz 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 #-------------------------------------------------------------- # Give these policies a custom theme. I can activate just # these policies by saying `perlcritic -theme larry` [Modules::RequireFilenameMatchesPackage] add_theme = larry [TestingAndDebugging::RequireTestLables] add_theme = 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. 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. 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. The Policies that ship with Perl::Critic have been grouped into themes that are roughly analogous to their severity levels. Folks who find the numeric severity levels awkward can use these mnemonic theme names instead. Severity Level Equivalent Theme --------------------------------------------------------------------------- 5 danger 4 risky 3 unreliable 2 readability 1 cosmetic Say "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 .perlcriticrc file. See the "CONFIGURATION" section for more information about that. Using the "-theme" command-line option, you can combine themes with mathematical and boolean operators to create an arbitrarily complex expression that represents a custom "set" of Policies. The following operators are supported Operator Altertative Meaning ---------------------------------------------------------------------------- * and Intersection - not Difference + or Union Operator precedence is the same as that of normal mathematics. You can also use parenthesis to enforce precedence. Here are some examples: Expression Meaning ---------------------------------------------------------------------------- pbp * risky All policies that are "pbp" AND "risky" pbp and risky Ditto danger + risky All policies that are "danger" OR "risky" pbp or risky Ditto pbp - cosmetic All policies that are "pbp" BUT NOT "risky" pbp not cosmetic Ditto -unreliable All policies that are NOT "unreliable" not unreliable Ditto (pbp - danger) * risky All policies that are "pbp" BUT NOT "danger", AND "risky" (pbp not danger) and risky Ditto Theme names are case-insensitive. If "-theme" is set to an empty string, then it is equivalent to the set of all policies. A theme name that doesn't exist is equivalent to an empty set. Please See for a discussion on set theory. 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 "## 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, so 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 0.21 In version 0.21, we introduced the concept of policy "themes". All you existing custom Policies should still be compatible. But to take advantage of the theme feature, you should add a "default_themes" method to your custom Policy modules. See Perl::Critic::DEVELOPER for an up-to-date guide on creating Policy modules. The internals of Perl::Critic were also refactored significantly. The public API is largely unchanged, but if you've been accessing bits inside Perl::Critic, then you may be in for a surprise. 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 Perl::Critic::DEVELOPER 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 progressively 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 Perl::Critic::DEVELOPER for an up-to-date guide on creating Policy modules. THE 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. 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 . 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 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 . 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 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.