Perl::Critic - Critique Perl source for style and standards
use Perl::Critic; #Create Critic and load Policies from default config file $critic = Perl::Critic->new(); #Create Critic and load only the most important Polices $critic = Perl::Critic->new(-priority => 1); #Create Critic and load Policies from specific config file $critic = Perl::Critic->new(-profile => $file); #Create Critic and load Policy by hand $critic = Perl::Critic->new(-profile => 'NONE'); $critic->add_policy('MyPolicyModule'); #Analyze code for policy violations @violations = $critic->critique($source_code);
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 Policies are based on Damian Conway's book Perl Best Practices. You can choose 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 a nice interface that is suitable for test scripts.
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 it defaults to include all the Policy modules that ship with Perl::Critic. See "CONFIGURATION" for more information.
$FILE
PERLCRITIC
-priority is the maximum priority value of Policies that should be added to the Perl::Critic::Config. 1 is the "highest" priority, and all numbers larger than 1 have "lower" priority. Once the user-preferences have been read from the -profile, All Policies that are configured with a priority greater than $N will be removed from this Config. For a given -profile, increasing $N will result in more Policy violations. The default -priority is 1. See "CONFIGURATION" for more information.
-profile
$N
-priority
-include is a reference to a list of @PATTERNS. Once the user-preferences have been read from the -profile, all Policies that do not match at least one m/$PATTERN/imx will be removed from this Config. Using the -include option causes the <-priority> option to be ignored.
@PATTERNS
m/$PATTERN/imx
-include
-exclude is a reference to a list of @PATTERNS. Once the user-preferences have been read from the -profile, all Policies that match at least one m/$PATTERN/imx will be removed from the Config. Using the -exclude option causes the <-priority> option to be ignored. The -exclude patterns are applied after the <-include> patterns, therefore, the -exclude patterns take precedence.
-exclude
-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 overlook code that is tagged with these comments. See "BENDING THE RULES" for more information.
"no critic"
Loads a Policy into this Critic engine. The engine will attempt to require the module named by $STRING and instantiate it. If the module fails to load or cannot be instantiated, it will throw a warning and return a false value. Otherwise, it returns a reference to this Critic engine.
require
-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.
'Perl::Critic::Policy'
-config is an optional reference to a hash of Policy configuration parameters (Note that this is not 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.
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. Otherwise, it is treated as a path to a file containing Perl code. 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, returns an empty list.
$source_code
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.
The default configuration file is called .perlcriticrc. Perl::Critic::Config 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, Perl::Critic::Config defaults to include all the policies that are shipped with Perl::Critic.
The format of the configuration file is a series of named 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] priority = 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. All Policy modules must be a subclass of Perl::Critic::Policy.
Perl::Critic::Policy::Category::PolicyName
priority is the level of importance you wish to assign to this policy. 1 is the "highest" priority level, and all numbers greater than 1 have increasingly "lower" priority. Only those policies with a priority less than or equal to the -priority value given to the constructor will be loaded. The priority can be an arbitrarily large positive integer. If the priority is not defined, it defaults to 1.
priority
The remaining key-value pairs are configuration parameters for that specific Policy and will be passed into the constructor of the Perl::Critic::Policy subclass. The constructors for most Policy modules do not support arguments, and those that do should have reasonable defaults. See the documentation on the appropriate Policy module for more details.
By default, all the policies that are distributed with Perl::Critic are added to the Config. Rather than assign a priority level to a Policy, you can simply "turn off" a Policy by prepending a '-' to the name of the module in the config file. In this manner, the Policy will never be loaded, regardless of the -priority given to the constructor.
A simple configuration might look like this:
#-------------------------------------------------------------- # These are really important, so always load them [TestingAndDebugging::RequirePackageStricture] priority = 1 [TestingAndDebugging::RequirePackageWarnings] priority = 1 #-------------------------------------------------------------- # These are less important, so only load when asked [Variables::ProhibitPackageVars] priority = 2 [ControlStructures::ProhibitPostfixControls] priority = 2 #-------------------------------------------------------------- # I do not agree with these, so never load them [-NamingConventions::ProhibitMixedCaseVars] [-NamingConventions::ProhibitMixedCaseSubs]
The following Policy modules are distributed with Perl::Critic. The Policy modules have been categorized according to the table of contents in Damian Conway's book Perl Best Practices. Since most coding standards take the form "do this..." or "don't do that...", I have adopted the convention of naming each module RequireSomething or ProhibitSomething. See the documentation of each module for it's specific details.
RequireSomething
ProhibitSomething
Use 4-argument substr instead of writing substr($foo, 2, 6) = $bar
substr
substr($foo, 2, 6) = $bar
Use Time::HiRes instead of select(undef, undef, undef, .05)
select(undef, undef, undef, .05)
Write eval { my $foo; bar($foo) } instead of eval "my $foo; bar($foo);"
eval { my $foo; bar($foo) }
eval "my $foo; bar($foo);"
Write grep { $_ =~ /$pattern/ } @list instead of grep /$pattern/, @list
grep { $_ =~ /$pattern/ } @list
grep /$pattern/, @list
Write map { $_ =~ /$pattern/ } @list instead of map /$pattern/, @list
map { $_ =~ /$pattern/ } @list
map /$pattern/, @list
Use glob q{*} instead of <*>
glob q{*}
Write bless {}, $class; instead of just bless {};
bless {}, $class;
bless {};
Use spaces instead of tabs
Write open $handle, $path instead of open($handle, $path)
open $handle, $path
open($handle, $path)
Write qw(foo bar baz) instead of ('foo', 'bar', 'baz')
qw(foo bar baz)
('foo', 'bar', 'baz')
Must run code through perltidy
Put a comma at the end of every multi-line list declaration, including the last one
Don't write long "if-elsif-elsif-elsif-elsif...else" chains
Write for(0..20) instead of for($i=0; $i<=20; $i++)
for(0..20)
for($i=0; $i<=20; $i++)
Write if($condition){ do_something() } instead of do_something() if $condition
if($condition){ do_something() }
do_something() if $condition
Write if(! $condition) instead of unless($condition)
if(! $condition)
unless($condition)
Write while(! $condition) instead of until($condition)
while(! $condition)
until($condition)
Discourage stuff like @files = `ls $directory`
@files = `ls $directory`
Write open my $fh, q{<}, $filename; instead of open FH, q{<}, $filename;
open my $fh, q{<}, $filename;
open FH, q{<}, $filename;
Never write select($fh)
select($fh)
Write open $fh, q{<}, $filename; instead of open $fh, "<$filename";
open $fh, q{<}, $filename;
open $fh, "<$filename";
Put source-control keywords in every file.
Put packages (especially subclasses) in separate files
Write require Module instead of require 'Module.pm'
require Module
require 'Module.pm'
Don't use evil modules
Always make the package explicit
package
Give every module a $VERSION number
$VERSION
Always use the /m modifier with regular expressions
/m
Always use the /x modifier with regular expressions
/x
Write sub my_function{} instead of sub MyFunction{}
sub my_function{}
sub MyFunction{}
Write $my_variable = 42 instead of $MyVariable = 42
$my_variable = 42
$MyVariable = 42
Don't declare your own open function.
open
Return failure with bare return instead of return undef
return
return undef
Don't write sub my_function (@@) {}
sub my_function (@@) {}
Always use strict
use strict
Always use warnings
use warnings
Don't use constant $FOO = 15 >
use constant $FOO =
Write q{} instead of ''
q{}
''
Always use single quotes for literal strings.
Write oct(755) instead of 0755
oct(755)
0755
Use q{} or qq{} instead of quotes for awkward-looking strings
qq{}
Warns that you might have used single quotes when you really wanted double-quotes.
Write 141_234_397.0145 instead of 141234397.0145
141_234_397.0145
141234397.0145
Write print <<'THE_END' or print <<"THE_END"
print <<'THE_END'
print <<"THE_END"
Write <<'THE_END'; instead of <<'theEnd';
<<'THE_END';
<<'theEnd';
Use my instead of local, except when you have to.
my
local
Eliminate globals declared with our or use vars
our
use vars
Write $EVAL_ERROR instead of $@
$EVAL_ERROR
$@
NOTE: This feature changed in version 0.09 and is not backward compatible with earlier versions.
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 overlook 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.
"## no critic"
"## use critic"
-force
Use this feature wisely. "## no critic" should be used in the smallest possible scope, or only on individual lines of code. If Perl::Critic complains about your code, try and find a compliant solution before resorting to this feature.
The modular design of Perl::Critic is intended to facilitate the addition of new Policies. To create a new Policy, make a subclass of Perl::Critic::Policy and override the violates() method. Your module should go somewhere in the Perl::Critic::Policy namespace. To use the new Policy, just add it to your .perlcriticrc file. You'll need to have some understanding of PPI, but most Policy modules are pretty straightforward and only require about 20 lines of code.
violates()
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.
As new Policy modules were added to Perl::Critic, the overall performance started to deteriorate rapidly. Since each module would traverse the document (several times for some modules), a lot of time was spent iterating over the same document nodes. So starting in version 0.11, I have switched to a stream-based approach where the document is traversed once and every Policy module is tested at each node. The result is roughly a 300% improvement.
Unfortunately, Policy modules prior to version 0.11 won't be compatible. Hopefully, few people have started creating their own Policy modules. Converting them to the stream-based model is fairly easy, and actually results in somewhat cleaner code. Look at the ControlStrucutres::* modules for some examples.
Perl::Critic requires the following modules:
PPI
Config::Tiny
File::Spec
List::Util
List::MoreUtils
Pod::Usage
Pod::PlainText
IO::String
String::Format
The following modules are optional, but recommended for complete testing:
Test::Pod
Test::Pod::Coverage
Test::Perl::Critic
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.
Adam Kennedy - For creating PPI, the heart and soul of Perl::Critic.
Damian Conway - For writing Perl Best Practices
Giuseppe Maxia - For all the great ideas and enhancements.
Chris Dolan - For numerous bug reports and suggestions.
Sharon, my wife - For putting up with my all-night code sessions
Jeffrey Ryan Thalhammer <thaljef@cpan.org>
Copyright (c) 2005 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.
To install Perl::Critic, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Perl::Critic
CPAN shell
perl -MCPAN -e shell install Perl::Critic
For more information on module installation, please visit the detailed CPAN module installation guide.