1Perl::Critic::Policy(3)User Contributed Perl DocumentatioPnerl::Critic::Policy(3)
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NAME

6       Perl::Critic::Policy - Base class for all Policy modules.
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DESCRIPTION

9       Perl::Critic::Policy is the abstract base class for all Policy objects.
10       If you're developing your own Policies, your job is to implement and
11       override its methods in a subclass.  To work with the Perl::Critic
12       engine, your implementation must behave as described below.  For a
13       detailed explanation on how to make new Policy modules, please see the
14       Perl::Critic::DEVELOPER document included in this distribution.
15

INTERFACE SUPPORT

17       This is considered to be a public class.  Any changes to its interface
18       will go through a deprecation cycle.
19

METHODS

21       "new( ... )"
22           Don't call this.  As a Policy author, do not implement this.  Use
23           the "initialize_if_enabled()" method for your Policy setup.  See
24           the developer documentation for more.
25
26       "initialize_if_enabled( $config )"
27           This receives an instance of Perl::Critic::PolicyConfig as a
28           parameter, and is only invoked if this Policy is enabled by the
29           user.  Thus, this is the preferred place for subclasses to do any
30           initialization.
31
32           Implementations of this method should return a boolean value
33           indicating whether the Policy should continue to be enabled.  For
34           most subclasses, this will always be $TRUE.  Policies that depend
35           upon external modules or other system facilities that may or may
36           not be available should test for the availability of these
37           dependencies and return $FALSE if they are not.
38
39       "prepare_to_scan_document( $document )"
40           The parameter is about to be scanned by this Policy.  Whatever this
41           Policy wants to do in terms of preparation should happen here.
42           Returns a boolean value indicating whether the document should be
43           scanned at all; if this is a false value, this Policy won't be
44           applied to the document.  By default, does nothing but return
45           $TRUE.
46
47       " violates( $element, $document ) "
48           Given a PPI::Element and a PPI::Document, returns one or more
49           Perl::Critic::Violation objects if the $element violates this
50           Policy.  If there are no violations, then it returns an empty list.
51           If the Policy encounters an exception, then it should "croak" with
52           an error message and let the caller decide how to handle it.
53
54           "violates()" is an abstract method and it will abort if you attempt
55           to invoke it directly.  It is the heart of all Policy modules, and
56           your subclass must override this method.
57
58       " violation( $description, $explanation, $element ) "
59           Returns a reference to a new "Perl::Critic::Violation" object. The
60           arguments are a description of the violation (as string), an
61           explanation for the policy (as string) or a series of page numbers
62           in PBP (as an ARRAY ref), a reference to the PPI element that
63           caused the violation.
64
65           These are the same as the constructor to Perl::Critic::Violation,
66           but without the severity.  The Policy itself knows the severity.
67
68       " new_parameter_value_exception( $option_name, $option_value, $source,
69       $message_suffix ) "
70           Create a
71           Perl::Critic::Exception::Configuration::Option::Policy::ParameterValue
72           for this Policy.
73
74       " throw_parameter_value_exception( $option_name, $option_value,
75       $source, $message_suffix ) "
76           Create and throw a
77           Perl::Critic::Exception::Configuration::Option::Policy::ParameterValue.
78           Useful in parameter parser implementations.
79
80       " get_long_name() "
81           Return the full package name of this policy.
82
83       " get_short_name() "
84           Return the name of this policy without the "Perl::Critic::Policy::"
85           prefix.
86
87       " is_enabled() "
88           Answer whether this policy is really active or not.  Returns a true
89           value if it is, a false, yet defined, value if it isn't, and an
90           undefined value if it hasn't yet been decided whether it will be.
91
92       " applies_to() "
93           Returns a list of the names of PPI classes that this Policy cares
94           about.  By default, the result is "PPI::Element".  Overriding this
95           method in Policy subclasses should lead to significant performance
96           increases.
97
98       " default_maximum_violations_per_document() "
99           Returns the default maximum number of violations for this policy to
100           report per document.  By default, this not defined, but subclasses
101           may override this.
102
103       " get_maximum_violations_per_document() "
104           Returns the maximum number of violations this policy will report
105           for a single document.  If this is not defined, then there is no
106           limit.  If "set_maximum_violations_per_document()" has not been
107           invoked, then "default_maximum_violations_per_document()" is
108           returned.
109
110       " set_maximum_violations_per_document() "
111           Specify the maximum violations that this policy should report for a
112           document.
113
114       " default_severity() "
115           Returns the default severity for violating this Policy.  See the
116           $SEVERITY constants in Perl::Critic::Utils for an enumeration of
117           possible severity values.  By default, this method returns
118           $SEVERITY_LOWEST.  Authors of Perl::Critic::Policy subclasses
119           should override this method to return a value that they feel is
120           appropriate for their Policy.  In general, Polices that are widely
121           accepted or tend to prevent bugs should have a higher severity than
122           those that are more subjective or cosmetic in nature.
123
124       " get_severity() "
125           Returns the severity of violating this Policy.  If the severity has
126           not been explicitly defined by calling "set_severity", then the
127           "default_severity" is returned.  See the $SEVERITY constants in
128           Perl::Critic::Utils for an enumeration of possible severity values.
129
130       " set_severity( $N ) "
131           Sets the severity for violating this Policy.  Clients of
132           Perl::Critic::Policy objects can call this method to assign a
133           different severity to the Policy if they don't agree with the
134           "default_severity".  See the $SEVERITY constants in
135           Perl::Critic::Utils for an enumeration of possible values.
136
137       " default_themes() "
138           Returns a sorted list of the default themes associated with this
139           Policy.  The default method returns an empty list.  Policy authors
140           should override this method to return a list of themes that are
141           appropriate for their policy.
142
143       " get_themes() "
144           Returns a sorted list of the themes associated with this Policy.
145           If you haven't added themes or set the themes explicitly, this
146           method just returns the default themes.
147
148       " set_themes( @THEME_LIST ) "
149           Sets the themes associated with this Policy.  Any existing themes
150           are overwritten.  Duplicate themes will be removed.
151
152       " add_themes( @THEME_LIST ) "
153           Appends additional themes to this Policy.  Any existing themes are
154           preserved.  Duplicate themes will be removed.
155
156       " get_abstract() "
157           Retrieve the abstract for this policy (the part of the NAME section
158           of the POD after the module name), if it is available.
159
160       " get_raw_abstract() "
161           Retrieve the abstract for this policy (the part of the NAME section
162           of the POD after the module name), if it is available, in the
163           unparsed form.
164
165       " parameter_metadata_available() "
166           Returns whether information about the parameters is available.
167
168       " get_parameters() "
169           Returns a reference to an array containing instances of
170           Perl::Critic::PolicyParameter.
171
172           Note that this will return an empty list if the parameters for this
173           policy are unknown.  In order to differentiate between this
174           circumstance and the one where this policy does not take any
175           parameters, it is necessary to call
176           "parameter_metadata_available()".
177
178       "set_format( $format )"
179           Class method.  Sets the format for all Policy objects when they are
180           evaluated in string context.  The default is "%p\n".  See
181           "OVERLOADS" for formatting options.
182
183       "get_format()"
184           Class method. Returns the current format for all Policy objects
185           when they are evaluated in string context.
186
187       "to_string()"
188           Returns a string representation of the policy.  The content of the
189           string depends on the current value returned by "get_format()".
190           See "OVERLOADS" for the details.
191
192       "is_safe()"
193           Answer whether this Policy can be used to analyze untrusted code,
194           i.e. the Policy doesn't have any potential side effects.
195
196           This method returns a true value by default.
197
198           An "unsafe" policy might attempt to compile the code, which, if you
199           have "BEGIN" or "CHECK" blocks that affect files or connect to
200           databases, is not a safe thing to do.  If you are writing a such a
201           Policy, then you should override this method to return false.
202
203           By default Perl::Critic will not run unsafe policies.
204

DOCUMENTATION

206       When your Policy module first "use"s Perl::Critic::Violation, it will
207       try and extract the DESCRIPTION section of your Policy module's POD.
208       This information is displayed by Perl::Critic if the verbosity level is
209       set accordingly.  Therefore, please include a DESCRIPTION section in
210       the POD for any Policy modules that you author.  Thanks.
211

OVERLOADS

213       Perl::Critic::Violation overloads the "" operator to produce neat
214       little messages when evaluated in string context.
215
216       Formats are a combination of literal and escape characters similar to
217       the way "sprintf" works.  If you want to know the specific formatting
218       capabilities, look at String::Format. Valid escape characters are:
219
220       %P  Name of the Policy module.
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222       %p  Name of the Policy without the "Perl::Critic::Policy::" prefix.
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224       %a  The policy abstract.
225
226       %O  List of supported policy parameters.  Takes an option of a format
227           string for "to_formatted_string" in Perl::Critic::PolicyParameter.
228           For example, this can be used like "%{%n - %d\n}O" to get a list of
229           parameter names followed by their descriptions.
230
231       %U  A message stating that the parameters for the policy are unknown if
232           "parameter_metadata_available()" returns false.  Takes an option of
233           what the message should be, which defaults to "Cannot
234           programmatically discover what parameters this policy takes.".  The
235           value of this option is interpolated in order to expand the
236           standard escape sequences ("\n", "\t", etc.).
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238       %S  The default severity level of the policy.
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240       %s  The current severity level of the policy.
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242       %T  The default themes for the policy.
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244       %t  The current themes for the policy.
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246       %V  The default maximum number of violations per document of the
247           policy.
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249       %v  The current maximum number of violations per document of the
250           policy.
251

AUTHOR

253       Jeffrey Ryan Thalhammer <jeff@imaginative-software.com>
254
256       Copyright (c) 2005-2011 Imaginative Software Systems.  All rights
257       reserved.
258
259       This program is free software; you can redistribute it and/or modify it
260       under the same terms as Perl itself.  The full text of this license can
261       be found in the LICENSE file included with this module.
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265perl v5.30.1                      2020-01-30           Perl::Critic::Policy(3)
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