Perl::Critic::Policy::Documentation::ProhibitDuplicateHeadings - don't duplicate =head names


This policy is part of the Perl::Critic::Pulp add-on. It asks you not to duplicate heading names in =head POD commands.

    =head1 SOMETHING

    =head1 SOMETHING      # bad, duplicate

Duplication is usually a mistake, perhaps too much cut-and-paste, or a leftover from a template, or perhaps text in two places which ought to be together. On that basis this policy is medium severity and under the "bugs" theme (see "POLICY THEMES" in Perl::Critic).

Default Uniqueness

The policy default is to demand that a given heading is unique to its ancestors, siblings, and to the immediately adjacent heading irrespective of level. This is designed to be how human readers perceive the scope of headings and subheadings, plus adjacency in case a mixture of heading levels would let a duplicate otherwise go undetected. For example

    =head1 Top

    =head2 Subhead

    =head3 Top              # bad, duplicates its ancestor head1

Or siblings

    =head1 Top

    =head2 Down

    =head2 Another

    =head2 Down             # bad, duplicates sibling head2

Or adjacent

    =head2 Blah

    =head1 Blah             # bad, duplicates adjacent

A subheading can be repeated if it's under a different higher heading. For example the following two "Details" are cousins, so allowed.

    =head1 One

    =head2 Details

    =head1 Two

    =head2 Details          # ok

All Unique

Option uniqueness=all (see "CONFIGURATION" below) applies a stricter rule so that all =head names must be unique throughout the document, irrespective of levels and structure.

    =head3 Foo

    =head1 Bar

    =head3 Foo             # bad

One use for this is to ensure all headings can be reached by an L<> link. An L<> only has the heading name, no level or path, so if there's any duplication among the names then only the first of each duplicate will be reachable. (The POD browsers usually go to the first among duplicates.)

This rule is often too strict. It can be good to have similar subheadings like "Details" as shown above, with no need to make such sub-parts reachable by a link.


If you don't care at all about this you can disable ProhibitDuplicateHeadings from your .perlcriticrc in the usual way (see "CONFIGURATION" in Perl::Critic),



uniqueness (string, default "default")

The uniqueness to be enforced on each heading. The value is a comma-separated list of

    default     currently "ancestor,sibling,adjacent"
    ancestor    don't duplicate parent, grandparent, etc
    sibling     same level and parent
    adjacent    immediately preceding, irrespective of level
    all         all headings

The default is "default" and the intention is to have default mean a sensible set of restrictions, though precisely what it might be could change.

For example in your .perlcriticrc file



Perl::Critic::Pulp, Perl::Critic

Perl::Critic::Policy::Documentation::ProhibitDuplicateSeeAlso, Perl::Critic::Policy::Documentation::RequirePodSections



Copyright 2013, 2014, 2015, 2016, 2017, 2019, 2021 Kevin Ryde

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