Perl::Critic::Policy::Miscellanea::TextDomainPlaceholders - check placeholder names in Locale::TextDomain calls

This policy is part of the Perl::Critic::Pulp|Perl::Critic::Pulp addon. It checks the placeholder arguments in format strings to the following functions from Locale::TextDomain.

    __x __nx __xn __px __npx

Calls with a key missing from the args or args unused by the format are reported.

    print __x('Searching for {data}',  # bad
              datum => 123);

    print __nx('Read one file',
               'Read {num} files',     # bad
               $n,
               count => 123);

This is normally a mistake, so this policy is under the bugs theme (see POLICY THEMES in Perl::Critic). An error can easily go unnoticed because (as of Locale::TextDomain version 1.16) a placeholder without a corresponding arg goes through unexpanded and any extra args are ignored.

The way Locale::TextDomain parses the format string allows anything between { } as a key, but for the purposes of this policy only symbols (alphanumeric plus "_") are taken to be a key. This is almost certainly what you'll want to use, and it's then possible to include literal braces in a format string without tickling this policy all the time. (Symbol characters are per Perl \w, so non-ASCII is supported, though the Gettext manual in node "Charset conversion" recommends message-IDs should be ASCII-only.)

If the format string is not a literal then it might use any args, so all are considered used.

    # ok, 'datum' might be used
    __x($my_format, datum => 123);

Literal portions of the format are still checked.

    # bad, 'foo' not present in args
    __x("{foo} $bar", datum => 123);

Conversely if the args have some non-literals then they could be anything, so everything in the format string is considered present.

    # ok, $something might be 'world'
    __x('hello {world}', $something => 123);

But again if some args are literals they can be checked.

    # bad, 'blah' is not used
    __x('hello {world}', $something => 123, blah => 456);

If there's non-literals both in the format and in the args then nothing is checked, since it could all match up fine at runtime.

A missing count argument to __nx, __xn and __npx is sometimes noticed by this policy. For example,

    print __nx('Read one file',
               'Read {numfiles} files',
               numfiles => $numfiles);   # bad

If the count argument looks like a key then it's reported as a probable mistake. This is not the main aim of this policy but it's done because otherwise no violations would be reported at all. (The next argument would be the key, and normally being an expression it would be assumed to fulfil the format strings at runtime.)

Perl::Critic::Pulp, Perl::Critic, Locale::TextDomain, Perl::Critic::Policy::Miscellanea::TextDomainUnused

http://user42.tuxfamily.org/perl-critic-pulp/index.html

Copyright 2008, 2009, 2010, 2011 Kevin Ryde

Perl-Critic-Pulp is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

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