NAME

       Perl::Critic::Policy::NamingConventions::Capitalization - Distinguish different program
       components by case.

AFFILIATION

       This Policy is part of the core Perl::Critic distribution.

DESCRIPTION

       Conway recommends to distinguish different program components by case.

       Normal subroutines, methods and variables are all in lower case.

           my $foo;            # ok
           my $foo_bar;        # ok
           sub foo {}          # ok
           sub foo_bar {}      # ok

           my $Foo;            # not ok
           my $foo_Bar;        # not ok
           sub Foo     {}      # not ok
           sub foo_Bar {}      # not ok

       Package and class names are capitalized.

           package IO::Thing;     # ok
           package Web::FooBar    # ok

           package foo;           # not ok
           package foo::Bar;      # not ok

       Constants are in all-caps.

           Readonly::Scalar my $FOO = 42;  # ok

           Readonly::Scalar my $foo = 42;  # not ok

       There are other opinions on the specifics, for example, in perlstyle.  This policy can be
       configured to match almost any style that you can think of.

CONFIGURATION

       You can specify capitalization rules for the following things: "packages", "subroutines",
       "local_lexical_variables", "scoped_lexical_variables", "file_lexical_variables",
       "global_variables", "constants", and "labels".

       "constants" are things declared via constant or Readonly.

           use constant FOO => 193;
           Readonly::Array my @BAR => qw< a b c >;

       "global_variables" are anything declared using "local", "our", or vars.
       "file_lexical_variables" are variables declared at the file scope.

       "scoped_lexical_variables" are variables declared inside bare blocks that are outside of
       any subroutines or other control structures; these are usually created to limit scope of
       variables to a given subset of subroutines.  E.g.

           sub foo { ... }

           {
               my $thingy;

               sub bar { ... $thingy ... }
               sub baz { ... $thingy ... }
           }

       All other variable declarations are considered "local_lexical_variables".

       Each of the "packages", "subroutines", "local_lexical_variables",
       "scoped_lexical_variables", "file_lexical_variables", "global_variables", "constants", and
       "labels" options can be specified as one of ":single_case", ":all_lower", ":all_upper:",
       ":starts_with_lower", ":starts_with_upper", or ":no_restriction" or a regular expression;
       any value that does not start with a colon, ":", is considered to be a regular expression.
       The ":single_case" tag means a name can be all lower case or all upper case.  If a regular
       expression is specified, it is surrounded by "\A" and "\z".

       "packages" defaults to ":starts_with_upper".  "subroutines", "local_lexical_variables",
       "scoped_lexical_variables", "file_lexical_variables", and "global_variables" default to
       ":single_case".  And "constants" and "labels" default to ":all_upper".

       There are corresponding "package_exemptions", "subroutine_exemptions",
       "local_lexical_variable_exemptions", "scoped_lexical_variable_exemptions",
       "file_lexical_variable_exemptions", "global_variable_exemptions", "constant_exemptions",
       and "label_exemptions" options that are lists of regular expressions to exempt from the
       corresponding capitalization rule.  These values also end up being surrounded by "\A" and
       "\z".

       "package_exemptions" defaults to "main".  "global_variable_exemptions" defaults to
       "\$VERSION @ISA @EXPORT(?:_OK)? %EXPORT_TAGS \$AUTOLOAD %ENV %SIG \$TODO".
       "subroutine_exemptions" defaults to "AUTOLOAD BUILD BUILDARGS CLEAR CLOSE DELETE DEMOLISH
       DESTROY EXISTS EXTEND FETCH FETCHSIZE FIRSTKEY GETC NEXTKEY POP PRINT PRINTF PUSH READ
       READLINE SCALAR SHIFT SPLICE STORE STORESIZE TIEARRAY TIEHANDLE TIEHASH TIESCALAR UNSHIFT
       UNTIE WRITE" which should cover all the standard Perl subroutines plus those from Moose.

       For example, if you want all local variables to be in all lower-case and global variables
       to start with "G_" and otherwise not contain underscores, but exempt any variable with a
       name that contains "THINGY", you could put the following in your .perlcriticrc:

           [NamingConventions::Capitalization]
           local_lexical_variables = :all_lower
           global_variables = G_(?:(?!_)\w)+
           global_variable_exemptions = .*THINGY.*

TODO

       Handle "use vars".  Treat constant subroutines like constant variables.  Handle bareword
       file handles.  There needs to be "schemes" or ways of specifying "perlstyle" or "pbp".
       Differentiate lexical Readonly constants in scopes.

BUGS

       This policy won't catch problems with the declaration of $y below:

           for (my $x = 3, my $y = 5; $x < 57; $x += 3) {
               ...
           }

AUTHOR

       Multiple people

COPYRIGHT

       Copyright (c) 2008-2023 Michael G Schwern.

       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.

perl v5.36.0                         Perl::Critic::Policy::NamingConventions::Capitalization(3pm)