Perl::Critic::Policy::NamingConventions::Capitalization(3pm)

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.

Note that that "package_exemptions" does not check complete package names. For "Foo::Bar::baz", it will check "Foo", "Bar" and "baz" sequentially.

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.