=head1 NAME Module::Runtime - runtime module handling =head1 SYNOPSIS use Module::Runtime qw( $module_name_rx is_module_name check_module_name require_module ); if($module_name =~ /\A$module_name_rx\z/o) { ... if(is_module_name($module_name)) { ... check_module_name($module_name); require_module($module_name); use Module::Runtime qw(use_module use_package_optimistically); $bi = use_module("Math::BigInt", 1.31)->new("1_234"); $widget = use_package_optimistically("Local::Widget")->new; use Module::Runtime qw( $top_module_spec_rx $sub_module_spec_rx is_module_spec check_module_spec compose_module_name ); if($spec =~ /\A$top_module_spec_rx\z/o) { ... if($spec =~ /\A$sub_module_spec_rx\z/o) { ... if(is_module_spec("Standard::Prefix", $spec)) { ... check_module_spec("Standard::Prefix", $spec); $module_name = compose_module_name("Standard::Prefix", $spec); =head1 DESCRIPTION The functions exported by this module deal with runtime handling of Perl modules, which are normally handled at compile time. =cut package Module::Runtime; { use 5.006; } use warnings; use strict; use Params::Classify qw(is_string); our $VERSION = "0.007"; use parent "Exporter"; our @EXPORT_OK = qw( $module_name_rx is_module_name is_valid_module_name check_module_name require_module use_module use_package_optimistically $top_module_spec_rx $sub_module_spec_rx is_module_spec is_valid_module_spec check_module_spec compose_module_name ); =head1 REGULAR EXPRESSIONS These regular expressions do not include any anchors, so to check whether an entire string matches a syntax item you must supply the anchors yourself. =over =item $module_name_rx Matches a valid Perl module name in bareword syntax. The rule for this, precisely, is: the string must consist of one or more segments separated by C<::>; each segment must consist of one or more identifier characters (alphanumerics plus "_"); the first character of the string must not be a digit. Thus "C", "C", and "C" are all valid module names, whereas "C" and "C<1foo::bar>" are not. Only ASCII characters are permitted; Perl's handling of non-ASCII characters in source code is inconsistent. C<'> separators are not permitted. =cut our $module_name_rx = qr/[A-Z_a-z][0-9A-Z_a-z]*(?:::[0-9A-Z_a-z]+)*/; =item $top_module_spec_rx Matches a module specification for use with L, where no prefix is being used. =cut my $qual_module_spec_rx = qr#(?:/|::)[A-Z_a-z][0-9A-Z_a-z]*(?:(?:/|::)[0-9A-Z_a-z]+)*#; my $unqual_top_module_spec_rx = qr#[A-Z_a-z][0-9A-Z_a-z]*(?:(?:/|::)[0-9A-Z_a-z]+)*#; our $top_module_spec_rx = qr/$qual_module_spec_rx|$unqual_top_module_spec_rx/o; =item $sub_module_spec_rx Matches a module specification for use with L, where a prefix is being used. =cut my $unqual_sub_module_spec_rx = qr#[0-9A-Z_a-z]+(?:(?:/|::)[0-9A-Z_a-z]+)*#; our $sub_module_spec_rx = qr/$qual_module_spec_rx|$unqual_sub_module_spec_rx/o; =back =head1 FUNCTIONS =head2 Basic module handling =over =item is_module_name(ARG) Returns a truth value indicating whether I is a plain string satisfying Perl module name syntax as described for L. =cut sub is_module_name($) { &is_string && $_[0] =~ /\A$module_name_rx\z/o } =item is_valid_module_name(ARG) Deprecated alias for L. =cut *is_valid_module_name = \&is_module_name; =item check_module_name(ARG) Check whether I is a plain string satisfying Perl module name syntax as described for L. Return normally if it is, or C if it is not. =cut sub check_module_name($) { unless(&is_module_name) { die +(&is_string ? "`$_[0]'" : "argument"). " is not a module name\n"; } } =item require_module(NAME) This is essentially the bareword form of C, in runtime form. The I is a string, which should be a valid module name (one or more C<::>-separated segments). If it is not a valid name, the function Cs. The module specified by I is loaded, if it hasn't been already, in the manner of the bareword form of C. That means that a search through C<@INC> is performed, and a byte-compiled form of the module will be used if available. The return value is as for C. That is, it is the value returned by the module itself if the module is loaded anew, or C<1> if the module was already loaded. =cut sub require_module($) { &check_module_name; my($name) = @_; # This translation to Unix-style filename is correct regardless # of platform. This is what ck_require() in the Perl core does # with a bareword, and pp_require() translates the Unix-style # filename to whatever is appropriate for the real platform. $name =~ s!::!/!g; $name .= ".pm"; return require($name); } =back =head2 Structured module use =over =item use_module(NAME[, VERSION]) This is essentially C in runtime form, but without the importing feature (which is fundamentally a compile-time thing). The I is handled just like in C above: it must be a module name, and the named module is loaded as if by the bareword form of C. If a I is specified, the C method of the loaded module is called with the specified I as an argument. This normally serves to ensure that the version loaded is at least the version required. This is the same functionality provided by the I parameter of C. On success, the name of the module is returned. This is unlike L, and is done so that the entire call to L can be used as a class name to call a constructor, as in the example in the synopsis. =cut sub use_module($;$) { my($name, $version) = @_; require_module($name); if(defined $version) { $name->VERSION($version); } return $name; } =item use_package_optimistically(NAME[, VERSION]) This is an analogue of L for the situation where there is uncertainty as to whether a package/class is defined in its own module or by some other means. It attempts to arrange for the named package to be available, either by loading a module or by doing nothing and hoping. If the package does not appear to already be loaded then an attempt is made to load the module of the same name (as if by the bareword form of C). If the module cannot be found then it is assumed that the package was actually already loaded but wasn't detected correctly, and no error is signalled. That's the optimistic bit. For the purposes of this function, package existence is checked by whether a C<$VERSION> variable exists in the package. If the module wasn't found, or if it was loaded but didn't create a C<$VERSION> variable, then such a variable is automatically created (with value C) so that repeated use of this function won't redundantly attempt to load the module. This is mostly the same operation that is performed by the L pragma to ensure that the specified base classes are available. The difference is that L does not allow the C<$VERSION> variable to remain undefined: it will set it to "C<-1, set by base.pm>" if it does not otherwise have a non-null value. If a I is specified, the C method of the loaded package is called with the specified I as an argument. This normally serves to ensure that the version loaded is at least the version required. On success, the name of the package is returned. These aspects of the function work just like L. =cut sub _has_version_var($) { my($name) = @_; no strict "refs"; my $vg = ${"${name}::"}{VERSION}; return $vg && *{$vg}{SCALAR}; } sub use_package_optimistically($;$) { my($name, $version) = @_; check_module_name($name); unless(_has_version_var($name)) { eval "local \$SIG{__DIE__}; require $name"; die $@ if $@ ne "" && $@ !~ /\ACan't locate .* at \(eval /; unless(_has_version_var($name)) { no strict "refs"; ${"${name}::VERSION"} = undef; } } $name->VERSION($version) if defined $version; return $name; } =back =head2 Module name composition =over =item is_module_spec(PREFIX, SPEC) Returns a truth value indicating whether I is valid input for L. See below for what that entails. Whether a I is supplied affects the validity of I, but the exact value of the prefix is unimportant, so this function treats I as a truth value. =cut sub is_module_spec($$) { my($prefix, $spec) = @_; return is_string($spec) && $spec =~ ($prefix ? qr/\A$sub_module_spec_rx\z/o : qr/\A$top_module_spec_rx\z/o); } =item is_valid_module_spec(PREFIX, SPEC) Deprecated alias for L. =cut *is_valid_module_spec = \&is_module_spec; =item check_module_spec(PREFIX, SPEC) Check whether I is valid input for L. Return normally if it is, or C if it is not. =cut sub check_module_spec($$) { unless(&is_module_spec) { die +(is_string($_[1]) ? "`$_[1]'" : "argument"). " is not a module specification\n"; } } =item compose_module_name(PREFIX, SPEC) This function is intended to make it more convenient for a user to specify a Perl module name at runtime. Users have greater need for abbreviations and context-sensitivity than programmers, and Perl module names get a little unwieldy. I is what the user specifies, and this function translates it into a module name in standard form, which it returns. I has syntax approximately that of a standard module name: it should consist of one or more name segments, each of which consists of one or more identifier characters. However, C is permitted as a separator, in addition to the standard C<::>. The two separators are entirely interchangeable. Additionally, if I is not C then it must be a module name in standard form, and it is prefixed to the user-specified name. The user can inhibit the prefix addition by starting I with a separator (either C or C<::>). =cut sub compose_module_name($$) { my($prefix, $spec) = @_; check_module_name($prefix) if defined $prefix; &check_module_spec; if($spec =~ s#\A(?:/|::)##) { # OK } else { $spec = $prefix."::".$spec if defined $prefix; } $spec =~ s#/#::#g; return $spec; } =back =head1 SEE ALSO L, L, L =head1 AUTHOR Andrew Main (Zefram) =head1 COPYRIGHT Copyright (C) 2004, 2006, 2007, 2009, 2010 Andrew Main (Zefram) =head1 LICENSE This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. =cut 1;