circular::require - detect circularity in use/require statements
package Foo; use Bar; package Bar; use Foo; package main; no circular::require; use Foo; # warns
perl -M-circular::require foo.pl
Perl by default just ignores cycles in require statements - if Foo.pm does
use Bar and Bar.pm does
use Foo, doing
use Foo elsewhere will start loading Foo.pm, then hit the
use statement, start loading Bar.pm, hit the
use statement, notice that Foo.pm has already started loading and ignore it, and continue loading Bar.pm. But Foo.pm hasn't finished loading yet, so if Bar.pm uses anything from Foo.pm (which it likely does, if it's loading it), those won't be accessible while the body of Bar.pm is being executed. This can lead to some very confusing errors, especially if introspection is happening at load time (
make_immutable in Moose classes, for example). This module generates a warning whenever a module is skipped due to being loaded, if that module has not finished executing.
This module works as a pragma, and typically pragmas have lexical scope. Lexical scope doesn't make a whole lot of sense for this case though, because the effect it's tracking isn't lexical (what does it mean to disable the pragma inside of a cycle vs. outside of a cycle? does disabling it within a cycle cause it to always be disabled for that cycle, or only if it's disabled at the point where the warning would otherwise be generated? etc.), but dynamic scope (the scope that, for instance,
local uses) does, and that's how this module works. Saying
no circular::require enables the module for the current dynamic scope, and
use circular::require disables it for the current dynamic scope. Hopefully, this will just do what you mean.
In some situations, other modules might be handling the module loading for you -
use base and
Class::Load::load_class, for instance. To avoid these modules showing up as the source of cycles, you can use the
-hide parameter when using this module. For example:
no circular::require -hide => [qw(base parent Class::Load)];
perl -M'-circular::require -hide => [qw(base parent Class::Load)];' foo.pl
This module works by overriding
CORE::GLOBAL::require, and so other modules which do this may cause issues if they aren't written properly. See Devel::OverrideGlobalRequire for more information.
No known bugs.
Please report any bugs to GitHub Issues at https://github.com/doy/circular-require/issues.
You can find this documentation for this module with the perldoc command.
You can also look for information at:
Jesse Luehrs <email@example.com>
This software is copyright (c) 2013 by Jesse Luehrs.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.