NAME

       Eval::Closure - safely and cleanly create closures via string eval

VERSION

       version 0.14

SYNOPSIS

         use Eval::Closure;

         my $code = eval_closure(
             source      => 'sub { $foo++ }',
             environment => {
                 '$foo' => \1,
             },
         );

         warn $code->(); # 1
         warn $code->(); # 2

         my $code2 = eval_closure(
             source => 'sub { $code->() }',
         ); # dies, $code isn't in scope

DESCRIPTION

       String eval is often used for dynamic code generation. For instance, "Moose" uses it
       heavily, to generate inlined versions of accessors and constructors, which speeds code up
       at runtime by a significant amount. String eval is not without its issues however - it's
       difficult to control the scope it's used in (which determines which variables are in scope
       inside the eval), and it's easy to miss compilation errors, since eval catches them and
       sticks them in $@ instead.

       This module attempts to solve these problems. It provides an "eval_closure" function,
       which evals a string in a clean environment, other than a fixed list of specified
       variables. Compilation errors are rethrown automatically.

FUNCTIONS

   eval_closure(%args)
       This function provides the main functionality of this module. It is exported by default.
       It takes a hash of parameters, with these keys being valid:

       source
           The string to be evaled. It should end by returning a code reference. It can access
           any variable declared in the "environment" parameter (and only those variables). It
           can be either a string, or an arrayref of lines (which will be joined with newlines to
           produce the string).

       environment
           The environment to provide to the eval. This should be a hashref, mapping variable
           names (including sigils) to references of the appropriate type. For instance, a valid
           value for environment would be "{ '@foo' => [] }" (which would allow the generated
           function to use an array named @foo). Generally, this is used to allow the generated
           function to access externally defined variables (so you would pass in a reference to a
           variable that already exists).

           In perl 5.18 and greater, the environment hash can contain variables with a sigil of
           "&". This will create a lexical sub in the evaluated code (see "The 'lexical_subs'
           feature" in feature). Using a "&" sigil on perl versions before lexical subs were
           available will throw an error.

       alias
           If set to true, the coderef returned closes over the variables referenced in the
           environment hashref. (This feature requires Devel::LexAlias.) If set to false, the
           coderef closes over a shallow copy of the variables.

           If this argument is omitted, Eval::Closure will currently assume false, but this
           assumption may change in a future version.

       description
           This lets you provide a bit more information in backtraces. Normally, when a function
           that was generated through string eval is called, that stack frame will show up as
           "(eval n)", where 'n' is a sequential identifier for every string eval that has
           happened so far in the program. Passing a "description" parameter lets you override
           that to something more useful (for instance, Moose overrides the description for
           accessors to something like "accessor foo at MyClass.pm, line 123").

       line
           This lets you override the particular line number that appears in backtraces, much
           like the "description" option. The default is 1.

       terse_error
           Normally, this function appends the source code that failed to compile, and prepends
           some explanatory text. Setting this option to true suppresses that behavior so you get
           only the compilation error that Perl actually reported.

BUGS

       No known bugs.

       Please report any bugs to GitHub Issues at <https://github.com/doy/eval-closure/issues>.

SEE ALSO

       •   Class::MOP::Method::Accessor

           This module is a factoring out of code that used to live here

SUPPORT

       You can find this documentation for this module with the perldoc command.

           perldoc Eval::Closure

       You can also look for information at:

       •   MetaCPAN

           <https://metacpan.org/release/Eval-Closure>

       •   Github

           <https://github.com/doy/eval-closure>

       •   RT: CPAN's request tracker

           <http://rt.cpan.org/NoAuth/Bugs.html?Dist=Eval-Closure>

       •   CPAN Ratings

           <http://cpanratings.perl.org/d/Eval-Closure>

NOTES

       Based on code from Class::MOP::Method::Accessor, by Stevan Little and the Moose Cabal.

AUTHOR

       Jesse Luehrs <doy@tozt.net>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2016 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.