# Eval::Closure - phpMan

## 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.