Eval::TypeTiny

utility to evaluate a string of Perl code in a clean environment

Status

This module is covered by the Type-Tiny stability policy.

Description

This module is used by Type::Tiny to compile coderefs from strings of Perl code, and hashrefs of variables to close over.

Functions

By default this module exports one function, which works much like the similarly named function from Eval::Closure:

eval_closure(source => $source, environment => \%env, %opt)

Other functions can be imported on request:

set_subname( $fully_qualified_name, $coderef )

Works like the similarly named function from Sub::Util, but will fallback to doing nothing if neither Sub::Util nor Sub::Name are available. Also will cowardly refuse the set the name of a coderef a second time if it's already named it.

type_to_coderef( $type, %options )

Turns a Type::Tiny object into a coderef, suitable for installing into a symbol table to create a function like ArrayRef or Int. (Actually should work for any object which provides is_parameterizable, parameterize, and qualified_name methods, such as Type::Coercion.)

$options{post_method} can be a string of Perl indicating a method to call on the type constraint before returning it. For example '->moose_type'.

$options{description} can be a description of the coderef which may be shown in stack traces, etc.

The coderef will be named using set_subname unless $options{anonymous} is true.

If $type is undef, then it is assumed that the type constraint hasn't been defined yet but will later, yet you still want a function now. $options{type_library} and $options{type_name} will be used to find the type constraint when the function gets called.

Constants

The following constants may be exported, but are not by default.

HAS_LEXICAL_SUBS

Boolean indicating whether Eval::TypeTiny has support for lexical subs. (This feature requires Perl 5.18.)

ALIAS_IMPLEMENTATION

Returns a string indicating what implementation of alias => 1 is being used. Eval::TypeTiny will automatically choose the best implementation. This constant can be matched against the IMPLEMENTAION_* constants.

IMPLEMENTATION_NATIVE

If ALIAS_IMPLEMENTATION eq IMPLEMENTATION_NATIVE then Eval::TypeTiny is currently using Perl 5.22's native alias feature. This requires Perl 5.22.

IMPLEMENTATION_DEVEL_LEXALIAS

If ALIAS_IMPLEMENTATION eq IMPLEMENTATION_DEVEL_LEXALIAS then Eval::TypeTiny is currently using Devel::LexAlias to provide aliases.

IMPLEMENTATION_PADWALKER

If ALIAS_IMPLEMENTATION eq IMPLEMENTATION_PADWALKER then Eval::TypeTiny is currently using PadWalker to provide aliases.

IMPLEMENTATION_TIE

If ALIAS_IMPLEMENTATION eq IMPLEMENTATION_TIE then Eval::TypeTiny is using the fallback implementation of aliases using tie. This is the slowest implementation, and may cause problems in certain edge cases, like trying to alias already-tied variables, but it's the only way to implement alias => 1 without a recent version of Perl or one of the two optional modules mentioned above.

NICE_PROTOTYPES

If this is true, then type_to_coderef will give parameterizable type constraints the slightly nicer prototype of (;$) instead of the default (;@). This allows constructs like:

   ArrayRef[Int] | HashRef[Int]

... to "just work".

Evaluation Environment

The evaluation is performed in the presence of strict, but the absence of warnings. (This is different to Eval::Closure which enables warnings for compiled closures.)

The feature pragma is not active in the evaluation environment, so the following will not work:

   use feature qw(say);
   use Eval::TypeTiny qw(eval_closure);
   
   my $say_all = eval_closure(
      source => 'sub { say for @_ }',
   );
   $say_all->("Hello", "World");

The feature pragma does not "carry over" into the stringy eval. It is of course possible to import pragmas into the evaluated string as part of the string itself:

   use Eval::TypeTiny qw(eval_closure);
   
   my $say_all = eval_closure(
      source => 'sub { use feature qw(say); say for @_ }',
   );
   $say_all->("Hello", "World");

Bugs

Please report any bugs to https://github.com/tobyink/p5-type-tiny/issues.

See Also

Eval::Closure, Error::TypeTiny::Compilation.

Manual
The best place to start learning about this module is the manual.