# NAME

Params::ValidationCompiler - Build an optimized subroutine parameter validator once, use it forever

# VERSION

version 0.23

# SYNOPSIS

    use Types::Standard qw( Int Str );
    use Params::ValidationCompiler qw( validation_for );

    {
        my $validator = validation_for(
            params => {
                foo => { type => Int },
                bar => {
                    type     => Str,
                    optional => 1,
                },
                baz => {
                    type    => Int,
                    default => 42,
                },
            },
        );

        sub foo {
            my %args = $validator->(@_);
        }
    }

    {
        my $validator = validation_for(
            params => [
                { type => Int },
                {
                    type     => Str,
                    optional => 1,
                },
            ],
        );

        sub bar {
            my ( $int, $str ) = $validator->(@_);
        }
    }

    {
        my $validator = validation_for(
            params => [
                foo => { type => Int },
                bar => {
                    type     => Str,
                    optional => 1,
                },
            ],
            named_to_list => 1,
        );

        sub baz {
            my ( $foo, $bar ) = $validator->(@_);
        }
    }

# DESCRIPTION

This module creates a customized, highly efficient parameter checking
subroutine. It can handle named or positional parameters, and can return the
parameters as key/value pairs or a list of values.

In addition to type checks, it also supports parameter defaults, optional
parameters, and extra "slurpy" parameters.

# EXPORTS

This module has two options exports, `validation_for` and `source_for`. Both
of these subs accept the same options:

- params

    An arrayref or hashref containing a parameter specification.

    If you pass a hashref then the generated validator sub will expect named
    parameters. The `params` value should be a hashref where the parameter names
    are keys and the specs are the values.

    If you pass an arrayref and `named_to_list` is false, the validator will
    expect positional params. Each element of the `params` arrayref should be a
    parameter spec.

    If you pass an arrayref and `named_to_list` is false, the validator will
    expect named params, but will return a list of values. In this case the
    arrayref should contain a _list_ of key/value pairs, where parameter names
    are the keys and the specs are the values.

    Each spec can contain either a boolean or hashref. If the spec is a boolean,
    this indicates required (true) or optional (false).

    The spec hashref accepts the following keys:

    - type

        A type object. This can be a [Moose](https://metacpan.org/pod/Moose) type (from [Moose](https://metacpan.org/pod/Moose) or
        [MooseX::Types](https://metacpan.org/pod/MooseX::Types)), a [Type::Tiny](https://metacpan.org/pod/Type::Tiny) type, or a [Specio](https://metacpan.org/pod/Specio) type.

        If the type has coercions, those will always be used.

    - default

        This can either be a simple (non-reference) scalar or a subroutine
        reference. The sub ref will be called without any arguments (for now).

    - optional

        A boolean indicating whether or not the parameter is optional. By default,
        parameters are required unless you provide a default.

- slurpy

    If this is a simple true value, then the generated subroutine accepts
    additional arguments not specified in `params`. By default, extra arguments
    cause an exception.

    You can also pass a type constraint here, in which case all extra arguments
    must be values of the specified type.

- named\_to\_list

    If this is true, the generated subroutine will expect a list of key-value
    pairs or a hashref and it will return a list containing only the values.
    `params` must be a arrayref of key-value pairs in the order of which the
    values should be returned.

    You cannot combine `slurpy` with `named_to_list` as there is no way to know
    how the order in which extra values should be returned.

## validation\_for(...)

This returns a subroutine that implements the specific parameter
checking. This subroutine expects to be given the parameters to validate in
`@_`. If all the parameters are valid, it will return the validated
parameters (with defaults as appropriate), either as a list of key-value pairs
or as a list of just values. If any of the parameters are invalid it will
throw an exception.

For validators expected named params, the generated subroutine accepts either
a list of key-value pairs or a single hashref. Otherwise the validator expects
a list of values.

For now, you must shift off the invocant yourself.

This subroutine accepts an additional parameter:

- name

    If this is given, then the generated subroutine will be named using
    [Sub::Util](https://metacpan.org/pod/Sub::Util). This is strongly recommended as it makes it possible to
    distinguish different check subroutines when profiling or in stack traces.

    Note that you must install [Sub::Util](https://metacpan.org/pod/Sub::Util) yourself separately, as it is not
    required by this distribution, in order to avoid requiring a compiler.

- name\_is\_optional

    If this is true, then the name is ignored when `Sub::Util` is not
    installed. If this is false, then passing a name when [Sub::Util](https://metacpan.org/pod/Sub::Util) cannot be
    loaded causes an exception.

    This is useful for CPAN modules where you want to set a name if you can, but
    you do not want to add a prerequisite on [Sub::Util](https://metacpan.org/pod/Sub::Util).

## source\_for(...)

This returns a two element list. The first is a string containing the source
code for the generated sub. The second is a hashref of "environment" variables
to be used when generating the subroutine. These are the arguments that are
passed to [Eval::Closure](https://metacpan.org/pod/Eval::Closure).

# SUPPORT

Bugs may be submitted at [https://github.com/houseabsolute/Params-ValidationCompiler/issues](https://github.com/houseabsolute/Params-ValidationCompiler/issues).

I am also usually active on IRC as 'autarch' on `irc://irc.perl.org`.

# SOURCE

The source code repository for Params-ValidationCompiler can be found at [https://github.com/houseabsolute/Params-ValidationCompiler](https://github.com/houseabsolute/Params-ValidationCompiler).

# DONATIONS

If you'd like to thank me for the work I've done on this module, please
consider making a "donation" to me via PayPal. I spend a lot of free time
creating free software, and would appreciate any support you'd care to offer.

Please note that **I am not suggesting that you must do this** in order for me
to continue working on this particular software. I will continue to do so,
inasmuch as I have in the past, for as long as it interests me.

Similarly, a donation made in this way will probably not make me work on this
software much more, unless I get so many donations that I can consider working
on free software full time (let's all have a chuckle at that together).

To donate, log into PayPal and send money to autarch@urth.org, or use the
button at [http://www.urth.org/~autarch/fs-donation.html](http://www.urth.org/~autarch/fs-donation.html).

# AUTHOR

Dave Rolsky <autarch@urth.org>

# CONTRIBUTORS

- Gregory Oschwald <goschwald@maxmind.com>
- Tomasz Konojacki <me@xenu.pl>

# COPYRIGHT AND LICENSE

This software is Copyright (c) 2016 - 2017 by Dave Rolsky.

This is free software, licensed under:

    The Artistic License 2.0 (GPL Compatible)

The full text of the license can be found in the
`LICENSE` file included with this distribution.