=pod

=encoding UTF-8

=for stopwords schema subschema metaschema validator evaluator

=head1 NAME

JSON::Schema::Tiny - Validate data against a schema, minimally

=head1 VERSION

version 0.031

=head1 SYNOPSIS

my $data = { hello => 1 }; my$schema = { type => "object", properties => { hello => { type => "integer" } }, };

functional interface:

use JSON::Schema::Tiny qw(evaluate); my $result = evaluate($data, $schema); # { valid => true }

object-oriented interface:

use JSON::Schema::Tiny; my $js = JSON::Schema::Tiny->new; my$result = $js->evaluate($data, $schema); # { valid => true }

=head1 DESCRIPTION

This module aims to be a slimmed-down L<JSON Schema|https://json-schema.org/> evaluator and validator, supporting the most popular keywords. (See L</UNSUPPORTED JSON SCHEMA FEATURES> below for exclusions.)

=head1 FUNCTIONS

=for Pod::Coverage is_type get_type is_bool is_bignum is_equal is_elements_unique jsonp canonical_uri E abort assert_keyword_type assert_pattern assert_uri assert_non_negative_integer assert_array_schemas new assert_uri_reference sprintf_num HAVE_BUILTIN

=head2 evaluate

my $result = evaluate($data, $schema);

Evaluates the provided instance data against the known schema document.

The data is in the form of an unblessed nested Perl data structure representing any type that JSON allows: null, boolean, string, number, object, array. (See L below.)

The schema must represent a valid JSON Schema in the form of a Perl data structure, such as what is returned from a JSON decode operation.

With default configuration settings, the return value is a hashref indicating the validation success or failure, plus (when validation failed), an arrayref of error strings in standard JSON Schema format. For example:

running:

$result = evaluate(1, { type => 'number' });

C<$result> is:

{ valid => true }

running:

$result = evaluate(1, { type => 'number', multipleOf => 2 });

C<$result> is:

{ valid => false, errors => [ { instanceLocation => '', keywordLocation => '/multipleOf', error => 'value is not a multiple of 2', }, ], }

When L</C<$BOOLEAN_RESULT>> is true, the return value is a boolean (indicating evaluation success or failure).

=head1 OPTIONS

All options are available as package-scoped global variables. Use L<local|perlfunc/local> to configure them for a local scope. They may also be set via the constructor, as lower-cased values in a hash, e.g.: C<< JSON::Schema::Tiny->new(boolean_result => 1, max_traversal_depth => 10); >>

=head2 C<$BOOLEAN_RESULT>

When true, L will return a true or false result only, with no error strings. This enables short-circuit mode internally as this cannot affect results except get there faster. Defaults to false.

=head2 C<$SHORT_CIRCUIT>

When true, L will return from evaluating each subschema as soon as a true or false result can be determined. When C<$BOOLEAN_RESULT> is false, an incomplete list of errors will be returned. Defaults to false.

=head2 C<$MAX_TRAVERSAL_DEPTH>

The maximum number of levels deep a schema traversal may go, before evaluation is halted. This is to protect against accidental infinite recursion, such as from two subschemas that each reference each other, or badly-written schemas that could be optimized. Defaults to 50.

=head2 C<$SCALARREF_BOOLEANS>

When true, any value that is expected to be a boolean B may also be expressed as the scalar references C<\0> or C<\1> (which are serialized as booleans by JSON backends). Defaults to false.

=head2 C<$STRINGY_NUMBERS>

When true, any value that is expected to be a number or integer B may also be expressed as a string. This applies only to the following keywords:

=over 4

=item *

C (where both C and C (and possibly C) are considered types

=item *

C and C (where the string C<"1"> will match with C<"const": 1>)

=item *

C (where strings and numbers are compared numerically to each other, if either or both are numeric)

=item *

C

=item *

C

=item *

C

=item *

C

=item *

C

=back

This allows you to write a schema like this (which validates a string representing an integer):

type: string pattern: ^[0-9]$ multipleOf: 4 minimum: 16 maximum: 256

Such keywords are only applied if the value looks like a number, and do not generate a failure otherwise. Values are determined to be numbers via L<perlapi/looks_like_number>. Defaults to false.

=head2 C<$SPECIFICATION_VERSION>

When set, the version of the draft specification is locked to one particular value, and use of keywords inconsistent with that specification version will result in an error. Will be set internally automatically with the use of the C<$schema> keyword. When not set, all keywords will be honoured (when otherwise supported).

Supported values for this option, and the corresponding values for the C<$schema> keyword, are:

=over 4

=item *

L<C or C<2020-12>|https://json-schema.org/specification-links.html#2020-12>, corresponding to metaschema Chttps://json-schema.org/draft/2020-12/schema

=item *

L<C or C<2019-09>|https://json-schema.org/specification-links.html#2019-09-formerly-known-as-draft-8>, corresponding to metaschema Chttps://json-schema.org/draft/2019-09/schema

=item *

L<C or C<7>|https://json-schema.org/specification-links.html#draft-7>, corresponding to metaschema Chttp://json-schema.org/draft-07/schema#

=back

Defaults to undef.

=head1 UNSUPPORTED JSON SCHEMA FEATURES

Unlike LJSON::Schema::Modern, this is not a complete implementation of the JSON Schema specification. Some features and keywords are left unsupported in order to keep the code small and the execution fast. These features are not available:

=over 4

=item *

any output format other than C (when C<$BOOLEAN_RESULT> is true) or C (when it is false)

=item *

L<annotations|https://json-schema.org/draft/2019-09/json-schema-core.html#rfc.section.7.7> in successful evaluation results

=item *

use of C<$ref> other than to locations in the local schema in json-pointer format (e.g. C<#/path/to/property>). This means that references to external documents, either those available locally or on the network, are not permitted.

=back

In addition, these keywords are implemented only partially or not at all (their presence in a schema will be ignored or possibly result in an error):

=over 4

=item *

C<$schema> - only accepted if set to one of the specification metaschema URIs (see L<$SPECIFICATION_VERSION> for supported values)

=item *

C<$id>

=item *

C<$anchor>

=item *

C<$recursiveAnchor> and C<$recursiveRef> (draft2019-09), and C<$dynamicAnchor> and C<$dynamicRef> (draft2020-12 and thereafter)

=item *

C<$vocabulary>

=item *

C and C (which require annotation support)

=item *

C (does not cause an error when used)

=back

For a more full-featured implementation of the JSON Schema specification, see LJSON::Schema::Modern.

=head1 LIMITATIONS

=head2 Types

Perl is a more loosely-typed language than JSON. This module delves into a value's internal representation in an attempt to derive the true "intended" type of the value. This should not be an issue if data validation is occurring immediately after decoding a JSON payload, or if the JSON string itself is passed to this module. If you are having difficulties, make sure you are using Perl's fastest and most trusted and reliable JSON decoder, LCpanel::JSON::XS. Other JSON decoders are known to produce data with incorrect data types, and data from other sources may also be problematic.

For more information, see LCpanel::JSON::XS/MAPPING.

=head1 SECURITY CONSIDERATIONS

The C and C keywords evaluate regular expressions from the schema. No effort is taken (at this time) to sanitize the regular expressions for embedded code or potentially pathological constructs that may pose a security risk, either via denial of service or by allowing exposure to the internals of your application. B

=head1 SEE ALSO

=over 4

=item *

LJSON::Schema::Modern: a more specification-compliant JSON Schema evaluator

=item *

LTest::JSON::Schema::Acceptance: contains the official JSON Schema test suite

=item *

Lhttps://json-schema.org

=item *

L<Understanding JSON Schema|https://json-schema.org/understanding-json-schema>: tutorial-focused documentation

=back

=for stopwords OpenAPI

=head1 GIVING THANKS

=for stopwords MetaCPAN GitHub

If you found this module to be useful, please show your appreciation by adding a +1 in L<MetaCPAN|https://metacpan.org/dist/JSON-Schema-Tiny> and a star in L<GitHub|https://github.com/karenetheridge/JSON-Schema-Tiny>.

=head1 SUPPORT

Bugs may be submitted through Lhttps://github.com/karenetheridge/JSON-Schema-Tiny/issues.

I am also usually active on irc, as 'ether' at C<irc.perl.org> and C<irc.libera.chat>.

You can also find me on the L<JSON Schema Slack server|https://json-schema.slack.com> and L<OpenAPI Slack server|https://open-api.slack.com>, which are also great resources for finding help.

=head1 AUTHOR

Karen Etheridge ether@cpan.org

=head1 CONTRIBUTOR

=for stopwords Matt S Trout

Matt S Trout mst@shadowcat.co.uk

=head1 COPYRIGHT AND LICENCE

This software is copyright (c) 2021 by Karen Etheridge.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.

=cut