JSONSchemer

JSON Schema validator. Supports drafts 4, 6, 7, 2019-09, 2020-12, OpenAPI 3.0, and OpenAPI 3.1.

Installation

Add this line to your application's Gemfile:

gem 'json_schemer'

And then execute:

$ bundle

Or install it yourself as:

$ gem install json_schemer

Usage

require 'json_schemer'

schema = {
  'type' => 'object',
  'properties' => {
    'abc' => {
      'type' => 'integer',
      'minimum' => 11
    }
  }
}
schemer = JSONSchemer.schema(schema)

# true/false validation

schemer.valid?({ 'abc' => 11 })
# => true

schemer.valid?({ 'abc' => 10 })
# => false

# error validation (`validate` returns an enumerator)

schemer.validate({ 'abc' => 10 }).to_a
# => [{"data"=>10,
#      "data_pointer"=>"/abc",
#      "schema"=>{"type"=>"integer", "minimum"=>11},
#      "schema_pointer"=>"/properties/abc",
#      "root_schema"=>{"type"=>"object", "properties"=>{"abc"=>{"type"=>"integer", "minimum"=>11}}},
#      "type"=>"minimum",
#      "error"=>"number at `/abc` is less than: 11"}]

# default property values

data = {}
JSONSchemer.schema(
  {
    'properties' => {
      'foo' => {
        'default' => 'bar'
      }
    }
  },
  insert_property_defaults: true
).valid?(data)
data
# => {"foo"=>"bar"}

# schema files

require 'pathname'

schema = Pathname.new('/path/to/schema.json')
schemer = JSONSchemer.schema(schema)

# schema json string

schema = '{ "type": "integer" }'
schemer = JSONSchemer.schema(schema)

# schema validation

JSONSchemer.valid_schema?({ '$id' => 'valid' })
# => true

JSONSchemer.validate_schema({ '$id' => '#invalid' }).to_a
# => [{"data"=>"#invalid",
#      "data_pointer"=>"/$id",
#      "schema"=>{"$ref"=>"#/$defs/uriReferenceString", "$comment"=>"Non-empty fragments not allowed.", "pattern"=>"^[^#]*#?$"},
#      "schema_pointer"=>"/properties/$id",
#      "root_schema"=>{...meta schema},
#      "type"=>"pattern",
#      "error"=>"string at `/$id` does not match pattern: ^[^#]*#?$"}]

JSONSchemer.schema({ '$id' => 'valid' }).valid_schema?
# => true

JSONSchemer.schema({ '$id' => '#invalid' }).validate_schema.to_a
# => [{"data"=>"#invalid",
#      "data_pointer"=>"/$id",
#      "schema"=>{"$ref"=>"#/$defs/uriReferenceString", "$comment"=>"Non-empty fragments not allowed.", "pattern"=>"^[^#]*#?$"},
#      "schema_pointer"=>"/properties/$id",
#      "root_schema"=>{...meta schema},
#      "type"=>"pattern",
#      "error"=>"string at `/$id` does not match pattern: ^[^#]*#?$"}]

# subschemas

schema = {
  'type' => 'integer',
  '$defs' => {
    'foo' => {
      'type' => 'string'
    }
  }
}
schemer = JSONSchemer.schema(schema)

schemer.ref('#/$defs/foo').validate(1).to_a
# => [{"data"=>1,
#      "data_pointer"=>"",
#      "schema"=>{"type"=>"string"},
#      "schema_pointer"=>"/$defs/foo",
#      "root_schema"=>{"type"=>"integer", "$defs"=>{"foo"=>{"type"=>"string"}}},
#      "type"=>"string",
#      "error"=>"instance at root is not a string"}]

# schema bundling (https://json-schema.org/draft/2020-12/json-schema-core.html#section-9.3)

schema = {
  '$id' => 'http://example.com/schema',
  'allOf' => [
    { '$ref' => 'schema/one' },
    { '$ref' => 'schema/two' }
  ]
}
refs = {
  URI('http://example.com/schema/one') => {
    'type' => 'integer'
  },
  URI('http://example.com/schema/two') => {
    'minimum' => 11
  }
}
schemer = JSONSchemer.schema(schema, :ref_resolver => refs.to_proc)

schemer.bundle
# => {"$id"=>"http://example.com/schema",
#     "allOf"=>[{"$ref"=>"schema/one"}, {"$ref"=>"schema/two"}],
#     "$schema"=>"https://json-schema.org/draft/2020-12/schema",
#     "$defs"=>
#      {"http://example.com/schema/one"=>{"type"=>"integer", "$id"=>"http://example.com/schema/one", "$schema"=>"https://json-schema.org/draft/2020-12/schema"},
#       "http://example.com/schema/two"=>{"minimum"=>11, "$id"=>"http://example.com/schema/two", "$schema"=>"https://json-schema.org/draft/2020-12/schema"}}}

Options

JSONSchemer.schema(
  schema,

  # meta schema to use for vocabularies (keyword behavior) and schema validation
  # String/JSONSchemer::Schema
  # 'https://json-schema.org/draft/2020-12/schema': JSONSchemer.draft202012
  # 'https://json-schema.org/draft/2019-09/schema': JSONSchemer.draft201909
  # 'http://json-schema.org/draft-07/schema#': JSONSchemer.draft7
  # 'http://json-schema.org/draft-06/schema#': JSONSchemer.draft6
  # 'http://json-schema.org/draft-04/schema#': JSONSchemer.draft4
  # 'http://json-schema.org/schema#': JSONSchemer.draft4
  # 'https://spec.openapis.org/oas/3.1/dialect/base': JSONSchemer.openapi31
  # 'json-schemer://openapi30/schema': JSONSchemer.openapi30
  # default: JSONSchemer.draft202012
  meta_schema: 'https://json-schema.org/draft/2020-12/schema',

  # validate `format` (https://json-schema.org/draft/2020-12/json-schema-validation.html#section-7)
  # true/false
  # default: true
  format: true,

  # insert default property values during validation
  # true/false
  # default: false
  insert_property_defaults: true,

  # modify properties during validation. You can pass one Proc or a list of Procs to modify data.
  # Proc/[Proc]
  # default: nil
  before_property_validation: proc do |data, property, property_schema, _parent|
    data[property] ||= 42
  end,

  # modify properties after validation. You can pass one Proc or a list of Procs to modify data.
  # Proc/[Proc]
  # default: nil
  after_property_validation: proc do |data, property, property_schema, _parent|
    data[property] = Date.iso8601(data[property]) if property_schema.is_a?(Hash) && property_schema['format'] == 'date'
  end,

  # resolve external references
  # 'net/http'/proc/lambda/respond_to?(:call)
  # 'net/http': proc { |uri| JSON.parse(Net::HTTP.get(uri)) }
  # default: proc { |uri| raise UnknownRef, uri.to_s }
  ref_resolver: 'net/http',

  # use different method to match regexes
  # 'ruby'/'ecma'/proc/lambda/respond_to?(:call)
  # 'ruby': proc { |pattern| Regexp.new(pattern) }
  # default: 'ruby'
  regexp_resolver: proc do |pattern|
    RE2::Regexp.new(pattern)
  end,

  # output formatting (https://json-schema.org/draft/2020-12/json-schema-core.html#section-12)
  # 'classic'/'flag'/'basic'/'detailed'/'verbose'
  # default: 'classic'
  output_format: 'basic',

  # validate `readOnly`/`writeOnly` keywords (https://spec.openapis.org/oas/v3.0.3#fixed-fields-19)
  # 'read'/'write'/nil
  # default: nil
  access_mode: 'read'
)

OpenAPI

document = JSONSchemer.openapi({
  'openapi' => '3.1.0',
  'info' => {
    'title' => 'example'
  },
  'components' => {
    'schemas' => {
      'example' => {
        'type' => 'integer'
      }
    }
  }
})

# document validation using meta schema

document.valid?
# => false

document.validate.to_a
# => [{"data"=>{"title"=>"example"},
#      "data_pointer"=>"/info",
#      "schema"=>{...info schema},
#      "schema_pointer"=>"/$defs/info",
#      "root_schema"=>{...meta schema},
#      "type"=>"required",
#      "details"=>{"missing_keys"=>["version"]}},
#     ...]

# data validation using schema by name (in `components/schemas`)

document.schema('example').valid?(1)
# => true

document.schema('example').valid?('one')
# => false

# data validation using schema by ref

document.ref('#/components/schemas/example').valid?(1)
# => true

document.ref('#/components/schemas/example').valid?('one')
# => false

CLI

The json_schemer executable takes a JSON schema file as the first argument followed by one or more JSON data files to validate. If there are any validation errors, it outputs them and returns an error code.

Validation errors are output as single-line JSON objects. The --errors option can be used to limit the number of errors returned or prevent output entirely (and fail fast).

The schema or data can also be read from stdin using -.

% json_schemer --help
Usage:
  json_schemer [options] <schema> <data>...
  json_schemer [options] <schema> -
  json_schemer [options] - <data>...
  json_schemer -h | --help
  json_schemer --version

Options:
  -e, --errors MAX                 Maximum number of errors to output
                                   Use "0" to validate with no output
  -h, --help                       Show help
  -v, --version                    Show version

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Build Status

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/davishmcclurg/json_schemer.

License

The gem is available as open source under the terms of the MIT License.