philiprehberger-json_schema

JSON Schema validator supporting common draft-07 keywords with schema composition, conditional validation, and compiled schemas

Requirements

• Ruby >= 3.1

Installation

Add to your Gemfile:

gem "philiprehberger-json_schema"

Or install directly:

gem install philiprehberger-json_schema

Usage

require "philiprehberger/json_schema"

schema = {
  type: 'object',
  required: %w[name age],
  properties: {
    'name' => { type: 'string', minLength: 1 },
    'age' => { type: 'integer', minimum: 0 }
  }
}

errors = Philiprehberger::JsonSchema.validate({ 'name' => 'Alice', 'age' => 30 }, schema)
# => []

Philiprehberger::JsonSchema.valid?({ 'name' => 'Alice', 'age' => 30 }, schema)
# => true

Schema Composition (allOf, anyOf, oneOf)

schema = {
  anyOf: [
    { type: 'string' },
    { type: 'integer' }
  ]
}
Philiprehberger::JsonSchema.valid?('hello', schema)  # => true
Philiprehberger::JsonSchema.valid?(42, schema)        # => true
Philiprehberger::JsonSchema.valid?(true, schema)      # => false

# allOf — data must match every sub-schema
schema = { allOf: [{ type: 'object', required: %w[name] }, { type: 'object', required: %w[age] }] }

# oneOf — data must match exactly one sub-schema
schema = { oneOf: [{ type: 'string', minLength: 5 }, { type: 'string', maxLength: 3 }] }

Negation (not)

schema = { not: { type: 'string' } }
Philiprehberger::JsonSchema.valid?(42, schema)      # => true
Philiprehberger::JsonSchema.valid?('hello', schema)  # => false

Conditional Validation (if/then/else)

schema = {
  type: 'object',
  if: { properties: { 'type' => { const: 'business' } }, required: %w[type] },
  then: { required: %w[company] },
  else: { required: %w[first_name] }
}

Philiprehberger::JsonSchema.valid?({ 'type' => 'business', 'company' => 'Acme' }, schema)
# => true

Philiprehberger::JsonSchema.valid?({ 'type' => 'personal', 'first_name' => 'Alice' }, schema)
# => true

Schema References ($ref and $defs)

schema = {
  type: 'object',
  properties: {
    'billing' => { '$ref' => '#/$defs/address' },
    'shipping' => { '$ref' => '#/$defs/address' }
  },
  '$defs' => {
    'address' => {
      type: 'object',
      required: %w[city],
      properties: { 'city' => { type: 'string' } }
    }
  }
}

Philiprehberger::JsonSchema.valid?({ 'billing' => { 'city' => 'NYC' }, 'shipping' => { 'city' => 'LA' } }, schema)
# => true

Additional and Pattern Properties

# Reject unknown properties
schema = {
  type: 'object',
  properties: { 'name' => { type: 'string' } },
  additionalProperties: false
}
Philiprehberger::JsonSchema.validate({ 'name' => 'Alice', 'extra' => 'nope' }, schema)
# => ["$.extra: additional property 'extra' is not allowed"]

# Validate properties matching a pattern
schema = {
  type: 'object',
  patternProperties: { '^x-' => { type: 'string' } }
}
Philiprehberger::JsonSchema.valid?({ 'x-custom' => 'ok' }, schema)  # => true
Philiprehberger::JsonSchema.valid?({ 'x-custom' => 42 }, schema)    # => false

Const Validation

schema = { const: 'fixed_value' }
Philiprehberger::JsonSchema.valid?('fixed_value', schema)  # => true
Philiprehberger::JsonSchema.valid?('other', schema)        # => false

Numeric Bounds (exclusive and multipleOf)

# exclusive bounds
schema = { type: 'integer', exclusiveMinimum: 0, exclusiveMaximum: 10 }
Philiprehberger::JsonSchema.valid?(5, schema)   # => true
Philiprehberger::JsonSchema.valid?(0, schema)   # => false (equal to exclusiveMinimum)
Philiprehberger::JsonSchema.valid?(10, schema)  # => false (equal to exclusiveMaximum)

# multipleOf (BigDecimal-backed, safe for fractions)
schema = { type: 'number', multipleOf: 0.1 }
Philiprehberger::JsonSchema.valid?(0.3, schema)   # => true
Philiprehberger::JsonSchema.valid?(0.25, schema)  # => false

Unique Array Items

schema = { type: 'array', uniqueItems: true }
Philiprehberger::JsonSchema.valid?([1, 2, 3], schema)                     # => true
Philiprehberger::JsonSchema.valid?([1, 2, 2], schema)                     # => false
Philiprehberger::JsonSchema.valid?([{ 'a' => 1 }, { 'a' => 1 }], schema)  # => false (deep equality)

Object Property Counts

schema = { type: 'object', minProperties: 1, maxProperties: 3 }
Philiprehberger::JsonSchema.valid?({ 'a' => 1 }, schema)                               # => true
Philiprehberger::JsonSchema.valid?({}, schema)                                          # => false
Philiprehberger::JsonSchema.valid?({ 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4 }, schema) # => false

Compiled Schemas

compiled = Philiprehberger::JsonSchema.compile({
  type: 'object',
  required: %w[id],
  properties: { 'id' => { type: 'integer' } }
})

compiled.valid?({ 'id' => 1 })    # => true
compiled.validate({ 'id' => 'x' }) # => ["$.id: expected type integer..."]

API

Philiprehberger::JsonSchema

Method	Description
.validate(data, schema)	Validate data against a schema, returns array of error strings
.valid?(data, schema)	Returns true if data passes validation
.compile(schema)	Returns a CompiledSchema for repeated validation

Philiprehberger::JsonSchema::CompiledSchema

Method	Description
#validate(data)	Validate data against the compiled schema
#valid?(data)	Returns true if data passes validation

Supported Keywords

Keyword	Description
type	Type validation (string, integer, number, boolean, array, object, null)
required	Required object properties
properties	Per-property sub-schemas
additionalProperties	Boolean or schema for properties not in properties
patternProperties	Regex-keyed sub-schemas for matching property names
pattern	Regex match for strings
minLength / maxLength	String length constraints
minimum / maximum	Numeric range constraints (inclusive)
exclusiveMinimum / exclusiveMaximum	Numeric range constraints (exclusive)
multipleOf	Value must be a multiple of the given number (BigDecimal-backed)
enum	Allowed value list
const	Exact value match
items	Schema for array elements
minItems / maxItems	Array length constraints
uniqueItems	Require all array items to be unique (deep equality)
minProperties / maxProperties	Object property-count constraints
allOf	Data must match all sub-schemas
anyOf	Data must match at least one sub-schema
oneOf	Data must match exactly one sub-schema
not	Data must not match the sub-schema
if / then / else	Conditional validation
$ref	Reference to a sub-schema (supports #/ JSON Pointer)
$defs	Schema definitions for $ref resolution

Development

bundle install
bundle exec rspec
bundle exec rubocop

Support

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License

MIT