betto_schema

Initial development release. Pure Dart JSON Schema validation primitives aligned with JSON Schema Validation 2020-12.

Primitive validators (validation.dart)

Typed, composable validators that form the primary public API. Dart developers construct and combine these directly without touching JSON Schema format.

Validator	Description
EnumValidator<T>	Value must be one of a declared set
ConstValidator<T>	Value must equal a constant (deep equality)
Minimum<T> / Maximum<T>	Inclusive numeric bounds
ExclusiveMinimum<T> / ExclusiveMaximum<T>	Exclusive numeric bounds
MultipleOf<T>	Divisibility check (floating-point-safe)
InRange	Value within a Range
MinimumLength / MaximumLength / ExactLength	Unicode-aware string length
InRangeLength	String length within a Range
PatternValidator	Regex match (unanchored, per JSON Schema §6.3.3)
MinItems<T> / MaxItems<T> / ItemCount<T>	Array size bounds
UniqueItems<T>	All array elements pairwise distinct (deep equality)
ItemsValidator<T>	Every array element satisfies a sub-validator
MinProperties / MaxProperties	Object property count bounds
Required	All named properties present in a map
TypeValidator	JSON Schema type check — single string and array form
PropertiesValidator	Per-key validators for a map
AdditionalPropertiesValidator	Rejects undeclared object keys
DependentRequired	Conditional required properties

JSON Schema rule tree (schema_rule.dart)

A sealed SchemaRule hierarchy compiled from a JSON Schema by SchemaParser. All rules collect every violation in a single pass so callers receive the complete error list at once.

Rule	JSON Schema keyword(s)
TypeRule	type (string and array forms)
RequiredRule	required
PropertiesRule	properties
AdditionalPropertiesRule	additionalProperties: false
AdditionalPropertiesSchemaRule	additionalProperties: <schema>
EnumRule	enum
ConstRule	const
NumericRule	minimum, maximum, exclusiveMinimum, exclusiveMaximum
MultipleOfRule	multipleOf
StringRule	minLength, maxLength, pattern
FormatRule	format
ArrayRule	minItems, maxItems, items
PrefixItemsRule	prefixItems
ContainsRule	contains, minContains, maxContains
UniqueItemsRule	uniqueItems
ObjectSizeRule	minProperties, maxProperties
PatternPropertiesRule	patternProperties
DependentRequiredRule	dependentRequired
CompositeRule	(internal — runs multiple rules in one pass)
AlwaysInvalidRule	false boolean schema (e.g. items: false)

Format validators (formats/)

StringFormatValidator provides named format validators. The set covers all standard JSON Schema 2020-12 format strings implemented in this release, plus project-specific extensions.

Standard JSON Schema formats

Format	Spec
uri	RFC 3986
urn	RFC 8141
email	RFC 5322 (pragmatic subset)
date-time	ISO 8601
date	RFC 3339
time	RFC 3339
uuid	RFC 9562
duration	ISO 8601 / RFC 3339
hostname	RFC 1123
idn-hostname	RFC 5890 (best-effort; Punycode conformance not enforced)
ipv4	RFC 2673 — four decimal octets 0–255, leading zeros rejected
ipv6	RFC 4291 — full and :: compressed forms, IPv4-mapped accepted
uri-reference	RFC 3986 §4.1 — absolute URI or relative reference
json-pointer	RFC 6901
relative-json-pointer	IETF draft
regex	ECMA-262 dialect

Deferred to v1: idn-email, iri, iri-reference, uri-template.

Project-specific extensions

Format	Description
hex-string	Hexadecimal digit string
digit-string	Decimal digit string
roman-numeral	Roman numeral string
isbn-13	ISBN-13 with check-digit verification
doi	Digital Object Identifier
lang	BCP 47 / RFC 5646 language tag

Porcelain (json_schema_validator.dart)

JsonSchemaValidator accepts a JSON Schema as a String or Map<String, dynamic>, delegates to SchemaParser, and returns List<SchemaViolation>. No validation logic of its own.

Supporting types

• SchemaViolation — dot-path (path) and human-readable message; root violations use an empty path
• SchemaParser — compiles Map<String, dynamic> JSON Schema to a SchemaRule tree; unknown keywords are silently ignored
• Range — inclusive/exclusive numeric range helper used by primitive validators

Spec-correctness fixes applied during this release

• pattern is unanchored — hasMatch() not a full-string check (JSON Schema §6.3.3)
• integer accepts whole-number doubles (e.g. 1.0); non-finite values rejected (§6.1.1)
• type array form (["string", "null"]) is parsed and validated correctly (§6.1.1)
• uri and urn format validators correctly distinguished (were swapped)

Examples (example/)

Six runnable examples are included:

Entry point	Demonstrates
example/main.dart	Parsing a JSON Schema with SchemaParser and collecting SchemaViolations
example/validators.dart	Composing Validator primitives directly (MaximumLength, StringFormatValidator)
example/violation.dart	Constructing and printing SchemaViolation values
example/book/main.dart	A book schema: enum genres, prefixItems, additionalProperties, contains, format strings
example/contact/main.dart	A contact schema: nested address object, email/uri/date formats, uniqueItems, patterns
example/recipe/main.dart	A recipe schema: nested ingredient objects, numeric ranges, enum values, uniqueItems

Each domain example (book, contact, recipe) ships with a schema.json and sample data files so it can be run standalone with dart run.

CLI

• Added bin/validate.dart — a command-line tool that validates a JSON data file (or stdin) against a JSON Schema file. Exits 0 on success, 1 on validation failures (violations printed to stdout), and 2 on usage or I/O errors.

Out of scope (planned for v1)

$ref, allOf / anyOf / oneOf / not, if / then / else, nested $schema declarations, idn-email, iri, iri-reference, uri-template.