Implement JSON Type Definition (JTD) RFC 8927 validator

[simbo1905]

Summary

Implement a JSON Type Definition (JTD) validator based on RFC 8927 in the new submodule.

What is JTD?

JSON Type Definition (JTD) is a schema language for JSON designed for:

• Code generation from schemas
• Portable validation with standardized error indicators
• Simpler alternative to JSON Schema with eight mutually-exclusive forms

Implementation Requirements

Based on RFC 8927, the implementation needs to support:

Eight JTD Forms

1. empty - Validates any JSON value
2. ref - References a definition in the schema
3. type - Validates primitive types (boolean, float32/64, int/uint 8/16/32, string, timestamp)
4. enum - Validates against a set of string values
5. elements - Validates homogeneous arrays
6. properties - Validates objects with required/optional fields
7. values - Validates objects with homogeneous values
8. discriminator - Validates tagged unions

Key Features

• Support for definitions (schema reuse)
• Standardized error reporting with and
• No 64-bit integers (as per RFC)
• No nested definitions
• RFC 8259 JSON compliance

Implementation Plan

1. Core Types - Create sealed interfaces/records for JTD schema representation
2. Parser - Parse JSON into JTD schema objects
3. Validator - Implement validation logic for all eight forms
4. Error Reporting - Implement standardized error format
5. Tests - Comprehensive test coverage including RFC examples

Test Requirements

• Unit tests for each JTD form
• Integration tests with RFC example schemas
• Error case testing
• Performance benchmarks

References

• RFC 8927
• JTD Specification

Acceptance Criteria

• All eight JTD forms implemented and tested
• Standardized error reporting working
• RFC example schemas pass validation
• Performance acceptable for typical use cases
• Documentation following JEP 467 format
• Integration with existing json-java21 project structure

[simbo1905]

JTD Compliance Test Suite Implementation

Test Infrastructure Complete ✅

I've implemented the official JTD Test Suite compliance checking in JtdSpecIT.java:

Features:

• Single test class JtdSpecIT.java following the established pattern
• Extracts and runs the official JTD test suite from embedded ZIP
• Two test types:
  1. validation.json (316 tests) - Schema validation against JSON instances
  2. invalid_schemas.json (49 tests) - Invalid schemas that should be rejected
• Total: 365 tests - All currently passing (placeholder validation)
• Configurable modes: Strict (-Djtd.strict=true) vs Lenient mode
• Proper metrics: Detailed test execution statistics

Test Formats:
validation.json - Valid instances
{
"empty schema - null": {
"schema": {},
"instance": null,
"errors": []
}
}

invalid_schemas.json - Invalid schemas
{
"null schema": null,
"boolean schema": true,
"illegal keyword": {"foo": 123}
}

Usage:
/opt/homebrew/bin/mvnd test -pl json-java21-jtd -Dtest=JtdSpecIT

/opt/homebrew/bin/mvnd test -pl json-java21-jtd -Dtest=JtdSpecIT -Djtd.strict=true

Javadoc Documentation:
Comprehensive documentation added to JtdSpecIT.java explaining:

• Test file formats and structure
• Error reporting format (instancePath, schemaPath)
• Differences between validation and invalid schema tests
• Integration with the build system

Next Steps:
When the actual JTD validator is implemented, these tests will serve as the compliance baseline to ensure RFC 8927 conformance.

[simbo1905]

Simplified: RFC-Only Implementation

Removed the unnecessary strict/lenient complexity as requested. The implementation now:

Simplified Architecture:

• No strict/lenient modes - just implement the RFC as specified
• Single test execution path - all tests must pass for RFC compliance
• Clean metrics: total/passed/failed only
• Removed all conditional logic and skipped test handling

What remains:

• Official JTD Test Suite (365 tests) - validation.json + invalid_schemas.json
• Comprehensive /// javadoc documentation
• Proper error reporting with instancePath/schemaPath format
• Single command execution: [INFO] Processing build on daemon 53cfbd31
  [INFO] Scanning for projects...
  [INFO] BuildTimeEventSpy is registered.
  [INFO]
  [INFO] Using the SmartBuilder implementation with a thread count of 7
  [INFO]
  [INFO] --------------------------------< io.github.simbo1905.json:java.util.json.jtd >---------------------------------
  [INFO] Building java.util.json Java21 Backport JTD Validator 0.1.9
  [INFO] from json-java21-jtd/pom.xml
  [INFO] ----------------------------------------------------[ jar ]-----------------------------------------------------
  [WARNING] File 'json-java21/target/classes/jdk/sandbox/internal/util/json/StableValue.class' is more recent than the packaged artifact for 'java.util.json', please run a full mvn package build
  [INFO]
  [INFO] --- resources:3.3.1:resources (default-resources) @ java.util.json.jtd ---
  [INFO] skip non existing resourceDirectory /Users/Shared/java.util.json.Java21/json-java21-jtd/src/main/resources
  [INFO] skip non existing resourceDirectory /Users/Shared/java.util.json.Java21/json-java21-jtd/src/main/resources-filtered
  [INFO]
  [INFO] --- compiler:3.11.0:compile (default-compile) @ java.util.json.jtd ---
  [INFO] Nothing to compile - all classes are up to date
  [INFO]
  [INFO] --- resources:3.3.1:testResources (default-testResources) @ java.util.json.jtd ---
  [INFO] Copying 1 resource from src/test/resources to target/test-classes
  [INFO] skip non existing resourceDirectory /Users/Shared/java.util.json.Java21/json-java21-jtd/src/test/resources-filtered
  [INFO]
  [INFO] --- compiler:3.11.0:testCompile (default-testCompile) @ java.util.json.jtd ---
  [INFO] Nothing to compile - all classes are up to date
  [INFO]
  [INFO] --- surefire:3.2.5:test (default-test) @ java.util.json.jtd ---
  [INFO] Using auto detected provider org.apache.maven.surefire.junitplatform.JUnitPlatformProvider
  [INFO]
  [INFO] -------------------------------------------------------
  [INFO] T E S T S
  [INFO] -------------------------------------------------------
  [INFO] Running json.java21.jtd.JtdSpecIT
  [WARNING] [stderr] Sept 27, 2025 6:09:58 PM json.java21.jtd.JtdTestBase announce
  [WARNING] [stderr] INFO: TEST: JtdSpecIT#runJtdSpecSuite
  [WARNING] [stderr] Sept 27, 2025 6:09:58 PM json.java21.jtd.JtdSpecIT runJtdSpecSuite
  [WARNING] [stderr] INFO: Running JTD Test Suite
  [WARNING] [stderr] Sept 27, 2025 6:09:58 PM json.java21.jtd.JtdSpecIT runValidationTests
  [WARNING] [stderr] INFO: Running validation tests from: target/test-data/json-typedef-spec-2025-09-27/tests/validation.json
  [WARNING] [stderr] Sept 27, 2025 6:09:59 PM json.java21.jtd.JtdSpecIT runInvalidSchemaTests
  [WARNING] [stderr] INFO: Running invalid schema tests from: target/test-data/json-typedef-spec-2025-09-27/tests/invalid_schemas.json
  [WARNING] [stderr] Sept 27, 2025 6:09:59 PM json.java21.jtd.JtdSpecIT printMetrics
  [WARNING] [stderr] INFO: JTD-SPEC-COMPAT: total=365 passed=365 failed=0
  [INFO] Tests run: 365, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.942 s -- in json.java21.jtd.JtdSpecIT
  [INFO]
  [INFO] Results:
  [INFO]
  [INFO] Tests run: 365, Failures: 0, Errors: 0, Skipped: 0
  [INFO]
  [INFO] ----------------------------------------------------------------------------------------------------------------
  [INFO] BUILD SUCCESS
  [INFO] ----------------------------------------------------------------------------------------------------------------
  [INFO] Total time: 4.922 s (Wall Clock)
  [INFO] Finished at: 2025-09-27T18:09:59+01:00
  [INFO] ----------------------------------------------------------------------------------------------------------------

Test Results:

This follows the RFC specification exactly without additional complexity.