v0.3.0 to v0.3.7

v0.3.7 (15 March 2026)

v0.3.7 on GitHub

WriterT Transformer, For-Comprehension Power-Ups, Build Tooling, and Spring Virtual Thread Support

This release introduces the WriterT monad transformer with MTL-style capability interfaces, enriches for-comprehensions with parallel composition, traversal operations, and optics integration, adds compile-time Path type checking via the new hkj-checker javac plugin, delivers one-line project setup through build tool plugins (hkj-gradle-plugin and hkj-maven-plugin), and extends Spring MVC with virtual-thread-native return value handlers for VTaskPath and VStreamPath.

• WriterT: Monad transformer for output accumulation across effect boundaries, wrapping Kind<F, Pair<A, W>> with automatic Monoid-based combining during flatMap chains
• MonadWriter: MTL-style capability interface with tell, listen, pass, listens, and censor for output accumulation
• MonadReader: MTL-style capability interface with ask, local, reader, and asks for shared environment access
• MonadState: MTL-style capability interface with get, put, modify, and gets for stateful computation
• par(): Parallel/applicative composition for For and ForPath comprehensions; true concurrency on VTask, intent-documenting on sequential monads
• traverse/sequence/flatTraverse: Bulk effectful operations within comprehension chains: apply an effectful function across a structure, flip Structure<Effect<A>> to Effect<Structure<A>>, or traverse-and-flatten in one step
• For-Comprehension Optics Integration: through(Iso) for type-safe value conversion in For; traverseOver(), modifyThrough(), modifyVia(), and updateVia() for optics-driven state operations in ForState
• Fold Combinators: Fold.plus(), Fold.empty(), and Fold.sum() forming a monoid on folds for multi-path data extraction
• Compile-Time Path Checks: hkj-checker javac plugin detecting Path type mismatches at compile time for via, then, zipWith, zipWith3, recoverWith, and orElse
• Build Plugins: hkj-gradle-plugin (one-line Gradle setup) and hkj-maven-plugin (Maven lifecycle extension) that auto-configure HKJ dependencies, --enable-preview flags, compile-time checking, and optional Spring Boot integration
• hkj-bom: Bill of Materials POM for version-aligned dependency management across all HKJ modules in both Gradle and Maven
• Diagnostics: hkjDiagnostics Gradle task and mvn hkj:diagnostics goal reporting active dependencies, compiler arguments, and checks
• VTaskPath Spring MVC: VTaskPathReturnValueHandler converting controller return values to async DeferredResult responses on virtual threads
• VStreamPath SSE: VStreamPathReturnValueHandler converting controller return values to Server-Sent Events with pull-based backpressure, no Reactor required
• Dependency updates: Gradle 9.4.0, JUnit 6.0.3, Jackson 3.1.0, Spring Boot 4.0.3, jOOQ 3.20.11, javapoet 0.12.0, and others
• Faster FunctionValidator and KindValidator with simplified implementation
• Test reliability improvements: replaced Thread.sleep with Awaitility across test suite

v0.3.6 (6 March 2026)

v0.3.6 on GitHub

VStream Lazy Streaming, Resilience Patterns, and ForState Comprehensions

This release introduces VStream, a lazy pull-based streaming type built on virtual threads with full HKT integration, adds four core resilience patterns (Circuit Breaker, Bulkhead, Retry, Saga) with Effect Path integration, extends ForState with filtering and pattern matching, and delivers a Market Data Pipeline capstone example.

• VStream: Lazy pull-based streaming on virtual threads with Step protocol (Emit/Done/Skip), factory methods (of, range, iterate, generate, unfold), transformation combinators, and error recovery
• VStream HKT Integration: VStreamKind witness type with Functor, Applicative, Monad, Foldable, Traverse, and Alternative type class instances
• VStream Parallel Operations: VStreamPar with parEvalMap, parEvalMapUnordered, parEvalFlatMap, merge, parCollect, and chunking combinators
• VStream Resources: bracket/onFinalize resource lifecycle management and VStreamReactive bidirectional Flow.Publisher bridge with backpressure
• VStreamPath: Effect Path bridge with factory methods, PathOps operations, terminal operations bridging to VTaskPath, and optics focus bridge
• Circuit Breaker: State machine (Closed/Open/HalfOpen) with configurable failure thresholds and recovery timeouts
• Bulkhead: Concurrency limiting for isolating resource access
• Retry: Configurable retry policies with fixed delay, exponential backoff, and jitter
• Saga: Distributed transaction compensation with ordered rollback
• Combined Resilience: Composing multiple resilience patterns and Path API ergonomic methods: retry(), circuitBreaker(), bulkhead(), timeout()
• ForState: Filtering (when), pattern matching (matchThen), traversals, zoom, and toState() bridge from For comprehensions at all arities (1–12)
• traverseWith(): Parallel effectful optics traversal for FocusPath, AffinePath, and TraversalPath via VTaskPath and StructuredTaskScope
• Market Data Pipeline: 14-feature capstone example demonstrating concurrent feed merging, parallel enrichment, risk assessment, windowed aggregation, anomaly detection, and circuit breaker failover
• Refreshed Monads chapter with problem-first structure, real-world analogies, and consistent formatting
• FunctionValidator optimisation: deferred error-message construction avoids String allocation on the happy path; fixed Gradle benchmark commands (-Pincludes)
• Javadoc generation fix to include annotation-processor-generated sources (Tuple2–Tuple12, MonadicSteps, etc.)
• JMH benchmarks for VStream construction, combinators, terminals, and parallel operations

v0.3.5 (15 February 2026)

v0.3.5 on GitHub

Extended For-Comprehensions, VTask API Refinement, and Documentation Restructure

This release extends for-comprehension arity to 12, simplifies the VTask API, adds Maybe-to-Either conversions, upgrades to JUnit 6, and delivers a comprehensive documentation restructure with quickstart guides, cheat sheets, migration cookbooks, and railway diagrams.

• For-Comprehension Arity 12: For and ForPath now support up to 12 monadic bindings (previously 5), with generated Tuple9–Tuple12 and Function9–Function12
• VTask API: VTask.run() no longer declares throws Throwable; checked exceptions are wrapped in VTaskExecutionException
• Maybe.toEither: New toEither(L) and toEither(Supplier<L>) conversion methods for seamless Maybe → Either transitions
• Quickstart: New getting-started guide with Gradle and Maven setup including --enable-preview configuration
• Cheat Sheet: Quick-reference for Path types, operators, escape hatches, and type conversions
• Stack Archetypes: 7 named transformer stack archetypes with colour-coded railway diagrams
• Migration Cookbook: 6 recipes for migrating from try/catch, Optional chains, null checks, CompletableFuture, validation, and nested records
• Compiler Error Guide: Solutions for the 5 most common Effect Path compiler errors
• Effects-Optics Capstone: Combined effects and optics pipeline example
• Railway operator diagrams for all 8 Effect Path operators and for EitherT, MaybeT, OptionalT transformers
• JUnit 6.0.2 upgrade (from 5.14.1) across all test modules
• Golden file test infrastructure with automated sync verification and pitest mutation coverage improvements

v0.3.4 (31 January 2026)

v0.3.4 on GitHub

External Type Optics and Examples Gallery

This release introduces powerful optics generation for external types you cannot modify, plus a new Examples Gallery chapter documenting all runnable examples.

• @ImportOptics: Generate optics for JDK classes and third-party library types via auto-detection of withers and accessors
• Spec Interfaces: Fine-grained control over external type optics with OpticsSpec<S> for complex types like Jackson's JsonNode
• @ThroughField Auto-Detection: Automatic traversal type detection for List, Set, Optional, arrays, and Map fields
• Examples Gallery: New chapter with categorised, runnable examples demonstrating core types, transformers, Effect Path API, and optics
• Comprehensive hkj-processor testing improvements with enhanced coverage

v0.3.3 (24 January 2026)

v0.3.3 on GitHub

Structured Concurrency, Atomic Optics, and Enhanced Examples

This release introduces structured concurrency primitives, atomic coupled-field updates, and a comprehensive Order Workflow example demonstrating these patterns.

• Structured Concurrency: Scope for parallel operations with allSucceed(), anySucceed(), firstComplete(), and accumulating() joiners
• Resource Management: Resource for bracket-pattern cleanup with guaranteed release
• Coupled Fields: Lens.paired for atomic multi-field updates bypassing invalid intermediate states
• Order Workflow Overview: Reorganised documentation with focused sub-pages
• Concurrency and Scale: Context, Scope, Resource, VTaskPath patterns in practice
• EnhancedOrderWorkflow: Full workflow demonstrating Context, Scope, Resource, VTaskPath
• OrderContext: ScopedValue keys for trace ID, tenant isolation, and deadline enforcement
• Scope & Resource Tutorials: 18 exercises on concurrency patterns
• Release History: New page documenting all releases

v0.3.2 (17 January 2026)

v0.3.2 on GitHub

Virtual Thread Concurrency with VTask

This release introduces VTask<A>, a lazy computation effect leveraging Java 25's virtual threads for lightweight concurrent programming.

• VTask: Lazy computation effect for virtual thread execution
• Structured Concurrency: Scope for parallel operations with allSucceed(), anySucceed(), and accumulating() patterns
• Resource Management: Resource for bracket-pattern cleanup guarantees
• VTaskPath: Integration with the Effect Path API
• Concurrency and Scale: Practical patterns in the Order Workflow example
• Par parallel combinators for concurrent execution
• Comprehensive benchmarks comparing virtual vs. platform threads

v0.3.1 (15 January 2026)

v0.3.1 on GitHub

Static Analysis Utilities

This release adds utilities for statically analysing Free Applicative and Selective functors without execution.

• Choosing Abstraction Levels: Guide to selecting Functor, Applicative, Selective, or Monad
• Free Applicative: Static analysis with FreeApAnalyzer
• Selective: Conditional effects with SelectiveAnalyzer
• Tutorial 11 on static analysis patterns

v0.3.0 (4 January 2026)

v0.3.0 on GitHub

Effect Path Focus Integration

Major release introducing the unified Effect Path API and Focus DSL integration. Requires Java 25 baseline.

• Effect Path Overview: The railway model for composable effects
• Path Types: 17+ composable Path types including EitherPath, MaybePath, IOPath
• Focus DSL: Type-safe optics with annotation-driven generation
• Focus-Effect Integration: Bridge between optics and effects
• ForPath Comprehension: For-comprehension syntax for Path types
• Spring Boot Integration: Spring Boot 4.0.1+ support
• Order Workflow: Complete example demonstrating Effect Path patterns

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