Changelog#

All notable changes to this project will be documented in this file.

[0.1.0-alpha.15] - 2026-04-18#

Fixed#

• traverseResult / traverseOption mutation and early returns — rewritten as pure reduce folds over Result<readonly B[], E> / Option<readonly B[]> accumulators, removing the mutable local arrays and multi-return control flow that violated the project's FP rules
• apOption / liftA2Option raw None literals — now use the exported none singleton for referential-identity consistency with mapOption / flatMapOption

Changed#

• Exit namespace consolidated — removed the Exit.succeed / Exit.fail / Exit.interrupt aliases; use the canonical Exit.success / Exit.failure / Exit.interrupted instead. Examples and docs-site updated accordingly.

Documentation#

• Collapsed duplicate "Type Class Interfaces" section headers in prelude/typeclasses.ts and removed the redundant HKT paragraph already covered by the module docstring

[0.1.0-alpha.14] - 2026-04-03#

Fixed#

• Bracket resource leak on fiber interruption — release handlers now run when a fiber is interrupted during async use phase, preventing resource leaks
• Unsafe toResult non-null assertion — invalid() now requires at least one error (readonly [E, ...E[]]), eliminating the errors[0]! assertion that could produce undefined
• matchValidation error type — onInvalid callback now receives readonly [E, ...E[]] matching the Invalid type

Removed#

• Duplicate eachTraversal from bridges module — use each() from the traversal module instead

Added#

• 35 new tests (414 total)
  • Bracket + fiber interruption tests verifying release runs and exit is Interrupted
  • yieldNow and fiberId test coverage
  • 8 additional optics compose overload tests (prism+lens, prism+prism, lens+optional, optional+lens, optional+optional, lens+traversal, traversal+lens, prism+optional)
  • Optional algebraic law tests (getOption-set, set-getOption)
  • Traversal algebraic law tests (identity, composition)

[0.1.0-alpha.13] - 2026-03-19#

Added#

• Optics module (src/optics/) — composable, law-abiding immutable data accessors
  • Lens — focus on a value that always exists (view, set, over, prop)
  • Prism — focus on a sum type variant (preview, review)
  • Optional — focus that may be absent (getOption, setOptional, modifyOptional, index)
  • Traversal — focus on many values (getAll, modifyTraversal, each)
  • Type-safe compose — 16 overloads enforcing composition rules (Lens+Lens=Lens, Lens+Prism=Optional, etc.)
  • Bridges — pre-built optics for Result (okPrism, errPrism), Option (somePrism), Validation (validPrism)
  • 44 law-based tests verifying get-set, set-get, set-set, preview-review, and review-preview laws

[0.1.0-alpha.12] - 2026-02-28#

Fixed#

• ifElse inverted arguments — onTrue was called when predicate was false and vice versa; swapped parameter order and ternary to match naming
• matchLiteral soundness gap — Split into exhaustive matchLiteral (requires all cases) and partial matchLiteralOr (with default fallback)
• Fiber interrupt doesn't cancel async — Interrupt now calls cleanup on in-flight async operations and force-resolves blocked promises
• zip fiber leak — When the second effect fails, the first fiber is now interrupted instead of being abandoned
• traverseResult unnecessary cast — Removed redundant as unknown as double-cast; TypeScript narrows correctly
• Generic guards missing type predicates — Added explicit : x is T annotations to isDefined, isNotNull, isNotNullish (TS 5.5 inference doesn't apply to generics)
• Interpreter null assertion — Replaced result! with null guard in Blocked handler's next thunk
• Documentation: race() array syntax — Fixed race([fast, slow]) to race(fast, slow) in testing strategies
• Documentation: timeout test — Fixed test to expect Success(null) instead of Failure on timeout
• Documentation: yield* pseudo-code — Replaced generator syntax with actual pipe/flatMap in fiber example
• Documentation: all() return type — Corrected type comment from tuple to union array
• Documentation: dead link — Fixed /concepts/01-branded-types-and-refinements/ to /concepts/02-branded-types/
• Examples: comma-expression patterns — Replaced (sideEffect, expr) with explicit block bodies in http-client and task-queue
• Examples: redundant as casts — Removed unnecessary as MessageError casts in forest-election story
• Documentation: task-queue key concepts — Updated from fork/join to allSequential/timeout/retry
• Documentation: unused imports — Removed unused fork/join from forest-election story

Added#

• 39 new tests (261 → 300 total) covering: ifElse, matchLiteral, matchLiteralOr, mapErr, isOk/isErr, toNullable, flatMapOption edge cases, accessEff, tapEff, repeatEff, interruptFiber, matchExit, liftA2Option both-None, Option Functor laws, Option Monad laws

[0.1.0-alpha.11] - 2026-02-28#

Added#

• tapEffect — Effectful success tap: observe a success value with an effect-returning side-effect, discard the result, return the original value. Errors from the side-effect propagate into the error union.
• tapError — Effectful error tap: observe an error with an effect-returning side-effect, discard the result, re-raise the original error.
• tapBoth — Effectful dual tap: observe both success and failure with independent effectful handlers. Each handler can have its own error and requirement types.

Changed#

• tapBoth handlers have independent type params — onSuccess and onFailure can use different error (E2/E3) and requirement (R2/R3) types, enabling different effect types per branch.

[0.1.0-alpha.10] - 2026-02-28#

Fixed#

• Type errors in examples (stories, task-queue, user-registration)
• isSet / isMap guards now return ReadonlySet / ReadonlyMap for stricter type safety
• and guard combinator returns intersection type (B & C) instead of requiring C extends B

Changed#

• Expanded guard tests (137+ assertions covering edge cases)
• Added tsconfig.test.json path mappings

[0.1.0-alpha.9] - 2026-02-07#

Added#

• Emptiness predicates — isEmpty / isNonEmpty for strings, arrays, Sets, Maps, and objects
• Uses FP naming convention (isNonEmpty mirrors the NonEmpty type from Haskell/Scala/PureScript)

[0.1.0-alpha.8] - 2026-02-07#

Added#

• Docs site — Astro Starlight documentation site with tutorials, concepts, stories, and examples
• Nullability guards — isDefined, isNotNull, isNotNullish for piping and filtering
• hasProperties guard — Multi-property object checking: hasProperties("id", "name", "email")(data)
• Recursion over loops concept article — Why pure functional code avoids loops and how to replace them with expressions

Changed#

• TS 5.5+ inferred type predicates — Removed redundant : x is T annotations from simple guards where TypeScript infers them automatically
• Stricter tsconfig — Added exactOptionalPropertyTypes and noPropertyAccessFromIndexSignature
• Replaced all forEach/imperative loops in docs and examples with map+join, reduce, and test.each
• Replaced switch statements with match() in story examples
• Replaced manual null/undefined checks with library guards (isDefined, isObject, hasProperties) in docs and examples

[0.1.0-alpha.7] - 2026-02-07#

Added#

• flatMap error/requirement widening — flatMap now automatically unions error and requirement types across composed effects, removing the need for manual type annotations
• matchOn / matchOnOr — Pattern matching on custom discriminant fields (not just _tag), useful for third-party types or domain events
• zip / zipWith / zip3 — Typed parallel effect composition returning tuples with automatic error union
• ensure — Predicate-based failure combinator for guarding success values in pipelines
• tapErr — Error observation side effect (symmetric with tapEff), error still propagates
• traverseResult / sequenceResult — Apply a fallible function to each element and collect results, short-circuiting on first error
• traverseOption / sequenceOption — Apply an Option-returning function to each element, short-circuiting on first None
• orElseResult / orElseOption — Recover from errors or None via a fallback function
• fromNullableResult — Convert nullable values to Result with a custom error
• validate2 / validate3 / validate4 — Ergonomic combinators for combining 2-4 validations with error accumulation
• bracket — Guaranteed resource cleanup pattern (acquire/use/release) where release always runs

Changed#

• flatMap signature changed from <A, B, E, R> to split generics <A, B, E2, R2> + <E, R> for automatic widening

[0.1.0-alpha.6] - 2026-02-07#

Added#

• Beaver's Big System story trilogy teaching Branded Types, Typestate, ADTs, and Tracked Arrays
• Forest Election story trilogy teaching Validation, Result, and Effects
• Concept documentation for typestate, effects, fibers, DI, and testing
• Pattern matching examples and O(n) array documentation

[0.1.0-alpha.5] - 2026-02-06#

Added#

• Tutorial guide chapters 1-10
• Concept deep-dive articles
• Side-by-side examples (http-client, workflow-engine, task-queue)

[0.1.0-alpha.4] - 2026-02-05#

Added#

• Multi-file architecture (prelude, effect, data modules)
• Validation type with error accumulation
• Entity helpers and type guards

[0.1.0-alpha.3] - 2026-02-04#

Added#

• Effect combinators (race, all, timeout, retry, repeat)
• Fiber-based concurrency with cancellation

[0.1.0-alpha.2] - 2026-02-03#

Added#

• Effect system with typed errors and dependency injection
• Fork/join concurrency model

[0.1.0-alpha.1] - 2026-02-02#

Added#

• Initial release with Result, Option, branded types, refinements, pattern matching, tracked arrays, units, and typestate