v2.5.0

2.5.0 - 2026-08-04

New Features

Redesign ReleasableResource as a pure description ADT with the UseResource interpreter (#705)

ReleasableResource[F[*], +A] is now a sealed, covariant, constraint-free data type describing acquisition and release. It follows effectie's own Fx pattern: one shared contract with per-effect-system instances, so the same code behaves identically for Try, Future, cats-effect 2/3 IO, and Monix Task.

• Constructors (no typeclass needed): ReleasableResource.pure / eval / make / makeCase / fromAutoCloseable (requires FxCtor[F]) / raiseError / unit
• Combinators: map, flatMap, evalMap, evalTap, flatTap, onFinalize, onFinalizeCase, attempt, handleErrorWith, surround, use_
• ReleasableResource.ExitCase (Completed / Errored / Canceled): release actions registered with makeCase / onFinalizeCase observe how the scope ended. Canceled only occurs for cancellable effect systems (cats-effect, Monix).
• Constraint-free MonadError[ReleasableResource[F, *], Throwable] in the companion object — no ResourceMaker required, with a stack-safe tailRecM (replaces the previous ResourceMaker-gated Applicative instance).

New UseResource[F] typeclass — the capability of running a ReleasableResource

Running .use(...) now requires an implicit effectie.resource.UseResource[F]:

• Try / Future: provided automatically (companion object instances; Future needs an implicit ExecutionContext)
• cats-effect 3: import effectie.instances.ce3.resource._ (IO) or import effectie.instances.ce3.f.resource._ (any F[_]: MonadCancelThrow)
• cats-effect 2: import effectie.instances.ce2.resource._ (IO) or import effectie.instances.ce2.f.resource._ (any F[_]: BracketThrow)
• Monix 3: import effectie.instances.monix3.resource._ (Task)
• Scala 3: use .given instead of ._ (e.g. import effectie.instances.ce3.resource.given), or import the instance by name (e.g. ioUseResource, taskUseResource) which works in both Scala 2 and Scala 3

The cats-effect and Monix instances interpret the description through a real cats.effect.Resource, so bracketing and cancellation safety are exactly cats-effect's. There is deliberately no generic fallback instance, so cancellable effect types can never silently lose cancellation safety.

cats-effect interop

• Ce3UseResource.toCatsEffectResource / Ce3UseResource.fromCatsEffectResource — two-way conversion with cats.effect.Resource (cats-effect 3)
• Ce2UseResource.toCatsEffectResource / Ce2UseResource.fromCatsEffectResource — the same for cats-effect 2 (note: CE2's allocated exposes no exit case, so a wrapped foreign finalizer cannot observe it)

Behavior Fixes

• Lazy acquisition: constructing a ReleasableResource no longer performs any effects for Try / Future (previously the resource was acquired eagerly at construction, leaking when never used). Acquisition now happens on each use, and a second use acquires a fresh resource instead of reusing a closed one.
• Release errors are no longer swallowed: previously Try discarded them silently and Future printed to stdout. Now, when use succeeded but release fails, the release error is raised; when both fail, the use error is raised with the release error attached via addSuppressed (cats-effect parity).
• Future resource leak fixed: a synchronous throw inside the use function now still releases the resource.
• ResourceMaker[F].eval for cats-effect now maps to Resource.eval semantics (previously it created an uncancelable no-op-release acquisition).

Deprecations

ResourceMaker and its instances (ResourceMaker.tryResourceMaker, ResourceMaker.futureResourceMaker, Ce2ResourceMaker.maker, Ce3ResourceMaker.maker), the old ReleasableResource companion constructors (usingResource, usingResourceFromTry, futureResource, makeTry, pureTry, makeFuture, pureFuture), and the Ce2Resource / Ce3Resource constructor objects are deprecated but keep working as thin shims over the new API. Each deprecation message contains the exact replacement and the UseResource import to add.

Breaking Changes

• ReleasableResource is now sealed; the public traits Ce2Resource and Ce3Resource are removed (their companion objects remain as deprecated constructors).
• .use(...) requires an implicit UseResource[F]: Try / Future users need no change; cats-effect / Monix users add one import (a descriptive implicitNotFound message shows exactly which).
• The Applicative[ReleasableResource[F, *]] instance requiring ResourceMaker[F] is replaced by the constraint-free MonadError instance.
• Try / Future resource semantics intentionally changed as listed under Behavior Fixes.

What's Changed

• Close #705: Redesign ReleasableResource as a pure description ADT with the UseResource interpreter by @kevin-lee in #706
• Fix IORuntime file-descriptor leak in effectie-cats-effect3 tests by @kevin-lee in #707
• Add missing tests for the UseResource interpreter and ReleasableResource ADT by @kevin-lee in #708
• Verify resources are actually closed across Try, Future and cats-effect by @kevin-lee in #709
• effectie v2.5.0 by @kevin-lee in #710

Full Changelog: v2.4.0...v2.5.0