Capabilities

Declaration and Access

import { Context } from "vibelang/context"
 
abstract class Service extends Context {
  abstract operation(input: Input): Result<Output, ServiceError>
}
 
function run(): Result<Output, ServiceError> {
  const service = Service.context()
  return service.operation(input)
}

The abstract class is both the service contract and nominal capability identity. Service.context() returns its instance and adds Service to the enclosing function's inferred requirement channel.

Multiple Requirements

function run() {
  const db = Database.context()
  const clock = Clock.context()
  const log = Logger.context()
}

The requirement set is Database | Clock | Logger; duplicate nominal identities collapse.

Layer Type

Layer<Provides, InitError, Requires>

Constructors

Layer.succeed(Service, implementation)
Layer.merge(left, right, ...rest)
Layer.provide(layer, callback)

These names are API direction, not a stable published surface.

Composition Rules

• merge unions provided capabilities and acquisition Errors.
• construction requirements propagate until another Layer satisfies them.
• provide removes satisfied requirements from the callback's requirement set.
• acquisition Result errors enter the provided callback's Result contract.
• a missing capability is a compile error when the closure is statically known.

Provider composition is a library API from vibelang/provider; there is no special provider statement syntax.

Platform Services

Planned standard capabilities include FileSystem, HttpClient, Clock, Random, Environment, and Console. Targets provide live implementations; tests supply deterministic ones.

Open Lifecycle Semantics

Scoped acquisition/disposal, sharing, override precedence, cycle diagnostics, asynchronous acquisition, and finalizer failure policy remain to be specified.