Conditionals

• Conditional
• ConditionContext

Both types are exported from the main package:

import type { Conditional, ConditionContext } from '@caffeine-projects/dicaf'

---

Conditional

type Conditional = (ctx: ConditionContext) => boolean | Promise<boolean>

A predicate evaluated once during init(). When it returns false, the binding is skipped — it is not registered in the container for that run.

Used by:

• binder.conditional() — fluent API
• @ConditionalOn — decorator API

// synchronous
const hasRedis: Conditional = ctx => ctx.container.has(RedisClient)

// async
const featureEnabled: Conditional = async ctx => {
  const flags = ctx.container.get(FeatureFlags)
  return flags.isEnabled('new-cache')
}

Multiple predicates passed to .conditional() are ANDed — all must return true for the binding to be registered.

---

ConditionContext

interface ConditionContext {
  readonly container: {
    has(key: Key): boolean
  }
  readonly key: Key
  readonly binding: BindingDecoratorConfig
}

Passed to every Conditional predicate at evaluation time.

Property	Description
container.has	Checks whether a binding is registered for the given key.
key	The key of the binding being tested.
binding	The full decorator config for the binding: scope, name, labels, tags, and other metadata set by decorators.

// guard on another binding being present
di.bind(RedisCacheService)
  .toSelf()
  .conditional(ctx => ctx.container.has(RedisClient))

// inspect the binding's own key
di.bind(MetricsReporter)
  .toSelf()
  .conditional(ctx => ctx.key !== Symbol.for('noop'))