Context

The Context namespace contains tag constructors and immutable service-map operations.

import { Context } from '@fuiste/dependencies'

Context.Tag

Creates a stable typed service identifier.

const Logger = Context.Tag<{ log: (message: string) => void }>('app/logger')

Tags are cached by key, so repeated calls with the same key return the same runtime tag.

Constructors

const empty = Context.empty()
const single = Context.of(Logger, { log: console.log })

empty creates a context with no services. of creates a context with one service.

Updates

const next = Context.add(single, Clock, { now: () => new Date() })
const merged = Context.merge(left, right)
const replaced = Context.override(left, right)

add and merge reject duplicate tags. override lets the right context win for duplicate tags.

Lookup

Context.has(context, Logger)
Context.get(context, Logger)
Context.unsafeGet(context, Logger)

get is the normal typed lookup. unsafeGet throws MissingServiceLookupError if the tag is absent.

Runtime Checks

Context.isTag(value)
Context.isContext(value)

These are useful at dynamic boundaries, such as adapters or test helpers.