Scope Inputs

Scope inputs are values supplied by the code that opens a scope: an HTTP request, authenticated user, tenant, job payload, or trace context. InferDI carries those requirements through the graph and prevents you from resolving a service before its inputs exist.

Declare the Inputs

declareScopeInputs() adds keys to the type-level graph. It does not create runtime registrations or values.

interface RequestContext {
  requestId: string
}

interface AuthContext {
  userId: string
}

class PublicService {
  constructor(readonly request: RequestContext) {}
}

class AccountService {
  constructor(
    readonly request: RequestContext,
    readonly auth: AuthContext
  ) {}
}

const root = new Container()
  .declareScopeInputs<{
    request: RequestContext
    auth: AuthContext
  }>()
  .registerClass('publicService', PublicService, ['request'], 'scoped')
  .registerClass(
    'accountService',
    AccountService,
    ['request', 'auth'],
    'scoped'
  )

Scope inputs have scoped lifetime. A singleton cannot depend on one, so the compiler rejects an omitted or explicit singleton lifetime for both services above.

Open Typed Profiles

createScope(inputs) accepts any subset of missing inputs. Each returned container records which requirements are ready.

const publicScope = root.createScope({request})
publicScope.get('publicService')

// @ts-expect-error: auth has not been provided
publicScope.get('accountService')

const authenticatedScope = publicScope.createScope({auth})
authenticatedScope.get('accountService')

Use functions to name the profiles used by your application. Their return types preserve the exact ready-key set without handwritten container annotations.

const openPublicScope = (request: RequestContext) =>
  root.createScope({request})

const openAuthenticatedScope = (
  request: RequestContext,
  auth: AuthContext
) => root.createScope({request, auth})

type PublicScope = ReturnType<typeof openPublicScope>
type AuthenticatedScope = ReturnType<typeof openAuthenticatedScope>

Open the profile at the request, message, or job boundary. Keep the root graph independent from framework objects.

Requirements Follow the Graph

InferDI propagates input requirements through classes, lazy companions, deps-aware sync factories, and declarative async factories.

const app = root
  .registerFactory(
    'requestId',
    (c) => c.get('request').requestId,
    ['request'],
    'scoped'
  )
  .registerAsyncFactory(
    'session',
    async (auth: AuthContext) => loadSession(auth.userId),
    ['auth'],
    'scoped'
  )

The dependency tuple in the deps-aware registerFactory overload declares type-level edges and limits the callback to a resolver for those keys. InferDI still calls the callback with that resolver. registerAsyncFactory has a different contract: it resolves the tuple and passes positional values to the callback.

The distinction also changes argument order:

registerFactory(key, factory, deps, lifetime)
registerAsyncFactory(key, factory, deps, lifetime)

Nested Scope Ownership

A child inherits input values and creates its own scoped instances. Input values remain application-owned and are not disposed by the container.

await using publicScope = openPublicScope(request)
await using authenticatedScope = publicScope.createScope({auth})

await authenticatedScope.getAsync('session')

JavaScript disposes these declarations in reverse order, so the refined child closes before its parent. root.dispose() does not close either scope.

Reusable Type Contracts

ScopeInputMap describes inputs in a named Module. WithRequirements attaches input requirements to a module output.

import {
  type ScopeInputMap,
  type Spec,
  type WithRequirements
} from '@inferdi/inferdi'

type RequestInputs = ScopeInputMap<{
  request: RequestContext
  auth: AuthContext
}>

type RequestServices = {
  accountService: WithRequirements<
    Spec<AccountService, 'scoped'>,
    'request' | 'auth'
  >
}

Generic helpers must also preserve readiness:

function resolveSync<
  T extends DependenciesMap,
  K extends Container.SyncReadyKeys<Container<T>>
>(container: Container<T>, key: K) {
  return container.get(key)
}

function resolveAny<
  T extends DependenciesMap,
  K extends Container.ReadyKeys<Container<T>>
>(container: Container<T>, key: K) {
  return container.getAsync(key)
}

Input Contract

• Declarations require finite, required string or symbol keys. Optional keys, numeric keys, __proto__, broad index signatures, and unions with different key sets are rejected.
• A required property with value undefined counts as provided. InferDI tracks property presence, not truthiness.
• createScope(inputs) takes a shallow snapshot of enumerable own string and symbol properties. Getters and Proxy traps run during that copy, so pass a passive data record.
• The input schema exists only in TypeScript. JavaScript, any, or a cast can add unknown keys or shadow a registration in the child cache.
• {fast: true} supports input refinement but keeps its fixed-graph rule: finish registration before the first .get() or .createScope().

See Scopes and Disposal for ownership rules and Async Dependencies for async services that depend on scope inputs.