ExternalContextCreator

Kind: Class

Source: packages/core/helpers/external-context-creator.ts

Part of: Core

ExternalContextCreator builds executable handlers for framework-managed entry points outside the standard HTTP request pipeline. It resolves parameter metadata, guards, pipes, interceptors, and request-scoped providers, then wraps the target method in an external execution context.

Methods

Where it refuses work

• ExternalContextCreator stops the work with ForbiddenException when !canActivate.
• ExternalContextCreator stops the work with an early return when cacheMetadata.
• ExternalContextCreator stops the work with an early return when !moduleCtor.
• ExternalContextCreator stops the work with an early return when moduleRef.hasProvider(moduleCtor).
• ExternalContextCreator stops the work with an early return when isObservable(resultOrDeferred).

Diagram

mermaid
graph LR
  A[DI Container] --> B[ExternalContextCreator.fromContainer]
  B --> C[ExternalContextCreator]
  D[Target Instance and Method] --> E[create]
  C --> E
  E --> F[Read Handler Metadata]
  F --> G[Resolve Parameters]
  G --> H[Run Guards]
  H --> I[Apply Pipes]
  I --> J[Execute Interceptors]
  J --> K[Invoke Target Method]
  K --> L[Transform Result]

Usage

ts
import { ExternalContextCreator } from '@nestjs/core/helpers/external-context-creator';

// `container` is the application's NestContainer instance.
const contextCreator = ExternalContextCreator.fromContainer(container);

class ReportService {
  async rebuild(): Promise<{ status: string }> {
    return { status: 'completed' };
  }
}

const reportService = new ReportService();

const handler = contextCreator.create(
  reportService,
  reportService.rebuild,
  'rebuild',
);

// Executes the method through Nest's external context pipeline.
const result = await handler();

console.log(result.status); // "completed"

AI Coding Instructions

• Create instances through ExternalContextCreator.fromContainer() so guards, pipes, interceptors, and module references use the application container.
• Pass the target instance, callback, and method name consistently to create(); the method name is used to retrieve handler metadata.
• Preserve the execution order: resolve parameters first, then guards, pipes, interceptors, and finally the target callback.
• Use registerRequestProvider() when creating request-scoped execution contexts; otherwise scoped dependencies may not resolve correctly.
• Avoid invoking decorated handlers directly when framework behavior is required; use the created proxy to retain metadata-driven processing.