Pipeline Internals — Series 2

Preview — 3 of 10 questions

Given this, what is true of a guard that returns false?

javascript

// simplified GuardsConsumer
const canActivate = await guard.canActivate(context);
if (!canActivate) throw new ForbiddenException();

AThe request is silently dropped without a response, since no exception is constructed

BThe 403 is produced by the HTTP adapter, so exception filters cannot intercept it

CThe consumer throws a real ForbiddenException on your behalf, so the failure travels the normal exception path and a filter matching HttpException (or ForbiddenException) can reshape the response

DThe framework returns 403 directly from the guard's stack frame, bypassing the interceptor chain entirely

Which filter handles the exception?

javascript

@Catch()
export class AllExceptionsFilter implements ExceptionFilter {
  catch(exception: unknown, host: ArgumentsHost) { /* ... */ }
}

@UseFilters(AllExceptionsFilter, HttpExceptionFilter)
@Get() findAll() { throw new BadRequestException(); }

AAllExceptionsFilter — @Catch() with no arguments matches every exception type, and within one binding the filters are tried in declaration order, so the catch-all shadows anything listed after it

BHttpExceptionFilter, because a more specific @Catch() always wins over a catch-all

CBoth, with the more specific one running second to refine the response

DNeither; two filters on the same binding cancel each other out

What does the option change?

javascript

export const Tenant = createParamDecorator((_: unknown, ctx: ExecutionContext) =>
  ctx.switchToHttp().getRequest().headers['x-tenant'],
);

@Get() findAll(@Tenant() tenant: TenantDto) {}
// global: new ValidationPipe({ validateCustomDecorators: true })

AIt allows custom decorators to declare their own pipes, which is otherwise forbidden

BIt validates the decorator's data argument rather than its returned value

CIt disables validation for built-in decorators so only custom ones are checked

DValues produced by createParamDecorator carry the metadata type 'custom', which the global ValidationPipe skips by default; enabling the option makes it validate those arguments too

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