I have simple custom decorator:
export const User: () => ParameterDecorator = createParamDecorator(
(data: any, req): UserIdentity => {
const user = getUser(req);
return user;
},
);
And now, I need to validate if we have email in user object.
The problem is that I can't update my current decorator.
Could I extend my current decorator?
Create a new decorator based on the previous one or create a new decorator and combine it?
Yes, you can do "decorator composition" with Nest, but this might not be a perfect solution for your case, depending on what you intend to do when user has no email property.
As per the example from the documentation:
import { applyDecorators } from '@nestjs/common';
export function Auth(...roles: Role[]) {
return applyDecorators(
SetMetadata('roles', roles),
UseGuards(AuthGuard, RolesGuard),
ApiBearerAuth(),
ApiUnauthorizedResponse({ description: 'Unauthorized"' }),
);
}
In this example, Auth is a decorator that can be used to combine all the one passed in applyDecorators.
Thus, I'd recommend extending your decorator using a pipe.
As stated by the documentation:
Nest treats custom param decorators in the same fashion as the built-in ones (@Body(), @Param() and @Query()). This means that pipes are executed for the custom annotated parameters as well (in our examples, the user argument). Moreover, you can apply the pipe directly to the custom decorator:
@Get()
async findOne(@User(new ValidationPipe()) user: UserEntity) {
console.log(user);
}
In this example, User is a custom parameter decorator. And ValidationPipe is passed, but you can imagine passing any pipe.
