Custom decorators for NestJS: from simple to complex

Introduction

NestJS is a rapidly gaining popularity framework built on ideas for IoC / DI, modular design and decorators. Thanks to the latter, Nest has a concise and expressive syntax, which improves the usability of development.

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, , . , , Nest.

http-. , , . Nest .

Guard — , CanActivate @UseGuard.

@Injectable()
export class RoleGuard implements CanActivate {
  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    const request = context.switchToHttp().getRequest();
    return getRole(request) === 'superuser'
  }
}

@Controller()
export class MyController {
  @Post('secure-path')
  @UseGuards(RoleGuard)
  async method() {
    return
  }
}

superuser — , .

Nest @SetMetadata. , — .

Reflector, reflect-metadata.

@Injectable()
export class RoleGuard implements CanActivate {
  constructor(private reflector: Reflector) {}
  canActivate(
    context: ExecutionContext,
  ): boolean | Promise<boolean> | Observable<boolean> {
    const role = this.reflector.get<string>('role', context.getHandler());
    const request = context.switchToHttp().getRequest();
    return getRole(request) === role
  }
}

@Controller()
export class MyController {
  @Post('secure-path')
  @SetMetadata('role', 'superuser')
  @UseGuards(RoleGuard)
  async test() {
    return
  }
}

.

- -. .

applyDecorators.

const Role = (role) => applyDecorators(UseGuards(RoleGuard), SetMetadata('role', role))

:

const Role = role => (proto, propName, descriptor) => {
  UseGuards(RoleGuard)(proto, propName, descriptor)
  SetMetadata('role', role)(proto, propName, descriptor)
}

@Controller()
export class MyController {
  @Post('secure-path')
  @Role('superuser')
  async test() {
    return
  }
}

, .

@Controller()
@UseGuards(RoleGuard)
export class MyController {
  @Post('secure-path')
  @Role('superuser')
  async test1() {
    return
  }

  @Post('almost-securest-path')
  @Role('superuser')
  async test2() {
    return
  }

  @Post('securest-path')
  @Role('superuser')
  async test3() {
    return
  }
}

, . , , -.

— — .

typescript , .

type ClassDecorator = <TFunction extends Function>(target: TFunction) => TFunction | void;
type MethodDecorator = <T>(target: Object, propertyKey: string | symbol, descriptor: TypedPropertyDescriptor<T>) => TypedPropertyDescriptor<T> | void;
type ParameterDecorator = (target: Object, propertyKey: string | symbol, parameterIndex: number) => void;

const Role = (role: string): MethodDecorator | ClassDecorator => (...args) => {
  if (typeof args[0] === 'function') {
    //  
    const ctor = args[0]
    //  
    const proto = ctor.prototype
    //  
    const methods = Object
      .getOwnPropertyNames(proto)
      .filter(prop => prop !== 'constructor')

    //    
    methods.forEach((propName) => {
      RoleMethodDecorator(
        proto,
        propName,
        Object.getOwnPropertyDescriptor(proto, propName),
        role,
      )
    })
  } else {
    const [proto, propName, descriptor] = args
    RoleMethodDecorator(proto, propName, descriptor, role)
  }
}

, : lukehorvat/decorator-utils, qiwi/decorator-utils.

.

import { constructDecorator, CLASS, METHOD } from '@qiwi/decorator-utils'

const Role = constructDecorator(
  ({ targetType, descriptor, proto, propName, args: [role] }) => {
    if (targetType === METHOD) {
      RoleMethodDecorator(proto, propName, descriptor, role)
    }

    if (targetType === CLASS) {
      const methods = Object.getOwnPropertyNames(proto)
      methods.forEach((propName) => {
        RoleMethodDecorator(
          proto,
          propName,
          Object.getOwnPropertyDescriptor(proto, propName),
          role,
        )
      })
    }
  },
)

:

@DecForClass, @DecForMethood, @DecForParam @Dec.

, , - , @Role.

.

, createParamDecorator .

/ ( ParamsTokenFactory RouterExecutionContext).

//  
  if (typeof args[2] === 'number') {
    const [proto, propName, paramIndex] = args
    createParamDecorator((_data: unknown, ctx: ExecutionContext) => {
      return getRole(ctx.switchToHttp().getRequest())
    })()(proto, propName, paramIndex)
  }

, , , .

, , . ?

. , , .

class SomeController {
   @RequestSize(1000)
   @RequestSize(5000)
   @Post('foo')
   method(@Body() body) {
   }
}

: . , , , .

class SomeController {
   @Port(9092)
   @Port(8080)
   @Post('foo')
   method(@Body() body) {
   }
}

.

class SomeController {
  @Post('securest-path')
  @Role('superuser')
  @Role('usert')
  @Role('otheruser')
  method(@Role() role) {

  }
}

, reflect-metadata :

import { ExecutionContext, createParamDecorator } from '@nestjs/common'
import { constructDecorator, METHOD, PARAM } from '@qiwi/decorator-utils'

@Injectable()
export class RoleGuard implements CanActivate {
  canActivate(context: ExecutionContext): boolean | Promise<boolean> {
    const roleMetadata = Reflect.getMetadata(
      'roleMetadata',
      context.getClass().prototype,
    )
    const request = context.switchToHttp().getRequest()
    const role = getRole(request)
    return roleMetadata.find(({ value }) => value === role)
  }
}

const RoleMethodDecorator = (proto, propName, decsriptor, role) => {
  UseGuards(RoleGuard)(proto, propName, decsriptor)
  const meta = Reflect.getMetadata('roleMetadata', proto) || []

  Reflect.defineMetadata(
    'roleMetadata',
    [
      ...meta, {
        repeatable: true,
        value: role,
      },
    ],
    proto,
  )
}

export const Role = constructDecorator(
  ({ targetType, descriptor, proto, propName, paramIndex, args: [role] }) => {
    if (targetType === METHOD) {
      RoleMethodDecorator(proto, propName, descriptor, role)
    }

    if (targetType === PARAM) {
      createParamDecorator((_data: unknown, ctx: ExecutionContext) =>
        getRole(ctx.switchToHttp().getRequest()),
      )()(proto, propName, paramIndex)
    }
  },
)

Nest , . , , , . , @Controller «»

JSON-RPC.

, , : , Nest.

import {
  ControllerOptions,
  Controller,
  Post,
  Req,
  Res,
  HttpCode,
  HttpStatus,
} from '@nestjs/common'

import { Request, Response } from 'express'
import { Extender } from '@qiwi/json-rpc-common'
import { JsonRpcMiddleware } from 'expressjs-json-rpc'

export const JsonRpcController = (
  prefixOrOptions?: string | ControllerOptions,
): ClassDecorator => {
  return <TFunction extends Function>(target: TFunction) => {
    const extend: Extender = (base) => {
      @Controller(prefixOrOptions as any)
      @JsonRpcMiddleware()
      class Extended extends base {
        @Post('/')
        @HttpCode(HttpStatus.OK)
        rpc(@Req() req: Request, @Res() res: Response): any {
          return this.middleware(req, res)
        }
      }

      return Extended
    }

    return extend(target as any)
  }
}

@Req() rpc-method , , @JsonRpcMethod.

, :

import {
  JsonRpcController,
  JsonRpcMethod,
  IJsonRpcId,
  IJsonRpcParams,
} from 'nestjs-json-rpc'

@JsonRpcController('/jsonrpc/endpoint')
export class SomeJsonRpcController {
  @JsonRpcMethod('some-method')
  doSomething(
    @JsonRpcId() id: IJsonRpcId,
    @JsonRpcParams() params: IJsonRpcParams,
  ) {
    const { foo } = params

    if (foo === 'bar') {
      return new JsonRpcError(-100, '"foo" param should not be equal "bar"')
    }

    return 'ok'
  }
  @JsonRpcMethod('other-method')
  doElse(@JsonRpcId() id: IJsonRpcId) {
    return 'ok'
  }
}

Nest . . , , . , , .

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