replace all == null (google style) to isNil for clarity

server/src/auth/auth.service.ts

@@ -1,7 +1,8 @@
 import { BadRequestException, Injectable, Logger } from '@nestjs/common';
-import { UserService } from '../user/user.service';
+import { isNil } from 'src/common/utils';
 import User from '../entities/user.entity';
 import { ProviderInfo } from '../types/user';
+import { UserService } from '../user/user.service';
 
 @Injectable()
 export class AuthService {
@@ -23,7 +24,7 @@ export class AuthService {
     const user =
       await this.userService.findUserByProviderInfo(mockProviderInfo);
 
-    if (user == null) {
+    if (isNil(user)) {
       this.logger.debug('잘못된 로그인 요청입니다!');
       throw new BadRequestException('잘못된 로그인 요청입니다!');
     }

server/src/common/middleware/session.ts

@@ -1,10 +1,11 @@
 import RedisStore from 'connect-redis';
 import session from 'express-session';
 import Redis from 'ioredis';
+import { isNil } from '../utils';
 
 export const makeRedisStore = () => {
   const REDIS_HOST = process.env.REDIS_HOSTNAME;
-  if (REDIS_HOST == null) throw new Error('REDIS_HOST is not defined');
+  if (isNil(REDIS_HOST)) throw new Error('REDIS_HOST is not defined');
 
   const redis = new Redis({
     host: REDIS_HOST,

server/src/problem/problem.service.ts

@@ -1,7 +1,8 @@
 import { Injectable } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
-import Problem from '../entities/problem.entity';
+import { isNil } from 'src/common/utils';
 import { ILike, In, Raw, Repository } from 'typeorm';
+import Problem from '../entities/problem.entity';
 import { RandomProblemDto } from './dto/random.problem.dto';
 import { SearchProblemDto } from './dto/search.problem.dto';
 
@@ -57,7 +58,7 @@ export class ProblemService {
     const problemEntities: Problem[] = [];
     for (const bojProblemId of bojProblemIds) {
       const problem = await this.getProblemByBojProblemId(bojProblemId);
-      if (problem == null) {
+      if (isNil(problem)) {
         throw new Error(`bojProblemId ${bojProblemId} not found`);
       }
       problemEntities.push(problem);

server/src/room/room.service.ts

@@ -8,6 +8,7 @@ import {
 } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import * as crypto from 'crypto';
+import { isNil } from 'src/common/utils';
 import { SubmissionService } from 'src/submission/submission.service';
 import { Repository } from 'typeorm';
 import Room from '../entities/room.entity';
@@ -43,7 +44,7 @@ export class RoomService {
       throw new BadRequestException('이미 참가한 방이 있습니다.');
     }
 
-    if (user.username == null)
+    if (isNil(user.username))
       throw new BadRequestException('username이 없습니다.');
     const code = await this.createRoomCode(user.username);
 
@@ -81,7 +82,7 @@ export class RoomService {
       throw new BadRequestException('존재하지 않는 방입니다.');
     }
     const room = roomUsers[0].room;
-    if (room == null) {
+    if (isNil(room)) {
       throw new InternalServerErrorException('방을 찾을 수 없습니다.');
     }
     this.logger.debug(`user ${user.username} joining room ${room.code}...`);
@@ -96,7 +97,7 @@ export class RoomService {
 
   async exitRoom(user: User) {
     const joinedRooms = await user.joinedRooms;
-    if (joinedRooms == null) {
+    if (isNil(joinedRooms) || joinedRooms.length === 0) {
       throw new InternalServerErrorException(
         '참가 중인 방을 찾을 수 없습니다.',
       );
@@ -110,14 +111,14 @@ export class RoomService {
     await this.roomUserRepository.remove(roomUser);
 
     const room = roomUser.room;
-    if (room == null) {
+    if (isNil(room)) {
       throw new InternalServerErrorException('방을 찾을 수 없습니다.');
     }
 
     await this.socketService.notifyExit(user.username, room);
 
     const numberOfJoinedUsers = (await room.joinedUsers)?.length;
-    if (numberOfJoinedUsers == null || numberOfJoinedUsers === 0) {
+    if (isNil(numberOfJoinedUsers) || numberOfJoinedUsers === 0) {
       await this.destroyRoom(room);
     }
   }

server/src/socket/socket.gateway.ts

@@ -1,3 +1,5 @@
+import { Logger, UseFilters } from '@nestjs/common';
+import { InjectRepository } from '@nestjs/typeorm';
 import {
   ConnectedSocket,
   MessageBody,
@@ -9,17 +11,16 @@ import {
   WsException,
 } from '@nestjs/websockets';
 import { Server, Socket } from 'socket.io';
+import { isNil } from 'src/common/utils';
+import { Repository } from 'typeorm';
+import Room from '../entities/room.entity';
+import User from '../entities/user.entity';
+import { ProblemService } from '../problem/problem.service';
 import { ChatEvent, MessageInterface } from '../types/message-interface';
-import { Logger, UseFilters } from '@nestjs/common';
+import { RoomInfoType } from '../types/room-info';
 import { UserService } from '../user/user.service';
-import User from '../entities/user.entity';
 import { WebsocketExceptionsFilter } from './socket.filter';
-import Room from '../entities/room.entity';
-import { RoomInfoType } from '../types/room-info';
 import { SocketService } from './socket.service';
-import { ProblemService } from '../problem/problem.service';
-import { InjectRepository } from '@nestjs/typeorm';
-import { Repository } from 'typeorm';
 
 @WebSocketGateway({
   cors: {
@@ -91,7 +92,7 @@ export class SocketGateway implements OnGatewayConnection, OnGatewayDisconnect {
       provider,
       providerId,
     });
-    if (user == null) throw new WsException('user is null');
+    if (isNil(user)) throw new WsException('user is null');
 
     await this.socketService.gameStart(user, roomInfo);
   }
@@ -109,7 +110,7 @@ export class SocketGateway implements OnGatewayConnection, OnGatewayDisconnect {
       message,
     );
 
-    if (this.server == null) throw new WsException('server is null');
+    if (isNil(this.server)) throw new WsException('server is null');
 
     this.logger.debug(`--> ws: chat-message ${message.body}`);
     this.server.to(room.code).emit('chat-message', message);
@@ -143,9 +144,9 @@ export class SocketGateway implements OnGatewayConnection, OnGatewayDisconnect {
 
   getUser(client: Socket): User {
     const request = client.request as any;
-    if (request == null) throw new WsException('request is null');
+    if (isNil(request)) throw new WsException('request is null');
     const user = request.user;
-    if (user == null) throw new WsException('user is null');
+    if (isNil(user)) throw new WsException('user is null');
     return user as User;
   }
 }

server/src/socket/socket.service.ts

@@ -1,16 +1,17 @@
 import { Injectable, Logger } from '@nestjs/common';
-import Room from '../entities/room.entity';
+import { InjectRepository } from '@nestjs/typeorm';
 import { WsException } from '@nestjs/websockets';
-import { RoomInfoType } from '../types/room-info';
 import { Server } from 'socket.io';
+import { isNil } from 'src/common/utils';
+import { Repository } from 'typeorm';
+import * as util from 'util';
 import { Status } from '../const/boj-results';
-import { ChatEvent, MessageInterface } from '../types/message-interface';
-import { ProblemType } from '../types/problem-type';
+import Room from '../entities/room.entity';
 import User from '../entities/user.entity';
-import * as util from 'util';
-import { Repository } from 'typeorm';
-import { InjectRepository } from '@nestjs/typeorm';
 import { ProblemService } from '../problem/problem.service';
+import { ChatEvent, MessageInterface } from '../types/message-interface';
+import { ProblemType } from '../types/problem-type';
+import { RoomInfoType } from '../types/room-info';
 import { UserService } from '../user/user.service';
 
 @Injectable()
@@ -54,10 +55,10 @@ export class SocketService {
     const host = await room.host;
     const problems = await room.problems;
 
-    if (roomUsers == null) throw new WsException('roomUsers is null');
-    if (host == null) throw new WsException('host is null');
-    if (problems == null || problems.length === 0)
-      throw new WsException('problems is null');
+    if (isNil(roomUsers)) throw new WsException('roomUsers is null');
+    if (isNil(host)) throw new WsException('host is null');
+    if (isNil(problems) || problems.length === 0)
+      throw new WsException('problems do not exist');
 
     const problemTypes: ProblemType[] = problems.map((problem) => {
       return {
@@ -144,7 +145,7 @@ export class SocketService {
     // check if the user is the host of the room
 
     const host = await roomUser.room.host;
-    if (host == null) throw new WsException('host is null');
+    if (isNil(host)) throw new WsException('host is null');
     if (host.id !== user.id) {
       throw new WsException('방장이 아닙니다.');
     }
@@ -154,8 +155,8 @@ export class SocketService {
     // update room entity properties: problems, isStarted, endAt
 
     const { problems, duration } = startingRoomInfo;
-    if (problems == null) throw new WsException('problems is null');
-    if (duration == null) throw new WsException('duration is null');
+    if (isNil(problems)) throw new WsException('problems is null');
+    if (isNil(duration)) throw new WsException('duration is null');
     const bojProblemIds = problems.map((problem) => problem.bojProblemId);
     const problemEntities =
       await this.problemService.getProblemsByBojProblemIds(bojProblemIds);

server/src/submission/submission.service.ts

@@ -7,6 +7,7 @@ import {
 } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import * as cheerio from 'cheerio';
+import { isNil } from 'src/common/utils';
 import Room from 'src/entities/room.entity';
 import { RankingResponseDto } from 'src/room-user/dto/ranking-response.dto';
 import { EntityManager, Repository } from 'typeorm';
@@ -52,7 +53,7 @@ export class SubmissionService {
     if (!user) throw new BadRequestException('존재하지 않는 유저입니다.');
 
     const roomUsers = await user.joinedRooms;
-    if (roomUsers == null || roomUsers.length === 0)
+    if (isNil(roomUsers) || roomUsers.length === 0)
       throw new BadRequestException('참여중인 방이 없습니다.');
 
     const roomUser = roomUsers[0];
@@ -64,17 +65,17 @@ export class SubmissionService {
     }
 
     const endAt = room.endAt;
-    if (endAt == null || endAt < new Date()) {
+    if (isNil(endAt) || endAt < new Date()) {
       throw new BadRequestException('이미 종료된 방입니다.');
     }
 
     const problems = await room.problems;
-    if (problems == null || problems.length === 0)
+    if (isNil(problems) || problems.length === 0)
       throw new BadRequestException('문제가 없는 방입니다.');
 
     const problem =
       await this.problemService.getProblemByBojProblemId(bojProblemId);
-    if (problem == null)
+    if (isNil(problem))
       throw new BadRequestException('존재하지 않는 문제입니다.');
 
     if (
@@ -83,7 +84,7 @@ export class SubmissionService {
       throw new BadRequestException('참여중인 방에 없는 문제입니다.');
     }
 
-    if (user.username == null)
+    if (isNil(user.username))
       throw new BadRequestException('username이 없습니다.');
 
     await this.socketService.submitCode(

server/src/user/user.service.ts

@@ -4,9 +4,10 @@ import {
   InternalServerErrorException,
 } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
-import { ProviderInfo } from '../types/user';
+import { isNil } from 'src/common/utils';
 import { Repository } from 'typeorm';
 import User from '../entities/user.entity';
+import { ProviderInfo } from '../types/user';
 import { CreateUserDto } from './dto/create.user.dto';
 
 @Injectable()
@@ -48,15 +49,15 @@ export class UserService {
 
   async findJoinedRooms(user: User) {
     const joinedRooms = await user.joinedRooms;
-    if (joinedRooms == null) {
+    if (isNil(joinedRooms)) {
       throw new BadRequestException('joinedRooms is null');
     }
     return joinedRooms;
   }
 
   async getSingleJoinedRoom(user: User) {
     const joinedRooms = await user.joinedRooms;
-    if (joinedRooms == null) {
+    if (isNil(joinedRooms)) {
       throw new InternalServerErrorException('joinedRooms is null');
     }
     if (joinedRooms.length !== 1) {