Javascript – Nest can't resolve dependencies of the JwtAuthGuard

I have a NestJS application with a JwtAuthGuard that I’m trying to use to protect an endpoint. The JwtAuthGuard is responsible for authenticating and authorizing requests based on JWT tokens.

import { Injectable, CanActivate, ExecutionContext } from '@nestjs/common';
import { AuthService } from 'src/auth/auth.service';

@Injectable()
export class JwtAuthGuard implements CanActivate {
  constructor(private readonly authService: AuthService) {}

  canActivate(context: ExecutionContext): boolean {
    const request = context.switchToHttp().getRequest();
    return true;
  }
}

I tried to use it on this endpoint

  @Get('/user-data')
  @UseGuards(JwtAuthGuard)
  userData(@Req() req: Request) {
    const jwt = req.cookies['jwt'];
    return { jwt };
  }

but it throws this error

ERROR [ExceptionHandler] Nest can't resolve dependencies of the JwtAuthGuard (?). Please make sure that the argument dependency at index [0] is available in the AuthModule context.

Potential solutions:
- Is AuthModule a valid NestJS module?
- If dependency is a provider, is it part of the current AuthModule?
- If dependency is exported from a separate @Module, is that module imported within AuthModule?
  @Module({
    imports: [ /* the Module containing dependency */ ]
  })

This error suggests that there’s an issue with the dependency injection in the JwtAuthGuard constructor. Specifically, it’s unable to resolve the AuthService dependency.
even though I exported the AuthService
and refreshed everything

Auth Module:

import { Module } from '@nestjs/common';
import { AuthService } from './auth.service';
import { PrismaModule } from 'src/prisma/prisma.module';
import { AuthController } from './auth.controller';
import { GoogleStrategy } from './google.strategy';
import { PassportModule } from '@nestjs/passport';
import { JwtService } from '@nestjs/jwt';

@Module({
  controllers: [AuthController],
  providers: [AuthService, GoogleStrategy, JwtService],
  imports: [
    PrismaModule,
    PassportModule.register({ defaultStrategy: 'google' }),
  ],
  exports: [AuthService],
})
export class AuthModule {}

App Module:

import { Module, ValidationPipe } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';
import { AuthModule } from './auth/auth.module';
import { APP_PIPE } from '@nestjs/core';
import { JwtModule, JwtService } from '@nestjs/jwt';
import { AuthService } from './auth/auth.service';
import { PrismaService } from './prisma/prisma.service';

@Module({
  imports: [
    ConfigModule.forRoot(),
    AuthModule,
    JwtModule.register({
      secret: process.env.TOKEN,
      signOptions: { expiresIn: '30d' },
    }),
  ],
  providers: [
    AuthService,
    PrismaService,
    JwtService,
    {
      provide: APP_PIPE,
      useClass: ValidationPipe,
    },
  ],
})
export class AppModule {}

What is the problem

the problem is here

constructor(private readonly authService: AuthService) {}

if I remove this line it will work!

The problem seems to revolve around the AuthService not being injected correctly into the JwtAuthGuard. If I remove the constructor line constructor(private readonly authService: AuthService) {}, the error goes away, but this is not a solution to the problem.

I hope this additional information helps provide a clearer picture of the issue I’m facing with my NestJS application. If you have any suggestions or solutions, please feel free to share.