Documentation/USERID_MISMATCH_DEBUG.md

UserId Mismatch Debug Analysis

Problem Description

• User ID 25 enrolls → DB shows userId 11
• User ID 25 enrolls again → DB shows userId 12 (incremented by 1)
• User ID 25 enrolls again → DB shows userId 13 (incremented by 1)

Pattern: First enrollment gets a random ID, subsequent enrollments increment by 1

Root Cause Analysis

Hypothesis 1: JWT Payload Contains Wrong UserId ❌

• Auth service creates payload: { sub: user.userId, ... }
• JWT Strategy validates: userId: payload.sub
• JWT payload is correct ✅

Hypothesis 2: Controller Extracts Wrong UserId ✅ LIKELY

File: src/modules/enrollments/controllers/enrollments.controller.ts

@Post('register')
@Roles(RoleName.STUDENT)
async enrollCourse(
  @Request() req,
  @Body() enrollCourseDto: EnrollCourseDto,
): Promise<EnrollmentResponseDto> {
  return this.enrollmentsService.enrollStudent(req.user.userId, enrollCourseDto);
  //                                             ^^^^^^ THIS IS WRONG
}

The Real Issue: User Entity Property Name

The problem is likely that req.user object has a different property name than userId.

Common issues:

1. req.user.id instead of req.user.userId
2. req.user.sub from JWT payload instead of req.user.userId
3. req.user is the User entity with database column user_id but property userId

Check: What Properties Does req.user Have?

Looking at JWT strategy's validate() method (line 43):

return user;  // Returns full User entity object

The User entity has:

@PrimaryGeneratedColumn({ name: 'user_id' })
userId: number;  // TypeORM property name

So req.user.userId should work... UNLESS

The Real Problem: Multiple Calls Creating Different Users! 🔴

Pattern observed:

• 1st enrollment: userId becomes 11
• 2nd enrollment: userId becomes 12
• 3rd enrollment: userId becomes 13

This looks like req.user is not the user entity, but something else is being auto-incremented.

Possible explanations:

1. req.user.userId is undefined → defaults to undefined or null
2. Auto-increment is being triggered for a related table
3. Session table userId is being used instead (which is auto-increment)

Most Likely: req.user.id vs req.user.userId

Passport typically returns req.user with the returned object from validate().

The validate() returns the User entity, but Passport might transform it.

Check the exact property name that JWT strategy is returning.

Solution

Add debugging to controller to check what req.user contains:

@Post('register')
@Roles(RoleName.STUDENT)
async enrollCourse(
  @Request() req,
  @Body() enrollCourseDto: EnrollCourseDto,
): Promise<EnrollmentResponseDto> {
  console.log('req.user:', req.user);  // Debug
  console.log('req.user properties:', Object.keys(req.user));  // Show all keys
  console.log('req.user.userId:', req.user.userId);  // Check this value
  console.log('req.user.id:', req.user.id);  // Check this too
  
  return this.enrollmentsService.enrollStudent(req.user.userId, enrollCourseDto);
}

Likely Fixes

Fix 1: Use req.user.id instead of req.user.userId

// Change this:
return this.enrollmentsService.enrollStudent(req.user.userId, enrollCourseDto);

// To this:
return this.enrollmentsService.enrollStudent(req.user.id, enrollCourseDto);

Fix 2: Check if userId is null and handle

const userId = req.user.userId || req.user.id;
if (!userId) {
  throw new BadRequestException('User ID not found in token');
}
return this.enrollmentsService.enrollStudent(userId, enrollCourseDto);

Fix 3: Check JWT Strategy's validate method

Make sure it returns the correct user object with userId property.

Files to Check

1. src/modules/auth/strategies/jwt.strategy.ts - Line 43 (return user)
2. src/modules/enrollments/controllers/enrollments.controller.ts - Line 63 (req.user.userId)
3. src/modules/auth/entities/user.entity.ts - Verify userId property

Next Steps

1. Add console.log statements to debug
2. Check what req.user actually contains
3. Verify the property name matches
4. Fix in all enrollment controller methods
5. Test enrollment again