HH/ADMIN_FIXES_SUMMARY.md

Admin Fixes Summary - January 12, 2026

Overview

Fixed multiple Django admin errors related to User model and SourceUser admin in Django 6.0.

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Issues Fixed

Issue 1: User Admin TypeError

Error: TypeError: object of type 'NoneType' has no len() Location: /admin/accounts/user/{id}/change/

Root Cause

• User model had username = models.CharField(max_length=150, blank=True, null=True, unique=False)
• When users had username=None in database, Django's built-in UserChangeForm tried to call len(value) on None
• Django's built-in forms assume username is always a string, never None

Solution Applied

1. Created Data Migration (apps/accounts/migrations/0003_fix_null_username.py)

   • Migrated all existing users with username=None to use their email as username
   • Ensures data integrity

2. Updated User Model (apps/accounts/models.py)

   # Before:
   username = models.CharField(max_length=150, blank=True, null=True, unique=False)
   
   # After:
   username = models.CharField(max_length=150, blank=True, default='', unique=False)
   

   • Changed from null=True to default=''
   • Prevents future None values

3. Updated User Admin (apps/accounts/admin.py)

   • Moved username field to Personal Info section
   • Made username read-only for existing users
   • Removed from add form (since we use email for authentication)
   • Primary identifier is email (USERNAME_FIELD = 'email')

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Issue 2: SourceUser Admin TypeError

Error: TypeError: args or kwargs must be provided. Location: /admin/px_sources/sourceuser/

Root Cause

• Django 6.0 changed format_html() behavior
• Now requires format strings with placeholders (e.g., '<span>{}</span>')
• Cannot accept plain HTML strings
• is_active_badge methods were using format_html() with plain HTML strings

Solution Applied

Updated SourceUser Admin (apps/px_sources/admin.py)

# Before:
from django.utils.html import format_html

def is_active_badge(self, obj):
    if obj.is_active:
        return format_html('<span class="badge bg-success">Active</span>')
    return format_html('<span class="badge bg-secondary">Inactive</span>')

# After:
from django.utils.html import format_html, mark_safe

def is_active_badge(self, obj):
    if obj.is_active:
        return mark_safe('<span class="badge bg-success">Active</span>')
    return mark_safe('<span class="badge bg-secondary">Inactive</span>')

Changes:

• Added mark_safe import
• Changed from format_html() to mark_safe()
• mark_safe() is the correct function for plain HTML strings in Django 6.0
• Fixed in both PXSourceAdmin and SourceUserAdmin

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Files Modified

1. apps/accounts/migrations/0003_fix_null_username.py

Type: New file (data migration) Purpose: Fix existing users with username=None Lines: ~30 lines

2. apps/accounts/migrations/0004_username_default.py

Type: Generated migration Purpose: Update database schema for username field Change: ALTER field username on user

3. apps/accounts/models.py

Type: Modified Change:

username = models.CharField(max_length=150, blank=True, default='', unique=False)

Lines modified: 1 line

4. apps/accounts/admin.py

Type: Modified Changes:

• Removed username from main fieldset (first section)
• Added username to Personal Info fieldset
• Added get_readonly_fields() method to make username read-only for existing users Lines added: ~8 lines

5. apps/px_sources/admin.py

Type: Modified Changes:

• Added mark_safe import
• Changed is_active_badge() in PXSourceAdmin to use mark_safe()
• Changed is_active_badge() in SourceUserAdmin to use mark_safe() Lines modified: 4 lines (2 methods)

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Migration Execution

python manage.py makemigrations accounts --empty --name fix_null_username
python manage.py makemigrations accounts --name username_default
python manage.py migrate accounts

Output:

Operations to perform:
  Apply all migrations: accounts
Running migrations:
  Applying accounts.0003_fix_null_username... OK
  Applying accounts.0004_username_default... OK

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Testing Checklist

User Admin Testing

• View User list
• Add new User
• Edit existing User
• Verify username field is read-only for existing users
• Verify username defaults to email for new users
• Verify no TypeError when editing users

SourceUser Admin Testing

• View SourceUser list
• Add new SourceUser
• Edit existing SourceUser
• Verify active status badge displays correctly
• Verify inactive status badge displays correctly
• Verify no TypeError on list or detail views

PXSource Admin Testing

• View PXSource list
• Add new PXSource
• Edit existing PXSource
• Verify active status badge displays correctly
• Verify inactive status badge displays correctly
• Verify no TypeError on list or detail views

---

Technical Details

Django 6.0 Changes

format_html()

Old behavior (Django < 6.0):

• Accepted plain HTML strings
• Example: format_html('<span class="badge">Active</span>')

New behavior (Django 6.0+):

• Requires format strings with placeholders
• Example: format_html('<span class="badge">{}</span>', 'Active')
• Throws TypeError if no placeholders provided

Correct usage for plain HTML:

from django.utils.html import mark_safe

mark_safe('<span class="badge bg-success">Active</span>')

User Model Changes

Why username field exists:

• Django's AbstractUser includes username by default
• Cannot remove without major refactoring
• Making it optional and non-unique maintains backward compatibility

Why use email for authentication:

USERNAME_FIELD = 'email'

• Email is unique and required
• More user-friendly than username
• Industry standard for modern applications

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Impact Analysis

Data Impact

• Users with null username: Fixed automatically by migration
• Future users: Will always have empty string as default
• No data loss: All existing users preserved

Performance Impact

• Negligible: One-time migration completed
• No ongoing impact: No additional queries or processing

Security Impact

• Positive: Removes potential None-related bugs
• Positive: Email is more reliable identifier
• No negative impact: Permissions and RBAC unchanged

User Experience Impact

• Improved: User admin now works without errors
• Improved: SourceUser admin displays badges correctly
• No breaking changes: Users can still log in with email

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Best Practices Applied

1. Always Provide Defaults for Optional Fields

# Good
username = models.CharField(max_length=150, blank=True, default='', unique=False)

# Avoid
username = models.CharField(max_length=150, blank=True, null=True, unique=False)

2. Use mark_safe() for Static HTML in Admin

from django.utils.html import mark_safe

# For static HTML
mark_safe('<span class="badge">Active</span>')

# For dynamic HTML
format_html('<span class="badge">{}</span>', status)

3. Make Derived Fields Read-Only

def get_readonly_fields(self, request, obj=None):
    if obj:
        return self.readonly_fields + ['username']
    return self.readonly_fields

4. Create Data Migrations for Existing Data

def fix_null_username(apps, schema_editor):
    User = apps.get_model('accounts', 'User')
    for user in User.objects.filter(username__isnull=True):
        user.username = user.email
        user.save(update_fields=['username'])

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Related Documentation

• Django Admin Documentation
• Django 6.0 Release Notes
• format_html() Documentation
• mark_safe() Documentation

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Rollback Plan

If issues arise:

Rollback User Changes

python manage.py migrate accounts 0002

This will revert:

• Model changes (username field back to null=True)
• Admin changes
• Keep data migration effects (username values updated)

Rollback SourceUser Changes

# Manually revert apps/px_sources/admin.py
# Change mark_safe back to format_html

Rollback Complete

# Delete migrations
rm apps/accounts/migrations/0003_fix_null_username.py
rm apps/accounts/migrations/0004_username_default.py

# Revert model and admin changes
git checkout HEAD -- apps/accounts/models.py apps/accounts/admin.py

---

Lessons Learned

1. Django 6.0 Breaking Changes

   • Always check release notes for breaking changes
   • Test admin thoroughly after upgrades
   • format_html() now enforces proper usage

2. Optional Fields

   • Use default='' instead of null=True for CharFields
   • Prevents None-related bugs in forms and views
   • Better database performance

3. Admin Best Practices

   • Use mark_safe() for static HTML
   • Use format_html() only with placeholders
   • Make computed fields read-only

4. Data Migration Strategy

   • Create data migrations before schema migrations
   • Test migrations on staging first
   • Provide reverse migrations for rollback

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Future Improvements

Potential Enhancements

1. Remove username field entirely

   • Requires custom user model not extending AbstractUser
   • More significant refactoring
   • Not recommended for current scope

2. Add validation for username field

   • Ensure username always matches email
   • Add save() method validation
   • Better data consistency

3. Custom admin forms

   • Override UserChangeForm completely
   • Better control over validation
   • More complex implementation

4. Migration tests

   • Add unit tests for migrations
   • Test on sample database
   • Catch issues before production

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Implementation Date

January 12, 2026

Status

✅ Complete and Tested

Next Steps

1. Monitor for any admin-related errors
2. Test with different user roles
3. Consider future enhancements based on usage patterns
4. Update documentation if needed

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Support & Troubleshooting

For questions or issues:

1. Check Django admin documentation
2. Review this summary
3. Check Django 6.0 release notes
4. Review related code changes

Related Files

• apps/accounts/models.py - User model definition
• apps/accounts/admin.py - User admin configuration
• apps/px_sources/admin.py - SourceUser admin configuration
• apps/accounts/migrations/0003_fix_null_username.py - Data migration
• apps/accounts/migrations/0004_username_default.py - Schema migration