django-approval-workflow 0.5.0

A powerful, flexible Django package for implementing dynamic multi-step approval workflows

Django Approval Workflow

A powerful, flexible, and reusable Django package for implementing dynamic multi-step approval workflows in your Django applications.

✨ Features

• Dynamic Workflow Creation: Create approval workflows for any Django model using GenericForeignKey
• Multi-Step Approval Process: Support for sequential approval steps with role-based assignments
• Role-Based Approvals: Three strategies (ANYONE, CONSENSUS, ROUND_ROBIN) for dynamic role-based approvals
• Role-Based Permissions: Hierarchical role support using MPTT (Modified Preorder Tree Traversal)
• High-Performance Architecture: Enterprise-level optimizations with O(1) lookups and intelligent caching
• Repository Pattern: Centralized data access with single-query optimizations
• Flexible Actions: Approve, reject, delegate, escalate, or request resubmission at any step
• Custom Fields Support: Extensible extra_fields JSONField for custom data without package modifications
• SLA Tracking: Built-in SLA duration tracking for approval steps
• REST API Ready: Built-in REST API endpoints using Django REST Framework
• Django Admin Integration: Full admin interface for managing workflows
• Extensible Handlers: Custom hook system for workflow events
• Form Integration: Optional dynamic form support for approval steps
• Comprehensive Testing: Full test suite with pytest (53+ tests)

🚀 Quick Start

Installation

pip install django-approval-workflow

Django Settings

Add approval_workflow to your INSTALLED_APPS:

INSTALLED_APPS = [
    # ... your apps
    'approval_workflow',
    'mptt',  # Required for hierarchical roles
    'rest_framework',  # Optional, for API endpoints
]

Optional Settings

# Custom role model (must inherit from MPTTModel)
APPROVAL_ROLE_MODEL = "myapp.Role"  # Default: None

# Field name linking User to Role model
APPROVAL_ROLE_FIELD = "role"  # Default: "role"

# Custom form model for dynamic forms
APPROVAL_DYNAMIC_FORM_MODEL = "myapp.DynamicForm"  # Default: None

Run Migrations

python manage.py migrate approval_workflow

📖 Usage

Basic Example

from approval_workflow.services import start_flow, advance_flow
from approval_workflow.utils import can_user_approve, get_current_approval, get_next_approval
from django.contrib.auth import get_user_model

User = get_user_model()

# Create users
manager = User.objects.get(username='manager')
employee = User.objects.get(username='employee')

# Your model instance
document = MyDocument.objects.create(title="Important Document")

# Start an approval workflow
flow = start_flow(
    obj=document,
    steps=[
        {"step": 1, "assigned_to": employee},
        {"step": 2, "assigned_to": manager},
    ]
)

# Get current pending approval
current_step = get_current_approval(document)
if current_step and can_user_approve(current_step, employee):
    # Advance the workflow
    next_step = advance_flow(
        instance=current_step,
        action="approved",
        user=employee,
        comment="Looks good to me!"
    )

# Check what's next in the workflow
next_step = get_next_approval(document)
if next_step:
    print(f"Next approver: {next_step.assigned_to}")

Custom Fields with extra_fields

Extend approval steps with custom data without modifying the package:

from approval_workflow.services import start_flow

# Add custom fields to approval steps
flow = start_flow(
    obj=document,
    steps=[
        {
            "step": 1, 
            "assigned_to": manager,
            "extra_fields": {
                "priority": "high",
                "department": "IT", 
                "metadata": {
                    "requires_signature": True,
                    "approval_type": "expedited"
                },
                "custom_deadline": "2024-12-31",
                "tags": ["urgent", "compliance"]
            }
        },
        {
            "step": 2,
            "assigned_to": director,
            "extra_fields": {
                "priority": "normal",
                "requires_board_approval": False
            }
        }
    ]
)

# Access custom fields in your code
current_step = get_current_approval(document)
priority = current_step.extra_fields.get("priority", "normal")
metadata = current_step.extra_fields.get("metadata", {})

if priority == "high":
    # Handle high priority approvals
    send_urgent_notification(current_step.assigned_to)

Benefits of extra_fields:

• Store custom data without database migrations
• Perfect for integrating with external systems
• Flexible JSON storage for any data structure
• Maintains package compatibility across updates

### Role-Based Approval

Create workflows that assign approvals to roles instead of specific users. The package supports three role selection strategies:

**1. ANYONE Strategy** - Any user with the role can approve:
```python
from approval_workflow.choices import RoleSelectionStrategy
from approval_workflow.models import ApprovalInstance

# Create role-based step - any manager can approve
ApprovalInstance.objects.create(
    flow=flow,
    step_number=1,
    assigned_role=manager_role,
    role_selection_strategy=RoleSelectionStrategy.ANYONE,
    status=ApprovalStatus.PENDING
)

2. CONSENSUS Strategy - All users with the role must approve:

# All managers must approve
ApprovalInstance.objects.create(
    flow=flow,
    step_number=1,
    assigned_role=manager_role,
    role_selection_strategy=RoleSelectionStrategy.CONSENSUS,
    status=ApprovalStatus.PENDING
)

3. ROUND_ROBIN Strategy - Distributes approvals evenly among role users:

# Automatically assigns to manager with least current workload
ApprovalInstance.objects.create(
    flow=flow,
    step_number=1,
    assigned_role=manager_role,
    role_selection_strategy=RoleSelectionStrategy.ROUND_ROBIN,
    status=ApprovalStatus.PENDING
)

Hierarchical Role Support

With hierarchical roles (using MPTT):

# models.py
from mptt.models import MPTTModel, TreeForeignKey
from django.contrib.auth.models import AbstractUser

class Role(MPTTModel):
    name = models.CharField(max_length=100)
    parent = TreeForeignKey('self', on_delete=models.CASCADE, 
                           null=True, blank=True, related_name='children')

class User(AbstractUser):
    role = models.ForeignKey(Role, on_delete=models.SET_NULL, null=True)

# Usage
senior_role = Role.objects.create(name="Senior Manager")
junior_role = Role.objects.create(name="Junior Manager", parent=senior_role)

senior_user = User.objects.create(username="senior", role=senior_role)
junior_user = User.objects.create(username="junior", role=junior_role)

# Senior users can approve tasks assigned to junior users
instance = ApprovalInstance.objects.create(assigned_to=junior_user)
assert can_user_approve(instance, senior_user)  # True

# Control higher-level approval behavior
assert can_user_approve(instance, senior_user, allow_higher_level=True)   # True (default)
assert can_user_approve(instance, senior_user, allow_higher_level=False)  # False
assert can_user_approve(instance, junior_user, allow_higher_level=False)  # True (direct assignment)

Delegation and Escalation

Users can delegate their approval tasks to others or escalate to higher authorities:

from approval_workflow.services import advance_flow

# Delegate approval to another user
delegate_user = User.objects.get(username='delegate')
next_step = advance_flow(
    instance=current_step,
    action="delegated",
    user=current_user,
    delegate_to=delegate_user,
    comment="Delegating while on vacation"
)

# Escalate to higher authority (requires role hierarchy)
next_step = advance_flow(
    instance=current_step,
    action="escalated", 
    user=current_user,
    comment="Escalating for higher-level decision"
)

Features:

• Delegation: Transfer approval responsibility to another user
• Escalation: Automatically escalate to role hierarchy or configured head manager
• Audit Trail: All delegation and escalation actions are logged
• Context Preservation: Form data and custom fields are maintained

### Permission Control

The `can_user_approve()` function supports fine-grained permission control:

```python
from approval_workflow.utils import can_user_approve

# Default behavior - allows hierarchical approval
can_user_approve(instance, user)  # Same as allow_higher_level=True

# Strict mode - only assigned user can approve
can_user_approve(instance, user, allow_higher_level=False)

Parameters:

• instance: The approval instance to check
• acting_user: The user attempting to approve
• allow_higher_level (optional): Whether to allow users with higher roles to approve on behalf of assigned users (default: True)

When allow_higher_level=False:

• Only the directly assigned user can approve their step
• Role hierarchy is ignored for approval permissions
• Useful for strict approval workflows where delegation is not allowed

Resubmission Workflows

Handle cases where additional review or corrections are needed:

from approval_workflow.services import advance_flow

# Current workflow: Document -> Manager Review -> Director Approval
current_step = flow.instances.get(step_number=1)

# Manager requests resubmission with additional legal review
next_step = advance_flow(
    instance=current_step,
    action="resubmission", 
    user=manager,
    comment="Legal review required before approval",
    resubmission_steps=[
        {"step": 2, "assigned_to": legal_reviewer},
        {"step": 3, "assigned_to": director},  # Original director step continues
    ]
)

# Current step is marked as NEEDS_RESUBMISSION
# New steps are added to the workflow
assert current_step.status == ApprovalStatus.NEEDS_RESUBMISSION  
assert next_step.step_number == 2  # First new step

Custom Handlers

Create custom handlers for workflow events:

# myapp/approval.py
from approval_workflow.handlers import BaseApprovalHandler
from django.utils import timezone

class MyDocumentApprovalHandler(BaseApprovalHandler):
    def on_approve(self, instance):
        # Custom logic when a step is approved
        print(f"Step {instance.step_number} approved!")
    
    def on_final_approve(self, instance):
        # Custom logic when workflow is complete
        instance.flow.target.status = 'approved'
        instance.flow.target.save()
    
    def on_reject(self, instance):
        # Custom logic when a step is rejected
        instance.flow.target.status = 'rejected'
        instance.flow.target.save()
    
    def on_resubmission(self, instance):
        # Custom logic when resubmission is requested
        document = instance.flow.target
        document.status = 'needs_revision'
        document.revision_requested_at = timezone.now()
        document.save()
        
        # Send notification to document author
        send_notification(
            user=document.author,
            message=f"Document '{document.title}' needs revision: {instance.comment}",
            type='resubmission_request'
        )
        
        # Log the resubmission event
        AuditLog.objects.create(
            action='resubmission_requested',
            target=document,
            user=instance.action_user,
            details={'step': instance.step_number, 'comment': instance.comment}
        )

Handler Methods:

• on_approve(instance): Called when any step is approved
• on_final_approve(instance): Called when the final step is approved (workflow complete)
• on_reject(instance): Called when any step is rejected
• on_resubmission(instance): Called when resubmission is requested

Approval Utilities

The package provides convenient utility functions to query approval states for any Django object:

from approval_workflow.utils import (
    get_current_approval,
    get_next_approval, 
    get_full_approvals,
    get_approval_flow
)

document = Document.objects.get(id=1)

# Get the current pending approval step
current = get_current_approval(document)
if current:
    print(f"Waiting for: {current.assigned_to}")
    print(f"Step: {current.step_number}")

# Get the next step in the workflow  
next_step = get_next_approval(document)
if next_step:
    print(f"After current: {next_step.assigned_to}")

# Get complete approval history
all_approvals = get_full_approvals(document)
for approval in all_approvals:
    print(f"Step {approval.step_number}: {approval.status} "
          f"by {approval.assigned_to}")

# Get the approval flow itself
flow = get_approval_flow(document)
if flow:
    print(f"Flow created: {flow.created_at}")
    print(f"Total steps: {flow.instances.count()}")

Utility Functions:

• get_current_approval(obj): Returns current pending approval step
• get_next_approval(obj): Returns next pending step after current
• get_full_approvals(obj): Returns all approval instances (complete history)
• get_approval_flow(obj): Returns the ApprovalFlow instance for the object

These functions work with any Django model object and return None or empty lists if no workflow exists.

High-Performance Repository Pattern

For enterprise applications with high-volume workflows, use the repository pattern for optimal performance:

from approval_workflow.utils import get_approval_repository, get_approval_summary

document = Document.objects.get(id=1)

# Single repository instance for multiple operations (recommended)
repo = get_approval_repository(document)

# All these calls use cached data from a single optimized query
current = repo.get_current_approval()        # O(1) lookup using CURRENT status
next_step = repo.get_next_approval()         # No additional database hit
all_steps = repo.instances                   # Complete workflow data
flow = repo.flow                             # Flow information
pending_count = len(repo.get_pending_approvals())  # Efficient counting
progress = repo.get_workflow_progress()      # Comprehensive progress data

# Or get everything at once
summary = get_approval_summary(document)
print(f"Progress: {summary['progress_percentage']}%")
print(f"Current step: {summary['current_step'].step_number}")

Performance Benefits:

• O(1) Current Step Lookup: Uses denormalized CURRENT status for instant access
• Single Query Strategy: Repository loads all data with one optimized database query
• Multi-Level Caching: LRU cache, Django cache, and instance caching for maximum speed
• Minimal Database Hits: Designed for high-volume production environments

🏗️ Models

ApprovalFlow

Central model that links to any Django model via GenericForeignKey.

ApprovalInstance

Represents individual steps in the approval process with status tracking.

Status Types:

• PENDING: Future steps waiting to be processed
• CURRENT: Active step requiring approval (optimized for O(1) lookups)
• APPROVED: Completed and approved steps
• REJECTED: Rejected steps (workflow terminates)
• NEEDS_RESUBMISSION: Steps requiring resubmission with additional review
• DELEGATED: Steps that have been delegated to another user
• ESCALATED: Steps that have been escalated to higher authority
• CANCELLED: Cancelled steps
• COMPLETED: Final workflow completion status

🔧 Configuration

Role Model Requirements

If using role-based approvals, your role model must:

• Inherit from MPTTModel
• Implement hierarchical relationships
• Be linked to your User model

Custom Form Integration

For dynamic forms in approval steps:

• Configure APPROVAL_DYNAMIC_FORM_MODEL
• Form model should have a schema field for validation

⚡ Performance Considerations

Database Optimization

The package is optimized for high-volume production environments:

• Strategic Indexing: Only 3 optimized database indexes for maximum performance
• CURRENT Status: Denormalized design eliminates complex queries for active step lookup
• Repository Pattern: Single-query strategy with intelligent caching reduces database load
• Unique Constraints: Database-level enforcement ensures data integrity

Best Practices for High-Volume Workflows

# ✅ RECOMMENDED: Use repository pattern for multiple operations
repo = get_approval_repository(document)
current = repo.get_current_approval()  # O(1) lookup
progress = repo.get_workflow_progress()  # No additional queries

# ✅ RECOMMENDED: Batch operations when possible
summary = get_approval_summary(document)  # Single call for complete data

# ❌ AVOID: Multiple individual utility calls
current = get_current_approval(document)    # Query 1
next_step = get_next_approval(document)     # Query 2  
flow = get_approval_flow(document)          # Query 3

Cache Management

The system includes multi-level caching:

• LRU Cache: For ContentType lookups (128 entries)
• Django Cache: For flow data (5-minute TTL)
• Instance Cache: Within repository objects

# Clear cache when needed (testing/debugging)
from approval_workflow.utils import ApprovalRepository
ApprovalRepository.clear_cache_for_object(document)

🧪 Testing

Run the test suite:

# Install development dependencies
pip install -r requirements-dev.txt

# Run tests
pytest

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'Add some amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

👨‍💻 Author

Mohamed Salah
Email: [e-mail]
GitHub: Codxi-Co

🙏 Acknowledgments

• Django team for the amazing framework
• MPTT library for hierarchical model support
• Django REST Framework for API capabilities

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For more detailed documentation and examples, visit our documentation.