Plugin System

Overview

Pagoda’s plugin system enables extension through completely independent external plugins using a 3-layer architecture. This system separates plugins from core functionality and provides stable extension points.

3-Layer Architecture

┌─────────────────┐    ┌──────────────────┐    ┌──────────────────┐
│   Core Layer    │    │   Plugin Layer   │    │Extended App Layer│
│                 │    │                  │    │                  │
│pagoda-plugin-sdk│◄───│  External Plugin │◄───│     Pagoda       │
│                 │    │                  │    │                  │
│ • Interfaces    │    │ • Plugin Logic   │    │ • Bridge Impl.   │
│ • Base Classes  │    │ • API Endpoints  │    │ • URL Integration│
│ • Common Hooks  │    │ • Hook Handlers  │    │ • Django Setup   │
└─────────────────┘    └──────────────────┘    └──────────────────┘

Core Capabilities

Plugins enable the following extensions:

API v2 Endpoints: RESTful API extensions
Hook-Based Extensions: Intervention and extension of core operations
Custom Business Logic: Unique processing and data manipulation
Authentication & Authorization Integration: Utilizing Pagoda’s permission system

Architecture Deep Dive

Layer 1: pagoda-plugin-sdk (Core Framework)

Foundation layer provided as an independent PyPI package:

# pagoda_plugin_sdk provides:
from pagoda_plugin_sdk import Plugin, PluginAPIViewMixin
from pagoda_plugin_sdk.models import Entity, Entry, User
from pagoda_plugin_sdk.protocols import EntityProtocol, EntryProtocol, UserProtocol

Features:

Distributable via PyPI
Depends on Django/DRF but not on Pagoda application
Type-safe Protocol definitions for host models
Model injection mechanism for accessing host application data

Layer 2: External Plugin (Independent Extension)

Completely independent plugin that depends only on pagoda-plugin-sdk:

from pagoda_plugin_sdk import Plugin
from pagoda_plugin_sdk.decorators import entry_hook

class MyPlugin(Plugin):
    id = "my-plugin"
    name = "My Plugin"
    version = "1.0.0"
    django_apps = ["my_plugin"]
    api_v2_patterns = "my_plugin.api_v2.urls"

    @entry_hook("after_create")
    def log_entry_create(self, entity_name, user, entry, **kwargs):
        """Called after an entry is created"""
        logger.info(f"Entry created: {entry.name}")

Layer 3: Pagoda Application (Host Application)

Injects concrete model implementations into the plugin SDK:

# Pagoda injects actual models into the plugin SDK
from airone.plugins.integration import plugin_integration

# During initialization, real models are injected
plugin_integration.initialize()  # Injects Entity, Entry, User, etc.

# Plugins can then access models through the SDK
from pagoda_plugin_sdk.models import Entity, Entry, User

Model Access through Protocols

Overview

Plugins access host application models through a safe injection mechanism. The SDK provides Protocol-based type definitions that ensure type safety without creating implementation dependencies.

Protocol Definitions

The SDK defines type-safe protocols for all major models:

from pagoda_plugin_sdk.protocols import (
    EntityProtocol,
    EntryProtocol,
    UserProtocol,
    EntityAttrProtocol,
    AttributeProtocol,
    AttributeValueProtocol,
)

Available Protocols:

EntityProtocol - Schema definition (Entity model)
EntryProtocol - Data entry (Entry model)
UserProtocol - User account
EntityAttrProtocol - Entity attribute definition
AttributeProtocol - Entry attribute
AttributeValueProtocol - Attribute value

Model Injection Mechanism

Models are injected by the host application during initialization:

# In Pagoda application startup
from airone.plugins.integration import plugin_integration

# Initialize plugin system and inject models
plugin_integration.initialize()  # Automatically injects real models

The injection process:

Pagoda application starts
Plugin system initializes
Real Django models are injected into pagoda_plugin_sdk.models
Plugins can safely access models through the SDK

Accessing Models in Plugins

Basic Model Access:

from pagoda_plugin_sdk.models import Entity, Entry, User

def my_plugin_view(request):
    # Type-safe Entity access
    entities = Entity.objects.filter(is_active=True)

    # Type-safe Entry access
    entries = Entry.objects.filter(schema__name="MyEntity")

    # Access with relationships
    for entry in entries:
        entity_name = entry.schema.name  # Type-safe attribute access
        creator = entry.created_user.username

Checking Model Availability:

from pagoda_plugin_sdk import models

# Check if models are initialized
if models.is_initialized():
    from pagoda_plugin_sdk.models import Entity
    entities = Entity.objects.all()
else:
    # Handle case where plugin system is not initialized
    raise RuntimeError("Plugin system not initialized")

# Get list of available models
available = models.get_available_models()  # ['Entity', 'Entry', 'User', ...]

Model CRUD Operations:

from pagoda_plugin_sdk.models import Entity, Entry

# Create
entity = Entity.objects.create(
    name="New Entity",
    note="Created by plugin",
    created_user=request.user
)

# Read
entity = Entity.objects.get(id=123)
entries = Entry.objects.filter(schema=entity, is_active=True)

# Update
entity.note = "Updated by plugin"
entity.save()

# Delete (soft delete)
entity.is_active = False
entity.save()

Using Entry-Specific Methods:

from pagoda_plugin_sdk.models import Entry

# Get entry with attributes
entry = Entry.objects.get(id=456)

# Use Entry's custom methods (defined in EntryProtocol)
attrs = entry.get_attrs()  # Get all attributes as dict
entry.set_attrs(user=request.user, name="value", age=30)

# Permission checking
if entry.may_permitted(request.user, some_permission):
    # Perform operation
    pass

Type Safety Benefits

Using Protocols provides several advantages:

IDE Autocomplete: Full IntelliSense support in modern IDEs
Type Checking: Static type checkers (mypy) can verify correctness
No Import Errors: No circular dependency issues
Documentation: Protocol definitions serve as API documentation

Example with Type Hints:

from typing import List
from pagoda_plugin_sdk.models import Entity, Entry
from pagoda_plugin_sdk.protocols import EntityProtocol, EntryProtocol

def get_entries_for_entity(entity: EntityProtocol) -> List[EntryProtocol]:
    """Get all active entries for a given entity

    Args:
        entity: Entity to query entries for

    Returns:
        List of active Entry instances
    """
    return Entry.objects.filter(schema=entity, is_active=True)

Error Handling

Always handle cases where models might not be available:

from pagoda_plugin_sdk.models import Entity
from rest_framework.response import Response
from rest_framework import status

def my_view(request):
    try:
        if Entity is None:
            return Response(
                {"error": "Entity model not available"},
                status=status.HTTP_503_SERVICE_UNAVAILABLE
            )

        entities = Entity.objects.filter(is_active=True)
        # Process entities...

    except Exception as e:
        return Response(
            {"error": str(e)},
            status=status.HTTP_500_INTERNAL_SERVER_ERROR
        )

Getting Started

Prerequisites

# Install pagoda-plugin-sdk from Git repository (recommended)
pip install git+https://github.com/dmm-com/pagoda.git#subdirectory=plugin/sdk

# Or using uv (faster)
uv pip install git+https://github.com/dmm-com/pagoda.git#subdirectory=plugin/sdk

# Or from local source (for SDK development)
cd /path/to/pagoda/plugin/sdk
pip install -e .

Plugin Enablement

The plugin system loads only manually specified plugins:

# Enable a single plugin
export ENABLED_PLUGINS=my-plugin

# Enable multiple plugins (comma-separated)
export ENABLED_PLUGINS=my-plugin,another-plugin

Starting Server with Plugins

# Start with uv environment (recommended)
ENABLED_PLUGINS=my-plugin uv run python manage.py runserver

# Start with pip environment
ENABLED_PLUGINS=my-plugin python manage.py runserver

# Start after setting environment variable
export ENABLED_PLUGINS=my-plugin
python manage.py runserver

Important: Only plugins explicitly specified in ENABLED_PLUGINS are loaded. If none are specified, the plugin system is disabled.

Verifying Plugin Operation

Startup Logs

Logs when the plugin system is operating normally:

[INFO] Initializing plugin system...
[INFO] Starting plugin discovery...
[INFO] Loaded external plugin: hello-world
[INFO] Registered plugin: hello-world-plugin v1.0.0
[INFO] Connected Entry model signals to hook system
[INFO] Pagoda bridge manager initialized successfully
[INFO] Registered 2 hooks for plugin hello-world-plugin
[INFO] Plugin discovery completed. Found 1 plugins.
[INFO] Plugin system initialized successfully

Testing Plugin APIs

Sample plugin API endpoints:

# Authentication-free test endpoint (for verification)
curl http://localhost:8000/api/v2/plugins/hello-world-plugin/test/

# Authentication-required endpoints
curl -H "Authorization: Token YOUR_TOKEN" \
     http://localhost:8000/api/v2/plugins/hello-world-plugin/hello/

curl -H "Authorization: Token YOUR_TOKEN" \
     http://localhost:8000/api/v2/plugins/hello-world-plugin/greet/John/

curl -H "Authorization: Token YOUR_TOKEN" \
     http://localhost:8000/api/v2/plugins/hello-world-plugin/status/

Expected Response

{
  "message": "External Hello World Plugin is working via pagoda-core!",
  "plugin": {
    "id": "hello-world-plugin",
    "name": "Hello World Plugin",
    "version": "1.0.0",
    "type": "external",
    "core": "pagoda-core"
  },
  "test": "no-auth",
  "user": {
    "username": "anonymous",
    "is_authenticated": false
  },
  "pagoda_core_version": "1.0.0",
  "timestamp": "2025-09-15T02:09:45.658756"
}

Plugin Development

Development Workflow

1. Create Plugin Structure

mkdir my-pagoda-plugin
cd my-pagoda-plugin

# Copy from example
cp -r ../plugin/examples/pagoda-hello-world-plugin/* .

2. Plugin Package Structure

my-pagoda-plugin/
├── pyproject.toml              # Modern package configuration
├── Makefile                    # Development commands
├── README.md                   # Plugin documentation
└── my_plugin_package/          # Main package
    ├── __init__.py
    ├── plugin.py               # Plugin class definition
    ├── hooks.py                # Hook handlers
    ├── apps.py                 # Django app configuration
    └── api_v2/                 # API endpoints
        ├── __init__.py
        ├── urls.py             # URL configuration
        └── views.py            # API view implementation

3. pyproject.toml Configuration

[project]
name = "my-pagoda-plugin"
version = "1.0.0"
description = "My Pagoda Plugin"
dependencies = [
    "pagoda-plugin-sdk @ git+https://github.com/dmm-com/pagoda.git#subdirectory=plugin/sdk",
    "Django>=3.2",
    "djangorestframework>=3.12",
]
requires-python = ">=3.8"

[project.entry-points."pagoda.plugins"]
my-plugin = "my_plugin_package.plugin:MyPlugin"

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

4. Plugin Class Implementation

from pagoda_plugin_sdk import Plugin
from pagoda_plugin_sdk.decorators import entry_hook
import logging

logger = logging.getLogger(__name__)

class MyPlugin(Plugin):
    # Required metadata
    id = "my-plugin"
    name = "My Plugin"
    version = "1.0.0"
    description = "My custom Pagoda plugin"
    author = "Your Name"

    # Django integration
    django_apps = ["my_plugin_package"]
    api_v2_patterns = "my_plugin_package.api_v2.urls"

    # Hook handlers using decorators
    @entry_hook("after_create")
    def log_after_create(self, entity_name, user, entry, **kwargs):
        """Called after an entry is created"""
        logger.info(f"Entry created: {entry.name} in {entity_name}")

    @entry_hook("before_update")
    def log_before_update(self, entity_name, user, validated_data, entry, **kwargs):
        """Called before an entry is updated"""
        logger.info(f"Entry updating: {entry.name}")
        return validated_data

5. API View Implementation

from datetime import datetime
from rest_framework.response import Response
from rest_framework.permissions import AllowAny

from pagoda_plugin_sdk import PluginAPIViewMixin

class MyAPIView(PluginAPIViewMixin):
    permission_classes = [AllowAny]  # For testing

    def get(self, request):
        return Response({
            "message": "Hello from my plugin!",
            "plugin": {
                "id": self.plugin_id,
                "name": "My Plugin",
                "version": "1.0.0"
            },
            "timestamp": datetime.now().isoformat()
        })

Development Commands

Development Make commands in plugin directory:

make help              # Show available commands
make dev-setup         # Set up development environment
make install-dev       # Install in development mode
make test              # Run plugin tests
make test-integration  # Run Pagoda integration tests
make build             # Build distribution packages
make publish-test      # Publish to TestPyPI
make publish           # Publish to PyPI

Distribution Strategies

1. PyPI Distribution

# Build and publish
make build
make publish

# Users install the plugin
pip install my-pagoda-plugin

2. GitHub Releases

# Create tag and release
git tag v1.0.0
git push origin v1.0.0

# Users install from GitHub release
pip install https://github.com/user/my-plugin/releases/download/v1.0.0/my_plugin-1.0.0-py3-none-any.whl

3. Development Installation

# Development editable install
pip install -e .

# Development install in Poetry environment
pip install -e .

Sample Plugin Reference

Available Example

A complete sample plugin is available at plugin/examples/pagoda-hello-world-plugin/:

Endpoints:

GET /api/v2/plugins/hello-world-plugin/test/ - Authentication-free test
GET /api/v2/plugins/hello-world-plugin/hello/ - Basic Hello API
POST /api/v2/plugins/hello-world-plugin/hello/ - Custom message API
GET /api/v2/plugins/hello-world-plugin/greet/<name>/ - Personalized greeting
GET /api/v2/plugins/hello-world-plugin/status/ - Plugin status
GET /api/v2/plugins/hello-world-plugin/entities/ - List all entities (demonstrates model access)
GET /api/v2/plugins/hello-world-plugin/entities/<id>/ - Get entity details
GET /api/v2/plugins/hello-world-plugin/entries/ - List entries with filtering
GET /api/v2/plugins/hello-world-plugin/entries/<id>/ - Get entry with attributes

Model Access Examples:

The sample plugin demonstrates how to access host application models:

from pagoda_plugin_sdk import PluginAPIViewMixin
from pagoda_plugin_sdk.models import Entity, Entry

class EntityListView(PluginAPIViewMixin):
    def get(self, request):
        # Type-safe entity access
        entities = Entity.objects.filter(is_active=True)

        entity_list = [
            {
                "id": entity.id,
                "name": entity.name,
                "note": entity.note,
            }
            for entity in entities
        ]

        return Response({"entities": entity_list})

Configuration

Environment Variables

Variable	Default	Description
`ENABLED_PLUGINS`	`[]`	List of plugins to enable (comma-separated)

Django Settings Integration

# airone/settings_common.py
ENABLED_PLUGINS = env.list("ENABLED_PLUGINS", default=[])

# Plugin system is automatically enabled if any plugins are specified
PLUGINS_ENABLED = bool(ENABLED_PLUGINS)

# Plugin apps are dynamically added to INSTALLED_APPS
if PLUGINS_ENABLED:
    INSTALLED_APPS.extend(plugin_integration.get_installed_apps())

Manual Plugin Control

The plugin system adopts explicit control:

No Automatic Discovery: Does not automatically load available plugins
Explicit Specification: Only loads plugins specified in ENABLED_PLUGINS
Security: Prevents loading of unintended plugins
Controllability: Easy plugin control in development and production environments

Troubleshooting

Common Issues and Solutions

1. 404 Error on Plugin Endpoints

Symptoms: curl http://localhost:8000/api/v2/plugins/my-plugin/test/ returns 404

Causes and Solutions:

# Cause 1: Plugin not specified
❌ python manage.py runserver
✅ ENABLED_PLUGINS=my-plugin python manage.py runserver

# Cause 2: Plugin not installed
❌ pip install -e plugin_examples/my-plugin/
✅ cd plugin_examples/my-plugin/ && pip install -e .

# Cause 3: Incorrect Entry points path
❌ 'my-plugin = my_plugin:MyPlugin'
✅ 'my-plugin = my_plugin.plugin:MyPlugin'

# Cause 4: Incorrect Entry points group name
❌ [project.entry-points."airone.plugins"]
✅ [project.entry-points."pagoda.plugins"]

2. Plugin Discovery Failures

Log Example:

[ERROR] Failed to load external plugin my-plugin: No module named 'my_plugin'
[INFO] Plugin discovery completed. Found 0 plugins.

Resolution Steps:

Check Entry points:

python -c "
import pkg_resources
for ep in pkg_resources.iter_entry_points('pagoda.plugins'):
    print(f'{ep.name} -> {ep.module_name}:{ep.attrs[0]}')
    try:
        plugin_class = ep.load()
        print(f'✓ Load successful: {plugin_class}')
    except Exception as e:
        print(f'✗ Load failed: {e}')
"

Reinstall Plugin:

cd my-plugin/
pip uninstall -y my-plugin
rm -rf build/ dist/ *.egg-info/
pip install -e .

Check Path and Module:

python -c "
import sys
sys.path.insert(0, 'plugin_examples/my-plugin')
from my_plugin.plugin import MyPlugin
print(f'✓ Direct import works: {MyPlugin().name}')
"

3. Hook Execution Errors

Log Example:

[ERROR] Hook entry.after_create failed: missing required arguments

Solution: Implement correct hook handler signature with decorator

# ❌ Wrong (missing decorator)
def log_after_create(self, entity_name, user, entry, **kwargs):
    pass

# ❌ Wrong (incorrect signature)
@entry_hook("after_create")
def log_after_create(user, entry):
    pass

# ✅ Correct
@entry_hook("after_create")
def log_after_create(self, entity_name, user, entry, **kwargs):
    """
    entity_name: Name of the entity
    user: User who created the entry
    entry: The created Entry instance
    **kwargs: Additional context
    """
    logger.info(f"New entry created: {entry.name} in {entity_name}")

4. Plugin Development Environment Issues

Development with Poetry:

# If pagoda-core is not found
cd pagoda-core/
make install-dev

# Install plugin for development
cd ../plugin_examples/my-plugin/
pip install -e .

# Run integration tests
make test-integration

Debug Commands

# Check plugin status
ENABLED_PLUGINS=hello-world python manage.py shell -c "
from airone.plugins.integration import plugin_integration
plugin_integration.initialize()
print(f'Plugins: {plugin_integration.get_enabled_plugin_count()}')
for plugin in plugin_integration.get_enabled_plugins():
    print(f'  - {plugin.name} ({plugin.id}) v{plugin.version}')
"

# Test URL resolution
python -c "
import django
django.setup()
from django.urls import get_resolver
resolver = get_resolver()
match = resolver.resolve('/api/v2/plugins/hello-world-plugin/test/')
print(f'✓ URL resolved: {match.func}')
"

# Get hook statistics
python -c "
from airone.plugins.bridge_manager import bridge_manager
bridge_manager.initialize()
stats = bridge_manager.hooks.get_hook_statistics()
print(f'Total hooks: {stats[\"total_hooks\"]}')
print(f'Registered hooks: {stats[\"registered_hooks\"]}')
"

Architecture Details

Plugin Discovery Process

1. External Plugin Discovery (Entry Points)
   ├─ pkg_resources.iter_entry_points('pagoda.plugins')
   ├─ Load plugin class from entry point
   └─ Register with plugin_registry

2. Example Plugin Discovery (Directory Scan)
   ├─ Scan plugin_examples/ directory
   ├─ Import plugin.py from each plugin directory
   └─ Register discovered plugin classes

3. Plugin Integration
   ├─ Django Apps → INSTALLED_APPS integration
   ├─ URL Patterns → api_v2/urls.py integration
   ├─ Hook Registration → bridge_manager.hooks
   └─ Bridge System Initialization

Hook System Architecture

The plugin system provides a comprehensive hook system with 17 standard hooks organized into four categories:

Available Hook Types

1. Entry Lifecycle Hooks

entry.before_create - Called before an entry is created
entry.after_create - Called after an entry is created
entry.before_update - Called before an entry is updated
entry.after_update - Called after an entry is updated
entry.before_delete - Called before an entry is deleted
entry.before_restore - Called before an entry is restored
entry.after_restore - Called after an entry is restored

2. Entity Lifecycle Hooks

entity.before_create - Called before an entity is created
entity.after_create - Called after an entity is created
entity.before_update - Called before an entity is updated
entity.after_update - Called after an entity is updated

3. Validation Hooks

entry.validate - Custom validation for entry creation/update

4. Data Access Hooks

entry.get_attrs - Modify entry attributes before returning to client
entity.get_attrs - Modify entity attributes before returning to client

Hook Decorators

The plugin SDK provides four decorators for registering hook handlers:

1. @entry_hook(hook_name, entity=None, priority=100)

For Entry lifecycle hooks. Supports entity-specific filtering.

from pagoda_plugin_sdk.decorators import entry_hook

class MyPlugin(Plugin):
    # Apply to all entities
    @entry_hook("after_create")
    def log_all_entries(self, entity_name, user, entry, **kwargs):
        logger.info(f"Entry created: {entry.name}")

    # Apply only to specific entity
    @entry_hook("after_create", entity="customer")
    def log_customer_only(self, entity_name, user, entry, **kwargs):
        logger.info(f"Customer entry created: {entry.name}")

2. @entity_hook(hook_name, priority=100)

For Entity lifecycle hooks.

from pagoda_plugin_sdk.decorators import entity_hook

class MyPlugin(Plugin):
    @entity_hook("after_create")
    def log_entity_create(self, user, entity, **kwargs):
        logger.info(f"Entity created: {entity.name}")

3. @validation_hook(priority=100)

For entry validation (entry.validate hook).

from pagoda_plugin_sdk.decorators import validation_hook

class MyPlugin(Plugin):
    @validation_hook()
    def validate_entry(self, user, schema_name, name, attrs, instance, **kwargs):
        if "forbidden" in name.lower():
            raise ValueError("Name cannot contain 'forbidden'")

4. @get_attrs_hook(target, priority=100)

For data access hooks. Target must be either “entry” or “entity”.

from pagoda_plugin_sdk.decorators import get_attrs_hook

class MyPlugin(Plugin):
    @get_attrs_hook("entry")
    def modify_entry_attrs(self, entry, attrinfo, is_retrieve, **kwargs):
        # Add custom field
        for attr in attrinfo:
            attr["custom_flag"] = True
        return attrinfo

    @get_attrs_hook("entity")
    def modify_entity_attrs(self, entity, attrinfo, **kwargs):
        return attrinfo

Entity Filtering

Entry hooks support entity-specific filtering using the entity parameter:

class MyPlugin(Plugin):
    # Runs only for "product" entity
    @entry_hook("after_create", entity="product")
    def handle_product_create(self, entity_name, user, entry, **kwargs):
        # Only called when a product entry is created
        pass

    # Runs for all entities
    @entry_hook("after_create")
    def handle_any_create(self, entity_name, user, entry, **kwargs):
        # Called for all entry creations
        pass

When both entity-specific and generic hooks are registered, both will be executed in priority order.

Hook Priority System

Hooks are executed in priority order (lower number = higher priority, default is 100):

class MyPlugin(Plugin):
    # Runs first (priority 50)
    @entry_hook("after_create", priority=50)
    def first_handler(self, entity_name, user, entry, **kwargs):
        logger.info("Runs first")

    # Runs second (default priority 100)
    @entry_hook("after_create")
    def second_handler(self, entity_name, user, entry, **kwargs):
        logger.info("Runs second")

    # Runs last (priority 150)
    @entry_hook("after_create", priority=150)
    def third_handler(self, entity_name, user, entry, **kwargs):
        logger.info("Runs last")

This is useful for ensuring proper execution order when multiple plugins handle the same hook.

Hook Signatures

Each hook type has a specific signature:

Entry Lifecycle Hooks:

def handler(self, entity_name: str, user: User, entry: Entry, **kwargs) -> None:
    # For after_create, after_update, after_delete, after_restore
    pass

def handler(self, entity_name: str, user: User, validated_data: dict, **kwargs) -> dict:
    # For before_create - can modify data
    return validated_data

def handler(self, entity_name: str, user: User, validated_data: dict, entry: Entry, **kwargs) -> dict:
    # For before_update - can modify data
    return validated_data

def handler(self, entity_name: str, user: User, entry: Entry, **kwargs) -> None:
    # For before_delete, before_restore
    pass

Entity Lifecycle Hooks:

def handler(self, user: User, entity: Entity, **kwargs) -> None:
    # For after_create, after_update
    pass

def handler(self, user: User, validated_data: dict, **kwargs) -> dict:
    # For before_create - can modify data
    return validated_data

def handler(self, user: User, validated_data: dict, entity: Entity, **kwargs) -> dict:
    # For before_update - can modify data
    return validated_data

Validation Hook:

def handler(self, user: User, schema_name: str, name: str,
            attrs: list, instance: Optional[Entry], **kwargs) -> None:
    # Raise ValueError or ValidationError to reject
    if invalid_condition:
        raise ValueError("Validation error message")

Data Access Hooks:

def handler(self, entry: Entry, attrinfo: list, is_retrieve: bool, **kwargs) -> list:
    # For entry.get_attrs - must return modified attrinfo
    return attrinfo

def handler(self, entity: Entity, attrinfo: list, **kwargs) -> list:
    # For entity.get_attrs - must return modified attrinfo
    return attrinfo

Backward Compatibility

The hook system maintains backward compatibility with the legacy custom_view system through hook name aliases:

# Legacy custom_view hook names are automatically mapped to standard names
HOOK_ALIASES = {
    "before_create_entry_v2": "entry.before_create",
    "after_create_entry_v2": "entry.after_create",
    "before_update_entry_v2": "entry.before_update",
    "after_update_entry_v2": "entry.after_update",
    "before_delete_entry_v2": "entry.before_delete",
    "validate_entry": "entry.validate",
    "get_entry_attr": "entry.get_attrs",
    "get_entity_attr": "entity.get_attrs",
    # ... and more
}

This allows existing custom_view implementations to work with the new plugin system without modification.

Hook Execution Implementation

# Pagoda Hook Manager implementation
class HookManager:
    def execute_hook(self, hook_name, *args, entity_name=None, **kwargs):
        # 1. Normalize hook name (handle aliases)
        # 2. Get all registered handlers
        # 3. Filter by entity if specified
        # 4. Sort by priority
        # 5. Execute each handler with error isolation
        # 6. Collect and return results

Key features:

Error Isolation: One plugin’s failure doesn’t affect others
Priority Ordering: Handlers execute in priority order
Entity Filtering: Entity-specific hooks run only for matching entities
Flexible Signatures: Different hook types have different signatures

Model Injection Implementation

The host application (Pagoda) injects concrete model implementations into the plugin SDK during initialization. This allows plugins to access Pagoda’s data models without creating direct dependencies.

Injected Models

The following six models are automatically injected:

Entity - Schema definition (from entity.models.Entity)
EntityAttr - Entity attribute definition (from entity.models.EntityAttr)
Entry - Data entry (from entry.models.Entry)
Attribute - Entry attribute (from entry.models.Attribute)
AttributeValue - Attribute value (from entry.models.AttributeValue)
User - User account (from user.models.User)

Injection Process

# airone/plugins/integration.py
class PluginIntegration:
    def _inject_models(self):
        """Inject real models into the plugin SDK"""
        try:
            # Import real models from Pagoda
            import pagoda_plugin_sdk.models as sdk_models
            from entity.models import Entity, EntityAttr
            from entry.models import Entry, Attribute, AttributeValue
            from user.models import User

            # Inject real models into SDK namespace
            sdk_models.Entity = Entity
            sdk_models.Entry = Entry
            sdk_models.User = User
            sdk_models.AttributeValue = AttributeValue
            sdk_models.EntityAttr = EntityAttr
            sdk_models.Attribute = Attribute

            logger.info("Successfully injected models into plugin SDK")
        except ImportError as e:
            logger.error(f"Failed to inject models into plugin SDK: {e}")
            raise

Initialization Sequence

1. Pagoda Application Startup
   └─ settings_common.py loads ENABLED_PLUGINS from environment

2. Plugin System Initialization
   ├─ PluginIntegration.initialize() is called
   ├─ discover_plugins() finds and registers plugins
   └─ _inject_models() injects real models into SDK

3. Plugin Access
   └─ Plugins can now safely import and use models

Using Injected Models in Plugins

# In plugin code
from pagoda_plugin_sdk.models import Entity, Entry, User

class MyPlugin(Plugin):
    @entry_hook("after_create")
    def handle_entry_create(self, entity_name, user, entry, **kwargs):
        # Direct access to model methods
        entity = entry.schema  # Access related Entity
        creator = entry.created_user  # Access related User
        attrs = entry.get_attrs()  # Call Entry methods

        # Query operations
        all_entries = Entry.objects.filter(schema=entity)
        active_users = User.objects.filter(is_active=True)

Type Safety with Protocols

The SDK provides Protocol definitions for type checking without creating implementation dependencies:

from pagoda_plugin_sdk.protocols import (
    EntityProtocol,
    EntryProtocol,
    UserProtocol,
    EntityAttrProtocol,
    AttributeProtocol,
    AttributeValueProtocol,
)

def process_entry(entry: EntryProtocol) -> dict:
    """Type-safe entry processing with IDE support"""
    return {
        "id": entry.id,
        "name": entry.name,
        "schema": entry.schema.name,  # Full IntelliSense support
    }

Checking Model Availability

Always check if models are available before using them:

from pagoda_plugin_sdk import models
from pagoda_plugin_sdk.models import Entity

def safe_operation():
    # Check if plugin system is initialized
    if not models.is_initialized():
        raise RuntimeError("Plugin system not initialized")

    # Check specific model
    if Entity is None:
        raise RuntimeError("Entity model not available")

    # Safe to proceed
    entities = Entity.objects.all()

This injection mechanism ensures that plugins remain independent of Pagoda’s implementation while still having full access to its data models.

Best Practices

1. Plugin Development

Version Pinning: Ensure compatibility with pagoda-core>=1.0.0,<2.0.0
Testing: Implement both unit tests and Pagoda integration tests
Documentation: Include README and API specifications
Error Handling: Implement proper exception handling in hooks and APIs
Security: Implement proper authentication and authorization

2. Distribution

Semantic Versioning: Use appropriate major.minor.patch versioning
Changelog: Maintain release notes and change history
Compatibility: Clearly specify supported Pagoda/pagoda-plugin-sdk versions
Dependencies: Keep dependencies to a minimum

3. Production Deployment

Environment Isolation: Isolate virtual environments per plugin
Monitoring: Monitor plugin error logs
Rollback Strategy: Prepare procedures for disabling plugins
Performance: Evaluate performance impact of hook processing

This 3-layer architecture realizes a plugin system completely independent from Pagoda. Plugin developers can create safe and reusable plugins depending only on pagoda-plugin-sdk.