Platform Custom Exceptions

Domain-specific exception hierarchy for platform services

Platform custom exceptions provide domain-specific error handling for services instead of generic Python exceptions.

Quick Start

1. Import Exceptions

   from praisonai_platform.exceptions import (
       PlatformError,
       NotFoundError, 
       DuplicateError,
       AuthenticationError,
       AuthorizationError,
       ValidationError
   )
   
2. Raise Domain-Specific Errors

   # In a service
   def get_workspace(workspace_id: str):
       if not workspace_exists(workspace_id):
           raise NotFoundError(f"Workspace {workspace_id} not found")
       return workspace
   
   def create_project(project_data):
       if project_exists(project_data.name):
           raise DuplicateError(f"Project {project_data.name} already exists")
       return create_new_project(project_data)
   

---

How It Works

Exception	Purpose	HTTP Status
NotFoundError	Resource not found	404
DuplicateError	Resource already exists	409
AuthenticationError	Invalid credentials	401
AuthorizationError	Insufficient permissions	403
ValidationError	Invalid input data	422

---

Exception Types

Base Exception

The PlatformError base class provides common functionality:

from praisonai_platform.exceptions import PlatformError

# All platform exceptions inherit from this
try:
    # Platform operations
    pass
except PlatformError as e:
    # Catches any platform-specific error
    logger.error(f"Platform error: {e}")

Resource Errors

Handle resource-related errors with specific exceptions:

from praisonai_platform.exceptions import NotFoundError, DuplicateError

# Resource not found
raise NotFoundError("Workspace ws-123 not found")

# Resource already exists  
raise DuplicateError("Project 'my-project' already exists")

Authentication & Authorization

Secure your platform with auth-specific exceptions:

from praisonai_platform.exceptions import AuthenticationError, AuthorizationError

# Invalid credentials
raise AuthenticationError("Invalid API key provided")

# Insufficient permissions
raise AuthorizationError("User lacks permission to delete workspace")

Data Validation

Validate input with clear error messages:

from praisonai_platform.exceptions import ValidationError

# Invalid input data
raise ValidationError("Project name must be alphanumeric")

---

FastAPI Integration

Handle platform exceptions in FastAPI applications:

Exception Handlers

from fastapi import FastAPI, HTTPException
from fastapi.responses import JSONResponse
from praisonai_platform.exceptions import (
    PlatformError,
    NotFoundError,
    DuplicateError,
    AuthenticationError,
    AuthorizationError,
    ValidationError
)

app = FastAPI()

@app.exception_handler(NotFoundError)
async def not_found_handler(request, exc):
    return JSONResponse(
        status_code=404, 
        content={"detail": str(exc)}
    )

@app.exception_handler(DuplicateError)
async def duplicate_handler(request, exc):
    return JSONResponse(
        status_code=409, 
        content={"detail": str(exc)}
    )

@app.exception_handler(AuthenticationError)
async def auth_handler(request, exc):
    return JSONResponse(
        status_code=401, 
        content={"detail": str(exc)}
    )

@app.exception_handler(ValidationError)
async def validation_handler(request, exc):
    return JSONResponse(
        status_code=422, 
        content={"detail": str(exc)}
    )

Service Usage

from praisonai_platform.exceptions import NotFoundError, ValidationError

async def get_workspace(workspace_id: str):
    """Get workspace by ID."""
    if not workspace_id:
        raise ValidationError("Workspace ID is required")
        
    workspace = await workspace_service.get(workspace_id)
    if not workspace:
        raise NotFoundError(f"Workspace {workspace_id} not found")
        
    return workspace

@app.get("/workspaces/{workspace_id}")
async def get_workspace_endpoint(workspace_id: str):
    # Exceptions automatically handled by FastAPI handlers
    return await get_workspace(workspace_id)

---

Common Patterns

Service Layer Pattern

Use exceptions consistently across services:

class WorkspaceService:
    def get(self, workspace_id: str):
        workspace = self.db.get_workspace(workspace_id)
        if not workspace:
            raise NotFoundError(f"Workspace {workspace_id} not found")
        return workspace
    
    def create(self, workspace_data):
        if self.db.workspace_exists(workspace_data.name):
            raise DuplicateError(f"Workspace {workspace_data.name} already exists")
        return self.db.create_workspace(workspace_data)

Error Context

Include helpful context in exception messages:

# Good: Specific and actionable
raise NotFoundError(f"Workspace {workspace_id} not found")
raise ValidationError("Project name must be 3-50 characters")

# Avoid: Generic messages
raise NotFoundError("Not found")
raise ValidationError("Invalid input")

Exception Chaining

Chain exceptions to preserve original error context:

try:
    # Database operation
    result = db.create_project(project_data)
except DatabaseError as e:
    raise DuplicateError(f"Project {project_data.name} already exists") from e

---

Best Practices

Use Specific Exceptions

Always use the most specific exception type available. This helps with error handling and debugging.

# Good
raise NotFoundError(f"Workspace {workspace_id} not found")

# Avoid  
raise PlatformError("Workspace not found")

Include Helpful Messages

Provide clear, actionable error messages that help users understand what went wrong.

# Good
raise ValidationError("Project name must contain only letters, numbers, and hyphens")

# Avoid
raise ValidationError("Invalid project name")

Consistent HTTP Mapping

Each exception type maps to a specific HTTP status code. Use consistent exception handlers in your FastAPI applications.

# Consistent mapping
NotFoundError → 404
DuplicateError → 409  
AuthenticationError → 401
AuthorizationError → 403
ValidationError → 422

Exception Hierarchy

Take advantage of the exception hierarchy. Catch PlatformError to handle all platform exceptions, or catch specific types for targeted handling.

try:
    workspace_service.get(workspace_id)
except NotFoundError:
    # Handle specific case
    return create_default_workspace()
except PlatformError as e:
    # Handle any other platform error
    logger.error(f"Platform error: {e}")
    raise

---

Related

Platform Dependencies

Manage platform service dependencies

API Error Handling

Best practices for API error handling