user-registration-fastapi

FastAPI integration for the user-registration Python package.

This package provides FastAPI-specific request/response models, dependency integration, and HTTP exception handling while keeping the core registration business logic framework-independent.

Features

• FastAPI registration endpoint integration
• Pydantic request and response models
• Dependency injection for RegistrationService
• HTTP 201 Created for successful registration
• HTTP 409 Conflict for duplicate users
• HTTP 422 Unprocessable Entity for request/validation errors
• HTTP 500 Internal Server Error for persistence failures
• Compatible with the framework-agnostic user-registration package

Installation

Install the core package and FastAPI adapter:

pip install user-registration user-registration-fastapi

Or install the adapter directly:

pip install user-registration-fastapi

The adapter declares user-registration and fastapi as dependencies.

Basic Usage

The adapter exposes a FastAPI router that delegates registration to the core RegistrationService.

A typical application structure can look like:

my_app/
├── main.py
├── dependencies.py
└── ...

Example:

from fastapi import FastAPI

from user_registration_fastapi import router

app = FastAPI()

app.include_router(router)

The registration endpoint is:

POST /users/register

Example request:

{
  "username": "shuvo",
  "email": "shuvo@example.com",
  "password": "SecurePassword123!"
}

Example successful response:

{
  "id": "...",
  "username": "shuvo",
  "email": "shuvo@example.com"
}

The exact response fields depend on the adapter version and configured registration service.

Dependency Injection

The adapter intentionally does not create a database repository or application-specific RegistrationService automatically.

Instead, the application configures the service and provides it through FastAPI dependency injection.

Conceptually:

from fastapi import Depends


def get_registration_service() -> RegistrationService:
    return registration_service

The adapter then uses the configured service when handling:

POST /users/register

This keeps application infrastructure outside the adapter.

For example:

FastAPI
   │
   ▼
user-registration-fastapi
   │
   ▼
RegistrationService
   │
   ├── PasswordHasher
   ├── PasswordValidator
   ├── UserRepository
   └── ValidationRegistry

HTTP Behavior

The adapter translates domain/application results into HTTP responses.

Condition	HTTP Status
Registration successful	201 Created
Invalid request/validation	422 Unprocessable Entity
Duplicate username/email	409 Conflict
Persistence/application failure	500 Internal Server Error

The adapter does not contain the registration business rules themselves. Those remain in user-registration.

Architecture

The package follows an adapter architecture:

                FastAPI Application
                        │
                        ▼
            user-registration-fastapi
                        │
                        ▼
              RegistrationService
                        │
             ┌──────────┼──────────┐
             ▼          ▼          ▼
        Validation   Password    Repository
         Registry     Hasher      Protocol
                                    │
                                    ▼
                            Application Storage

The repository implementation can be supplied by another adapter, such as:

user-registration-sqlalchemy

or by an application's own repository implementation.

Testing

From the repository root:

.venv/bin/python -m pytest tests/integration/test_fastapi_registration.py -v

Run the complete test suite:

.venv/bin/python -m pytest -v

Development

Install the adapter in editable mode:

.venv/bin/python -m pip install -e "./adapters/fastapi[dev]"

Run Ruff:

.venv/bin/python -m ruff check adapters/fastapi

Check formatting:

.venv/bin/python -m ruff format --check adapters/fastapi

Run MyPy:

.venv/bin/python -m mypy adapters/fastapi

Compatibility

The adapter requires:

• Python 3.12+
• FastAPI >=0.115,<1.0
• user-registration >=0.1.0,<1.0.0

Related Packages

Core package:

• user-registration

SQLAlchemy adapter:

• user-registration-sqlalchemy

License

MIT License.

Visit https://github.com/ShamimurRahmanShuvo/user_registration/tree/main/docs for more detials.