All checks were successful
continuous-integration/drone/tag Build is passing
119 lines
3.6 KiB
Python
119 lines
3.6 KiB
Python
"""
|
|
openapi_first.app
|
|
=========================
|
|
|
|
OpenAPI-first application bootstrap for FastAPI.
|
|
|
|
This module provides `OpenAPIFirstApp`, a thin but strict abstraction
|
|
that enforces OpenAPI as the single source of truth for a FastAPI service.
|
|
|
|
Core principles
|
|
---------------
|
|
- The OpenAPI specification (JSON or YAML) defines the entire API surface.
|
|
- Every operationId in the OpenAPI spec must have a corresponding
|
|
Python handler function.
|
|
- Handlers are plain Python callables (no FastAPI decorators).
|
|
- FastAPI route registration is derived exclusively from the spec.
|
|
- FastAPI's autogenerated OpenAPI schema is fully overridden.
|
|
|
|
What this module does
|
|
---------------------
|
|
- Loads and validates an OpenAPI 3.x specification.
|
|
- Dynamically binds HTTP routes to handler functions using operationId.
|
|
- Registers routes with FastAPI at application startup.
|
|
- Ensures runtime behavior matches the OpenAPI contract exactly.
|
|
|
|
What this module does NOT do
|
|
----------------------------
|
|
- It does not generate OpenAPI specs.
|
|
- It does not generate client code.
|
|
- It does not introduce a new framework or lifecycle.
|
|
- It does not alter FastAPI dependency injection semantics.
|
|
|
|
Intended usage
|
|
--------------
|
|
This module is intended for teams that want:
|
|
|
|
- OpenAPI-first API development
|
|
- Strong contract enforcement
|
|
- Minimal FastAPI boilerplate
|
|
- Predictable, CI-friendly failures for spec/implementation drift
|
|
"""
|
|
|
|
from fastapi import FastAPI
|
|
|
|
from .loader import load_openapi
|
|
from .binder import bind_routes
|
|
|
|
|
|
class OpenAPIFirstApp(FastAPI):
|
|
"""
|
|
FastAPI application enforcing OpenAPI-first design.
|
|
|
|
`OpenAPIFirstApp` subclasses FastAPI and replaces manual route
|
|
registration with OpenAPI-driven binding. All routes are derived
|
|
from the provided OpenAPI specification, and each operationId is
|
|
mapped to a Python function in the supplied routes module.
|
|
|
|
Parameters
|
|
----------
|
|
openapi_path : str
|
|
Filesystem path to the OpenAPI 3.x specification file.
|
|
This specification is treated as the authoritative API contract.
|
|
|
|
routes_module : module
|
|
Python module containing handler functions whose names correspond
|
|
exactly to OpenAPI operationId values.
|
|
|
|
**fastapi_kwargs
|
|
Additional keyword arguments passed directly to `fastapi.FastAPI`
|
|
(e.g., title, version, middleware, lifespan handlers).
|
|
|
|
Raises
|
|
------
|
|
OpenAPIFirstError
|
|
If the OpenAPI specification is invalid, or if any declared
|
|
operationId does not have a corresponding handler function.
|
|
|
|
Behavior guarantees
|
|
-------------------
|
|
- No route can exist without an OpenAPI declaration.
|
|
- No OpenAPI operation can exist without a handler.
|
|
- Swagger UI and `/openapi.json` always reflect the provided spec.
|
|
- Handler functions remain framework-agnostic and testable.
|
|
|
|
Example
|
|
-------
|
|
>>> from openapi_first import OpenAPIFirstApp
|
|
>>> import app.routes as routes
|
|
>>>
|
|
>>> app = OpenAPIFirstApp(
|
|
... openapi_path="app/openapi.json",
|
|
... routes_module=routes,
|
|
... title="Example Service"
|
|
... )
|
|
"""
|
|
|
|
def __init__(
|
|
self,
|
|
*,
|
|
openapi_path: str,
|
|
routes_module,
|
|
**fastapi_kwargs,
|
|
):
|
|
# Initialize FastAPI normally
|
|
super().__init__(**fastapi_kwargs)
|
|
|
|
# Load and validate OpenAPI specification
|
|
self._openapi_spec = load_openapi(openapi_path)
|
|
|
|
# Bind routes strictly from OpenAPI spec
|
|
bind_routes(
|
|
app=self,
|
|
spec=self._openapi_spec,
|
|
routes_module=routes_module,
|
|
)
|
|
|
|
# Override FastAPI's OpenAPI generation
|
|
self.openapi = lambda: self._openapi_spec
|