Pythonversioned_api.py
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from fastapi import FastAPI, APIRouter, Request
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from pydantic import BaseModel
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app = FastAPI(title="Versioned API")
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# V1 schema (older)
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class UserV1(BaseModel):
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    id: int
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    name: str
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# V2 schema (expanded)
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class UserV2(BaseModel):
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    id: int
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    full_name: str
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    email: str
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    created_at: str
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v1_router = APIRouter(prefix="/v1", tags=["v1"])
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v2_router = APIRouter(prefix="/v2", tags=["v2"])
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@v1_router.get("/users/{user_id}", response_model=UserV1)
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async def get_user_v1(user_id: int):
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    return UserV1(id=user_id, name="John Doe")
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@v2_router.get("/users/{user_id}", response_model=UserV2)
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async def get_user_v2(user_id: int):
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    return UserV2(
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        id=user_id,
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        full_name="John Doe",
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        email="john@example.com",
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        created_at="2024-01-01T00:00:00Z",
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    )
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app.include_router(v1_router)
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app.include_router(v2_router)
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@app.middleware("http")
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async def add_deprecation_headers(request: Request, call_next):
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    response = await call_next(request)
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    if request.url.path.startswith("/v1/"):
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        response.headers["Deprecation"] = "true"
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        response.headers["Sunset"] = "Sat, 01 Jan 2026 00:00:00 GMT"
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        response.headers["Link"] = '</v2/users>; rel="successor-version"'
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    return response
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@app.get("/api/versions")
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async def list_versions():
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    return {
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        "versions": [
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            {"version": "v1", "status": "deprecated", "sunset": "2026-01-01"},
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            {"version": "v2", "status": "current", "sunset": None},
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        ]
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    }
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