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✨ Add dependencies with yield (used as context managers) (fastapi#595)
* ➕ Add development/testing dependencies for Python 3.6 * ✨ Add concurrency submodule with contextmanager_in_threadpool * ✨ Add AsyncExitStack to ASGI scope in FastAPI app call * ✨ Use async stack for contextmanager-able dependencies including running in threadpool sync dependencies * ✅ Add tests for contextmanager dependencies including internal raise checks when exceptions should be handled and when not * ✅ Add test for fake asynccontextmanager raiser * 🐛 Fix mypy errors and coverage * 🔇 Remove development logs and prints * ✅ Add tests for sub-contextmanagers, background tasks, and sync functions * 🐛 Fix mypy errors for Python 3.7 * 💬 Fix error texts for clarity * 📝 Add docs for dependencies with yield * ✨ Update SQL with SQLAlchemy tutorial to use dependencies with yield and add an alternative with a middleware (from the old tutorial) * ✅ Update SQL tests to remove DB file during the same tests * ✅ Add tests for example with middleware as a copy from the tests with dependencies with yield, removing the DB in the tests * ✏️ Fix typos with suggestions from code review Co-Authored-By: dmontagu <35119617+dmontagu@users.noreply.github.com>
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‎docs/src/dependencies/tutorial007.py

Lines changed: 6 additions & 21 deletions
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@@ -1,21 +1,6 @@
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from fastapi import Depends, FastAPI
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app = FastAPI()
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class FixedContentQueryChecker:
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def __init__(self, fixed_content: str):
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self.fixed_content = fixed_content
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def __call__(self, q: str = ""):
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if q:
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return self.fixed_content in q
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return False
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checker = FixedContentQueryChecker("bar")
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@app.get("/query-checker/")
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async def read_query_check(fixed_content_included: bool = Depends(checker)):
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return {"fixed_content_in_query": fixed_content_included}
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async def get_db():
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db = DBSession()
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try:
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yield db
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finally:
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db.close()

‎docs/src/dependencies/tutorial008.py

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@@ -0,0 +1,25 @@
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from fastapi import Depends
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async def dependency_a():
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dep_a = generate_dep_a()
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try:
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yield dep_a
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finally:
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dep_a.close()
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async def dependency_b(dep_a=Depends(dependency_a)):
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dep_b = generate_dep_b()
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try:
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yield dep_b
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finally:
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dep_b.close(dep_a)
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async def dependency_c(dep_b=Depends(dependency_b)):
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dep_c = generate_dep_c()
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try:
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yield dep_c
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finally:
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dep_c.close(dep_b)

‎docs/src/dependencies/tutorial009.py

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from fastapi import Depends
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async def dependency_a():
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dep_a = generate_dep_a()
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try:
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yield dep_a
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finally:
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dep_a.close()
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async def dependency_b(dep_a=Depends(dependency_a)):
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dep_b = generate_dep_b()
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try:
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yield dep_b
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finally:
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dep_b.close(dep_a)
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async def dependency_c(dep_b=Depends(dependency_b)):
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dep_c = generate_dep_c()
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try:
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yield dep_c
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finally:
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dep_c.close(dep_b)

‎docs/src/dependencies/tutorial010.py

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@@ -0,0 +1,14 @@
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class MySuperContextManager:
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def __init__(self):
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self.db = DBSession()
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def __enter__(self):
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return self.db
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def __exit__(self, exc_type, exc_value, traceback):
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self.db.close()
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async def get_db():
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with MySuperContextManager() as db:
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yield db

‎docs/src/dependencies/tutorial011.py

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from fastapi import Depends, FastAPI
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app = FastAPI()
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class FixedContentQueryChecker:
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def __init__(self, fixed_content: str):
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self.fixed_content = fixed_content
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def __call__(self, q: str = ""):
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if q:
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return self.fixed_content in q
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return False
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checker = FixedContentQueryChecker("bar")
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@app.get("/query-checker/")
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async def read_query_check(fixed_content_included: bool = Depends(checker)):
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return {"fixed_content_in_query": fixed_content_included}

‎docs/src/sql_databases/sql_app/alt_main.py

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from typing import List
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from fastapi import Depends, FastAPI, HTTPException
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from sqlalchemy.orm import Session
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from starlette.requests import Request
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from starlette.responses import Response
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from . import crud, models, schemas
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from .database import SessionLocal, engine
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models.Base.metadata.create_all(bind=engine)
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app = FastAPI()
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@app.middleware("http")
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async def db_session_middleware(request: Request, call_next):
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response = Response("Internal server error", status_code=500)
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try:
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request.state.db = SessionLocal()
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response = await call_next(request)
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finally:
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request.state.db.close()
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return response
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# Dependency
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def get_db(request: Request):
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return request.state.db
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@app.post("/users/", response_model=schemas.User)
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def create_user(user: schemas.UserCreate, db: Session = Depends(get_db)):
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db_user = crud.get_user_by_email(db, email=user.email)
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if db_user:
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raise HTTPException(status_code=400, detail="Email already registered")
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return crud.create_user(db=db, user=user)
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@app.get("/users/", response_model=List[schemas.User])
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def read_users(skip: int = 0, limit: int = 100, db: Session = Depends(get_db)):
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users = crud.get_users(db, skip=skip, limit=limit)
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return users
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@app.get("/users/{user_id}", response_model=schemas.User)
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def read_user(user_id: int, db: Session = Depends(get_db)):
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db_user = crud.get_user(db, user_id=user_id)
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if db_user is None:
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raise HTTPException(status_code=404, detail="User not found")
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return db_user
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@app.post("/users/{user_id}/items/", response_model=schemas.Item)
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def create_item_for_user(
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user_id: int, item: schemas.ItemCreate, db: Session = Depends(get_db)
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):
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return crud.create_user_item(db=db, item=item, user_id=user_id)
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@app.get("/items/", response_model=List[schemas.Item])
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def read_items(skip: int = 0, limit: int = 100, db: Session = Depends(get_db)):
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items = crud.get_items(db, skip=skip, limit=limit)
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return items

‎docs/src/sql_databases/sql_app/main.py

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from fastapi import Depends, FastAPI, HTTPException
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from sqlalchemy.orm import Session
5-
from starlette.requests import Request
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from starlette.responses import Response
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from . import crud, models, schemas
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from .database import SessionLocal, engine
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1311
app = FastAPI()
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@app.middleware("http")
17-
async def db_session_middleware(request: Request, call_next):
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response = Response("Internal server error", status_code=500)
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# Dependency
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def get_db():
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try:
20-
request.state.db = SessionLocal()
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response = await call_next(request)
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db = SessionLocal()
18+
yield db
2219
finally:
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request.state.db.close()
24-
return response
25-
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# Dependency
28-
def get_db(request: Request):
29-
return request.state.db
20+
db.close()
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@app.post("/users/", response_model=schemas.User)

‎docs/tutorial/dependencies/advanced-dependencies.md

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!!! danger
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!!! warning
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This is, more or less, an "advanced" chapter.
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If you are just starting with **FastAPI** you might want to skip this chapter and come back to it later.
@@ -22,7 +22,7 @@ Not the class itself (which is already a callable), but an instance of that clas
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To do that, we declare a method `__call__`:
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```Python hl_lines="10"
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{!./src/dependencies/tutorial007.py!}
25+
{!./src/dependencies/tutorial011.py!}
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```
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In this case, this `__call__` is what **FastAPI** will use to check for additional parameters and sub-dependencies, and this is what will be called to pass a value to the parameter in your *path operation function* later.
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3232
And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:
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```Python hl_lines="7"
35-
{!./src/dependencies/tutorial007.py!}
35+
{!./src/dependencies/tutorial011.py!}
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```
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In this case, **FastAPI** won't ever touch or care about `__init__`, we will use it directly in our code.
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4242
We could create an instance of this class with:
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```Python hl_lines="16"
45-
{!./src/dependencies/tutorial007.py!}
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{!./src/dependencies/tutorial011.py!}
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```
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And that way we are able to "parameterize" our dependency, that now has `"bar"` inside of it, as the attribute `checker.fixed_content`.
@@ -60,7 +60,7 @@ checker(q="somequery")
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...and pass whatever that returns as the value of the dependency in our path operation function as the parameter `fixed_content_included`:
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```Python hl_lines="20"
63-
{!./src/dependencies/tutorial007.py!}
63+
{!./src/dependencies/tutorial011.py!}
6464
```
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!!! tip

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