chore: add background dependency regression test

Add test to verify that background tasks added _after_ a `yield`
statement are executed correctly.

This is a regression introduced in 0.118.

Ref: fastapi/fastapi#14137
Signed-off-by: JP-Ellis <[email protected]>

tests/test_dependency_contextmanager.py

@@ -16,6 +16,12 @@ state = {
     "context_b": "not started b",
     "bg": "not set",
     "sync_bg": "not set",
+    "sync_bg_task_pre": "not executed",
+    "sync_bg_task_post": "not executed",
+    "async_bg_task_pre": "not executed",
+    "async_bg_task_post": "not executed",
+    "sync_bg_endpoint": "not started",
+    "async_bg_endpoint": "not started",
 }
 
 errors = []
@@ -87,6 +93,58 @@ async def context_b(state: dict = Depends(context_a)):
         state["context_b"] = f"finished b with a: {state['context_a']}"
 
 
+def sync_dependency_with_bg_tasks(
+    background_tasks: BackgroundTasks,
+    state: dict = Depends(get_state),
+):
+    """Sync generator dependency that adds background tasks before and after yield."""
+
+    def sync_bg_task_pre():
+        state["sync_bg_task_pre"] = "executed"
+
+    async def async_bg_task_pre():
+        state["async_bg_task_pre"] = "executed"
+
+    def sync_bg_task_post():
+        state["sync_bg_task_post"] = "executed"
+
+    async def async_bg_task_post():
+        state["async_bg_task_post"] = "executed"
+
+    state["sync_bg_endpoint"] = "started"
+    background_tasks.add_task(sync_bg_task_pre)
+    background_tasks.add_task(async_bg_task_pre)
+    yield state
+    background_tasks.add_task(sync_bg_task_post)
+    background_tasks.add_task(async_bg_task_post)
+
+
+async def async_dependency_with_bg_tasks(
+    background_tasks: BackgroundTasks,
+    state: dict = Depends(get_state),
+):
+    """Async generator dependency that adds background tasks before and after yield."""
+
+    def sync_bg_task_pre():
+        state["sync_bg_task_pre"] = "executed"
+
+    async def async_bg_task_pre():
+        state["async_bg_task_pre"] = "executed"
+
+    def sync_bg_task_post():
+        state["sync_bg_task_post"] = "executed"
+
+    async def async_bg_task_post():
+        state["async_bg_task_post"] = "executed"
+
+    state["async_bg_endpoint"] = "started"
+    background_tasks.add_task(sync_bg_task_pre)
+    background_tasks.add_task(async_bg_task_pre)
+    yield state
+    background_tasks.add_task(sync_bg_task_post)
+    background_tasks.add_task(async_bg_task_post)
+
+
 @app.get("/async")
 async def get_async(state: str = Depends(asyncgen_state)):
     return state
@@ -142,6 +200,20 @@ async def get_context_b_bg(tasks: BackgroundTasks, state: dict = Depends(context
     return state
 
 
+@app.get("/sync_bg_after_yield")
+def sync_bg_after_yield_endpoint(
+    state: dict = Depends(sync_dependency_with_bg_tasks),
+):
+    return state
+
+
+@app.get("/async_bg_after_yield")
+async def async_bg_after_yield_endpoint(
+    state: dict = Depends(async_dependency_with_bg_tasks),
+):
+    return state
+
+
 # Sync versions
 
 
@@ -398,3 +470,47 @@ def test_sync_background_tasks():
     assert state["context_b"] == "finished b with a: started a"
     assert state["context_a"] == "finished a"
     assert state["sync_bg"] == "sync_bg set - b: started b - a: started a"
+
+
+def test_sync_dependency_background_tasks_after_yield():
+    # Reset states before test
+    global state
+    state["sync_bg_task_pre"] = "not executed"
+    state["async_bg_task_pre"] = "not executed"
+    state["sync_bg_task_post"] = "not executed"
+    state["async_bg_task_post"] = "not executed"
+
+    response = client.get("/sync_bg_after_yield")
+    assert response.status_code == 200
+    data = response.json()
+    assert data["sync_bg_endpoint"] == "started"
+    assert data["sync_bg_task_pre"] == "not executed"
+    assert data["async_bg_task_pre"] == "not executed"
+    assert data["sync_bg_task_post"] == "not executed"
+    assert data["async_bg_task_post"] == "not executed"
+    assert state["sync_bg_task_pre"] == "executed"
+    assert state["async_bg_task_pre"] == "executed"
+    assert state["sync_bg_task_post"] == "executed"
+    assert state["async_bg_task_post"] == "executed"
+
+
+def test_async_dependency_background_tasks_after_yield():
+    # Reset states before test
+    global state
+    state["sync_bg_task_pre"] = "not executed"
+    state["async_bg_task_pre"] = "not executed"
+    state["sync_bg_task_post"] = "not executed"
+    state["async_bg_task_post"] = "not executed"
+
+    response = client.get("/async_bg_after_yield")
+    assert response.status_code == 200
+    data = response.json()
+    assert data["async_bg_endpoint"] == "started"
+    assert data["sync_bg_task_pre"] == "not executed"
+    assert data["async_bg_task_pre"] == "not executed"
+    assert data["sync_bg_task_post"] == "not executed"
+    assert data["async_bg_task_post"] == "not executed"
+    assert state["sync_bg_task_pre"] == "executed"
+    assert state["async_bg_task_pre"] == "executed"
+    assert state["sync_bg_task_post"] == "executed"
+    assert state["async_bg_task_post"] == "executed"