From 054139d15cb03ee2e8ec1031fa23dd5a6750adf0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebasti=C3=A1n=20Ram=C3=ADrez?= <tiangolo@gmail.com>
Date: Sun, 21 Sep 2025 15:47:13 +0200
Subject: [PATCH] =?UTF-8?q?=E2=9C=85=20Add=20tests=20for=20dependency=20wi?=
 =?UTF-8?q?th=20yield=20catching=20exceptions=20and=20re-raising?=
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---
 tests/test_dependency_after_yield_raise.py | 63 ++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 tests/test_dependency_after_yield_raise.py

diff --git a/tests/test_dependency_after_yield_raise.py b/tests/test_dependency_after_yield_raise.py
new file mode 100644
index 000000000..31c646e08
--- /dev/null
+++ b/tests/test_dependency_after_yield_raise.py
@@ -0,0 +1,63 @@
+from typing import Annotated, Any
+
+import pytest
+from fastapi import Depends, FastAPI, HTTPException
+from fastapi.testclient import TestClient
+
+
+class CustomError(Exception):
+    pass
+
+
+def catching_dep() -> Any:
+    try:
+        yield "s"
+    except CustomError as err:
+        raise HTTPException(status_code=418, detail="Session error") from err
+
+
+def broken_dep() -> Any:
+    yield "s"
+    raise ValueError("Broken after yield")
+
+
+app = FastAPI()
+
+
+@app.get("/catching")
+def catching(d: Annotated[str, Depends(catching_dep)]) -> Any:
+    raise CustomError("Simulated error during streaming")
+
+
+@app.get("/broken")
+def broken(d: Annotated[str, Depends(broken_dep)]) -> Any:
+    return {"message": "all good?"}
+
+
+client = TestClient(app)
+
+
+def test_catching():
+    response = client.get("/catching")
+    assert response.status_code == 418
+    assert response.json() == {"detail": "Session error"}
+
+
+def test_broken_catch():
+    """
+    When a dependency with yield raises after the yield (not in an except), the
+    response is already "successfully" sent back to the client, but there's still
+    an error in the server afterwards, an exception is raised and captured or shown
+    in the server logs.
+    """
+    with pytest.raises(ValueError, match="Broken after yield"):
+        response = client.get("/broken")
+        assert response.status_code == 200
+        assert response.json() == {"message": "all good?"}
+
+
+def test_broken_return_finishes():
+    client = TestClient(app, raise_server_exceptions=False)
+    response = client.get("/broken")
+    assert response.status_code == 200
+    assert response.json() == {"message": "all good?"}