starlette < 0.17.0 doesn't give exception tracebacks when testing app

[kevr]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
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• I already read and followed all the tutorial in the docs and didn't find an answer.
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Example Code

# asgi app definition
from fastapi import FastAPI, Request

app = FastAPI()

@app.get("/")
async def root(request: Request):
    raise Exception("Blah blah")

# pytest unit
import pytest

from fastapi.testclient import TestClient

from .asgi import app

@pytest.fixture
def client() -> TestClient:
    yield TestClient(app=app)

def test_app(client: TestClient):
    with client as request:
        response = request.get("/")
    assert response.status_code == 200

Description

Run the pytest suite, an exception is raised, causing a nonsensical traceback. This nonsensical traceback is generated by starlette==0.16.0.

It has been resolved in starlette==0.17.0 partially; enough that we actual get information about the original exception. FastAPI has not yet however released a version which depends on starlette==0.17.0, meaning we cannot yet use it through Python package managers which depend on version resolution.

If you run the aforementioned example, you will see exactly what I mean. You end up getting exceptions purely about anyio failing and not the original exception; essentially hiding the real cause of the test failure.

It currently emits a RuntimeError("No response returned.")

Operating System

Linux

Operating System Details

Arch Linux

FastAPI Version

0.70.0

Python Version

3.9.5

Additional Context

No response

[ehiggs]

This will be solved by #4145

[yezz123]

Downgrade your starlette version or wait until #4145 being merged to fix this issue

[Kludex]

You can also pin the commit/branch on your requirements i.e. https://stackoverflow.com/a/13754517

For simple install, you can do: python -m pip install git+git://github.com/simondale00/fastapi.git@upgrade-starlette-0.17.0

But better to fork and apply your own changes rather than using third-party branches, jfyk.

[kevr]

Ahh, gotcha. Sorry, I tried searching, but guess I searched incorrectly there.

Thanks guys!