[Bug] TestClient for fastapi cause the req.client None error

[CharlieSeastar]

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• I had searched in the issues and found no similar issues.

Apache SkyWalking Component

Python Agent (apache/skywalking-python)

What happened

sw-fastapi plugin fail to set span.peers when using Fastapi TestClient

What you expected to happen

Fastapi TestClient work properly

How to reproduce

Adding decorator @trace to a custom middleware in Fastapi, and use TestClient to invoke any router.
in custom_middleware.py

class RequestAroundMiddleware(BaseHTTPMiddleware):
    def __init__(self, app, dispatch=None) -> None:
        super().__init__(app=app, dispatch=dispatch)

    @trace("request_around")
    async def dispatch(self, request: Request, call_next):
        return await call_next(request)

in test_demo.py

from fastapi.testclient import TestClient
def test_read_main():
    from main import app
    client = TestClient(app)
    response = client.get("/health")
    assert response.status_code == 200

run pytest
then

async def create_span(self, method, scope, req, send, receive):
        carrier = Carrier()
    
        for item in carrier:
            if item.key.capitalize() in req.headers:
                item.val = req.headers[item.key.capitalize()]
    
        span = NoopSpan(NoopContext()) if config.ignore_http_method_check(method) \
            else get_context().new_entry_span(op=dict(scope)['path'], carrier=carrier, inherit=Component.General)
    
        with span:
            span.layer = Layer.Http
            span.component = Component.FastAPI
>           span.peer = f'{req.client.host}:{req.client.port}'
E           AttributeError: 'NoneType' object has no attribute 'host'

in skywalking/plugins/sw_fastapi.py line 59

Anything else

No response

Are you willing to submit a pull request to fix on your own?

• Yes I am willing to submit a pull request on my own!

Code of Conduct

• I agree to follow this project's Code of Conduct

[kezhenxu94]

I’m not sure why you want to trace a TestClient? I think TestClient is for test only and don’t have a peer as expected

[CharlieSeastar]

I’m not sure why you want to trace a TestClient? I think TestClient is for test only and don’t have a peer as expected

Since this decorator is used in the actual code, it isn’t necessary to trace when running the FastAPI TestClient. However, it does impact the actual test results. I shouldn’t have to modify my code just to run tests

[kezhenxu94]

OK make sense