GZipMiddleware appears to not honor minimize_size

[flashgorman-chorus]

I have installed GZipMiddleware with a minimize_size set to 1024. When I make a request that returns a response smaller than 1024, I expect the response will not be compressed and the Content-Encoding header will not be set to gzip.

My testing, however, shows that the responses are always compressed and Content-Encoding is always set to gzip.

Debugging the code, I see send_with_gzip is called but message["more_body"] is set to True the first time through, no matter what, from testclient.py:

    async def stream_response(self, send: Send) -> None:
        await send(
            {
                "type": "http.response.start",
                "status": self.status_code,
                "headers": self.raw_headers,
            }
        )
        async for chunk in self.body_iterator:
            if not isinstance(chunk, bytes):
                chunk = chunk.encode(self.charset)
            await send({"type": "http.response.body", "body": chunk, "more_body": True})

        await send({"type": "http.response.body", "body": b"", "more_body": False})

As a result, the key block of code in gzip.py that I expected to enter is skipped:

if len(body) < self.minimum_size and not more_body:
    # Don't apply GZip to small outgoing responses.
    await self.send(self.initial_message)
    await self.send(message)

Since more_body is True, it never enters this block. Perhaps this is just an aberration of the test client? Or I am doing something wrong?

[Kludex]

I've created #2003 from this discussion to make an investigation. Thanks. 👍