Response::chunk(...) will return Ok(Some([])) before returning Ok(None) at the end of the response under certain circumstances #2841
Description
When processing a response body one response.chunk() at a time, sometimes a single Ok(Some([])) (0-byte chunk) will be returned before the response starts returning Ok(None).
I am not 100% certain exactly what causes this but it seems to require both rustls and http2 to be enabled, and also be dependant on the remote server and the response being large enough.
here is a simple reproducer case
[package]
name = "httpbugtest"
version = "0.1.0"
edition = "2024"
[dependencies]
reqwest = { version = "0.12.24", default-features = false, features = ["rustls-tls", "rustls-tls-webpki-roots", "http2"] }
tokio = { version = "1.48.0", features = ["macros", "rt-multi-thread"] }
#[tokio::main]
async fn main() {
let client = reqwest::Client::new();
let mut response = client
.get("https://bunny.net/")
.send().await.unwrap();
let mut total_bytes = 0;
while let Some(chunk) = response.chunk().await.unwrap() {
total_bytes += chunk.len();
if chunk.len() == 0 {
eprintln!("Zero-length chunk received at offset={total_bytes}");
}
}
eprintln!("Total bytes received: {}", total_bytes);
}