From be9bc237f29d58778f426cdc456066bb4c5b8b5a Mon Sep 17 00:00:00 2001
From: Pat Hickey <p.hickey@f5.com>
Date: Tue, 25 Nov 2025 17:20:41 -0800
Subject: [PATCH] NFC: simplify internals of http::response::try_from_incoming

---
 src/http/response.rs | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/src/http/response.rs b/src/http/response.rs
index d0af77e..2ab8d87 100644
--- a/src/http/response.rs
+++ b/src/http/response.rs
@@ -2,7 +2,7 @@ use http::StatusCode;
 use wasip2::http::types::IncomingResponse;
 
 use crate::http::body::{Body, BodyHint};
-use crate::http::error::{Context, Error};
+use crate::http::error::Error;
 use crate::http::fields::{HeaderMap, header_map_from_wasi};
 
 pub use http::response::{Builder, Response};
@@ -22,10 +22,17 @@ pub(crate) fn try_from_incoming(incoming: IncomingResponse) -> Result<Response<B
     let body = Body::from_incoming(incoming_body, hint);
 
     let mut builder = Response::builder().status(status);
-
-    if let Some(headers_mut) = builder.headers_mut() {
-        *headers_mut = headers;
-    }
-
-    builder.body(body).context("building response")
+    // The [`http::response::Builder`] keeps internal state of whether the
+    // builder has errored, which is only reachable by passing
+    // [`Builder::header`] an erroring `TryInto<HeaderName>` or
+    // `TryInto<HeaderValue>`. Since the `Builder::header` method is never
+    // used, we know `Builder::headers_mut` will never give the None case, nor
+    // will `Builder::body` give the error case. So, rather than treat those
+    // as control flow, we unwrap if this invariant is ever broken because
+    // that would only be possible due to some unrecoverable bug in wstd,
+    // rather than incorrect use or invalid input.
+    *builder.headers_mut().expect("builder has not errored") = headers;
+    Ok(builder
+        .body(body)
+        .expect("response builder should not error"))
 }