Split out response header munging to separate function

src/commands/dev/mod.rs

@@ -7,6 +7,7 @@ use hyper::client::{HttpConnector, ResponseFuture};
 use hyper::header::{HeaderMap, HeaderName, HeaderValue};
 use hyper::service::{make_service_fn, service_fn};
 use hyper::{Body, Client, Request, Response, Server, Uri};
+use hyper::http::response::Parts;
 use hyper::http::uri::InvalidUri;
 
 use hyper_tls::HttpsConnector;
@@ -56,18 +57,7 @@ pub async fn dev(
 
                     let (mut parts, body) = resp.into_parts();
 
-                    let mut headers = HeaderMap::new();
-
-                    for header in &parts.headers {
-                        let (name, value) = header;
-                        let name = name.as_str();
-                        if name.starts_with(HEADER_PREFIX) {
-                            let header_name = &name[HEADER_PREFIX.len()..];
-                            let header_name = HeaderName::from_bytes(header_name.as_bytes())?;
-                            headers.insert(header_name, value.clone());
-                        }
-                    }
-                    parts.headers = headers;
+                    munge_response_headers(&mut parts)?;
 
                     let resp = Response::from_parts(parts, body);
                     Ok::<_, failure::Error>(resp)
@@ -84,6 +74,22 @@ pub async fn dev(
     Ok(())
 }
 
+fn munge_response_headers(parts: &mut Parts) -> Result<(), failure::Error> {
+    let mut headers = HeaderMap::new();
+
+    for header in &parts.headers {
+        let (name, value) = header;
+        let name = name.as_str();
+        if name.starts_with(HEADER_PREFIX) {
+            let header_name = &name[HEADER_PREFIX.len()..];
+            let header_name = HeaderName::from_bytes(header_name.as_bytes())?;
+            headers.insert(header_name, value.clone());
+        }
+    }
+    parts.headers = headers;
+    Ok(())
+}
+
 fn get_preview_url(path_string: &str) -> Result<Uri, InvalidUri> {
     format!("https://{}{}", PREVIEW_HOST, path_string).parse()
 }