feat: default to 204 No Content for empty response body

Author: cablehead

README.md

@@ -218,7 +218,7 @@ Set HTTP response status and headers using nushell's pipeline metadata:
 
 ```nushell
 "body" | metadata set --merge {'http.response': {
-  status: <number>  # Optional, HTTP status code (default: 200)
+  status: <number>  # Optional, defaults to 204 if body is empty, 200 otherwise
   headers: {        # Optional, HTTP headers
     <key>: <value>  # Single value: "text/plain"
     <key>: [<value>, <value>]  # Multiple values: ["cookie1=a", "cookie2=b"]

src/handler.rs

@@ -325,7 +325,11 @@ async fn build_normal_response(
 ) -> HTTPResult {
     let request_id = guard.request_id();
     let (inferred_content_type, http_meta, body) = pipeline_result;
-    let status = http_meta.status.unwrap_or(200);
+    let status = match (http_meta.status, &body) {
+        (Some(s), _) => s,
+        (None, ResponseTransport::Empty) => 204,
+        (None, _) => 200,
+    };
     let mut builder = hyper::Response::builder().status(status);
     let mut header_map = hyper::header::HeaderMap::new();
 

src/test_handler.rs

@@ -238,6 +238,17 @@ async fn test_content_type_precedence() {
         resp5.headers().get("content-type").is_none(),
         "Empty body should not have Content-Type header"
     );
+
+    // 6. Empty body defaults to 204 No Content
+    let req6 = Request::builder()
+        .uri("/")
+        .body(Empty::<Bytes>::new())
+        .unwrap();
+    let engine = Arc::new(ArcSwap::from_pointee(test_engine(r#"{|req| null}"#)));
+    let resp6 = handle(engine.clone(), None, no_trusted_proxies(), req6)
+        .await
+        .unwrap();
+    assert_eq!(resp6.status(), 204, "Empty body should default to 204");
 }
 
 #[tokio::test]