Avoid duplicate response headers on Elysia 1.4.18 and earlier

CHANGES.md

@@ -8,6 +8,16 @@ Version 1.8.16
 
 To be released.
 
+### @fedify/elysia
+
+ -  Fixed duplicate response headers on Elysia 1.4.18 and earlier, which
+    append both `set.headers` and the returned `Response`'s own headers
+    without deduplication.  The `fedify()` plugin no longer sets the headers
+    in both places.  [[#970], [#972] by dktsudgg]
+
+[#970]: https://github.com/fedify-dev/fedify/issues/970
+[#972]: https://github.com/fedify-dev/fedify/pull/972
+
 
 Version 1.8.15
 --------------

packages/elysia/src/index.ts

@@ -42,15 +42,15 @@ export const fedify = <TContextData = unknown>(
         if (!notFound && !notAcceptable) {
           set.status = response.status;
 
-          response.headers.forEach((value, key) => {
-            set.headers[key] = value;
-          });
-
           // Return response body if it exists
           if (response.body) {
             return response;
           }
 
+          response.headers.forEach((value, key) => {
+            set.headers[key] = value;
+          });
+
           // Return empty response for successful requests without body
           return new Response(null, { status: response.status });
         }