fix: response throwing error due to javascript bug (#117)

* fix: response throwing error due to javascript Typed Array prototype design fault

* server: support ArrayBuffer response

* Add comments

---------

Co-authored-by: Frank <wangfanjie@gmail.com>

.changeset/polite-rice-learn.md

@@ -0,0 +1,5 @@
+---
+"open-next": patch
+---
+
+server: support ArrayBuffer response

packages/open-next/src/adapters/response.ts

@@ -11,24 +11,29 @@ const BODY = Symbol();
 const HEADERS = Symbol();
 
 function getString(data) {
+  // Note: use `ArrayBuffer.isView()` to check for Uint8Array. Using
+  //       `instanceof Uint8Array` returns false in some cases. For example,
+  //       when the buffer is created in middleware and passed to NextServer.
   if (Buffer.isBuffer(data)) {
     return data.toString("utf8");
+  } else if (ArrayBuffer.isView(data)) {
+    return Buffer.from(data).toString("utf8");
   } else if (typeof data === "string") {
     return data;
   } else {
-    throw new Error(`response.write() of unexpected type: ${typeof data}`);
+    throw new Error(`response.getString() of unexpected type: ${typeof data}`);
   }
 }
 
 function addData(stream, data) {
   if (
     Buffer.isBuffer(data) ||
-    typeof data === "string" ||
-    data instanceof Uint8Array
+    ArrayBuffer.isView(data) ||
+    typeof data === "string"
   ) {
     stream[BODY].push(Buffer.from(data));
   } else {
-    throw new Error(`response.write() of unexpected type: ${typeof data}`);
+    throw new Error(`response.addData() of unexpected type: ${typeof data}`);
   }
 }