Discard Content-Length: NaN header, closes honojs/hono#520

Temporary workaround until cloudflare/kv-asset-handler#295 released

packages/http-server/src/index.ts

@@ -162,7 +162,8 @@ async function writeResponse(
       // @ts-expect-error getAll is added to the Headers prototype by
       // importing @miniflare/core
       headers["set-cookie"] = response.headers.getAll("set-cookie");
-    } else {
+    } else if (key !== "content-length") {
+      // Content-Length has special handling below
       headers[key] = value;
     }
   }
@@ -174,7 +175,9 @@ async function writeResponse(
   const contentLength =
     _getBodyLength(response) ??
     (contentLengthHeader === null ? null : parseInt(contentLengthHeader));
-  if (contentLength !== null) headers["content-length"] = contentLength;
+  if (contentLength !== null && !isNaN(contentLength)) {
+    headers["content-length"] = contentLength;
+  }
 
   // If a Content-Encoding is set, and the user hasn't encoded the body,
   // we're responsible for doing so.

packages/http-server/test/index.spec.ts

@@ -446,6 +446,20 @@ test("createRequestListener: displays appropriately-formatted error page", async
   });
   t.is(headers["content-type"], "text/plain; charset=UTF-8");
 });
+test("createRequestListener: discards Content-Length header if invalid", async (t) => {
+  // https://github.com/honojs/hono/issues/520
+  const mf = useMiniflareWithHandler({ HTTPPlugin }, {}, (globals) => {
+    const res = new globals.Response("string");
+    return new globals.Response(res.body, {
+      headers: { "Content-Length": "undefined" },
+    });
+  });
+  const port = await listen(t, http.createServer(createRequestListener(mf)));
+  const [body, headers] = await request(port);
+  t.is(body, "string");
+  t.is(headers["content-length"], undefined);
+  t.is(headers["transfer-encoding"], "chunked");
+});
 test("createRequestListener: includes live reload script in html responses if enabled", async (t) => {
   const mf = useMiniflareWithHandler({ HTTPPlugin }, {}, (globals) => {
     return new globals.Response(