fix(runtime/http): fix empty blob response (#10689)

cli/tests/unit/http_test.ts

@@ -317,3 +317,25 @@ unitTest(
     await promise;
   },
 );
+
+unitTest(
+  { perms: { net: true } },
+  async function httpServerEmptyBlobResponse() {
+    const promise = (async () => {
+      const listener = Deno.listen({ port: 4501 });
+      const conn = await listener.accept();
+      const httpConn = Deno.serveHttp(conn);
+      const event = await httpConn.nextRequest();
+      assert(event);
+      const { respondWith } = event;
+      await respondWith(new Response(new Blob([])));
+      httpConn.close();
+      listener.close();
+    })();
+
+    const resp = await fetch("http://127.0.0.1:4501/");
+    const respBody = await resp.text();
+    assertEquals("", respBody);
+    await promise;
+  },
+);

runtime/js/40_http.js

@@ -132,10 +132,13 @@
           } else {
             const reader = innerResp.body.stream.getReader();
             const r1 = await reader.read();
-            if (r1.done) throw new TypeError("Unreachable");
+            if (r1.done) {
-            respBody = r1.value;
+              respBody = new Uint8Array(0);
-            const r2 = await reader.read();
+            } else {
-            if (!r2.done) throw new TypeError("Unreachable");
+              respBody = r1.value;
+              const r2 = await reader.read();
+              if (!r2.done) throw new TypeError("Unreachable");
+            }
           }
         } else {
           innerResp.body.streamOrStatic.consumed = true;