Update event loop stall handling (#139)

builtins/web/fetch/fetch_event.cpp

@@ -594,7 +594,7 @@ bool handle_incoming_request(host_api::HttpIncomingRequest *request) {
   }
 
   if (!success) {
-    fprintf(stderr, "Internal error.");
+    fprintf(stderr, "Warning: JS event loop terminated without completing the request.\n");
   }
 
   if (ENGINE->debug_logging_enabled() && ENGINE->has_pending_async_tasks()) {

runtime/event_loop.cpp

@@ -80,8 +80,6 @@ bool EventLoop::run_event_loop(api::Engine *engine, double total_compute) {
     if (tasks_size == 0) {
       exit_event_loop();
       MOZ_ASSERT(!interest_complete());
-      fprintf(stderr, "event loop error - both task and job queues are empty, but expected "
-                      "operations did not resolve");
       return false;
     }
 

tests/e2e/eventloop-stall/eventloop-stall.js

@@ -0,0 +1,13 @@
+import { strictEqual, deepStrictEqual, throws } from "../../assert.js";
+
+addEventListener("fetch", (evt) =>
+  evt.respondWith(
+    (async () => {
+      return new Response(new ReadableStream({
+        start(_controller) {
+          // stall
+        },
+      }));
+    })()
+  )
+);

tests/e2e/eventloop-stall/expect_serve_stderr.txt

@@ -0,0 +1 @@
+stderr [0] :: Warning: JS event loop terminated without completing the request.

tests/tests.cmake

@@ -30,6 +30,7 @@ function(test_integration TEST_NAME)
     set_tests_properties(integration-${TEST_NAME} PROPERTIES TIMEOUT 120)
 endfunction()
 
+test_e2e(eventloop-stall)
 test_e2e(headers)
 test_e2e(runtime-err)
 test_e2e(smoke)