promises: refactor rejection handling

Remove the unnecessary microTasksTickObject for scheduling microtasks
and instead use TickInfo to keep track of whether promise rejections
exist that need to be emitted. Consequently allow the microtasks to
execute on average fewer times, in more predictable manner than
previously.

Simplify unhandled & handled rejection tracking to do more in C++ to
avoid needing to expose additional info in JS.

When new unhandledRejections are emitted within an unhandledRejection
handler, allow the event loop to proceed first instead. This means
that if the end-user code handles all promise rejections on nextTick,
rejections within unhandledRejection now won't spiral into an infinite
loop.

PR-URL: https://github.com/nodejs/node/pull/18207
Fixes: https://github.com/nodejs/node/issues/17913
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

2 files changed, 14 insertions, 4 deletions

diff --git a/test/message/unhandled_promise_trace_warnings.out b/test/message/unhandled_promise_trace_warnings.out
index c9c7a5c870..069e6cc678 100644
--- a/test/message/unhandled_promise_trace_warnings.out
+++ b/test/message/unhandled_promise_trace_warnings.out
@@ -14,7 +14,6 @@
     at *
     at *
     at *
-    at *
 (node:*) Error: This was rejected
     at * (*test*message*unhandled_promise_trace_warnings.js:*)
     at *
@@ -34,9 +33,7 @@
     at *
     at *
 (node:*) PromiseRejectionHandledWarning: Promise rejection was handled asynchronously (rejection id: 1)
-    at getAsynchronousRejectionWarningObject (internal/process/promises.js:*)
-    at rejectionHandled (internal/process/promises.js:*)
-    at *
+    at handledRejection (internal/process/promises.js:*)
     at Promise.catch *
     at Immediate.setImmediate (*test*message*unhandled_promise_trace_warnings.js:*)
     at *
diff --git a/test/parallel/test-promises-unhandled-rejections.js b/test/parallel/test-promises-unhandled-rejections.js
index ed5d485ac7..1ade061994 100644
--- a/test/parallel/test-promises-unhandled-rejections.js
+++ b/test/parallel/test-promises-unhandled-rejections.js
@@ -684,3 +684,16 @@ asyncTest('Throwing an error inside a rejectionHandled handler goes to' +
     }
   }, 1);
 });
+
+asyncTest('Rejected promise inside unhandledRejection allows nextTick loop' +
+          ' to proceed first', function(done) {
+  clean();
+  Promise.reject(0);
+  let didCall = false;
+  process.on('unhandledRejection', () => {
+    assert(!didCall);
+    didCall = true;
+    const promise = Promise.reject(0);
+    process.nextTick(() => promise.catch(() => done()));
+  });
+});