From 208c91b68f4ae1b59e65acbde3de729e7058bb5e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bartek=20Iwa=C5=84czuk?= <biwanczuk@gmail.com>
Date: Fri, 23 Dec 2022 19:46:24 +0100
Subject: fix(core): run macrotasks and next ticks after polling dynamic
 imports (#17173)

This commit fixes handling of rejected promises in dynamic imports
evaluation.

Previously we were running callbacks for next ticks and macrotasks
_before_ polling
dynamic imports and checked for unhandled rejections immediately after.
This is wrong,
as `unhandledrejection` event is dispatched and its callbacks are run as
macrotasks.

This commit changes order of actions performed by the event loop to
following:
- poll async ops
- poll dynamic imports
- run next tick callbacks
- run macrotask callbacks
- check for unhandled promise rejections
---
 core/runtime.rs | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

(limited to 'core/runtime.rs')

diff --git a/core/runtime.rs b/core/runtime.rs
index 2e417bb9d..f735f5575 100644
--- a/core/runtime.rs
+++ b/core/runtime.rs
@@ -1127,12 +1127,7 @@ impl JsRuntime {
     self.pump_v8_message_loop()?;
 
     // Ops
-    {
-      self.resolve_async_ops(cx)?;
-      self.drain_nexttick()?;
-      self.drain_macrotasks()?;
-      self.check_promise_exceptions()?;
-    }
+    self.resolve_async_ops(cx)?;
     // Dynamic module loading - ie. modules loaded using "import()"
     {
       // Run in a loop so that dynamic imports that only depend on another
@@ -1157,9 +1152,13 @@ impl JsRuntime {
           break;
         }
       }
-
-      self.check_promise_exceptions()?;
     }
+    // Run all next tick callbacks and macrotasks callbacks and only then
+    // check for any promise exceptions (`unhandledrejection` handlers are
+    // run in macrotasks callbacks so we need to let them run first).
+    self.drain_nexttick()?;
+    self.drain_macrotasks()?;
+    self.check_promise_exceptions()?;
 
     // Event loop middlewares
     let mut maybe_scheduling = false;
-- 
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