events: show throw stack trace for uncaught exception

Show the stack trace for the `eventemitter.emit('error')` call
in the case of an uncaught exception.

Previously, there would be no clue in Node’s output about where
the actual `throw` comes from.

PR-URL: https://github.com/nodejs/node/pull/19003
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/test/parallel/test-events-uncaught-exception-stack.js b/test/parallel/test-events-uncaught-exception-stack.js
new file mode 100644
index 0000000000..c55322a5aa
--- /dev/null
+++ b/test/parallel/test-events-uncaught-exception-stack.js
@@ -0,0 +1,16 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const EventEmitter = require('events');
+
+// Tests that the error stack where the exception was thrown is *not* appended.
+
+process.on('uncaughtException', common.mustCall((err) => {
+  const lines = err.stack.split('\n');
+  assert.strictEqual(lines[0], 'Error');
+  lines.slice(1).forEach((line) => {
+    assert(/^    at/.test(line), `${line} has an unexpected format`);
+  });
+}));
+
+new EventEmitter().emit('error', new Error());