From 655b12dbfaa2c48f9fd38bbe8311e6f935045b30 Mon Sep 17 00:00:00 2001
From: Oscar Franco <ospfranco@gmail.com>
Date: Thu, 28 Dec 2023 04:23:58 -0800
Subject: [PATCH] Unhandled promise rejection - attach non-standard Error
 object stack info if possible (#42079)

Summary:
This is a continuation of my [last PR](https://github.com/facebook/react-native/pull/40914) which improved the symbolication of unhandled promise rejections.

While I was developing another library I noticed I still got an error stack of the log adding and not of the error itself. The library I'm trying to debug does not throw a standard error object but rather a custom one, but it still contains the stack field. By passing this stack field to the logbox call I was able to get a better symbolicated stack trace. The exact line of the failure is not displayed but at least the correct file is.

## Changelog:

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Pick one each for the category and type tags:

[GENERAL] [ADDED] - Unhandled promise rejection - attach non-standard Error object stack info if possible

For more details, see:
https://reactnative.dev/contributing/changelogs-in-pull-requests

Pull Request resolved: https://github.com/facebook/react-native/pull/42079

Test Plan:
Test any unhandled promise rejection with a non-standard error (line 23, toString must not return `[object Error]`) and see if the correct (or at least a better) stack trace is shown.

Here is the one I got before and after this change:

<img src="https://github.com/facebook/react-native/assets/1634213/3d07faad-9535-42c9-8032-b4d8fe407e88" width="200" />

<img src="https://github.com/facebook/react-native/assets/1634213/2c39bd82-c7a1-4f58-8ac4-5c479bb96b6e" width="200" />

Reviewed By: huntie

Differential Revision: D52431711

Pulled By: cipolleschi

fbshipit-source-id: be2172d3b1e2fc3f72812faac372c83bc6dface2
---
 .../Libraries/promiseRejectionTrackingOptions.js             | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/packages/react-native/Libraries/promiseRejectionTrackingOptions.js b/packages/react-native/Libraries/promiseRejectionTrackingOptions.js
index 5f9c9a1dafd880..7bc3de0a6b5988 100644
--- a/packages/react-native/Libraries/promiseRejectionTrackingOptions.js
+++ b/packages/react-native/Libraries/promiseRejectionTrackingOptions.js
@@ -34,6 +34,11 @@ let rejectionTrackingOptions: $NonMaybeType<Parameters<enable>[0]> = {
             ? rejection
             : JSON.stringify((rejection: $FlowFixMe));
       }
+      // It could although this object is not a standard error, it still has stack information to unwind
+      // $FlowFixMe ignore types just check if stack is there
+      if (rejection.stack && typeof rejection.stack === 'string') {
+        stack = rejection.stack;
+      }
     }
 
     const warning = `Possible unhandled promise rejection (id: ${id}):\n${