From eb72c7fab63edaba536c240ab89b695e1c933254 Mon Sep 17 00:00:00 2001
From: David Maskasky <dmaskasky@gmail.com>
Date: Thu, 14 Nov 2024 12:37:14 -0800
Subject: [PATCH] fix: rethrow falsy errors thrown in flushPending

---
 src/vanilla/store.ts         | 10 +++++-----
 tests/vanilla/store.test.tsx | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/vanilla/store.ts b/src/vanilla/store.ts
index 3684c00e65c..215ef8948f5 100644
--- a/src/vanilla/store.ts
+++ b/src/vanilla/store.ts
@@ -199,13 +199,13 @@ const addPendingFunction = (pending: Pending, fn: () => void) => {
 }
 
 const flushPending = (pending: Pending) => {
-  let error: unknown | undefined
+  const ref: { e?: AnyError } = {}
   const call = (fn: () => void) => {
     try {
       fn()
     } catch (e) {
-      if (!error) {
-        error = e
+      if (!('e' in ref)) {
+        ref.e = e
       }
     }
   }
@@ -218,8 +218,8 @@ const flushPending = (pending: Pending) => {
     atomStates.forEach((atomState) => atomState.m?.l.forEach(call))
     functions.forEach(call)
   }
-  if (error) {
-    throw error
+  if ('e' in ref) {
+    throw ref.e
   }
 }
 
diff --git a/tests/vanilla/store.test.tsx b/tests/vanilla/store.test.tsx
index 8a765240a06..9905909ea8a 100644
--- a/tests/vanilla/store.test.tsx
+++ b/tests/vanilla/store.test.tsx
@@ -876,3 +876,23 @@ describe('should mount and trigger listeners even when an error is thrown', () =
     expect(listener).toHaveBeenCalledOnce()
   })
 })
+
+it('throws falsy errors in onMount, onUnmount, and listeners', () => {
+  const store = createStore()
+  const a = atom(0)
+  a.onMount = () => {
+    throw ''
+  }
+  expect(() => store.sub(a, () => {})).toThrow('')
+  const b = atom(0)
+  b.onMount = () => () => {
+    throw ''
+  }
+  const unsub = store.sub(b, () => {})
+  expect(() => unsub()).toThrow('')
+  const c = atom(0)
+  store.sub(c, () => {
+    throw ''
+  })
+  expect(() => store.set(c, 1)).toThrow('')
+})