From e8812dcada2310f3e9bc2ffdcc74ffa47428841e Mon Sep 17 00:00:00 2001
From: Justin Bennett <zephraph@gmail.com>
Date: Tue, 30 Mar 2021 22:55:03 -0400
Subject: [PATCH] Add flushSync to preact-compat

---
 compat/src/index.js | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/compat/src/index.js b/compat/src/index.js
index e0c907361e..2fa033cdab 100644
--- a/compat/src/index.js
+++ b/compat/src/index.js
@@ -101,6 +101,17 @@ function findDOMNode(component) {
 // eslint-disable-next-line camelcase
 const unstable_batchedUpdates = (callback, arg) => callback(arg);
 
+/** 
+ * In React, `flushSync` flushes the entire tree and forces a rerender. It's
+ * implmented here as a no-op.
+ * @template Arg
+ * @template Result
+ * @param {(arg: Arg) => Result} callback function that runs before the flush
+ * @param {Arg} [arg] Optional arugment that can be passed to the callback
+ * @returns 
+ */
+const flushSync = (callback, arg) => callback(arg)
+
 /**
  * Strict Mode is not implemented in Preact, so we provide a stand-in for it
  * that just renders its children without imposing any restrictions.
@@ -127,6 +138,7 @@ export {
 	PureComponent,
 	memo,
 	forwardRef,
+	flushSync,
 	// eslint-disable-next-line camelcase
 	unstable_batchedUpdates,
 	StrictMode,
@@ -166,6 +178,7 @@ export default {
 	PureComponent,
 	memo,
 	forwardRef,
+	flushSync,
 	unstable_batchedUpdates,
 	StrictMode,
 	Suspense,