From 1cb8cc840e604a1529f6458e60039bf401761841 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
Date: Tue, 23 Dec 2025 17:16:17 -0800
Subject: [PATCH] Error if __async decorator applied to JS-only symbol

The `__async` decorator marks JS function as async when they are
imported into Wasm.  It basically adds functions to `ASYNCIFY_IMPORTS`.

It makes not sense to apply this decorator to a JS-only symbol.
---
 src/lib/libpthread.js | 3 ---
 src/utility.mjs       | 7 +++++++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/lib/libpthread.js b/src/lib/libpthread.js
index 54c2f913cdc32..aa3a59f69eb29 100644
--- a/src/lib/libpthread.js
+++ b/src/lib/libpthread.js
@@ -1077,9 +1077,6 @@ var LibraryPThread = {
     '$runtimeKeepaliveCounter',
 #endif
   ],
-#if ASYNCIFY
-  $invokeEntryPoint__async: true,
-#endif
   $invokeEntryPoint: {{{ asyncIf(ASYNCIFY == 2) }}}(ptr, arg) => {
 #if PTHREADS_DEBUG
     dbg(`invokeEntryPoint: ${ptrToString(ptr)}`);
diff --git a/src/utility.mjs b/src/utility.mjs
index f3ffa770118ba..d9123a12be99b 100644
--- a/src/utility.mjs
+++ b/src/utility.mjs
@@ -151,6 +151,13 @@ export function mergeInto(obj, other, options = null) {
       const decoratorName = key.slice(index);
       const type = typeof other[key];
 
+      if (decoratorName == '__async') {
+        const decorated = key.slice(0, index);
+        if (isJsOnlySymbol(decorated)) {
+          error(`__async decorator applied to JS symbol: ${decorated}`);
+        }
+      }
+
       // Specific type checking for `__deps` which is expected to be an array
       // (not just any old `object`)
       if (decoratorName === '__deps') {