Make sure postRun is called after main() if main suspends (#24089)

await callMain(), which is an async function if JSPI is enabled.

Fixes #12402.

Author: msorvig

src/postamble.js

@@ -169,7 +169,7 @@ function run() {
     return;
   }
 
-  function doRun() {
+  {{{ asyncIf(ASYNCIFY == 2) }}}function doRun() {
     // run may have just been called through dependencies being fulfilled just in this very frame,
     // or while the async setStatus time below was happening
 #if ASSERTIONS
@@ -199,9 +199,9 @@ function run() {
 #if HAS_MAIN
     var noInitialRun = {{{ makeModuleReceiveExpr('noInitialRun', !INVOKE_RUN) }}};
 #if MAIN_READS_PARAMS
-    if (!noInitialRun) callMain(args);
+    if (!noInitialRun) {{{ awaitIf(ASYNCIFY == 2) }}}callMain(args);
 #else
-    if (!noInitialRun) callMain();
+    if (!noInitialRun) {{{ awaitIf(ASYNCIFY == 2) }}}callMain();
 #endif
 #else
 #if ASSERTIONS

test/other/hello_world_suspend.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2025 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+#include <stdio.h>
+#include <emscripten.h>
+
+int main() {
+  emscripten_sleep(1);
+  printf("hello, world!\n");
+  return 0;
+}

test/test_other.py

@@ -2865,6 +2865,13 @@ def test_prepost2(self):
     self.do_runf('hello_world.c', 'pre-run\nhello, world!\npost-run\n',
                  emcc_args=['--pre-js', 'pre.js', '--pre-js', 'pre2.js'])
 
+  @requires_jspi
+  def test_prepost_jspi(self):
+    create_file('pre.js', 'Module.preRun = () => out("pre-run");')
+    create_file('pre2.js', 'Module.postRun = () => out("post-run");')
+    self.do_runf('other/hello_world_suspend.c', 'pre-run\nhello, world!\npost-run\n',
+                 emcc_args=['--pre-js', 'pre.js', '--pre-js', 'pre2.js', '-sJSPI'])
+
   def test_prepre(self):
     create_file('pre.js', '''
       Module.preRun = [() => out('pre-run-0'), () => out('pre-run-1')];