[JSPI] Do not automatically wrap async library functions. (#24550)

In a number of places library functions (e.g.
`emscripten_async_wget_data`) use an `async` JS functions, but they do
not actually want to use JSPI wrappers. Change it so functions must
explicitly use `foo__async: true` to enable JSPI wrappers.

Fixes #20289

Author: brendandahl

ChangeLog.md

@@ -34,6 +34,10 @@ See docs/process.md for more on how version tagging works.
   for chrome, or
     emrun --browser=firefox --browser-args=-headless [..]
   for firefox. (#24537)
+- When JSPI is enabled `async` library functions are no longer automatically
+  wrapped with `WebAssembly.Suspending` functions. To automatically wrap library
+  functions for use with JSPI they must now explicitly set
+  `myLibraryFunction__async: true`.
 
 4.0.10 - 06/07/25
 -----------------

src/jsifier.mjs

@@ -534,9 +534,7 @@ function(${args}) {
       if (ASYNCIFY) {
         const original = LibraryManager.library[symbol];
         if (typeof original == 'function') {
-          isAsyncFunction =
-            LibraryManager.library[symbol + '__async'] ||
-            original.constructor.name == 'AsyncFunction';
+          isAsyncFunction = LibraryManager.library[symbol + '__async'];
         }
         if (isAsyncFunction) {
           asyncFuncs.push(symbol);

src/lib/libasync.js

@@ -559,6 +559,7 @@ addToLibrary({
 #endif
 
   _load_secondary_module__sig: 'v',
+  _load_secondary_module__async: true,
   _load_secondary_module: async function() {
     // Mark the module as loading for the wasm module (so it doesn't try to load it again).
     wasmExports['load_secondary_module_status'].value = 1;

src/lib/libpthread.js

@@ -1026,6 +1026,9 @@ var LibraryPThread = {
     '$runtimeKeepaliveCounter',
 #endif
   ],
+#if ASYNCIFY
+  $invokeEntryPoint__async: true,
+#endif
   $invokeEntryPoint: {{{ asyncIf(ASYNCIFY == 2) }}}(ptr, arg) => {
 #if PTHREADS_DEBUG
     dbg(`invokeEntryPoint: ${ptrToString(ptr)}`);

src/lib/libwasmfs_opfs.js

@@ -69,6 +69,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_init_root_directory__deps: ['$wasmfsOPFSDirectoryHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_init_root_directory__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_init_root_directory: async function(ctx) {
     // allocated.length starts off as 1 since 0 is a reserved handle
     if (wasmfsOPFSDirectoryHandles.allocated.length == 1) {
@@ -88,6 +89,7 @@ addToLibrary({
   // corresponding to the error.
   $wasmfsOPFSGetOrCreateFile__deps: ['$wasmfsOPFSDirectoryHandles',
                                      '$wasmfsOPFSFileHandles'],
+  $wasmfsOPFSGetOrCreateFile__async: {{{ !PTHREADS }}},
   $wasmfsOPFSGetOrCreateFile: async function(parent, name, create) {
     let parentHandle = wasmfsOPFSDirectoryHandles.get(parent);
     let fileHandle;
@@ -112,6 +114,7 @@ addToLibrary({
   // it if it doesn't exist and `create` or otherwise return a negative error
   // code corresponding to the error.
   $wasmfsOPFSGetOrCreateDir__deps: ['$wasmfsOPFSDirectoryHandles'],
+  $wasmfsOPFSGetOrCreateDir__async: {{{ !PTHREADS }}},
   $wasmfsOPFSGetOrCreateDir: async function(parent, name, create) {
     let parentHandle = wasmfsOPFSDirectoryHandles.get(parent);
     let childHandle;
@@ -135,6 +138,7 @@ addToLibrary({
 
   _wasmfs_opfs_get_child__deps: ['$wasmfsOPFSGetOrCreateFile',
                                  '$wasmfsOPFSGetOrCreateDir', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_get_child__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_get_child:
       async function(ctx, parent, namePtr, childTypePtr, childIDPtr) {
     let name = UTF8ToString(namePtr);
@@ -155,6 +159,7 @@ addToLibrary({
     '$stackRestore',
     '_wasmfs_opfs_record_entry',
   ],
+  _wasmfs_opfs_get_entries__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_get_entries: async function(ctx, dirID, entriesPtr, errPtr) {
     let dirHandle = wasmfsOPFSDirectoryHandles.get(dirID);
 
@@ -179,6 +184,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_insert_file__deps: ['$wasmfsOPFSGetOrCreateFile', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_insert_file__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_insert_file: async function(ctx, parent, namePtr, childIDPtr) {
     let name = UTF8ToString(namePtr);
     let childID = await wasmfsOPFSGetOrCreateFile(parent, name, true);
@@ -187,6 +193,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_insert_directory__deps: ['$wasmfsOPFSGetOrCreateDir', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_insert_directory__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_insert_directory:
       async function(ctx, parent, namePtr, childIDPtr) {
     let name = UTF8ToString(namePtr);
@@ -198,6 +205,7 @@ addToLibrary({
   _wasmfs_opfs_move_file__deps: ['$wasmfsOPFSFileHandles',
                                  '$wasmfsOPFSDirectoryHandles',
                                  '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_move_file__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_move_file: async function(ctx, fileID, newParentID, namePtr, errPtr) {
     let name = UTF8ToString(namePtr);
     let fileHandle = wasmfsOPFSFileHandles.get(fileID);
@@ -212,6 +220,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_remove_child__deps: ['$wasmfsOPFSDirectoryHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_remove_child__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_remove_child: async function(ctx, dirID, namePtr, errPtr) {
     let name = UTF8ToString(namePtr);
     let dirHandle = wasmfsOPFSDirectoryHandles.get(dirID);
@@ -240,6 +249,7 @@ addToLibrary({
                                    '$wasmfsOPFSCreateAsyncAccessHandle'
 #endif
                                   ],
+  _wasmfs_opfs_open_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_open_access: async function(ctx, fileID, accessIDPtr) {
     let fileHandle = wasmfsOPFSFileHandles.get(fileID);
     let accessID;
@@ -279,6 +289,7 @@ addToLibrary({
 
   _wasmfs_opfs_open_blob__deps: ['$wasmfsOPFSFileHandles',
                                  '$wasmfsOPFSBlobs', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_open_blob__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_open_blob: async function(ctx, fileID, blobIDPtr) {
     let fileHandle = wasmfsOPFSFileHandles.get(fileID);
     let blobID;
@@ -300,6 +311,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_close_access__deps: ['$wasmfsOPFSAccessHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_close_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_close_access: async function(ctx, accessID, errPtr) {
     let accessHandle = wasmfsOPFSAccessHandles.get(accessID);
     try {
@@ -319,6 +331,7 @@ addToLibrary({
 
   _wasmfs_opfs_read_access__i53abi: true,
   _wasmfs_opfs_read_access__deps: ['$wasmfsOPFSAccessHandles'],
+  _wasmfs_opfs_read_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_read_access: {{{ asyncIf(!PTHREADS) }}}function(accessID, bufPtr, len, pos) {
     let accessHandle = wasmfsOPFSAccessHandles.get(accessID);
     let data = HEAPU8.subarray(bufPtr, bufPtr + len);
@@ -337,6 +350,7 @@ addToLibrary({
 
   _wasmfs_opfs_read_blob__i53abi: true,
   _wasmfs_opfs_read_blob__deps: ['$wasmfsOPFSBlobs', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_read_blob__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_read_blob: async function(ctx, blobID, bufPtr, len, pos, nreadPtr) {
     let blob = wasmfsOPFSBlobs.get(blobID);
     let slice = blob.slice(pos, pos + len);
@@ -367,6 +381,7 @@ addToLibrary({
 
   _wasmfs_opfs_write_access__i53abi: true,
   _wasmfs_opfs_write_access__deps: ['$wasmfsOPFSAccessHandles'],
+  _wasmfs_opfs_write_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_write_access: {{{ asyncIf(!PTHREADS) }}}function(accessID, bufPtr, len, pos) {
     let accessHandle = wasmfsOPFSAccessHandles.get(accessID);
     let data = HEAPU8.subarray(bufPtr, bufPtr + len);
@@ -384,6 +399,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_get_size_access__deps: ['$wasmfsOPFSAccessHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_get_size_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_get_size_access: async function(ctx, accessID, sizePtr) {
     let accessHandle = wasmfsOPFSAccessHandles.get(accessID);
     let size;
@@ -404,6 +420,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_get_size_file__deps: ['$wasmfsOPFSFileHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_get_size_file__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_get_size_file: async function(ctx, fileID, sizePtr) {
     let fileHandle = wasmfsOPFSFileHandles.get(fileID);
     let size;
@@ -418,6 +435,7 @@ addToLibrary({
 
   _wasmfs_opfs_set_size_access__i53abi: true,
   _wasmfs_opfs_set_size_access__deps: ['$wasmfsOPFSAccessHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_set_size_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_set_size_access: async function(ctx, accessID, size, errPtr) {
     let accessHandle = wasmfsOPFSAccessHandles.get(accessID);
     try {
@@ -431,6 +449,7 @@ addToLibrary({
 
   _wasmfs_opfs_set_size_file__i53abi: true,
   _wasmfs_opfs_set_size_file__deps: ['$wasmfsOPFSFileHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_set_size_file__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_set_size_file: async function(ctx, fileID, size, errPtr) {
     let fileHandle = wasmfsOPFSFileHandles.get(fileID);
     try {
@@ -445,6 +464,7 @@ addToLibrary({
   },
 
   _wasmfs_opfs_flush_access__deps: ['$wasmfsOPFSAccessHandles', '$wasmfsOPFSProxyFinish'],
+  _wasmfs_opfs_flush_access__async: {{{ !PTHREADS }}},
   _wasmfs_opfs_flush_access: async function(ctx, accessID, errPtr) {
     let accessHandle = wasmfsOPFSAccessHandles.get(accessID);
     try {

test/test_other.py

@@ -3484,6 +3484,32 @@ def test_jspi_add_function(self):
       '-Wno-experimental']
     self.do_runf('other/test_jspi_add_function.c', 'done')
 
+  @requires_jspi
+  def test_jspi_async_function(self):
+    # Make sure async library functions are not automatically JSPI'd.
+    create_file('lib.js', r'''
+      addToLibrary({
+        foo: async function(f) { await Promise.resolve(); },
+      });
+    ''')
+    create_file('main.c', r'''
+      #include <emscripten.h>
+      extern void foo();
+      EMSCRIPTEN_KEEPALIVE void test() {
+        foo();
+      }
+    ''')
+    create_file('post.js', r'''
+      Module.onRuntimeInitialized = () => {
+        _test()
+        console.log('done');
+      };
+    ''')
+    self.do_runf('main.c', 'done', emcc_args=['-sJSPI',
+                                              '--js-library=lib.js',
+                                              '-Wno-experimental',
+                                              '--post-js=post.js'])
+
   @requires_dev_dependency('typescript')
   @parameterized({
     'commonjs': [['-sMODULARIZE'], ['--module', 'commonjs', '--moduleResolution', 'node']],