Add option to use source phase imports for wasm module loading

Fixes: #23047

Author: sbc100

ChangeLog.md

@@ -20,6 +20,9 @@ See docs/process.md for more on how version tagging works.
 
 4.0.5 (in development)
 ----------------------
+- Added initial support for wasm source phase imports via
+  `-sSOURCE_PHASE_IMPORTS`.  This is currently experimental and not yet
+  implemented in browsers.
 
 4.0.4 - 02/25/25
 ----------------

src/preamble.js

@@ -558,11 +558,40 @@ function instrumentWasmTableWithAbort() {
 }
 #endif
 
+#if LOAD_SOURCE_MAP
+var wasmSourceMap;
+#include "source_map_support.js"
+
+function receiveSourceMapJSON(sourceMap) {
+  wasmSourceMap = new WasmSourceMap(sourceMap);
+  {{{ runIfMainThread("removeRunDependency('source-map');") }}}
+}
+#endif
+
+#if (PTHREADS || WASM_WORKERS) && (LOAD_SOURCE_MAP || USE_OFFSET_CONVERTER)
+// When using postMessage to send an object, it is processed by the structured
+// clone algorithm.  The prototype, and hence methods, on that object is then
+// lost. This function adds back the lost prototype.  This does not work with
+// nested objects that has prototypes, but it suffices for WasmSourceMap and
+// WasmOffsetConverter.
+function resetPrototype(constructor, attrs) {
+  var object = Object.create(constructor.prototype);
+  return Object.assign(object, attrs);
+}
+#endif
+
+#if USE_OFFSET_CONVERTER
+var wasmOffsetConverter;
+#include "wasm_offset_converter.js"
+#endif
+
+#if !SOURCE_PHASE_IMPORTS
 #if SINGLE_FILE
 // In SINGLE_FILE mode the wasm binary is encoded inline here as a data: URL.
 var wasmBinaryFile = '{{{ WASM_BINARY_FILE }}}';
 #else
 var wasmBinaryFile;
+
 function findWasmBinary() {
 #if EXPORT_ES6 && !AUDIO_WORKLET
   if (Module['locateFile']) {
@@ -647,13 +676,6 @@ var splitModuleProxyHandler = {
 };
 #endif
 
-#if LOAD_SOURCE_MAP
-function receiveSourceMapJSON(sourceMap) {
-  wasmSourceMap = new WasmSourceMap(sourceMap);
-  {{{ runIfMainThread("removeRunDependency('source-map');") }}}
-}
-#endif
-
 #if SPLIT_MODULE || !WASM_ASYNC_COMPILATION
 function instantiateSync(file, info) {
   var module;
@@ -701,18 +723,6 @@ function instantiateSync(file, info) {
 }
 #endif
 
-#if (PTHREADS || WASM_WORKERS) && (LOAD_SOURCE_MAP || USE_OFFSET_CONVERTER)
-// When using postMessage to send an object, it is processed by the structured
-// clone algorithm.  The prototype, and hence methods, on that object is then
-// lost. This function adds back the lost prototype.  This does not work with
-// nested objects that has prototypes, but it suffices for WasmSourceMap and
-// WasmOffsetConverter.
-function resetPrototype(constructor, attrs) {
-  var object = Object.create(constructor.prototype);
-  return Object.assign(object, attrs);
-}
-#endif
-
 #if WASM_ASYNC_COMPILATION
 async function instantiateArrayBuffer(binaryFile, imports) {
   try {
@@ -815,6 +825,7 @@ async function instantiateAsync(binary, binaryFile, imports) {
   return instantiateArrayBuffer(binaryFile, imports);
 }
 #endif // WASM_ASYNC_COMPILATION
+#endif // SOURCE_PHASE_IMPORTS
 
 function getWasmImports() {
 #if PTHREADS
@@ -1016,10 +1027,14 @@ function getWasmImports() {
   }
 #endif
 
+#if SOURCE_PHASE_IMPORTS
+  var instance = await WebAssembly.instantiate(wasmModule, info);
+  var exports = receiveInstantiationResult({instance, 'module':wasmModule});
+  return exports;
+#else
 #if !SINGLE_FILE
   wasmBinaryFile ??= findWasmBinary();
 #endif
-
 #if WASM_ASYNC_COMPILATION
 #if RUNTIME_DEBUG
   dbg('asynchronously preparing wasm');
@@ -1051,6 +1066,7 @@ function getWasmImports() {
   return receiveInstance(result[0]);
 #endif
 #endif // WASM_ASYNC_COMPILATION
+#endif // SOURCE_PHASE_IMPORTS
 }
 
 #if !WASM_BIGINT

src/settings.js

@@ -2182,6 +2182,9 @@ var LEGACY_RUNTIME = false;
 // [link]
 var SIGNATURE_CONVERSIONS = [];
 
+// Experimental support for wasm source phase imports. Requires EXPORT_ES6
+var SOURCE_PHASE_IMPORTS = false;
+
 // For renamed settings the format is:
 // [OLD_NAME, NEW_NAME]
 // For removed settings (which now effectively have a fixed value and can no

test/test_other.py

@@ -358,13 +358,23 @@ def test_emcc_generate_config(self, compiler):
   @parameterized({
     '': ([],),
     'node': (['-sENVIRONMENT=node'],),
+    # load a worker before startup to check ES6 modules there as well
+    'pthreads': (['-pthread', '-sPTHREAD_POOL_SIZE=1'],),
   })
   def test_esm(self, args):
     self.run_process([EMCC, '-o', 'hello_world.mjs',
                       '--extern-post-js', test_file('modularize_post_js.js'),
                       test_file('hello_world.c')] + args)
-    src = read_file('hello_world.mjs')
-    self.assertContained('export default Module;', src)
+    self.assertContained('export default Module;', read_file('hello_world.mjs'))
+    self.assertContained('hello, world!', self.run_js('hello_world.mjs'))
+
+  @requires_node_canary
+  def test_esm_source_phase_imports(self):
+    self.node_args += ['--experimental-wasm-modules']
+    self.run_process([EMCC, '-o', 'hello_world.mjs', '-sSOURCE_PHASE_IMPORTS',
+                      '--extern-post-js', test_file('modularize_post_js.js'),
+                      test_file('hello_world.c')])
+    self.assertContained('import source wasmModule from', read_file('hello_world.mjs'))
     self.assertContained('hello, world!', self.run_js('hello_world.mjs'))
 
   @parameterized({

tools/building.py

@@ -511,9 +511,14 @@ def version_split(v):
 @ToolchainProfiler.profile()
 def transpile(filename):
   config = {
-    'sourceType': 'script',
-    'targets': {}
+    'sourceType': 'module',
+    'targets': {},
+    'plugins': [
+      '@babel/plugin-proposal-import-wasm-source'
+    ],
   }
+  if settings.EXPORT_ES6:
+    config['sourceType'] = 'module'
   if settings.MIN_CHROME_VERSION != UNSUPPORTED:
     config['targets']['chrome'] = str(settings.MIN_CHROME_VERSION)
   if settings.MIN_FIREFOX_VERSION != UNSUPPORTED:
@@ -529,8 +534,10 @@ def transpile(filename):
   config_file = shared.get_temp_files().get('babel_config.json').name
   logger.debug(config_json)
   utils.write_file(config_file, config_json)
+  env = os.environ.copy()
+  env['NODE_PATH'] = path_from_root('node_modules')
   cmd = shared.get_npm_cmd('babel') + [filename, '-o', outfile, '--presets', '@babel/preset-env', '--config-file', config_file]
-  check_call(cmd, cwd=path_from_root())
+  check_call(cmd, cwd=path_from_root(), env=env)
   return outfile
 
 

tools/link.py

@@ -1757,6 +1757,9 @@ def get_full_import_name(name):
     if settings.ASYNCIFY == 2:
       diagnostics.warning('experimental', '-sASYNCIFY=2 (JSPI) is still experimental')
 
+  if settings.SOURCE_PHASE_IMPORTS:
+    diagnostics.warning('experimental', '-sSOURCE_PHASE_IMPORTS is still experimental and not yet supported in browsers')
+
   if settings.WASM2JS:
     if settings.GENERATE_SOURCE_MAP:
       exit_with_error('wasm2js does not support source maps yet (debug in wasm for now)')
@@ -2478,6 +2481,9 @@ def modularize():
 })();
 ''' % {'EXPORT_NAME': settings.EXPORT_NAME}
 
+  if settings.SOURCE_PHASE_IMPORTS:
+    src = f"import source wasmModule from './{settings.WASM_BINARY_FILE}';\n\n" + src
+
   # Given the async nature of how the Module function and Module object
   # come into existence in AudioWorkletGlobalScope, store the Module
   # function under a different variable name so that AudioWorkletGlobalScope