[esm-integration] Allow JS library symbols to be exported (#24061)

See #24060

Author: sbc100

src/jsifier.mjs

@@ -735,6 +735,13 @@ function(${args}) {
         }
         contentText = `var ${mangled} = ${snippet};`;
       }
+
+      if (WASM_ESM_INTEGRATION && (EXPORT_ALL || EXPORTED_FUNCTIONS.has(mangled)) && !isStub) {
+        // It ESM integration mode we mark JS library symbols are exported at
+        // the point of declaration.
+        contentText = 'export ' + contentText;
+      }
+
       // Relocatable code needs signatures to create proper wrappers.
       if (sig && RELOCATABLE) {
         if (!WASM_BIGINT) {

src/modules.mjs

@@ -561,6 +561,9 @@ function exportLibrarySymbols() {
 }
 
 function exportJSSymbols() {
+  // In WASM_ESM_INTEGRATION mode JS library symbols are marked with `export`
+  // at the point of declaration.
+  if (WASM_ESM_INTEGRATION) return '';
   return exportRuntimeSymbols() + '  ' + exportLibrarySymbols();
 }
 

test/js_optimizer/JSDCE-output.js

@@ -47,6 +47,8 @@ export default function l(a) {
   return a + 1;
 }
 
+export var m = a => a + 1;
+
 (function() {
   var z = fleefl();
   var zz = fleefl();

test/js_optimizer/JSDCE.js

@@ -48,6 +48,11 @@ export default function l(a) {
   return a+1;
 }
 
+// ES6 exported var
+export var m = (a) => {
+  return a+1;
+}
+
 // inner workings
 (function() {
   var x;

test/test_core.py

@@ -9568,10 +9568,11 @@ def test_esm_integration(self):
     # TODO(sbc): WASM_ESM_INTEGRATION doesn't currently work with closure.
     # self.maybe_closure()
     self.node_args += ['--experimental-wasm-modules', '--no-warnings']
-    self.run_process([EMCC, '-o', 'hello_world.mjs', '-sWASM_ESM_INTEGRATION', '-Wno-experimental', test_file('hello_world_argv.c')] + self.get_emcc_args())
+    self.run_process([EMCC, '-o', 'hello_world.mjs', '-sEXPORTED_FUNCTIONS=_main,stringToNewUTF8', '-sWASM_ESM_INTEGRATION', '-Wno-experimental', test_file('hello_world_argv.c')] + self.get_emcc_args())
     create_file('runner.mjs', '''
-      import init from "./hello_world.mjs";
+      import init, { stringToNewUTF8, main } from "./hello_world.mjs";
       await init({arguments: ['foo', 'bar']});
+      console.log('this is a pointer:', stringToNewUTF8('hello'));
     ''')
     self.assertContained('hello, world! (3)', self.run_js('runner.mjs'))
 

tools/acorn-optimizer.mjs

@@ -447,8 +447,16 @@ function JSDCE(ast, aggressive) {
       },
       ExportNamedDeclaration(node, c) {
         if (node.declaration) {
-          const name = node.declaration.id.name;
-          ensureData(scopes[scopes.length - 1], name).use = 1;
+          if (node.declaration.type == 'FunctionDeclaration') {
+            const name = node.declaration.id.name;
+            ensureData(scopes[scopes.length - 1], name).use = 1;
+          } else {
+            assert(node.declaration.type == 'VariableDeclaration');
+            for (const decl of node.declaration.declarations) {
+              const name = decl.id.name;
+              ensureData(scopes[scopes.length - 1], name).use = 1;
+            }
+          }
           c(node.declaration);
         } else {
           for (const specifier of node.specifiers) {

tools/link.py

@@ -2114,12 +2114,16 @@ def create_worker_file(input_file, target_dir, output_file, options):
 
 def create_esm_wrapper(wrapper_file, support_target, wasm_target):
   wasm_exports = []
+  js_exports = []
   for f in settings.USER_EXPORTS:
     if f == '_main' and '__main_argc_argv' in settings.WASM_EXPORTS:
       wasm_exports.append('__main_argc_argv as main')
-    else:
+    elif f in settings.WASM_EXPORTS:
       wasm_exports.append(shared.demangle_c_symbol_name(f))
+    else:
+      js_exports.append(f)
   wasm_exports = ', '.join(wasm_exports)
+  js_exports = ', '.join(js_exports)
 
   wrapper = []
   if wasm_exports:
@@ -2132,7 +2136,10 @@ def create_esm_wrapper(wrapper_file, support_target, wasm_target):
     wrapper.append('// in order to avoid issues with circullr dependencies.')
     wrapper.append(f"import * as unused from './{settings.WASM_BINARY_FILE}';")
   support_url = f'./{os.path.basename(support_target)}'
-  wrapper.append(f"export {{ default }} from '{support_url}';")
+  if js_exports:
+    wrapper.append(f"export {{ default, {js_exports} }} from '{support_url}';")
+  else:
+    wrapper.append(f"export {{ default }} from '{support_url}';")
   write_file(wrapper_file, '\n'.join(wrapper) + '\n')
 
   # FIXME(sbc): This is a huge hack to rename the imports in the