[embind] Export embind exports as ESM exports for MODULARIZE=instance. (#23404)

Using the embind AOT mode we can generate a list of all the embind
bindings and export them as ES module exports.

Author: brendandahl

src/lib/libembind.js

@@ -32,7 +32,7 @@ var LibraryEmbind = {
   $PureVirtualError: class extends Error {},
   $GenericWireTypeSize: {{{ 2 * POINTER_SIZE }}},
 #if EMBIND_AOT
-  $InvokerFunctions: '<<< EMBIND_AOT_OUTPUT >>>',
+  $InvokerFunctions: '<<< EMBIND_AOT_INVOKERS >>>',
 #endif
   // If register_type is used, emval will be registered multiple times for
   // different type id's, but only a single type object is needed on the JS side

src/lib/libembind_gen.js

@@ -44,6 +44,7 @@ var LibraryEmbind = {
   },
   $FunctionDefinition__deps: ['$createJsInvoker', '$createJsInvokerSignature', '$emittedFunctions'],
   $FunctionDefinition: class {
+    hasPublicSymbol = true;
     constructor(name, returnType, argumentTypes, functionIndex, thisType = null, isNonnullReturn = false, isAsync = false) {
       this.name = name;
       this.returnType = returnType;
@@ -154,6 +155,7 @@ var LibraryEmbind = {
     }
   },
   $ClassDefinition: class {
+    hasPublicSymbol = true;
     constructor(typeId, name, base = null) {
       this.typeId = typeId;
       this.name = name;
@@ -265,6 +267,7 @@ var LibraryEmbind = {
     }
   },
   $ConstantDefinition: class {
+    hasPublicSymbol = true;
     constructor(type, name) {
       this.type = type;
       this.name = name;
@@ -275,6 +278,7 @@ var LibraryEmbind = {
     }
   },
   $EnumDefinition: class {
+    hasPublicSymbol = true;
     constructor(typeId, name) {
       this.typeId = typeId;
       this.name = name;
@@ -453,14 +457,21 @@ var LibraryEmbind = {
 
     print() {
       const out = ['{\n'];
+      const publicSymbols = [];
       for (const def of this.definitions) {
+        if (def.hasPublicSymbol) {
+          publicSymbols.push(def.name);
+        }
         if (!def.printJs) {
           continue;
         }
         def.printJs(out);
       }
-      out.push('}')
-      console.log(out.join(''));
+      out.push('}\n');
+      console.log(JSON.stringify({
+        'invokers': out.join(''),
+        publicSymbols,
+      }));
     }
   },
 

test/modularize_instance_embind.cpp

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <emscripten.h>
+#include <emscripten/bind.h>
+
+using namespace emscripten;
+
+void foo() {
+  printf("foo\n");
+}
+
+struct Bar {
+  void print() {
+    printf("bar\n");
+  }
+};
+
+int main() {
+  printf("main\n");
+}
+
+EMSCRIPTEN_BINDINGS(xxx) {
+  function("foo", &foo);
+  class_<Bar>("Bar")
+    .constructor<>()
+    .function("print", &Bar::print);
+}

test/test_core.py

@@ -9624,6 +9624,24 @@ def test_modularize_instance(self, args):
 
     self.assertContained('main1\nmain2\nfoo\nbar\nbaz\n', self.run_js('runner.mjs'))
 
+  def test_modularize_instance_embind(self):
+    self.run_process([EMCC, test_file('modularize_instance_embind.cpp'),
+                      '-sMODULARIZE=instance',
+                      '-lembind',
+                      '-sEMBIND_AOT',
+                      '-o', 'modularize_instance_embind.mjs'])
+
+    create_file('runner.mjs', '''
+      import init, { foo, Bar } from "./modularize_instance_embind.mjs";
+      await init();
+      foo();
+      const bar = new Bar();
+      bar.print();
+      bar.delete();
+    ''')
+
+    self.assertContained('main\nfoo\nbar\n', self.run_js('runner.mjs'))
+
 
 # Generate tests for everything
 def make_run(name, emcc_args, settings=None, env=None,

tools/link.py

@@ -1380,6 +1380,9 @@ def limit_incoming_module_api():
     settings.REQUIRED_EXPORTS.append('__getTypeName')
     if settings.PTHREADS or settings.WASM_WORKERS:
       settings.REQUIRED_EXPORTS.append('_embind_initialize_bindings')
+    # Needed to assign the embind exports to the ES exports.
+    if settings.MODULARIZE == 'instance':
+      settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$addOnPostCtor']
 
   if options.emit_tsd:
     settings.EMIT_TSD = True
@@ -2053,9 +2056,22 @@ def phase_emit_tsd(options, wasm_target, js_target, js_syms, metadata):
 def phase_embind_aot(options, wasm_target, js_syms):
   out = run_embind_gen(options, wasm_target, js_syms, {})
   if DEBUG:
-    write_file(in_temp('embind_aot.js'), out)
+    write_file(in_temp('embind_aot.json'), out)
+  out = json.loads(out)
   src = read_file(final_js)
-  src = do_replace(src, '<<< EMBIND_AOT_OUTPUT >>>', out)
+  src = do_replace(src, '<<< EMBIND_AOT_INVOKERS >>>', out['invokers'])
+  if settings.MODULARIZE == 'instance':
+    # Add ES module exports for the embind exports.
+    decls = '\n'.join([f'export var {name};' for name in out['publicSymbols']])
+    # Assign the runtime exports from Module to the ES export.
+    assigns = '\n'.join([f'{name} = Module[\'{name}\'];' for name in out['publicSymbols']])
+    exports = f'''
+// start embind exports
+function assignEmbindExports() {{ {assigns} }};
+addOnPostCtor(assignEmbindExports);
+{decls}
+// end embind exports'''
+    src += exports
   write_file(final_js, src)