esm: WebAssembly.namespaceInstance

doc/api/errors.md

@@ -3266,6 +3266,13 @@ The WASI instance has already started.
 
 The WASI instance has not been started.
 
+<a id="ERR_WEBASSEMBLY_NOT_MODULE_RECORD_NAMESPACE"></a>
+
+### `ERR_WEBASSEMBLY_NOT_MODULE_RECORD_NAMESPACE`
+
+The object passed to `WebAssembly.namespaceInstance` was not a valid WebAssembly
+Module Record namespace object.
+
 <a id="ERR_WEBASSEMBLY_RESPONSE"></a>
 
 ### `ERR_WEBASSEMBLY_RESPONSE`

lib/internal/errors.js

@@ -1892,6 +1892,7 @@ E('ERR_VM_MODULE_NOT_MODULE',
   'Provided module is not an instance of Module', Error);
 E('ERR_VM_MODULE_STATUS', 'Module status %s', Error);
 E('ERR_WASI_ALREADY_STARTED', 'WASI instance has already started', Error);
+E('ERR_WEBASSEMBLY_NOT_MODULE_RECORD_NAMESPACE', 'Not a WebAssembly Module Record namespace object.', TypeError);
 E('ERR_WEBASSEMBLY_RESPONSE', 'WebAssembly response %s', TypeError);
 E('ERR_WORKER_INIT_FAILED', 'Worker initialization failure: %s', Error);
 E('ERR_WORKER_INVALID_EXEC_ARGV', (errors, msg = 'invalid execArgv flags') =>

lib/internal/modules/esm/translators.js

@@ -10,7 +10,6 @@ const {
   SafeArrayIterator,
   SafeMap,
   SafeSet,
-  SafeWeakMap,
   StringPrototypeIncludes,
   StringPrototypeReplaceAll,
   StringPrototypeSlice,
@@ -55,6 +54,7 @@ const {
   ERR_UNKNOWN_BUILTIN_MODULE,
 } = require('internal/errors').codes;
 const { maybeCacheSourceMap } = require('internal/source_map/source_map_cache');
+const { wasmInstances } = require('internal/wasm_web_api');
 const moduleWrap = internalBinding('module_wrap');
 const { ModuleWrap } = moduleWrap;
 
@@ -491,7 +491,6 @@ translators.set('json', function jsonStrategy(url, source) {
  *   WebAssembly.Instance
  * >} [[Instance]] slot proxy for WebAssembly Module Record
  */
-const wasmInstances = new SafeWeakMap();
 translators.set('wasm', async function(url, source) {
   emitExperimentalWarning('Importing WebAssembly modules');
 
@@ -533,7 +532,7 @@ translators.set('wasm', async function(url, source) {
   const { module } = createDynamicModule([...importsList], [...exportsList], url, (reflect) => {
     for (const impt of importsList) {
       const importNs = reflect.imports[impt];
-      const wasmInstance = wasmInstances.get(importNs);
+      const wasmInstance = wasmInstances.get(importNs)?.exports;
       if (wasmInstance) {
         const wrappedModule = ObjectAssign({ __proto__: null }, reflect.imports[impt]);
         for (const { module, name } of wasmGlobalImports) {
@@ -549,8 +548,9 @@ translators.set('wasm', async function(url, source) {
     }
     // In cycles importing unexecuted Wasm, wasmInstance will be undefined, which will fail during
     // instantiation, since all bindings will be in the Temporal Deadzone (TDZ).
-    const { exports } = new WebAssembly.Instance(compiled, reflect.imports);
-    wasmInstances.set(module.getNamespace(), exports);
+    const instance = new WebAssembly.Instance(compiled, reflect.imports);
+    const { exports } = instance;
+    wasmInstances.set(module.getNamespace(), instance);
     for (const expt of exportsList) {
       let val = exports[expt];
       // Unwrap WebAssembly.Global for JS bindings

lib/internal/wasm_web_api.js

@@ -2,10 +2,13 @@
 
 const {
   PromiseResolve,
+  SafeWeakMap,
+  globalThis,
 } = primordials;
 const {
   ERR_INVALID_ARG_TYPE,
   ERR_WEBASSEMBLY_RESPONSE,
+  ERR_WEBASSEMBLY_NOT_MODULE_RECORD_NAMESPACE,
 } = require('internal/errors').codes;
 
 let undici;
@@ -61,6 +64,21 @@ function wasmStreamingCallback(streamState, source) {
   });
 }
 
+// WebAssembly ESM Integration extension pending V8 support - namespaceInstance property:
+// see https://webassembly.github.io/esm-integration/js-api/index.html#dom-webassembly-namespaceinstance.
+const wasmInstances = new SafeWeakMap();
+const { WebAssembly } = globalThis;
+if (WebAssembly && !WebAssembly.namespaceInstance) {
+  WebAssembly.namespaceInstance = function namespaceInstance(ns) {
+    const instance = wasmInstances.get(ns);
+    if (!instance) {
+      throw new ERR_WEBASSEMBLY_NOT_MODULE_RECORD_NAMESPACE();
+    }
+    return instance;
+  };
+}
+
 module.exports = {
   wasmStreamingCallback,
+  wasmInstances,
 };

test/es-module/test-esm-wasm.mjs

@@ -403,4 +403,28 @@ describe('ESM: WASM modules', { concurrency: !process.env.TEST_PARALLEL }, () =>
     strictEqual(stdout, '');
     notStrictEqual(code, 0);
   });
+
+  it('should return the underlying instance with shared state', async () => {
+    const { code, stderr, stdout } = await spawnPromisified(execPath, [
+      '--no-warnings',
+      '--experimental-wasm-modules',
+      '--input-type=module',
+      '--eval',
+      [
+        'import { strictEqual, ok } from "node:assert";',
+        `const wasmNamespace = await import(${JSON.stringify(fixtures.fileURL('es-modules/globals.wasm'))});`,
+        'const instance = WebAssembly.namespaceInstance(wasmNamespace);',
+        'ok(instance instanceof WebAssembly.Instance);',
+        '// Verify shared state between namespace and instance',
+        'wasmNamespace.setLocalMutI32(999);',
+        'strictEqual(instance.exports.getLocalMutI32(), 999);',
+        'instance.exports.setLocalMutI32(888);',
+        'strictEqual(wasmNamespace.getLocalMutI32(), 888);',
+      ].join('\n'),
+    ]);
+
+    strictEqual(stderr, '');
+    strictEqual(stdout, '');
+    strictEqual(code, 0);
+  });
 });