nodejs · guybedford · Apr 29, 2019 · Trott · May 13, 2019 · littledan
diff --git a/doc/api/esm.md b/doc/api/esm.md
@@ -441,6 +441,30 @@ node --experimental-modules index.mjs # fails
 node --experimental-modules --experimental-json-modules index.mjs # works
 ```
 
+## Experimental Wasm Modules
+
+Importing Web Assembly modules is supported under the
+`--experimental-wasm-modules` flag, allowing any `.wasm` files to be
+imported as normal modules while also supporting their module imports.
+
+This integration is in line with the
+[ES Module Integration Proposal for Web Assembly][].
+
+For example, an `index.mjs` containing:
+
+```js
+import * as M from './module.wasm';
+console.log(M);
+```
+
+executed under:
+
+```bash
+node --experimental-modules --experimental-wasm-modules index.mjs
+```
+
+would provide the exports interface for the instantiation of `module.wasm`.
+
 ## Experimental Loader hooks
 
 **Note: This API is currently being redesigned and will still change.**
@@ -484,11 +508,12 @@ module. This can be one of the following:
 
 | `format` | Description |
 | --- | --- |
-| `'module'` | Load a standard JavaScript module |
-| `'commonjs'` | Load a Node.js CommonJS module |
 | `'builtin'` | Load a Node.js builtin module |
-| `'json'` | Load a JSON file |
+| `'commonjs'` | Load a Node.js CommonJS module |
 | `'dynamic'` | Use a [dynamic instantiate hook][] |
+| `'json'` | Load a JSON file |
+| `'module'` | Load a standard JavaScript module |
+| `'wasm'` | Load a WebAssembly module |
 
 For example, a dummy loader to load JavaScript restricted to browser resolution
 rules with only JS file extension and Node.js builtin modules support could
@@ -585,8 +610,8 @@ format for that resolved URL given by the **ESM_FORMAT** routine.
 
 The _"module"_ format is returned for an ECMAScript Module, while the
 _"commonjs"_ format is used to indicate loading through the legacy
-CommonJS loader. Additional formats such as _"wasm"_ or _"addon"_ can be
-extended in future updates.
+CommonJS loader. Additional formats such as _"addon"_ can be extended in future
+updates.
 
 In the following algorithms, all subroutine errors are propagated as errors
 of these top-level routines.
@@ -739,5 +764,6 @@ success!
 [ECMAScript-modules implementation]: https://github.com/nodejs/modules/blob/master/doc/plan-for-new-modules-implementation.md
 [Node.js EP for ES Modules]: https://github.com/nodejs/node-eps/blob/master/002-es-modules.md
 [WHATWG JSON modules]: https://github.com/whatwg/html/issues/4315
+[ES Module Integration Proposal for Web Assembly]: https://github.com/webassembly/esm-integration
 [dynamic instantiate hook]: #esm_dynamic_instantiate_hook
 [the official standard format]: https://tc39.github.io/ecma262/#sec-modules
diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
@@ -658,7 +658,7 @@ Module.prototype.load = function(filename) {
         url,
         new ModuleJob(ESMLoader, url, async () => {
           return createDynamicModule(
-            ['default'], url, (reflect) => {
+            [], ['default'], url, (reflect) => {
               reflect.exports.default.set(exports);
             });
         })

diff --git a/lib/internal/modules/esm/create_dynamic_module.js b/lib/internal/modules/esm/create_dynamic_module.js
@@ -1,14 +1,18 @@
 'use strict';
 
-const { ArrayPrototype } = primordials;
+const { ArrayPrototype, JSON, Object } = primordials;
 
 const debug = require('internal/util/debuglog').debuglog('esm');
 
-const createDynamicModule = (exports, url = '', evaluate) => {
+const createDynamicModule = (imports, exports, url = '', evaluate) => {
   debug('creating ESM facade for %s with exports: %j', url, exports);
   const names = ArrayPrototype.map(exports, (name) => `${name}`);
 
   const source = `
+${ArrayPrototype.join(ArrayPrototype.map(imports, (impt, index) =>
+    `import * as $import_${index} from ${JSON.stringify(impt)};
+import.meta.imports[${JSON.stringify(impt)}] = $import_${index};`), '\n')
+}
 ${ArrayPrototype.join(ArrayPrototype.map(names, (name) =>
     `let $${name};
 export { $${name} as ${name} };
@@ -22,19 +26,21 @@ import.meta.done();
 `;
   const { ModuleWrap, callbackMap } = internalBinding('module_wrap');
   const m = new ModuleWrap(source, `${url}`);
-  m.link(() => 0);
-  m.instantiate();
 
   const readyfns = new Set();
   const reflect = {
-    namespace: m.namespace(),
-    exports: {},
+    exports: Object.create(null),
     onReady: (cb) => { readyfns.add(cb); },
   };
 
+  if (imports.length)
+    reflect.imports = Object.create(null);
+
   callbackMap.set(m, {
     initializeImportMeta: (meta, wrap) => {
       meta.exports = reflect.exports;
+      if (reflect.imports)
+        meta.imports = reflect.imports;
       meta.done = () => {
         evaluate(reflect);
         reflect.onReady = (cb) => cb(reflect);

diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
@@ -10,17 +10,14 @@ const preserveSymlinks = getOptionValue('--preserve-symlinks');
 const preserveSymlinksMain = getOptionValue('--preserve-symlinks-main');
 const experimentalJsonModules = getOptionValue('--experimental-json-modules');
 const typeFlag = getOptionValue('--input-type');
-
+const experimentalWasmModules = getOptionValue('--experimental-wasm-modules');
 const { resolve: moduleWrapResolve,
         getPackageType } = internalBinding('module_wrap');
 const { pathToFileURL, fileURLToPath } = require('internal/url');
 const { ERR_INPUT_TYPE_NOT_ALLOWED,
         ERR_UNKNOWN_FILE_EXTENSION } = require('internal/errors').codes;
 
-const {
-  Object,
-  SafeMap
-} = primordials;
+const { SafeMap } = primordials;
 
 const realpathCache = new SafeMap();
 
@@ -44,15 +41,11 @@ const legacyExtensionFormatMap = {
   '.node': 'commonjs'
 };
 
-if (experimentalJsonModules) {
-  // This is a total hack
-  Object.assign(extensionFormatMap, {
-    '.json': 'json'
-  });
-  Object.assign(legacyExtensionFormatMap, {
-    '.json': 'json'
-  });
-}
+if (experimentalWasmModules)
+  extensionFormatMap['.wasm'] = legacyExtensionFormatMap['.wasm'] = 'wasm';
+
+if (experimentalJsonModules)
+  extensionFormatMap['.json'] = legacyExtensionFormatMap['.json'] = 'json';
 
 function resolve(specifier, parentURL) {
   if (NativeModule.canBeRequiredByUsers(specifier)) {

diff --git a/lib/internal/modules/esm/loader.js b/lib/internal/modules/esm/loader.js
@@ -153,7 +153,7 @@ class Loader {
       loaderInstance = async (url) => {
         debug(`Translating dynamic ${url}`);
         const { exports, execute } = await this._dynamicInstantiate(url);
-        return createDynamicModule(exports, url, (reflect) => {
+        return createDynamicModule([], exports, url, (reflect) => {
           debug(`Loading dynamic ${url}`);
           execute(reflect.exports);
         });

diff --git a/lib/internal/modules/esm/translators.js b/lib/internal/modules/esm/translators.js
@@ -1,9 +1,12 @@
 'use strict';
 
+/* global WebAssembly */
+
 const {
+  JSON,
+  Object,
   SafeMap,
-  StringPrototype,
-  JSON
+  StringPrototype
 } = primordials;
 
 const { NativeModule } = require('internal/bootstrap/loaders');
@@ -72,11 +75,11 @@ translators.set('commonjs', async function commonjsStrategy(url, isMain) {
   ];
   if (module && module.loaded) {
     const exports = module.exports;
-    return createDynamicModule(['default'], url, (reflect) => {
+    return createDynamicModule([], ['default'], url, (reflect) => {
       reflect.exports.default.set(exports);
     });
   }
-  return createDynamicModule(['default'], url, () => {
+  return createDynamicModule([], ['default'], url, () => {
     debug(`Loading CJSModule ${url}`);
     // We don't care about the return val of _load here because Module#load
     // will handle it for us by checking the loader registry and filling the
@@ -97,7 +100,7 @@ translators.set('builtin', async function builtinStrategy(url) {
   }
   module.compileForPublicLoader(true);
   return createDynamicModule(
-    [...module.exportKeys, 'default'], url, (reflect) => {
+    [], [...module.exportKeys, 'default'], url, (reflect) => {
       debug(`Loading BuiltinModule ${url}`);
       module.reflect = reflect;
       for (const key of module.exportKeys)
@@ -116,7 +119,7 @@ translators.set('json', async function jsonStrategy(url) {
   let module = CJSModule._cache[modulePath];
   if (module && module.loaded) {
     const exports = module.exports;
-    return createDynamicModule(['default'], url, (reflect) => {
+    return createDynamicModule([], ['default'], url, (reflect) => {
       reflect.exports.default.set(exports);
     });
   }
@@ -136,8 +139,32 @@ translators.set('json', async function jsonStrategy(url) {
     throw err;
   }
   CJSModule._cache[modulePath] = module;
-  return createDynamicModule(['default'], url, (reflect) => {
+  return createDynamicModule([], ['default'], url, (reflect) => {
     debug(`Parsing JSONModule ${url}`);
     reflect.exports.default.set(module.exports);
   });
 });
+
+// Strategy for loading a wasm module
+translators.set('wasm', async function(url) {
+  const pathname = fileURLToPath(url);
+  const buffer = await readFileAsync(pathname);
+  debug(`Translating WASMModule ${url}`);
+  let compiled;
+  try {
+    compiled = await WebAssembly.compile(buffer);
+  } catch (err) {
+    err.message = pathname + ': ' + err.message;
+    throw err;
+  }
+
+  const imports =
+      WebAssembly.Module.imports(compiled).map(({ module }) => module);
+  const exports = WebAssembly.Module.exports(compiled).map(({ name }) => name);
+
+  return createDynamicModule(imports, exports, url, (reflect) => {
+    const { exports } = new WebAssembly.Instance(compiled, reflect.imports);
+    for (const expt of Object.keys(exports))
+      reflect.exports[expt].set(exports[expt]);
+  });
+});
diff --git a/src/node_options.cc b/src/node_options.cc
@@ -122,6 +122,11 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors) {
                       "--experimental-modules be enabled");
   }
 
+  if (experimental_wasm_modules && !experimental_modules) {
+    errors->push_back("--experimental-wasm-modules requires "
+                      "--experimental-modules be enabled");
+  }
+
   if (!es_module_specifier_resolution.empty()) {
     if (!experimental_modules) {
       errors->push_back("--es-module-specifier-resolution requires "
@@ -274,6 +279,10 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             "experimental ES Module support and caching modules",
             &EnvironmentOptions::experimental_modules,
             kAllowedInEnvironment);
+  AddOption("--experimental-wasm-modules",
+            "experimental ES Module support for webassembly modules",
+            &EnvironmentOptions::experimental_wasm_modules,
+            kAllowedInEnvironment);
   AddOption("--experimental-policy",
             "use the specified file as a "
             "security policy",

diff --git a/src/node_options.h b/src/node_options.h
@@ -94,6 +94,7 @@ class EnvironmentOptions : public Options {
   bool experimental_json_modules = false;
   bool experimental_modules = false;
   std::string es_module_specifier_resolution;
+  bool experimental_wasm_modules = false;
   std::string module_type;
   std::string experimental_policy;
   bool experimental_repl_await = false;

diff --git a/test/es-module/test-esm-wasm.mjs b/test/es-module/test-esm-wasm.mjs
@@ -0,0 +1,15 @@
+// Flags: --experimental-modules --experimental-wasm-modules
+import '../common/index.mjs';
+import { add, addImported } from '../fixtures/es-modules/simple.wasm';
+import { state } from '../fixtures/es-modules/wasm-dep.mjs';
+import { strictEqual } from 'assert';
+
+strictEqual(state, 'WASM Start Executed');
+
+strictEqual(add(10, 20), 30);
+
+strictEqual(addImported(0), 42);
+
+strictEqual(state, 'WASM JS Function Executed');
+
+strictEqual(addImported(1), 43);
diff --git a/test/fixtures/es-modules/simple.wasm b/test/fixtures/es-modules/simple.wasm
diff --git a/test/fixtures/es-modules/simple.wat b/test/fixtures/es-modules/simple.wat
@@ -0,0 +1,23 @@
+;; Compiled using the WebAssembly Tootkit (https://github.com/WebAssembly/wabt)
+;; $ wat2wasm simple.wat -o simple.wasm
+
+(module
+  (import "./wasm-dep.mjs" "jsFn" (func $jsFn (result i32)))
+  (import "./wasm-dep.mjs" "jsInitFn" (func $jsInitFn))
+  (export "add" (func $add))
+  (export "addImported" (func $addImported))
+  (start $startFn)
+  (func $startFn
+    call $jsInitFn
+  )
+  (func $add (param $a i32) (param $b i32) (result i32)
+    local.get $a
+    local.get $b
+    i32.add
+  )
+  (func $addImported (param $a i32) (result i32)
+    local.get $a
+    call $jsFn
+    i32.add
+  )
+)
diff --git a/test/fixtures/es-modules/wasm-dep.mjs b/test/fixtures/es-modules/wasm-dep.mjs
@@ -0,0 +1,13 @@
+import { strictEqual } from 'assert';
+
+export function jsFn () {
+  state = 'WASM JS Function Executed';
+  return 42;
+}
+
+export let state = 'JS Function Executed';
+
+export function jsInitFn () {
+  strictEqual(state, 'JS Function Executed');
+  state = 'WASM Start Executed';
+}