nits / check both hooks

doc/api/esm.md

@@ -1098,7 +1098,7 @@ a URL should be interpreted. The `format` returned also affects what the
 acceptable forms of source values are for a module when parsing. This can be one
 of the following:
 
-| `format` | Description | Acceptable Source Values |
+| `format` | Description | Acceptable Types For `source` Returned by `getSource` or `transformSource` |
 | --- | --- |
 | `'builtin'` | Load a Node.js builtin module | Not applicable |
 | `'commonjs'` | Load a Node.js CommonJS module | Not applicable |

lib/internal/modules/esm/translators.js

@@ -9,6 +9,11 @@ const {
   StringPrototypeReplace,
 } = primordials;
 
+const {
+  isArrayBufferView,
+  isAnyArrayBuffer
+} = require('internal/util/types');
+
 const {
   stripBOM,
   loadNativeModule
@@ -41,16 +46,24 @@ const translators = new SafeMap();
 exports.translators = translators;
 
 const DECODER = new TextDecoder();
+function assertBufferSource(body, allowString, hookName) {
+  if (allowString && typeof body === 'string') {
+    return;
+  }
+  if (isArrayBufferView(body) || isAnyArrayBuffer(body)) {
+    return;
+  }
+  throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
+    `${allowString ? 'string, ' : ''}array buffer, or typed array`,
+    hookName,
+    'source',
+    body
+  );
+}
+
 function stringify(body) {
   if (typeof body === 'string') return body;
-  if (typeof body !== 'object' || !body) {
-    throw new ERR_INVALID_RETURN_PROPERTY_VALUE(
-      'string, array buffer, or typed array',
-      'transformSource',
-      'source',
-      body
-    );
-  }
+  assertBufferSource(body, false, 'transformSource');
   return DECODER.decode(body);
 }
 
@@ -90,9 +103,10 @@ function initializeImportMeta(meta, { url }) {
 translators.set('module', async function moduleStrategy(url) {
   let { source } = await this._getSource(
     url, { format: 'module' }, defaultGetSource);
-  source = stringify(source);
+  assertBufferSource(source, true, 'getSource');
   ({ source } = await this._transformSource(
     source, { url, format: 'module' }, defaultTransformSource));
+  source = stringify(source);
   maybeCacheSourceMap(url, source);
   debug(`Translating StandardModule ${url}`);
   const module = new ModuleWrap(url, undefined, source, 0, 0);
@@ -167,9 +181,10 @@ translators.set('json', async function jsonStrategy(url) {
   }
   let { source } = await this._getSource(
     url, { format: 'json' }, defaultGetSource);
-  source = stringify(source);
+  assertBufferSource(source, true, 'getSource');
   ({ source } = await this._transformSource(
     source, { url, format: 'json' }, defaultTransformSource));
+  source = stringify(source);
   if (pathname) {
     // A require call could have been called on the same file during loading and
     // that resolves synchronously. To make sure we always return the identical
@@ -210,8 +225,10 @@ translators.set('wasm', async function(url) {
   emitExperimentalWarning('Importing Web Assembly modules');
   let { source } = await this._getSource(
     url, { format: 'wasm' }, defaultGetSource);
+  assertBufferSource(source, false, 'getSource');
   ({ source } = await this._transformSource(
     source, { url, format: 'wasm' }, defaultTransformSource));
+  assertBufferSource(source, false, 'transformSource');
   debug(`Translating WASMModule ${url}`);
   let compiled;
   try {