squash: harden string validation in fh.writeFile and fh.appendFile

doc/api/fs.md

@@ -695,6 +695,10 @@ the end of the file.
 <!-- YAML
 added: v10.0.0
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/41677
+    description: The `data` parameter no longer accepts objects with an
+                 own `toString` function property.
   - version:
       - v15.14.0
       - v14.18.0
@@ -710,17 +714,15 @@ changes:
                  strings anymore.
 -->
 
-* `data` {string|Buffer|TypedArray|DataView|Object|AsyncIterable|Iterable
-  |Stream}
+* `data` {string|Buffer|TypedArray|DataView|AsyncIterable|Iterable|Stream}
 * `options` {Object|string}
   * `encoding` {string|null} The expected character encoding when `data` is a
     string. **Default:** `'utf8'`
 * Returns: {Promise}
 
 Asynchronously writes data to a file, replacing the file if it already exists.
-`data` can be a string, a buffer, an {AsyncIterable} or {Iterable} object, or an
-object with an own `toString` function
-property. The promise is resolved with no arguments upon success.
+`data` can be a string, a buffer, an {AsyncIterable} or {Iterable} object.
+The promise is resolved with no arguments upon success.
 
 If `options` is a string, then it specifies the `encoding`.
 

lib/internal/fs/promises.js

@@ -65,7 +65,6 @@ const {
   validateOffsetLengthWrite,
   validateRmOptions,
   validateRmdirOptions,
-  validateStringAfterArrayBufferView,
   validatePrimitiveStringAfterArrayBufferView,
   warnOnNonPortableTemplate,
 } = require('internal/fs/utils');
@@ -823,7 +822,7 @@ async function writeFile(path, data, options) {
   const flag = options.flag || 'w';
 
   if (!isArrayBufferView(data) && !isCustomIterable(data)) {
-    validateStringAfterArrayBufferView(data, 'data');
+    validatePrimitiveStringAfterArrayBufferView(data, 'data');
     data = Buffer.from(data, options.encoding || 'utf8');
   }