fs: make promises/write and writeSync params optional

This change allows passing objects as "named parameters"

Fixes: nodejs#41666

doc/api/fs.md

@@ -619,6 +619,25 @@ On Linux, positional writes do not work when the file is opened in append mode.
 The kernel ignores the position argument and always appends the data to
 the end of the file.
 
+#### `filehandle.write(buffer, options)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `buffer` {Buffer|TypedArray|DataView}
+* `options` {Object}
+  * `offset` {integer} **Default:** `0`
+  * `length` {integer} **Default:** `buffer.byteLength - offset`
+  * `position` {integer} **Default:** `null`
+* Returns: {Promise}
+
+Write `buffer` to the file.
+
+Similar to the above `filehandle.write` function, this version takes an
+optional `options` object. If no `options` object is specified, it will
+default with the above values.
+
 #### `filehandle.write(string[, position[, encoding]])`
 
 <!-- YAML
@@ -5763,6 +5782,23 @@ changes:
 For detailed information, see the documentation of the asynchronous version of
 this API: [`fs.write(fd, buffer...)`][].
 
+### `fs.writeSync(fd, buffer, options)`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `fd` {integer}
+* `buffer` {Buffer|TypedArray|DataView}
+* `options` {Object}
+  * `offset` {integer} **Default:** `0`
+  * `length` {integer} **Default:** `buffer.byteLength - offset`
+  * `position` {integer} **Default:** `null`
+* Returns: {number} The number of bytes written.
+
+For detailed information, see the documentation of the asynchronous version of
+this API: [`fs.write(fd, buffer...)`][].
+
 ### `fs.writeSync(fd, string[, position[, encoding]])`
 
 <!-- YAML

lib/fs.js

@@ -854,15 +854,26 @@ ObjectDefineProperty(write, internalUtil.customPromisifyArgs,
  * specified `fd` (file descriptor).
  * @param {number} fd
  * @param {Buffer | TypedArray | DataView | string} buffer
- * @param {number} [offset]
- * @param {number} [length]
- * @param {number} [position]
+ * @param {{
+ *   offset?: number;
+ *   length?: number;
+ *   position?: number;
+ *   }} [offset]
  * @returns {number}
  */
 function writeSync(fd, buffer, offset, length, position) {
   fd = getValidatedFd(fd);
   const ctx = {};
   let result;
+
+  if (typeof offset === 'object' && offset !== null) {
+    ({
+      offset = 0,
+      length = buffer.byteLength - offset,
+      position = null
+    } = offset);
+  }
+
   if (isArrayBufferView(buffer)) {
     if (position === undefined)
       position = null;

lib/internal/fs/promises.js

@@ -561,7 +561,18 @@ async function readv(handle, buffers, position) {
 }
 
 async function write(handle, buffer, offset, length, position) {
-  if (buffer?.byteLength === 0)
+  let buffer = bufferOrOptions;
+  if (!isArrayBufferView(buffer) && typeof buffer !== 'string') {
+    validateBuffer(bufferOrOptions?.buffer);
+    ({
+      buffer,
+      offset = 0,
+      length = buffer.byteLength - offset,
+      position = null
+    } = bufferOrOptions);
+  }
+
+  if (buffer.byteLength === 0)
     return { bytesWritten: 0, buffer };
 
   if (isArrayBufferView(buffer)) {

test/parallel/test-fs-promises-write-optional-params.js

@@ -0,0 +1,87 @@
+'use strict';
+
+const common = require('../common');
+
+// This test ensures that filehandle.write accepts "named parameters" object
+// and doesn't interpret objects as strings
+
+const assert = require('assert');
+const fsPromises = require('fs').promises;
+const path = require('path');
+const tmpdir = require('../common/tmpdir');
+
+tmpdir.refresh();
+
+const dest = path.resolve(tmpdir.path, 'tmp.txt');
+const buffer = Buffer.from('zyx');
+
+async function testInvalid(dest, expectedCode, params) {
+  let fh;
+  try {
+    fh = await fsPromises.open(dest, 'w+');
+    await assert.rejects(
+      async () => fh.write(params),
+      { code: expectedCode });
+  } finally {
+    await fh?.close();
+  }
+}
+
+async function testValid(dest, params) {
+  let fh;
+  try {
+    fh = await fsPromises.open(dest, 'w+');
+    const writeResult = await fh.write(params);
+    const writeBufCopy = Uint8Array.prototype.slice.call(writeResult.buffer);
+    const readResult = await fh.read(params);
+    const readBufCopy = Uint8Array.prototype.slice.call(readResult.buffer);
+
+    assert.ok(writeResult.bytesWritten >= readResult.bytesRead);
+    if (params.length !== undefined && params.length !== null) {
+      assert.strictEqual(writeResult.bytesWritten, params.length);
+    }
+    if (params.offset === undefined || params.offset === 0) {
+      assert.deepStrictEqual(writeBufCopy, readBufCopy);
+    }
+    assert.deepStrictEqual(writeResult.buffer, readResult.buffer);
+  } finally {
+    await fh?.close();
+  }
+}
+
+(async () => {
+  // Test if first argument is not wrongly interpreted as ArrayBufferView|string
+  for (const badParams of [
+    undefined, null, true, 42, 42n, Symbol('42'), NaN, [],
+    {},
+    { buffer: 'amNotParam' },
+    { string: 'amNotParam' },
+    { buffer: new Uint8Array(1).buffer },
+    new Date(),
+    new String('notPrimitive'),
+    { toString() { return 'amObject'; } },
+    { [Symbol.toPrimitive]: (hint) => 'amObject' },
+  ]) {
+    await testInvalid(dest, 'ERR_INVALID_ARG_TYPE', badParams);
+  }
+
+  // Various invalid params
+  await testInvalid(dest, 'ERR_OUT_OF_RANGE', { buffer, length: 5 });
+  await testInvalid(dest, 'ERR_OUT_OF_RANGE', { buffer, offset: 5 });
+  await testInvalid(dest, 'ERR_OUT_OF_RANGE', { buffer, length: 1, offset: 3 });
+  await testInvalid(dest, 'ERR_OUT_OF_RANGE', { buffer, length: -1 });
+  await testInvalid(dest, 'ERR_OUT_OF_RANGE', { buffer, offset: -1 });
+
+  // Test compatibility with filehandle.read counterpart with reused params
+  for (const params of [
+    { buffer },
+    { buffer, length: 1 },
+    { buffer, position: 5 },
+    { buffer, length: 1, position: 5 },
+    { buffer, length: 1, position: -1, offset: 2 },
+    { buffer, length: null },
+    { buffer, offset: 1 },
+  ]) {
+    await testValid(dest, params);
+  }
+})().then(common.mustCall());

test/parallel/test-fs-write-sync-optional-params.js

@@ -0,0 +1,82 @@
+'use strict';
+
+require('../common');
+
+// This test ensures that fs.writeSync accepts "named parameters" object
+// and doesn't interpret objects as strings
+
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+const tmpdir = require('../common/tmpdir');
+
+tmpdir.refresh();
+
+const dest = path.resolve(tmpdir.path, 'tmp.txt');
+const buffer = Buffer.from('zyx');
+
+function testInvalid(dest, expectedCode, ...bufferAndParams) {
+  let fd;
+  try {
+    fd = fs.openSync(dest, 'w+');
+    assert.throws(
+      () => fs.writeSync(fd, ...bufferAndParams),
+      { code: expectedCode });
+  } finally {
+    if (fd != null) fs.closeSync(fd);
+  }
+}
+
+function testValid(dest, buffer, params) {
+  let fd;
+  try {
+    fd = fs.openSync(dest, 'w+');
+    const bytesWritten = fs.writeSync(fd, buffer, params);
+    const bytesRead = fs.readSync(fd, buffer, params);
+
+    assert.ok(bytesWritten >= bytesRead);
+    if (params.length !== undefined && params.length !== null) {
+      assert.strictEqual(bytesWritten, params.length);
+    }
+  } finally {
+    if (fd != null) fs.closeSync(fd);
+  }
+}
+
+{
+  // Test if second argument is not wrongly interpreted as string or params
+  for (const badBuffer of [
+    undefined, null, true, 42, 42n, Symbol('42'), NaN, [],
+    {},
+    { buffer: 'amNotParam' },
+    { string: 'amNotParam' },
+    { buffer: new Uint8Array(1) },
+    { buffer: new Uint8Array(1).buffer },
+    new Date(),
+    new String('notPrimitive'),
+    { toString() { return 'amObject'; } },
+    { [Symbol.toPrimitive]: (hint) => 'amObject' },
+  ]) {
+    testInvalid(dest, 'ERR_INVALID_ARG_TYPE', badBuffer);
+  }
+
+  // Various invalid params
+  testInvalid(dest, 'ERR_OUT_OF_RANGE', buffer, { length: 5 });
+  testInvalid(dest, 'ERR_OUT_OF_RANGE', buffer, { offset: 5 });
+  testInvalid(dest, 'ERR_OUT_OF_RANGE', buffer, { length: 1, offset: 3 });
+  testInvalid(dest, 'ERR_OUT_OF_RANGE', buffer, { length: -1 });
+  testInvalid(dest, 'ERR_OUT_OF_RANGE', buffer, { offset: -1 });
+
+  // Test compatibility with fs.readSync counterpart with reused params
+  for (const params of [
+    {},
+    { length: 1 },
+    { position: 5 },
+    { length: 1, position: 5 },
+    { length: 1, position: -1, offset: 2 },
+    { length: null },
+    { offset: 1 },
+  ]) {
+    testValid(dest, buffer, params);
+  }
+}