fs: add docs and tests for AsyncIterable support in fh.writeFile

Refs: nodejs#37490

Author: aduh95

doc/api/fs.md

@@ -545,6 +545,9 @@ the end of the file.
 <!-- YAML
 added: v10.0.0
 changes:
+  - version: v15.14.0
+    pr-url: https://github.com/nodejs/node/pull/37490
+    description: The `data` argument supports `AsyncIterable`, `Iterable` & `Stream`.
   - version: v14.12.0
     pr-url: https://github.com/nodejs/node/pull/34993
     description: The `data` parameter will stringify an object with an
@@ -555,14 +558,15 @@ changes:
                  strings anymore.
 -->
 
-* `data` {string|Buffer|TypedArray|DataView|Object}
+* `data` {string|Buffer|TypedArray|DataView|Object|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, or an object with an own `toString` function
+`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.
 
 If `options` is a string, then it specifies the `encoding`.

test/parallel/test-fs-promises-file-handle-writeFile.js

@@ -8,6 +8,7 @@ const common = require('../common');
 const fs = require('fs');
 const { open, writeFile } = fs.promises;
 const path = require('path');
+const { Readable } = require('stream');
 const tmpdir = require('../common/tmpdir');
 const assert = require('assert');
 const tmpDir = tmpdir.path;
@@ -43,6 +44,126 @@ async function doWriteAndCancel() {
   }
 }
 
-validateWriteFile()
-  .then(doWriteAndCancel)
-  .then(common.mustCall());
+const dest = path.resolve(tmpDir, 'tmp.txt');
+const otherDest = path.resolve(tmpDir, 'tmp-2.txt');
+const stream = Readable.from(['a', 'b', 'c']);
+const stream2 = Readable.from(['ümlaut', ' ', 'sechzig']);
+const iterable = {
+  expected: 'abc',
+  *[Symbol.iterator]() {
+    yield 'a';
+    yield 'b';
+    yield 'c';
+  }
+};
+function iterableWith(value) {
+  return {
+    *[Symbol.iterator]() {
+      yield value;
+    }
+  };
+}
+const bufferIterable = {
+  expected: 'abc',
+  *[Symbol.iterator]() {
+    yield Buffer.from('a');
+    yield Buffer.from('b');
+    yield Buffer.from('c');
+  }
+};
+const asyncIterable = {
+  expected: 'abc',
+  async* [Symbol.asyncIterator]() {
+    yield 'a';
+    yield 'b';
+    yield 'c';
+  }
+};
+
+async function doWriteStream() {
+  const fileHandle = await open(dest, 'w+');
+  await fileHandle.writeFile(stream);
+  const expected = 'abc';
+  const data = fs.readFileSync(dest, 'utf-8');
+  assert.deepStrictEqual(data, expected);
+}
+
+async function doWriteStreamWithCancel() {
+  const controller = new AbortController();
+  const { signal } = controller;
+  process.nextTick(() => controller.abort());
+  const fileHandle = await open(otherDest, 'w+');
+  assert.rejects(fileHandle.writeFile(stream, { signal }), {
+    name: 'AbortError'
+  });
+}
+
+async function doWriteIterable() {
+  const fileHandle = await open(dest, 'w+');
+  await fileHandle.writeFile(iterable);
+  const data = fs.readFileSync(dest, 'utf-8');
+  assert.deepStrictEqual(data, iterable.expected);
+  await fileHandle.close();
+}
+
+async function doWriteInvalidIterable() {
+  const fileHandle = await open(dest, 'w+');
+  await Promise.all(
+    [42, 42n, {}, Symbol('42'), true, undefined, null, NaN].map((value) =>
+      assert.rejects(fileHandle.writeFile(iterableWith(value)), {
+        code: 'ERR_INVALID_ARG_TYPE',
+      })
+    )
+  );
+  await fileHandle.close();
+}
+
+async function doWriteIterableWithEncoding() {
+  const fileHandle = await open(dest, 'w+');
+  await fileHandle.writeFile(stream2, 'latin1');
+  const expected = 'ümlaut sechzig';
+  const data = fs.readFileSync(dest, 'latin1');
+  assert.deepStrictEqual(data, expected);
+  await fileHandle.close();
+}
+
+async function doWriteBufferIterable() {
+  const fileHandle = await open(dest, 'w+');
+  await fileHandle.writeFile(bufferIterable);
+  const data = fs.readFileSync(dest, 'utf-8');
+  assert.deepStrictEqual(data, bufferIterable.expected);
+  await fileHandle.close();
+}
+
+async function doWriteAsyncIterable() {
+  const fileHandle = await open(dest, 'w+');
+  await fileHandle.writeFile(asyncIterable);
+  const data = fs.readFileSync(dest, 'utf-8');
+  assert.deepStrictEqual(data, asyncIterable.expected);
+  await fileHandle.close();
+}
+
+async function doWriteInvalidValues() {
+  const fileHandle = await open(dest, 'w+');
+  await Promise.all(
+    [42, 42n, {}, Symbol('42'), true, undefined, null, NaN].map((value) =>
+      assert.rejects(fileHandle.writeFile(value), {
+        code: 'ERR_INVALID_ARG_TYPE',
+      })
+    )
+  );
+  await fileHandle.close();
+}
+
+(async () => {
+  await validateWriteFile();
+  await doWriteAndCancel();
+  await doWriteStream();
+  await doWriteStreamWithCancel();
+  await doWriteIterable();
+  await doWriteInvalidIterable();
+  await doWriteIterableWithEncoding();
+  await doWriteBufferIterable();
+  await doWriteAsyncIterable();
+  await doWriteInvalidValues();
+})().then(common.mustCall());