test: fix fs write encoding coverage

Pass an encoding rather than a string length to FileHandle.write.
Cover invalid encodings in fs.write, fs.writeSync, and FileHandle.write,
along with valid encodings and unchanged files after rejected writes.

Rejecting previously accepted invalid encodings is an intentional
semver-major bug fix shared with the crypto validation changes.

Signed-off-by: Filip Skokan <panva.ip@gmail.com>
Assisted-by: Codex

Author: panva

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

@@ -41,11 +41,11 @@ async function validateEmptyWrite() {
 async function validateNonUint8ArrayWrite() {
   const filePathForHandle = path.resolve(tmpDir, 'tmp-data-write.txt');
   const fileHandle = await open(filePathForHandle, 'w+');
-  const buffer = Buffer.from('Hello world', 'utf8').toString('base64');
+  const string = Buffer.from('Hello world', 'utf8').toString('base64');
 
-  await fileHandle.write(buffer, 0, buffer.length);
+  await fileHandle.write(string, 0, 'utf8');
   const readFileData = fs.readFileSync(filePathForHandle);
-  assert.deepStrictEqual(Buffer.from(buffer, 'utf8'), readFileData);
+  assert.deepStrictEqual(Buffer.from(string, 'utf8'), readFileData);
 
   await fileHandle.close();
 }

test/parallel/test-fs-write-invalid-encoding.js

@@ -0,0 +1,56 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+const tmpdir = require('../common/tmpdir');
+
+tmpdir.refresh();
+
+async function main() {
+  const file = path.join(tmpdir.path, 'write-invalid-encoding');
+  const handle = await fs.promises.open(file, 'w+');
+  try {
+    for (const encoding of ['bad', 16]) {
+      const error = {
+        code: 'ERR_UNKNOWN_ENCODING',
+        message: `Unknown encoding: ${encoding}`,
+      };
+      assert.throws(() => fs.writeSync(handle.fd, '6162', 0, encoding), error);
+      assert.throws(
+        () => fs.write(handle.fd, '6162', 0, encoding, common.mustNotCall()),
+        error);
+      await assert.rejects(handle.write('6162', 0, encoding), error);
+    }
+    // Rejected writes must not change the file.
+    assert.strictEqual((await handle.stat()).size, 0);
+
+    for (const encoding of [undefined, null, '', 'utf8', 'UTF-8', 'hex']) {
+      const expected = encoding === 'hex' ? 'ab' : '6162';
+      await handle.truncate(0);
+      assert.strictEqual(fs.writeSync(handle.fd, '6162', 0, encoding),
+                         expected.length);
+      assert.strictEqual(fs.readFileSync(file, 'utf8'), expected);
+
+      await handle.truncate(0);
+      await new Promise((resolve, reject) => {
+        fs.write(handle.fd, '6162', 0, encoding, common.mustCall((err, written) => {
+          if (err) return reject(err);
+          assert.strictEqual(written, expected.length);
+          resolve();
+        }));
+      });
+      assert.strictEqual(fs.readFileSync(file, 'utf8'), expected);
+
+      await handle.truncate(0);
+      const { bytesWritten } = await handle.write('6162', 0, encoding);
+      assert.strictEqual(bytesWritten, expected.length);
+      assert.strictEqual(fs.readFileSync(file, 'utf8'), expected);
+    }
+  } finally {
+    await handle.close();
+  }
+}
+
+main().then(common.mustCall());