feat(node_compat): Add a write method to the FileHandle class

cli/tests/unit_node/_fs/_fs_handle_test.ts

@@ -1,21 +1,22 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
 import * as path from "../../../../test_util/std/path/mod.ts";
+import { Buffer } from "node:buffer";
 import * as fs from "node:fs/promises";
 import {
   assert,
   assertEquals,
 } from "../../../../test_util/std/testing/asserts.ts";
-import { Buffer } from "node:buffer";
 
 const moduleDir = path.dirname(path.fromFileUrl(import.meta.url));
 const testData = path.resolve(moduleDir, "testdata", "hello.txt");
+const decoder = new TextDecoder();
 
 Deno.test("readFileSuccess", async function () {
   const fileHandle = await fs.open(testData);
   const data = await fileHandle.readFile();
 
   assert(data instanceof Uint8Array);
-  assertEquals(new TextDecoder().decode(data as Uint8Array), "hello world");
+  assertEquals(decoder.decode(data as Uint8Array), "hello world");
 
   await fileHandle.close();
 });
@@ -27,7 +28,7 @@ Deno.test("read", async function () {
   const buf = new Buffer(byteLength);
   await fileHandle.read(buf, 0, byteLength, 0);
 
-  assertEquals(new TextDecoder().decode(buf as Uint8Array), "hello world");
+  assertEquals(decoder.decode(buf as Uint8Array), "hello world");
 
   await fileHandle.close();
 });
@@ -54,7 +55,37 @@ Deno.test("read specify opt", async function () {
   res = await fileHandle.read(opt2);
 
   assertEquals(res.bytesRead, byteLength);
-  assertEquals(new TextDecoder().decode(res.buffer as Uint8Array), "hello");
+  assertEquals(decoder.decode(res.buffer as Uint8Array), "hello");
+
+  await fileHandle.close();
+});
+
+Deno.test("[node/fs filehandle.write] Write from Buffer", async function () {
+  const tempFile: string = await Deno.makeTempFile();
+  const fileHandle = await fs.open(tempFile, "a+");
+
+  const buffer = Buffer.from("hello world");
+  const res = await fileHandle.write(buffer, 0, 5, 0);
 
+  const data = Deno.readFileSync(tempFile);
+  await Deno.remove(tempFile);
   await fileHandle.close();
+
+  assertEquals(res.bytesWritten, 5);
+  assertEquals(decoder.decode(data), "hello");
+});
+
+Deno.test("[node/fs filehandle.write] Write from string", async function () {
+  const tempFile: string = await Deno.makeTempFile();
+  const fileHandle = await fs.open(tempFile, "a+");
+
+  const str = "hello world";
+  const res = await fileHandle.write(str);
+
+  const data = Deno.readFileSync(tempFile);
+  await Deno.remove(tempFile);
+  await fileHandle.close();
+
+  assertEquals(res.bytesWritten, 11);
+  assertEquals(decoder.decode(data), "hello world");
 });

ext/node/polyfills/internal/fs/handle.ts

@@ -1,15 +1,19 @@
 // Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
 import { EventEmitter } from "ext:deno_node/events.ts";
 import { Buffer } from "ext:deno_node/buffer.ts";
-import { promises, read } from "ext:deno_node/fs.ts";
-import type { Buffer } from "ext:deno_node/buffer.ts";
+import { promises, read, write } from "ext:deno_node/fs.ts";
 import {
   BinaryOptionsArgument,
   FileOptionsArgument,
   ReadOptions,
   TextOptionsArgument,
 } from "ext:deno_node/_fs/_fs_common.ts";
 
+interface WriteResult {
+  bytesWritten: number;
+  buffer: Buffer | string;
+}
+
 interface ReadResult {
   bytesRead: number;
   buffer: Buffer;
@@ -69,6 +73,61 @@ export class FileHandle extends EventEmitter {
     return promises.readFile(this, opt);
   }
 
+  write(
+    buffer: Buffer,
+    offset: number,
+    length: number,
+    position: number,
+  ): Promise<WriteResult>;
+  write(
+    str: string,
+    position: number,
+    encoding: string,
+  ): Promise<WriteResult>;
+  write(
+    bufferOrStr: Buffer | string,
+    offsetOrPotition: number,
+    lengthOrEncoding: number | string,
+    position?: number,
+  ): Promise<WriteResult> {
+    if (bufferOrStr instanceof Buffer) {
+      const buffer = bufferOrStr;
+      const offset = offsetOrPotition;
+      const length = lengthOrEncoding;
+
+      return new Promise((resolve, reject) => {
+        write(
+          this.fd,
+          buffer,
+          offset,
+          length,
+          position,
+          (err, bytesWritten, buffer) => {
+            if (err) reject(err);
+            else resolve({ buffer, bytesWritten });
+          },
+        );
+      });
+    } else {
+      const str = bufferOrStr;
+      const position = offsetOrPotition;
+      const encoding = lengthOrEncoding;
+
+      return new Promise((resolve, reject) => {
+        write(
+          this.fd,
+          str,
+          position,
+          encoding,
+          (err, bytesWritten, buffer) => {
+            if (err) reject(err);
+            else resolve({ buffer, bytesWritten });
+          },
+        );
+      });
+    }
+  }
+
   close(): Promise<void> {
     // Note that Deno.close is not async
     return Promise.resolve(Deno.close(this.fd));