feat(node_compat): Added base implementation of FileHandle (#19294)

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## WHY

ref: https://github.com/denoland/deno/issues/19165

Node's fs/promises includes a FileHandle class, but deno does not. The
open function in Node's fs/promises returns a FileHandle, which provides
an IO interface to the file. However, deno's open function returns a
resource id.


### deno 

```js
> const fs = await import("node:fs/promises");
undefined
> const file3 = await fs.open("./README.md");
undefined
> file3
3
> file3.read
undefined
Node:
```

### Node
```js
> const fs = await import("fs/promises");
undefined
>   const file3 = await fs.open("./tests/e2e_unit/testdata/file.txt");
undefined
> file3
FileHandle {
  _events: [Object: null prototype] {},
  _eventsCount: 0,
  _maxListeners: undefined,
  close: [Function: close],
  [Symbol(kCapture)]: false,
  [Symbol(kHandle)]: FileHandle {},
  [Symbol(kFd)]: 24,
  [Symbol(kRefs)]: 1,
  [Symbol(kClosePromise)]: null
}
> file3.read
[Function: read]
```


To be compatible with Node, deno's open function should also return a
FileHandle.

## WHAT

I have implemented the first step in adding a FileHandle.

- Changed the return value of the open function to a FileHandle object
- Implemented the readFile method in FileHandle
- Add test code


## What to do next
This PR is the first step in adding a FileHandle, and there are things
that should be done next.

- Add functionality equivalent to Node's FileHandle to FileHandle
(currently there is only readFile)

---------

Co-authored-by: Matt Mastracci <matthew@mastracci.com>

cli/tests/integration/node_unit_tests.rs

@@ -25,6 +25,7 @@ util::unit_test_factory!(
     _fs_fsync_test = _fs / _fs_fsync_test,
     _fs_ftruncate_test = _fs / _fs_ftruncate_test,
     _fs_futimes_test = _fs / _fs_futimes_test,
+    _fs_handle_test = _fs / _fs_handle_test,
     _fs_link_test = _fs / _fs_link_test,
     _fs_lstat_test = _fs / _fs_lstat_test,
     _fs_mkdir_test = _fs / _fs_mkdir_test,

cli/tests/unit_node/_fs/_fs_handle_test.ts

@@ -0,0 +1,20 @@
+// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
+import * as path from "../../../../test_util/std/path/mod.ts";
+import {
+  assert,
+  assertEquals,
+} from "../../../../test_util/std/testing/asserts.ts";
+
+const moduleDir = path.dirname(path.fromFileUrl(import.meta.url));
+const testData = path.resolve(moduleDir, "testdata", "hello.txt");
+
+Deno.test("readFileSuccess", async function () {
+  const fs = await import("node:fs/promises");
+  const fileHandle = await fs.open(testData);
+  const data = await fileHandle.readFile();
+
+  assert(data instanceof Uint8Array);
+  assertEquals(new TextDecoder().decode(data as Uint8Array), "hello world");
+
+  Deno.close(fileHandle.fd);
+});

ext/node/lib.rs

@@ -392,6 +392,7 @@ deno_core::extension!(deno_node,
     "internal/fixed_queue.ts",
     "internal/fs/streams.mjs",
     "internal/fs/utils.mjs",
+    "internal/fs/handle.ts",
     "internal/hide_stack_frames.ts",
     "internal/http.ts",
     "internal/idna.ts",

ext/node/polyfills/_fs/_fs_open.ts

@@ -8,10 +8,10 @@ import {
   O_WRONLY,
 } from "ext:deno_node/_fs/_fs_constants.ts";
 import { getOpenOptions } from "ext:deno_node/_fs/_fs_common.ts";
-import { promisify } from "ext:deno_node/internal/util.mjs";
 import { parseFileMode } from "ext:deno_node/internal/validators.mjs";
 import { ERR_INVALID_ARG_TYPE } from "ext:deno_node/internal/errors.ts";
 import { getValidatedPath } from "ext:deno_node/internal/fs/utils.mjs";
+import { FileHandle } from "ext:deno_node/internal/fs/handle.ts";
 import type { Buffer } from "ext:deno_node/buffer.ts";
 
 function existsSync(filePath: string | URL): boolean {
@@ -139,16 +139,18 @@ export function open(
   }
 }
 
-export const openPromise = promisify(open) as (
-  & ((path: string | Buffer | URL) => Promise<number>)
-  & ((path: string | Buffer | URL, flags: openFlags) => Promise<number>)
-  & ((path: string | Buffer | URL, mode?: number) => Promise<number>)
-  & ((
-    path: string | Buffer | URL,
-    flags?: openFlags,
-    mode?: number,
-  ) => Promise<number>)
-);
+export function openPromise(
+  path: string | Buffer | URL,
+  flags?: openFlags = "r",
+  mode? = 0o666,
+): Promise<FileHandle> {
+  return new Promise((resolve, reject) => {
+    open(path, flags, mode, (err, fd) => {
+      if (err) reject(err);
+      else resolve(new FileHandle(fd));
+    });
+  });
+}
 
 export function openSync(path: string | Buffer | URL): number;
 export function openSync(

ext/node/polyfills/_fs/_fs_readFile.ts

@@ -6,6 +6,8 @@ import {
   TextOptionsArgument,
 } from "ext:deno_node/_fs/_fs_common.ts";
 import { Buffer } from "ext:deno_node/buffer.ts";
+import { readAll } from "ext:deno_io/12_io.js";
+import { FileHandle } from "ext:deno_node/internal/fs/handle.ts";
 import { fromFileUrl } from "ext:deno_node/path.ts";
 import {
   BinaryEncodings,
@@ -32,25 +34,26 @@ type TextCallback = (err: Error | null, data?: string) => void;
 type BinaryCallback = (err: Error | null, data?: Buffer) => void;
 type GenericCallback = (err: Error | null, data?: string | Buffer) => void;
 type Callback = TextCallback | BinaryCallback | GenericCallback;
+type Path = string | URL | FileHandle;
 
 export function readFile(
-  path: string | URL,
+  path: Path,
   options: TextOptionsArgument,
   callback: TextCallback,
 ): void;
 export function readFile(
-  path: string | URL,
+  path: Path,
   options: BinaryOptionsArgument,
   callback: BinaryCallback,
 ): void;
 export function readFile(
-  path: string | URL,
+  path: Path,
   options: null | undefined | FileOptionsArgument,
   callback: BinaryCallback,
 ): void;
 export function readFile(path: string | URL, callback: BinaryCallback): void;
 export function readFile(
-  path: string | URL,
+  path: Path,
   optOrCallback?: FileOptionsArgument | Callback | null | undefined,
   callback?: Callback,
 ) {
@@ -64,7 +67,13 @@ export function readFile(
 
   const encoding = getEncoding(optOrCallback);
 
-  const p = Deno.readFile(path);
+  let p: Promise<Uint8Array>;
+  if (path instanceof FileHandle) {
+    const fsFile = new Deno.FsFile(path.fd);
+    p = readAll(fsFile);
+  } else {
+    p = Deno.readFile(path);
+  }
 
   if (cb) {
     p.then((data: Uint8Array) => {
@@ -79,9 +88,9 @@ export function readFile(
 }
 
 export const readFilePromise = promisify(readFile) as (
-  & ((path: string | URL, opt: TextOptionsArgument) => Promise<string>)
-  & ((path: string | URL, opt?: BinaryOptionsArgument) => Promise<Buffer>)
-  & ((path: string | URL, opt?: FileOptionsArgument) => Promise<Buffer>)
+  & ((path: Path, opt: TextOptionsArgument) => Promise<string>)
+  & ((path: Path, opt?: BinaryOptionsArgument) => Promise<Buffer>)
+  & ((path: Path, opt?: FileOptionsArgument) => Promise<Buffer>)
 );
 
 export function readFileSync(

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

@@ -0,0 +1,31 @@
+// 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 } from "ext:deno_node/fs.ts";
+import {
+  BinaryOptionsArgument,
+  FileOptionsArgument,
+  TextOptionsArgument,
+} from "ext:deno_node/_fs/_fs_common.ts";
+
+export class FileHandle extends EventEmitter {
+  #rid: number;
+  constructor(rid: number) {
+    super();
+    this.rid = rid;
+  }
+
+  get fd() {
+    return this.rid;
+  }
+
+  readFile(
+    opt?: TextOptionsArgument | BinaryOptionsArgument | FileOptionsArgument,
+  ): Promise<string | Buffer> {
+    return promises.readFile(this, opt);
+  }
+}
+
+export default {
+  FileHandle,
+};