fs: make offset, position & length args in fh.read() optional

PR-URL: #51087
Fixes: #47183
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Vinícius Lourenço Claro Cardoso <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: James M Snell <[email protected]>

Author: pulkit-30

doc/api/fs.md

@@ -385,11 +385,14 @@ added: v10.0.0
 * `buffer` {Buffer|TypedArray|DataView} A buffer that will be filled with the
   file data read.
 * `offset` {integer} The location in the buffer at which to start filling.
-* `length` {integer} The number of bytes to read.
-* `position` {integer|null} The location where to begin reading data from the
-  file. If `null`, data will be read from the current file position, and
-  the position will be updated. If `position` is an integer, the current
-  file position will remain unchanged.
+  **Default:** `0`
+* `length` {integer} The number of bytes to read. **Default:**
+  `buffer.byteLength - offset`
+* `position` {integer|bigint|null} The location where to begin reading data
+  from the file. If `null` or `-1`, data will be read from the current file
+  position, and the position will be updated. If `position` is a non-negative
+  integer, the current file position will remain unchanged.
+  **Default:**: `null`
 * Returns: {Promise} Fulfills upon success with an object with two properties:
   * `bytesRead` {integer} The number of bytes read
   * `buffer` {Buffer|TypedArray|DataView} A reference to the passed in `buffer`

lib/internal/fs/promises.js

@@ -642,7 +642,7 @@ async function read(handle, bufferOrParams, offset, length, position) {
     validateInteger(offset, 'offset', 0);
   }
 
-  length |= 0;
+  length ??= buffer.byteLength - offset;
 
   if (length === 0)
     return { __proto__: null, bytesRead: length, buffer };

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

@@ -14,7 +14,7 @@ const assert = require('assert');
 const tmpDir = tmpdir.path;
 
 async function read(fileHandle, buffer, offset, length, position, options) {
-  return options.useConf ?
+  return options?.useConf ?
     fileHandle.read({ buffer, offset, length, position }) :
     fileHandle.read(buffer, offset, length, position);
 }
@@ -96,6 +96,21 @@ async function validateReadLength(len) {
   assert.strictEqual(bytesRead, len);
 }
 
+async function validateReadWithNoOptions(byte) {
+  const buf = Buffer.alloc(byte);
+  const filePath = fixtures.path('x.txt');
+  const fileHandle = await open(filePath, 'r');
+  let response = await fileHandle.read(buf);
+  assert.strictEqual(response.bytesRead, byte);
+  response = await read(fileHandle, buf, 0, undefined, 0);
+  assert.strictEqual(response.bytesRead, byte);
+  response = await read(fileHandle, buf, 0, null, 0);
+  assert.strictEqual(response.bytesRead, byte);
+  response = await read(fileHandle, buf, 0, undefined, 0, { useConf: true });
+  assert.strictEqual(response.bytesRead, byte);
+  response = await read(fileHandle, buf, 0, null, 0, { useConf: true });
+  assert.strictEqual(response.bytesRead, byte);
+}
 
 (async function() {
   tmpdir.refresh();
@@ -109,4 +124,6 @@ async function validateReadLength(len) {
   await validateReadWithPositionZero();
   await validateReadLength(0);
   await validateReadLength(1);
+  await validateReadWithNoOptions(0);
+  await validateReadWithNoOptions(1);
 })().then(common.mustCall());