readline: expose stream API in moveCursor()

This commit adds an optional callback to moveCursor(), which is
passed to the stream's write() method. It also exposes the
return value of write().

PR-URL: #28674
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Trivikram Kamat <[email protected]>

Author: cjihrig

doc/api/readline.md

@@ -525,14 +525,22 @@ if (process.stdin.isTTY)
   process.stdin.setRawMode(true);
 ```
 
-## readline.moveCursor(stream, dx, dy)
+## readline.moveCursor(stream, dx, dy[, callback])
 <!-- YAML
 added: v0.7.7
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/28674
+    description: The stream's write() callback and return value are exposed.
 -->
 
 * `stream` {stream.Writable}
 * `dx` {number}
 * `dy` {number}
+* `callback` {Function} Invoked once the operation completes.
+* Returns: {boolean} `false` if `stream` wishes for the calling code to wait for
+  the `'drain'` event to be emitted before continuing to write additional data;
+  otherwise `true`.
 
 The `readline.moveCursor()` method moves the cursor *relative* to its current
 position in a given [TTY][] `stream`.

lib/readline.js

@@ -1210,21 +1210,31 @@ function cursorTo(stream, x, y) {
  * moves the cursor relative to its current location
  */
 
-function moveCursor(stream, dx, dy) {
-  if (stream === null || stream === undefined)
-    return;
+function moveCursor(stream, dx, dy, callback) {
+  if (callback !== undefined && typeof callback !== 'function')
+    throw new ERR_INVALID_CALLBACK(callback);
+
+  if (stream == null || !(dx || dy)) {
+    if (typeof callback === 'function')
+      process.nextTick(callback);
+    return true;
+  }
+
+  let data = '';
 
   if (dx < 0) {
-    stream.write(CSI`${-dx}D`);
+    data += CSI`${-dx}D`;
   } else if (dx > 0) {
-    stream.write(CSI`${dx}C`);
+    data += CSI`${dx}C`;
   }
 
   if (dy < 0) {
-    stream.write(CSI`${-dy}A`);
+    data += CSI`${-dy}A`;
   } else if (dy > 0) {
-    stream.write(CSI`${dy}B`);
+    data += CSI`${dy}B`;
   }
+
+  return stream.write(data, callback);
 }
 
 /**

test/parallel/test-readline-csi.js

@@ -83,10 +83,28 @@ assert.strictEqual(readline.clearLine(undefined, 0, common.mustCall()), true);
   [1, -1, '\x1b[1C\x1b[1A'],
 ].forEach((set) => {
   writable.data = '';
-  readline.moveCursor(writable, set[0], set[1]);
+  assert.strictEqual(readline.moveCursor(writable, set[0], set[1]), true);
+  assert.deepStrictEqual(writable.data, set[2]);
+  writable.data = '';
+  assert.strictEqual(
+    readline.moveCursor(writable, set[0], set[1], common.mustCall()),
+    true
+  );
   assert.deepStrictEqual(writable.data, set[2]);
 });
 
+// Verify that moveCursor() throws on invalid callback.
+assert.throws(() => {
+  readline.moveCursor(writable, 1, 1, null);
+}, /ERR_INVALID_CALLBACK/);
+
+// Verify that moveCursor() does not throw on null or undefined stream.
+assert.strictEqual(readline.moveCursor(null, 1, 1), true);
+assert.strictEqual(readline.moveCursor(undefined, 1, 1), true);
+assert.strictEqual(readline.moveCursor(null, 1, 1, common.mustCall()), true);
+assert.strictEqual(readline.moveCursor(undefined, 1, 1, common.mustCall()),
+                   true);
+
 // Undefined or null as stream should not throw.
 readline.cursorTo(null);
 readline.cursorTo();