readline: add feature yank and yank pop

1. `Ctrl-Y` to yank previously deleted text
2. `Meta-Y` to do yank pop (cycle among deleted texts)
3. Use `getCursorPos().rows` to check if we have reached a new line,
instead of `getCursorPos().cols === 0`.
4. document and unittests.

PR-URL: nodejs#41301
Fixes: nodejs#41252
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Qingyu Deng <[email protected]>

Author: rayw000

doc/api/readline.md

@@ -1313,6 +1313,16 @@ const { createInterface } = require('readline');
     <td>Delete from the current position to the end of line</td>
     <td></td>
   </tr>
+  <tr>
+    <td><kbd>Ctrl</kbd>+<kbd>Y</kbd></td>
+    <td>Yank (Recall) the previously deleted text</td>
+    <td>Only works with text deleted by <kbd>Ctrl</kbd>+<kbd>U</kbd> or <kbd>Ctrl</kbd>+<kbd>K</kbd></td>
+  </tr>
+  <tr>
+    <td><kbd>Meta</kbd>+<kbd>Y</kbd></td>
+    <td>Cycle among previously deleted lines</td>
+    <td>Only available when the last keystroke is <kbd>Ctrl</kbd>+<kbd>Y</kbd></td>
+  </tr>
   <tr>
     <td><kbd>Ctrl</kbd>+<kbd>A</kbd></td>
     <td>Go to start of line</td>

lib/internal/readline/interface.js

@@ -81,6 +81,9 @@ const kQuestionCancel = Symbol('kQuestionCancel');
 // GNU readline library - keyseq-timeout is 500ms (default)
 const ESCAPE_CODE_TIMEOUT = 500;
 
+// Max length of the kill ring
+const kMaxLengthOfKillRing = 32;
+
 const kAddHistory = Symbol('_addHistory');
 const kBeforeEdit = Symbol('_beforeEdit');
 const kDecoder = Symbol('_decoder');
@@ -96,12 +99,15 @@ const kHistoryPrev = Symbol('_historyPrev');
 const kInsertString = Symbol('_insertString');
 const kLine = Symbol('_line');
 const kLine_buffer = Symbol('_line_buffer');
+const kKillRing = Symbol('_killRing');
+const kKillRingCursor = Symbol('_killRingCursor');
 const kMoveCursor = Symbol('_moveCursor');
 const kNormalWrite = Symbol('_normalWrite');
 const kOldPrompt = Symbol('_oldPrompt');
 const kOnLine = Symbol('_onLine');
 const kPreviousKey = Symbol('_previousKey');
 const kPrompt = Symbol('_prompt');
+const kPushToKillRing = Symbol('_pushToKillRing');
 const kPushToUndoStack = Symbol('_pushToUndoStack');
 const kQuestionCallback = Symbol('_questionCallback');
 const kRedo = Symbol('_redo');
@@ -118,6 +124,9 @@ const kUndoStack = Symbol('_undoStack');
 const kWordLeft = Symbol('_wordLeft');
 const kWordRight = Symbol('_wordRight');
 const kWriteToOutput = Symbol('_writeToOutput');
+const kYank = Symbol('_yank');
+const kYanking = Symbol('_yanking');
+const kYankPop = Symbol('_yankPop');
 
 function InterfaceConstructor(input, output, completer, terminal) {
   this[kSawReturnAt] = 0;
@@ -211,6 +220,15 @@ function InterfaceConstructor(input, output, completer, terminal) {
   this[kRedoStack] = [];
   this.history = history;
   this.historySize = historySize;
+
+  // The kill ring is a global list of blocks of text that were previously
+  // killed (deleted). If its size exceeds kMaxLengthOfKillRing, the oldest
+  // element will be removed to make room for the latest deletion. With kill
+  // ring, users are able to recall (yank) or cycle (yank pop) among previously
+  // killed texts, quite similar to the behavior of Emacs.
+  this[kKillRing] = [];
+  this[kKillRingCursor] = 0;
+
   this.removeHistoryDuplicates = !!removeHistoryDuplicates;
   this.crlfDelay = crlfDelay ?
     MathMax(kMincrlfDelay, crlfDelay) :
@@ -606,10 +624,12 @@ class Interface extends InterfaceConstructor {
       this.cursor += c.length;
       this[kRefreshLine]();
     } else {
+      const oldPos = this.getCursorPos();
       this.line += c;
       this.cursor += c.length;
+      const newPos = this.getCursorPos();
 
-      if (this.getCursorPos().cols === 0) {
+      if (oldPos.rows < newPos.rows) {
         this[kRefreshLine]();
       } else {
         this[kWriteToOutput](c);
@@ -792,17 +812,57 @@ class Interface extends InterfaceConstructor {
 
   [kDeleteLineLeft]() {
     this[kBeforeEdit](this.line, this.cursor);
+    const del = StringPrototypeSlice(this.line, 0, this.cursor);
     this.line = StringPrototypeSlice(this.line, this.cursor);
     this.cursor = 0;
+    this[kPushToKillRing](del);
     this[kRefreshLine]();
   }
 
   [kDeleteLineRight]() {
     this[kBeforeEdit](this.line, this.cursor);
+    const del = StringPrototypeSlice(this.line, this.cursor);
     this.line = StringPrototypeSlice(this.line, 0, this.cursor);
+    this[kPushToKillRing](del);
     this[kRefreshLine]();
   }
 
+  [kPushToKillRing](del) {
+    if (!del || del === this[kKillRing][0]) return;
+    ArrayPrototypeUnshift(this[kKillRing], del);
+    this[kKillRingCursor] = 0;
+    while (this[kKillRing].length > kMaxLengthOfKillRing)
+      ArrayPrototypePop(this[kKillRing]);
+  }
+
+  [kYank]() {
+    if (this[kKillRing].length > 0) {
+      this[kYanking] = true;
+      this[kInsertString](this[kKillRing][this[kKillRingCursor]]);
+    }
+  }
+
+  [kYankPop]() {
+    if (!this[kYanking]) {
+      return;
+    }
+    if (this[kKillRing].length > 1) {
+      const lastYank = this[kKillRing][this[kKillRingCursor]];
+      this[kKillRingCursor]++;
+      if (this[kKillRingCursor] >= this[kKillRing].length) {
+        this[kKillRingCursor] = 0;
+      }
+      const currentYank = this[kKillRing][this[kKillRingCursor]];
+      const head =
+            StringPrototypeSlice(this.line, 0, this.cursor - lastYank.length);
+      const tail =
+            StringPrototypeSlice(this.line, this.cursor);
+      this.line = head + currentYank + tail;
+      this.cursor = head.length + currentYank.length;
+      this[kRefreshLine]();
+    }
+  }
+
   clearLine() {
     this[kMoveCursor](+Infinity);
     this[kWriteToOutput]('\r\n');
@@ -984,6 +1044,11 @@ class Interface extends InterfaceConstructor {
     key = key || {};
     this[kPreviousKey] = key;
 
+    if (!key.meta || key.name !== 'y') {
+      // Reset yanking state unless we are doing yank pop.
+      this[kYanking] = false;
+    }
+
     // Activate or deactivate substring search.
     if (
       (key.name === 'up' || key.name === 'down') &&
@@ -1094,6 +1159,10 @@ class Interface extends InterfaceConstructor {
           this[kHistoryPrev]();
           break;
 
+        case 'y': // Yank killed string
+          this[kYank]();
+          break;
+
         case 'z':
           if (process.platform === 'win32') break;
           if (this.listenerCount('SIGTSTP') > 0) {
@@ -1158,6 +1227,10 @@ class Interface extends InterfaceConstructor {
         case 'backspace': // Delete backwards to a word boundary
           this[kDeleteWordLeft]();
           break;
+
+        case 'y': // Doing yank pop
+          this[kYankPop]();
+          break;
       }
     } else {
       /* No modifier keys used */

test/parallel/test-readline-interface.js

@@ -674,6 +674,77 @@ function assertCursorRowsAndCols(rli, rows, cols) {
   rli.close();
 }
 
+// yank
+{
+  const [rli, fi] = getInterface({ terminal: true, prompt: '' });
+  fi.emit('data', 'the quick brown fox');
+  assertCursorRowsAndCols(rli, 0, 19);
+
+  // Go to the start of the line
+  fi.emit('keypress', '.', { ctrl: true, name: 'a' });
+  // Move forward one char
+  fi.emit('keypress', '.', { ctrl: true, name: 'f' });
+  // Delete the right part
+  fi.emit('keypress', '.', { ctrl: true, shift: true, name: 'delete' });
+  assertCursorRowsAndCols(rli, 0, 1);
+
+  // Yank
+  fi.emit('keypress', '.', { ctrl: true, name: 'y' });
+  assertCursorRowsAndCols(rli, 0, 19);
+
+  rli.on('line', common.mustCall((line) => {
+    assert.strictEqual(line, 'the quick brown fox');
+  }));
+
+  fi.emit('data', '\n');
+  rli.close();
+}
+
+// yank pop
+{
+  const [rli, fi] = getInterface({ terminal: true, prompt: '' });
+  fi.emit('data', 'the quick brown fox');
+  assertCursorRowsAndCols(rli, 0, 19);
+
+  // Go to the start of the line
+  fi.emit('keypress', '.', { ctrl: true, name: 'a' });
+  // Move forward one char
+  fi.emit('keypress', '.', { ctrl: true, name: 'f' });
+  // Delete the right part
+  fi.emit('keypress', '.', { ctrl: true, shift: true, name: 'delete' });
+  assertCursorRowsAndCols(rli, 0, 1);
+  // Yank
+  fi.emit('keypress', '.', { ctrl: true, name: 'y' });
+  assertCursorRowsAndCols(rli, 0, 19);
+
+  // Go to the start of the line
+  fi.emit('keypress', '.', { ctrl: true, name: 'a' });
+  // Move forward four chars
+  fi.emit('keypress', '.', { ctrl: true, name: 'f' });
+  fi.emit('keypress', '.', { ctrl: true, name: 'f' });
+  fi.emit('keypress', '.', { ctrl: true, name: 'f' });
+  fi.emit('keypress', '.', { ctrl: true, name: 'f' });
+  // Delete the right part
+  fi.emit('keypress', '.', { ctrl: true, shift: true, name: 'delete' });
+  assertCursorRowsAndCols(rli, 0, 4);
+  // Go to the start of the line
+  fi.emit('keypress', '.', { ctrl: true, name: 'a' });
+  assertCursorRowsAndCols(rli, 0, 0);
+
+  // Yank: 'quick brown fox|the '
+  fi.emit('keypress', '.', { ctrl: true, name: 'y' });
+  // Yank pop: 'he quick brown fox|the'
+  fi.emit('keypress', '.', { meta: true, name: 'y' });
+  assertCursorRowsAndCols(rli, 0, 18);
+
+  rli.on('line', common.mustCall((line) => {
+    assert.strictEqual(line, 'he quick brown foxthe ');
+  }));
+
+  fi.emit('data', '\n');
+  rli.close();
+}
+
 // Close readline interface
 {
   const [rli, fi] = getInterface({ terminal: true, prompt: '' });