repl,readline: clean up code

This simplifies code that was more complicated than it had to be
and removes code that should never be reached.

PR-URL: #31288
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

lib/internal/readline/utils.js

@@ -136,8 +136,7 @@ if (internalBinding('config').hasIntl) {
       (code >= 0x1b000 && code <= 0x1b001) ||
       // Enclosed Ideographic Supplement
       (code >= 0x1f200 && code <= 0x1f251) ||
-      // Miscellaneous Symbols and Pictographs 0x1f300 - 0x1f5ff
-      // Emoticons 0x1f600 - 0x1f64f
+      // Miscellaneous Symbols and Pictographs .. Emoticons
       (code >= 0x1f300 && code <= 0x1f64f) ||
       // CJK Unified Ideographs Extension B .. Tertiary Ideographic Plane
       (code >= 0x20000 && code <= 0x3fffd)
@@ -459,9 +458,6 @@ function* emitKeys(stream) {
 
 // This runs in O(n log n).
 function commonPrefix(strings) {
-  if (!strings || strings.length === 0) {
-    return '';
-  }
   if (strings.length === 1) {
     return strings[0];
   }

lib/internal/repl/utils.js

@@ -320,10 +320,8 @@ function setupPreview(repl, contextSymbol, bufferSymbol, active) {
     // Enter should automatically add the suffix to the current line as long as
     // escape was not pressed. We might even remove the preview in case any
     // cursor movement is triggered.
-    if (typeof repl.completer === 'function') {
-      const insertPreview = false;
-      showCompletionPreview(repl.line, insertPreview);
-    }
+    const insertPreview = false;
+    showCompletionPreview(repl.line, insertPreview);
 
     // Do not preview if the command is buffered.
     if (repl[bufferSymbol]) {

lib/readline.js

@@ -735,27 +735,13 @@ Interface.prototype._getDisplayPos = function(str) {
   return { cols, rows };
 };
 
-
 // Returns current cursor's position and line
 Interface.prototype.getCursorPos = function() {
-  const columns = this.columns;
   const strBeforeCursor = this._prompt + this.line.substring(0, this.cursor);
-  const dispPos = this._getDisplayPos(strBeforeCursor);
-  let cols = dispPos.cols;
-  let rows = dispPos.rows;
-  // If the cursor is on a full-width character which steps over the line,
-  // move the cursor to the beginning of the next line.
-  if (cols + 1 === columns &&
-      this.cursor < this.line.length &&
-      getStringWidth(this.line[this.cursor]) > 1) {
-    rows++;
-    cols = 0;
-  }
-  return { cols, rows };
+  return this._getDisplayPos(strBeforeCursor);
 };
 Interface.prototype._getCursorPos = Interface.prototype.getCursorPos;
 
-
 // This function moves cursor dx places to the right
 // (-dx for left) and refreshes the line if it is needed.
 Interface.prototype._moveCursor = function(dx) {
@@ -1119,42 +1105,39 @@ function emitKeypressEvents(stream, iface = {}) {
   stream[ESCAPE_DECODER] = emitKeys(stream);
   stream[ESCAPE_DECODER].next();
 
-  const escapeCodeTimeout = () => stream[ESCAPE_DECODER].next('');
+  const triggerEscape = () => stream[ESCAPE_DECODER].next('');
+  const { escapeCodeTimeout = ESCAPE_CODE_TIMEOUT } = iface;
   let timeoutId;
 
-  function onData(b) {
+  function onData(input) {
     if (stream.listenerCount('keypress') > 0) {
-      const string = stream[KEYPRESS_DECODER].write(b);
+      const string = stream[KEYPRESS_DECODER].write(input);
       if (string) {
         clearTimeout(timeoutId);
 
         // This supports characters of length 2.
         iface._sawKeyPress = charLengthAt(string, 0) === string.length;
-        const escapeTimeout = iface.escapeCodeTimeout || ESCAPE_CODE_TIMEOUT;
+        iface.isCompletionEnabled = false;
 
         let length = 0;
         for (const character of string) {
           length += character.length;
-          if (character === '\t' && length !== string.length) {
-            iface.isCompletionEnabled = false;
+          if (length === string.length) {
+            iface.isCompletionEnabled = true;
           }
 
           try {
             stream[ESCAPE_DECODER].next(character);
             // Escape letter at the tail position
-            if (character === kEscape && length === string.length) {
-              timeoutId = setTimeout(escapeCodeTimeout, escapeTimeout);
+            if (length === string.length && character === kEscape) {
+              timeoutId = setTimeout(triggerEscape, escapeCodeTimeout);
             }
           } catch (err) {
             // If the generator throws (it could happen in the `keypress`
             // event), we need to restart it.
             stream[ESCAPE_DECODER] = emitKeys(stream);
             stream[ESCAPE_DECODER].next();
             throw err;
-          } finally {
-            if (iface) {
-              iface.isCompletionEnabled = true;
-            }
           }
         }
       }

lib/repl.js

@@ -1369,15 +1369,13 @@ REPLServer.prototype.completeOnEditorMode = (callback) => (err, results) => {
   if (err) return callback(err);
 
   const [completions, completeOn = ''] = results;
-  const prefixLength = completeOn.length;
+  let result = completions.filter((v) => v);
 
-  if (prefixLength === 0) return callback(null, [[], completeOn]);
-
-  const isNotEmpty = (v) => v.length > 0;
-  const trimCompleteOnPrefix = (v) => v.substring(prefixLength);
-  const data = completions.filter(isNotEmpty).map(trimCompleteOnPrefix);
+  if (completeOn && result.length !== 0) {
+    result = [commonPrefix(result)];
+  }
 
-  callback(null, [[`${completeOn}${commonPrefix(data)}`], completeOn]);
+  callback(null, [result, completeOn]);
 };
 
 REPLServer.prototype.defineCommand = function(keyword, cmd) {