readline,repl: support tabs properly

PR-URL: #31112Fixes: #25272
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: BridgeAR

lib/readline.js

@@ -490,9 +490,6 @@ Interface.prototype._insertString = function(c) {
 }else{
 this._writeToOutput(c);
 }
-
-// A hack to get the line refreshed if it's needed
-this._moveCursor(0);
 }
 };
 
@@ -731,6 +728,12 @@ Interface.prototype._getDisplayPos = function(str) {
 offset=0;
 continue;
 }
+// Tabs must be aligned by an offset of 8.
+// TODO(BridgeAR): Make the tab size configurable.
+if(char==='\t'){
+offset+=8-(offset%8);
+continue;
+}
 constwidth=getStringWidth(char);
 if(width===0||width===1){
 offset+=width;
@@ -768,33 +771,27 @@ 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
+// (-dx for left) and refreshes the line if it is needed.
 Interface.prototype._moveCursor=function(dx){
-constoldcursor=this.cursor;
+if(dx===0){
+return;
+}
 constoldPos=this.getCursorPos();
 this.cursor+=dx;
 
-// bounds check
-if(this.cursor<0)this.cursor=0;
-elseif(this.cursor>this.line.length)this.cursor=this.line.length;
+// Bounds check
+if(this.cursor<0){
+this.cursor=0;
+}elseif(this.cursor>this.line.length){
+this.cursor=this.line.length;
+}
 
 constnewPos=this.getCursorPos();
 
-// Check if cursors are in the same line
+// Check if cursor stayed on the line.
 if(oldPos.rows===newPos.rows){
-constdiffCursor=this.cursor-oldcursor;
-letdiffWidth;
-if(diffCursor<0){
-diffWidth=-getStringWidth(
-this.line.substring(this.cursor,oldcursor)
-);
-}elseif(diffCursor>0){
-diffWidth=getStringWidth(
-this.line.substring(this.cursor,oldcursor)
-);
-}
+constdiffWidth=newPos.cols-oldPos.cols;
 moveCursor(this.output,diffWidth,0);
-this.prevRows=newPos.rows;
 }else{
 this._refreshLine();
 }

test/parallel/test-repl-preview.js

@@ -93,9 +93,9 @@ async function tests(options) {
 '\x1B[33mtrue\x1B[39m',
 '\x1B[1G\x1B[0Jrepl > \x1B[8G'],
 [' \t { a: true};',[2,5],'\x1B[33mtrue\x1B[39m',
-' \t { a: tru\x1B[90me\x1B[39m\x1B[19G\x1B[0Ke}',
-'\x1B[90m{ a: true }\x1B[39m\x1B[8C\x1B[1A\x1B[1B\x1B[2K\x1B[1A;',
-'\x1B[90mtrue\x1B[39m\x1B[16C\x1B[1A\x1B[1B\x1B[2K\x1B[1A\r',
+' \t { a: tru\x1B[90me\x1B[39m\x1B[26G\x1B[0Ke}',
+'\x1B[90m{ a: true }\x1B[39m\x1B[16C\x1B[1A\x1B[1B\x1B[2K\x1B[1A;',
+'\x1B[90mtrue\x1B[39m\x1B[24C\x1B[1A\x1B[1B\x1B[2K\x1B[1A\r',
 '\x1B[33mtrue\x1B[39m',
 '\x1B[1G\x1B[0Jrepl > \x1B[8G']
 ];