readline: inform line event about separator used

pass separator as a parameter to the callback
alongwith line to inform line event about separator
used to break lines
fixes: #7952 (comment)

Author: Sayanc93

lib/readline.js

@@ -57,7 +57,8 @@ let StringDecoder;
 const kHistorySize = 30;
 const kMincrlfDelay = 100;
 // \r\n, \n, or \r followed by something other than \n
-const lineEnding = /\r?\n|\r(?!\n)/;
+const lineEndingWithSeparator = /(?<=\r?\n|\r(?!\n))/;
+const lineEndingSeparatorInclusion = /[\r?\n|\r(?!\n)]$/;
 
 const KEYPRESS_DECODER = Symbol('keypress-decoder');
 const ESCAPE_DECODER = Symbol('escape-decoder');
@@ -290,14 +291,14 @@ Interface.prototype.question = function(query, cb) {
 };
 
 
-Interface.prototype._onLine = function(line) {
+Interface.prototype._onLine = function(line, separator = '\n') {
   if (this._questionCallback) {
     var cb = this._questionCallback;
     this._questionCallback = null;
     this.setPrompt(this._oldPrompt);
     cb(line);
   } else {
-    this.emit('line', line);
+    this.emit('line', line, separator);
   }
 };
 
@@ -425,7 +426,7 @@ Interface.prototype._normalWrite = function(b) {
   }
 
   // Run test() on the new string chunk, not on the entire line buffer.
-  var newPartContainsEnding = lineEnding.test(string);
+  var newPartContainsEnding = lineEndingWithSeparator.test(string);
 
   if (this._line_buffer) {
     string = this._line_buffer + string;
@@ -435,12 +436,21 @@ Interface.prototype._normalWrite = function(b) {
     this._sawReturnAt = string.endsWith('\r') ? Date.now() : 0;
 
     // got one or more newlines; process into "line" events
-    var lines = string.split(lineEnding);
+    var lines = string.split(lineEndingWithSeparator);
     // either '' or (conceivably) the unfinished portion of the next line
     string = lines.pop();
     this._line_buffer = string;
-    for (var n = 0; n < lines.length; n++)
-      this._onLine(lines[n]);
+    for (var n = 0; n < lines.length; n++) {
+      const _line = lines[n];
+      if (lineEndingSeparatorInclusion.test(_line)) {
+        const lineWithoutSeparator = _line.slice(0, -1);
+        const separator = _line.slice(-1);
+
+        this._onLine(lineWithoutSeparator, separator);
+      } else {
+        this._onLine(_line, '\n');
+      }
+    }
   } else if (string) {
     // no newlines this time, save what we have for next time
     this._line_buffer = string;
@@ -642,10 +652,10 @@ Interface.prototype.clearLine = function() {
 };
 
 
-Interface.prototype._line = function() {
+Interface.prototype._line = function(separator = '\n') {
   var line = this._addHistory();
   this.clearLine();
-  this._onLine(line);
+  this._onLine(line, separator);
 };
 
 
@@ -924,7 +934,7 @@ Interface.prototype._ttyWrite = function(s, key) {
     switch (key.name) {
       case 'return':  // carriage return, i.e. \r
         this._sawReturnAt = Date.now();
-        this._line();
+        this._line('\r');
         break;
 
       case 'enter':

test/parallel/test-readline-interface.js

@@ -118,9 +118,10 @@ function isWarned(emitter) {
       { input: fi, output: fi, terminal: terminal }
     );
     let called = false;
-    rli.on('line', function(line) {
+    rli.on('line', function(line, separator) {
       called = true;
       assert.strictEqual(line, 'asdf');
+      assert.strictEqual(separator, '\n');
     });
     fi.emit('data', 'asdf\n');
     assert.ok(called);