Properly handle CR LF in LineScanner.

lib/src/line_scanner.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library string_scanner.line_scanner;
 
+import 'package:charcode/ascii.dart';
+
 import 'string_scanner.dart';
 
+/// A regular expression matching newlines across platforms.
+final _newlineRegExp = new RegExp(r"\r\n?|\n");
+
 /// A subclass of [StringScanner] that tracks line and column information.
 class LineScanner extends StringScanner {
   /// The scanner's current (zero-based) line number.
   int get line => _line;
   int _line = 0;
 
   /// The scanner's current (zero-based) column number.
   int get column => _column;
   int _column = 0;
 
   /// The scanner's state, including line and column information.
   ///
   /// This can be used to efficiently save and restore the state of the scanner
   /// when backtracking. A given [LineScannerState] is only valid for the
   /// [LineScanner] that created it.
   LineScannerState get state =>
       new LineScannerState._(this, position, line, column);
 
+  /// Whether the current position is between a CR character and an LF
+  /// charactet.
+  bool get _betweenCRLF => peekChar(-1) == $cr && peekChar() == $lf;
+
   set state(LineScannerState state) {
     if (!identical(state._scanner, this)) {
       throw new ArgumentError("The given LineScannerState was not returned by "
           "this LineScanner.");
     }
 
     super.position = state.position;
     _line = state.line;
     _column = state.column;
   }
 
   set position(int newPosition) {
     var oldPosition = position;
     super.position = newPosition;
 
     if (newPosition > oldPosition) {
-      var newlines =
-          "\n".allMatches(string.substring(oldPosition, newPosition)).toList();
+      var newlines = _newlineRegExp
+          .allMatches(string.substring(oldPosition, newPosition)).toList();
+      if (_betweenCRLF) newlines.removeLast();

[Bob Nystrom, 2015/09/02 00:07:24]

How about hoisting this to a function:

int _newlinesIn(String text) { ... }

and reusing it below too.

[nweiz, 2015/09/02 00:10:57]

Done.

+
       _line += newlines.length;
       if (newlines.isEmpty) {
         _column += newPosition - oldPosition;
       } else {
         _column = newPosition - newlines.last.end;
       }
     } else {
-      var newlines =
-          "\n".allMatches(string.substring(newPosition, oldPosition)).toList();
+      var newlines = _newlineRegExp
+          .allMatches(string.substring(newPosition, oldPosition)).toList();
+      if (_betweenCRLF) newlines.removeLast();
+
       _line -= newlines.length;
       if (newlines.isEmpty) {
         _column -= oldPosition - newPosition;
       } else {
-        _column = newPosition - string.lastIndexOf("\n", newPosition) - 1;
+        _column = newPosition -
+            string.lastIndexOf(_newlineRegExp, newPosition) - 1;
       }
     }
   }
 
   LineScanner(String string, {sourceUrl, int position})
       : super(string, sourceUrl: sourceUrl, position: position);
 
   int readChar() {
     var char = super.readChar();
-    if (char == 0xA) {
+    if (char == $lf || (char == $cr && peekChar() != $lf)) {
       _line += 1;
       _column = 0;
     } else {
       _column += 1;
     }
     return char;
   }
 
   bool scan(Pattern pattern) {
     if (!super.scan(pattern)) return false;
 
-    var newlines = "\n".allMatches(lastMatch[0]).toList();
+    var newlines = _newlineRegExp.allMatches(lastMatch[0]).toList();
+    if (_betweenCRLF) newlines.removeLast();
     _line += newlines.length;

[Bob Nystrom, 2015/09/02 00:07:24]

Even here.

[nweiz, 2015/09/02 00:10:57]

Done.

     if (newlines.isEmpty) {
       _column += lastMatch[0].length;
     } else {
       _column = lastMatch[0].length - newlines.last.end;
     }
 
     return true;
   }
 }
 
 /// A class representing the state of a [LineScanner].
 class LineScannerState {
   /// The [LineScanner] that created this.
   final LineScanner _scanner;
 
   /// The position of the scanner in this state.
   final int position;
 
   /// The zero-based line number of the scanner in this state.
   final int line;
 
   /// The zero-based column number of the scanner in this state.
   final int column;
 
   LineScannerState._(this._scanner, this.position, this.line, this.column);
 }