dartfmt line wrapping bypass option support.

pkg/analyzer/lib/src/services/writer.dart

 // Copyright (c) 2013, 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 source_writer;
 
 
-/// DEBUG flag indicating whether to use the experimental line-breaker
-const _USE_LINE_BREAKER = false;
-
 
 class Line {
 
   final tokens = <LineToken>[];
   final bool useTabs;
   final int spacesPerIndent;
   final int indent;
   final LinePrinter printer;
 
   Line({this.indent: 0, this.useTabs: false, this.spacesPerIndent: 2,
@@ skipping 94 matching lines @@
           if (current.length > 0) {
             chunks.add(current);
           }
           current = work;
         }
         work = new Chunk(start: tok, maxLength: maxLength - current.length);
       } else {
         if (work.fits(tok)) {
           work.add(tok);
         } else {
-          if (!isAllWhitespace(work)) {
+          if (!isAllWhitespace(work) || isLineStart(current)) {
             current.add(work);
-          }
-          if (current.length > 0) {
+          } else if (current.length > 0) {
             chunks.add(current);
             current = new Chunk(maxLength: maxLength);
           }
           work = new Chunk(maxLength: maxLength);
           work.add(tok);
         }
       }
 
     });
 
@@ skipping 30 matching lines @@
     }
 
     return tokens;
   }
 
   static LineToken merge(LineToken first, LineToken second) =>
       new LineToken(first.value + second.value);
 
   bool isAllWhitespace(Chunk chunk) => isWhitespace(chunk.buffer.toString());
 
+  bool isLineStart(chunk) => chunk.length == 0 && chunk.start == LINE_START;
+
   /// Test whether this token is a good start for a new working chunk
   bool goodStart(LineToken tok, Chunk workingChunk) =>
       tok is SpaceToken && tok.breakWeight >= workingChunk.start.breakWeight;
 
 }
 
 /// Test if this [string] contains only whitespace characters
 bool isWhitespace(String string) => string.codeUnits.every(
       (c) => c == 0x09 || c == 0x20 || c == 0x0A || c == 0x0D);
 
@@ skipping 97 matching lines @@
   Line currentLine;
 
   final String lineSeparator;
   int indentCount = 0;
 
   LinePrinter linePrinter;
   LineToken _lastToken;
 
   SourceWriter({this.indentCount: 0, this.lineSeparator: NEW_LINE,
       bool useTabs: false, int spacesPerIndent: 2, int maxLineLength: 80}) {
-    if (_USE_LINE_BREAKER) {
+    if (maxLineLength > 0) {
       linePrinter = new SimpleLineBreaker(maxLineLength, (n) =>
           getIndentString(n, useTabs: useTabs, spacesPerIndent: spacesPerIndent));
     } else {
       linePrinter = new SimpleLinePrinter();
     }
     currentLine = new Line(indent: indentCount, printer: linePrinter);
   }
 
   LineToken get lastToken => _lastToken;
 
@@ skipping 100 matching lines @@
 
 String getTabs(int n) => n < TABS.length ? TABS[n] : repeat('\t', n);
 
 String repeat(String ch, int times) {
   var sb = new StringBuffer();
   for (var i = 0; i < times; ++i) {
     sb.write(ch);
   }
   return sb.toString();
 }