Support unmapped areas in source maps.

pkg/source_maps/lib/builder.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.
 
 /// Contains a builder object useful for creating source maps programatically.
 library source_maps.builder;
 
 // TODO(sigmund): add a builder for multi-section mappings.
 
 import 'dart:collection';
@@ skipping 33 matching lines @@
 
   void addLocation(Location source, Location target, String identifier) {
     _entries.add(new Entry(source, target, identifier));
   }
 
   /// Encodes all mappings added to this builder as a json map.
   Map build(String fileUrl) {
     var buff = new StringBuffer();
     var line = 0;
     var column = 0;
-    var srcLine = 0;
-    var srcColumn = 0;
-    var srcUrlId = 0;
-    var srcNameId = 0;
+    var srcLine = null;
+    var srcColumn = null;
+    var srcUrlId = null;
+    var srcNameId = null;
     var first = true;
 
     // The encoding needs to be sorted by the target offsets.
     _entries.sort();
     for (var entry in _entries) {
       int nextLine = entry.target.line;
       if (nextLine > line) {
         for (int i = line; i < nextLine; ++i) {
           buff.write(';');
         }
         line = nextLine;
         column = 0;
         first = true;
       }
 
       if (!first) buff.write(',');
       first = false;
       column = _append(buff, column, entry.target.column);
 
       // Encoding can be just the column offset if there is no source
-      // information, or if two consecutive mappings share exactly the same
-      // source information.
+      // information.
       var source = entry.source;
       if (source == null) continue;
       var newUrlId = _indexOf(_urls, source.sourceUrl);
-      if (newUrlId == srcUrlId && source.line == srcLine
-          && source.column == srcColumn && entry.identifierName == null) {
-        continue;
-      }
 
       srcUrlId = _append(buff, srcUrlId, newUrlId);
       srcLine = _append(buff, srcLine, source.line);
       srcColumn = _append(buff, srcColumn, source.column);
 
       if (entry.identifierName == null) continue;
       srcNameId = _append(buff, srcNameId,
           _indexOf(_names, entry.identifierName));
     }
 
@@ skipping 18 matching lines @@
     return map.putIfAbsent(value, () {
       int index = map.length;
       map[value] = index;
       return index;
     });
   }
 
   /// Appends to [buff] a VLQ encoding of [newValue] using the difference
   /// between [oldValue] and [newValue]
   static int _append(StringBuffer buff, int oldValue, int newValue) {
+    if (oldValue == null) {

[Siggi Cherem (dart-lang), 2014/04/18 02:00:31]

I might be missing something, could we simply revert this line and all the
initializations in line 54 back to 0 instead of null?

[zarah, 2014/04/23 07:52:12]

I don't think you are :-), Done.

+      oldValue = 0;
+    }
     buff.writeAll(encodeVlq(newValue - oldValue));
     return newValue;
   }
 }
 
 /// An entry in the source map builder.
 class Entry implements Comparable {
   /// Span denoting the original location in the input source file
   final Location source;
 
@@ skipping 10 matching lines @@
   /// because source map files are encoded by printing each mapping in order as
   /// they appear in the target file.
   int compareTo(Entry other) {
     int res = target.compareTo(other.target);
     if (res != 0) return res;
     res = source.sourceUrl.compareTo(other.source.sourceUrl);
     if (res != 0) return res;
     return source.compareTo(other.source);
   }
 }