Support unmapped areas in source maps.

pkg/source_maps/lib/builder.dart

Index: pkg/source_maps/lib/builder.dart
diff --git a/pkg/source_maps/lib/builder.dart b/pkg/source_maps/lib/builder.dart
index 12587cd84bf1ee2d235987e1310e36760b0016dc..d063bf5dab2e0389514c7f922f8c7f47b52203f0 100644
--- a/pkg/source_maps/lib/builder.dart
+++ b/pkg/source_maps/lib/builder.dart
@@ -51,10 +51,10 @@ class SourceMapBuilder {
     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.
@@ -75,15 +75,10 @@ class SourceMapBuilder {
       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);
@@ -122,6 +117,9 @@ class SourceMapBuilder {
   /// 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;
   }