Fixed YAML output for a list of maps

pkg/docgen/lib/dart2yaml.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.
 
 /**
  * This library is used to convert data from a map to a YAML string.
  */
 library dart2yaml;
 
 /**
  * Gets a String representing the input Map in YAML format.
  */
 String getYamlString(Map documentData) {
   StringBuffer yaml = new StringBuffer();
   _addLevel(yaml, documentData, 0);
   return yaml.toString();
 }
 
 /**
- * This recursive function adds to its input StringBuffer and builds
- * a YAML string from the input Map.
+ * This recursive function builds a YAML string from [documentData] and
+ * adds it to [yaml].
+ * The [level] input determines the indentation of the block being processed.
+ * The [isList] input determines whether [documentData] is a member of an outer
+ * lists of maps. A map must be preceeded with a '-' if it is to exist at the
+ * same level of indentation in the YAML output as other members of the list.
  */
-// TODO(tmandel): Fix quotes with String objects.
-void _addLevel(StringBuffer yaml, Map documentData, int level) {
-  documentData.keys.forEach( (key) {
+void _addLevel(StringBuffer yaml, Map documentData, int level,
+               {bool isList: false}) {
+  // Since the ordering of the keys could be non-deterministic, the keys
+  // are sorted to ensure consistency in the output.
+  var keys = documentData.keys.toList();
+  keys.sort((String first, String second) => first.compareTo(second));

[Alan Knight, 2013/07/26 20:51:03]

Real nit. You can omit the argument to sort and the default will work for
sorting strings in alphabetical order.

+  keys.forEach((key) {
     _calcSpaces(level, yaml);
+    // Only the first entry of the map should be preceeded with a '-' since
+    // the map is a member of an outer list and the map as a whole must be 
+    // marked as a single member of that list. See example 2.4 at
+    // http://www.yaml.org/spec/1.2/spec.html#id2759963
+    if (isList && key == keys.first) {
+      yaml.write("- ");
+      level++;
+    }
     yaml.write("\"$key\" : ");
-
     if (documentData[key] is Map) {
       yaml.write("\n");
       _addLevel(yaml, documentData[key], level + 1);
-
     } else if (documentData[key] is List) {
       var elements = documentData[key];
       yaml.write("\n");
       elements.forEach( (element) {
         if (element is Map) {
-          _addLevel(yaml, element, level + 1);
+          _addLevel(yaml, element, level + 1, isList: true);
         } else {
           _calcSpaces(level + 1, yaml);
           yaml.write("- ${_processElement(element)}");
         }
       });
-      
     } else {
       yaml.write(_processElement(documentData[key]));
     }
   });
 }
 
 /**
  * Returns an escaped String form of the inputted element.
  */
 String _processElement(var element) {
   var contents = element.toString()
       .replaceAll('\\', r'\\')
       .replaceAll('"', r'\"')
       .replaceAll('\n', r'\n');
   return '"$contents"\n';
 }
 
 /**
  * Based on the depth in the file, this function returns the correct spacing
  * for an element in the YAML output.
  */
 void _calcSpaces(int spaceLevel, StringBuffer yaml) {
   for (int i = 0; i < spaceLevel; i++) {
     yaml.write("  ");
   }
 }