Add a DateTimeRule to default serialization

pkg/serialization/lib/serialization.dart

 // Copyright (c) 2012, 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 provides a general-purpose serialization facility for Dart objects. A
  * [Serialization] is defined in terms of [SerializationRule]s and supports
  * reading and writing to different formats.
  *
  * ## Installing ##
@@ skipping 240 matching lines @@
 
   /**
    * When we write out data using this serialization, should we also write
    * out a description of the rules. This is on by default unless using
    * CustomRule subclasses, in which case it requires additional setup and
    * is off by default.
    */
   bool get selfDescribing {
     // TODO(alanknight): Should this be moved to the format?
     // TODO(alanknight): Allow self-describing in the presence of CustomRule.
+    // TODO(alanknight): Don't do duplicate work creating a writer and
+    // serialization here and then re-creating when we actually serialize.
     if (_selfDescribing != null) return _selfDescribing;
-    _selfDescribing = !rules.any((x) => x is CustomRule && x is! SymbolRule);
+    var meta = ruleSerialization();
+    var w = meta.newWriter();
+    _selfDescribing = !rules.any((rule) =>
+        meta.rulesFor(rule, w, false).isEmpty);
     return _selfDescribing;
   }
 
   /**
    * When we write out data using this serialization, should we also write
    * out a description of the rules. This is on by default unless using
    * CustomRule subclasses, in which case it requires additional setup and
    * is off by default.
    */
   void set selfDescribing(bool value) {
@@ skipping 58 matching lines @@
 
   /** Set up the default rules, for lists and primitives. */
   void addDefaultRules() {
     addRule(new PrimitiveRule());
     addRule(new ListRule());
     // Both these rules apply to lists, so unless otherwise indicated,
     // it will always find the first one.
     addRule(new ListRuleEssential());
     addRule(new MapRule());
     addRule(new SymbolRule());
+    addRule(new DateTimeRule());
   }
 
   /**
    * Add a new SerializationRule [rule]. The addRuleFor method will probably
    * handle most simple cases, but for adding an arbitrary rule, including
    * a SerializationRule subclass which you have created, you can use this
    * method.
    */
   void addRule(SerializationRule rule) {
     rule.number = rules.length;
@@ skipping 36 matching lines @@
    * Return a new [Reader] object for this serialization. This is useful if
    * you want to do something more complex with the reader than just returning
    * the final result.
    */
   Reader newReader([Format format]) => new Reader(this, format);
 
   /**
    * Return the list of SerializationRule that apply to [object]. For
    * internal use, but public because it's used in testing.
    */
-  Iterable<SerializationRule> rulesFor(object, Writer w) {
+  Iterable<SerializationRule> rulesFor(object, Writer w, [create = true]) {

[Jennifer Messerly, 2013/05/14 23:18:33]

consider: named argument here, they tend to be a bit more descriptive for
booleans.

[Alan Knight, 2013/05/14 23:32:55]

Done.

     // This has a couple of edge cases.
     // 1) The owning object may have indicated we should use a different
     // rule than the default.
     // 2) We may not have a rule, in which case we lazily create a BasicRule.
     // 3) Rules are allowed to say mustBePrimary, meaning that they can be used
     // iff no other rule was chosen first.
     // TODO(alanknight): Can the mustBePrimary mechanism be removed or changed.
     // It adds an order dependency to the rules, and is messy. Reconsider in the
     // light of a more general mechanism for multiple rules per object.
     // TODO(alanknight): Finding which rules apply seems likely to be a
     // bottleneck, particularly with the current reflective implementation.
     // Consider how to improve it. e.g. cache the list of rules by class. But
     // be careful of issues like rules which have arbitrary predicates. Or
     // consider having the arbitrary predicates be secondary to an initial
     // class-based lookup mechanism.
     var target, candidateRules;
     if (object is DesignatedRuleForObject) {
       target = object.target;
       candidateRules = object.possibleRules(rules);
     } else {
       target = object;
       candidateRules = rules;
     }
     Iterable applicable = candidateRules.where(
         (each) => each.appliesTo(target, w));
 
     if (applicable.isEmpty) {
-      return [addRuleFor(target)];
+      return create ? [addRuleFor(target)] : applicable;
     }
 
     if (applicable.length == 1) return applicable;
     var first = applicable.first;
     var finalRules = applicable.where(
         (x) => !x.mustBePrimary || (x == first));
 
     if (finalRules.isEmpty) throw new SerializationException(
         'No valid rule found for object $object');
     return finalRules;
@@ skipping 23 matching lines @@
       ..addRuleFor(new PrimitiveRule())
       ..addRuleFor(new ListRuleEssential())
       ..addRuleFor(basicRule,
           constructorFields: ['type',
             'constructorName',
             'constructorFields', 'regularFields', []],
           fields: [])
       ..addRule(new NamedObjectRule())
       ..addRule(new MirrorRule())
       ..addRuleFor(new MirrorRule())
-      ..addRuleFor(new SymbolRule());
+      ..addRuleFor(new SymbolRule())
+      ..addRuleFor(new DateTimeRule());
     meta.namedObjects = namedObjects;
     return meta;
   }
 
   /** Return true if our [namedObjects] collection has an entry for [object].*/
   bool _hasNameFor(object) {
     var sentinel = const _Sentinel();
     return _nameFor(object, () => sentinel) != sentinel;
   }
 
@@ skipping 10 matching lines @@
 }
 
 /**
  * An exception class for errors during serialization.
  */
 class SerializationException implements Exception {
   final String message;
   const SerializationException([this.message]);
   toString() => "SerializationException($message)";
 }