Implement referenceable notation for cyclical dependencies.

Fix #33

example/serializer_example.dart

@@ -35,7 +35,7 @@ class ModelC extends JsonObject {
 }
 
 class Id extends SerializedName {
-  const Id() : super("_id");
+  const Id(): super("_id");
 }
 
 main() {

lib/src/annotations.dart

@@ -24,6 +24,18 @@ class Ignore {
 
 const ignore = const Ignore();
 
+class Referenceable {
+  const Referenceable();
+}
+
+const referenceable = const Referenceable();
+
+class Reference {
+  const Reference();
+}
+
+const reference = const Reference();
+
 class SerializedName {
   final String name;
   const SerializedName(this.name);
@@ -47,4 +59,6 @@ class _MetadataManager<T> {
 }
 
 const _MetadataManager<SerializedName> serializedNameMetadataManager = const _MetadataManager<SerializedName>();
+const _MetadataManager<Referenceable>  referenceableMetadataManager  = const _MetadataManager<Referenceable>();
+const _MetadataManager<Reference>      referenceMetadataManager      = const _MetadataManager<Reference>();
 const _MetadataManager<Ignore>         ignoreMetadataManager         = const _MetadataManager<Ignore>();

lib/src/api.dart

@@ -63,7 +63,7 @@ abstract class TypedJsonObject extends Serialize {
 
 /// Utility class to access to the serializer api
 class Serializer {
-  static final Map<String, ClassMirror> _classes = singletonClasses;
+  static final Map<String, ClassSerialiazerInfo> _classes = singletonClasses;
 
   ///////////////////
   // Public
@@ -113,10 +113,10 @@ class Serializer {
       _classes.containsKey(type.toString());
 
   /// Convert the object to a Map
-  Map toMap(Object input) => _toMap(input);
+  Map toMap(Object input) => _toMap(input, true);
 
   /// Encode the object to serialized string
-  String encode(Object input) => _encode(input);
+  String encode(Object input) => _encode(input, true);
 
   /// Decode the object from a seriablized string
   Object decode(String encoded, [Type type]) => _decode(encoded, type);
@@ -176,7 +176,7 @@ class Serializer {
         } else if (_typeCodecs.containsKey(name)) {
           return _typeCodecs[name].type;
         } else {
-          ClassMirror classMirror = _classes[name];
+          ClassMirror classMirror = _classes[name]?.classMirror;
           return classMirror?.dynamicReflectedType;
         }
     }
@@ -272,21 +272,21 @@ class Serializer {
     return null;
   }
 
-  Object _encodeValue(value) {
+  Object _encodeValue(value, [bool withReferenceable = false]) {
     if (hasTypeCodec(value.runtimeType)) {
       return typeCodec(value.runtimeType).encode(value);
     } else if (value is Map || isSerializable(value.runtimeType)) {
-      return _toMap(value);
+      return _toMap(value, withReferenceable);
     } else if (value is List) {
-      return _encodeList(value);
+      return _encodeList(value, withReferenceable);
     } else if (isPrimaryType(value.runtimeType)) {
       return value;
     }
     return null;
   }
 
-  List _encodeList(List list) {
-    return list.map((elem) => _encodeValue(elem))
+  List _encodeList(List list, [bool withReferenceable = false]) {
+    return list.map((elem) => _encodeValue(elem, withReferenceable))
         .toList(growable: false);
   }
 
@@ -297,7 +297,7 @@ class Serializer {
     }
   }
 
-  Map _toMap(Object obj) {
+  Map _toMap(Object obj, [bool withReferenceable = false]) {
     if (obj == null || obj is List) {
       return null;
     }
@@ -323,7 +323,8 @@ class Serializer {
         if (   !data.containsKey(name)
             && !ignoreMetadataManager.hasMetadata(dec)
             && (   (dec is VariableMirror && isSerializableVariable(dec))
-                || (dec is MethodMirror && dec.isGetter))) {
+                || (dec is MethodMirror && dec.isGetter))
+            && isEncodeableField(_classes, cm, dec, withReferenceable)) {
           _encodeMap(data, name, mir.invokeGetter(originalName));
         }
       });
@@ -332,13 +333,13 @@ class Serializer {
     return data;
   }
 
-  String _encode(Object obj) {
+  String _encode(Object obj, [bool withReferenceable = false]) {
     if (obj == null) {
       return null;
     }
     if (obj is List) {
-      return _codec.encode(_encodeList(obj));
+      return _codec.encode(_encodeList(obj, withReferenceable));
     }
-    return _codec.encode(_toMap(obj));
+    return _codec.encode(_toMap(obj, withReferenceable));
   }
 }

lib/src/convert.dart

@@ -10,7 +10,7 @@ import 'annotations.dart';
 final String MapTypeString  = {}.runtimeType.toString();
 final String ListTypeString = [].runtimeType.toString();
 
-bool isSerializableClassMirror(Map<String, ClassMirror> serializables, ClassMirror cm) {
+bool isSerializableClassMirror(Map<String, ClassSerialiazerInfo> serializables, ClassMirror cm) {
   return serializables.containsKey(cm.mixin.simpleName);
 }
 
@@ -35,15 +35,23 @@ String serializedName(DeclarationMirror dec) {
   }
 }
 
+bool isEncodeableField(Map<String, ClassSerialiazerInfo> serializables, ClassMirror cm, DeclarationMirror dec, bool withReferenceable) {
+  return withReferenceable || !serializables[cm.mixin.simpleName].isReferenceable || referenceMetadataManager.hasMetadata(dec);
+}
+
 _printToString(String data) => "$data\n";
 
 String printAndDumpSerializables() {
   String output = "";
   initSingletonClasses();
-  singletonClasses.values.forEach((classMirror) {
-    var cm = classMirror;
+  singletonClasses.values.forEach((classInfo) {
+    var cm = classInfo.classMirror;
     output += _printToString(cm.mixin.simpleName);
-    print(cm.mixin.simpleName);
+    if (classInfo.isReferenceable) {
+      print(cm.mixin.simpleName + " (with Reference)");
+    } else {
+      print(cm.mixin.simpleName);
+    }
     while (cm != null
         && cm.superclass != null
         && isSerializableClassMirror(singletonClasses, cm)) {
@@ -56,6 +64,7 @@ String printAndDumpSerializables() {
           bool isSetter  = false;
           bool isGetter  = false;
           bool isIgnored = ignoreMetadataManager.hasMetadata(decl);
+          bool isRef     = referenceMetadataManager.hasMetadata(decl);
           String renamed = serializedName(decl);
 
           if (decl is VariableMirror) {
@@ -81,6 +90,7 @@ String printAndDumpSerializables() {
 
           if (type != null) {
             var line = "    ";
+            line += isRef     ? "R" : "-";
             line += isSetter  ? "G" : "-";
             line += isGetter  ? "S" : "-";
             line += isIgnored ? "I" : "-";
@@ -98,14 +108,29 @@ String printAndDumpSerializables() {
 }
 
 // Singleton that maps every class annotated with @serializable
-final singletonClasses = <String, ClassMirror>{};
+class ClassSerialiazerInfo {
+  ClassMirror classMirror;
+  bool        isReferenceable;
+  ClassSerialiazerInfo(this.classMirror, this.isReferenceable);
+}
+
+final singletonClasses = <String, ClassSerialiazerInfo>{};
 initSingletonClasses() {
   if (singletonClasses.isEmpty) {
     for (ClassMirror classMirror in serializable.annotatedClasses) {
       if (classMirror != null
           && classMirror.simpleName != null
           && classMirror.metadata.contains(serializable)) {
-        singletonClasses[classMirror.simpleName] = classMirror;
+
+        // Searching for referenceable annotation
+        var isReferenceable = false;
+        var cm = classMirror;
+        while (cm != null && cm.superclass != null) {
+          isReferenceable = isReferenceable || referenceableMetadataManager.hasMetadata(cm);
+          cm = cm?.superclass;
+        }
+
+        singletonClasses[classMirror.simpleName] = new ClassSerialiazerInfo(classMirror, isReferenceable);
       }
     }
   }

test/json_test.dart

@@ -144,6 +144,25 @@ class M2 {
   String m2;
 }
 
+@referenceable
+@serializable
+class Employee {
+  @reference
+  int id;
+  String name;
+  Address address;
+  Employee manager;
+}
+
+@referenceable
+@serializable
+class Address {
+  @reference
+  int id;
+  String location;
+  Employee owner;
+}
+
 Serializer serializer;
 
 main() {
@@ -529,4 +548,34 @@ main() {
       expect(mixin.m2, "M2");
     });
   });
+
+  group("Referenceable", () {
+    test("Serialize", () {
+      Address addressManager = new Address()
+        ..id       = 1337
+        ..location = "Somewhere";
+
+      Address addressEmployee = new Address()
+        ..id       = 1338
+        ..location = "Somewhere else";
+
+      Employee manager = new Employee()
+        ..id      = 43
+        ..name    = "Alice Doo"
+        ..address = addressManager;
+      addressManager.owner = manager;
+
+      Employee employee = new Employee()
+        ..id      = 42
+        ..name    = "Bob Smith"
+        ..address = addressEmployee
+        ..manager = manager;
+      addressEmployee.owner = employee;
+
+      expect(serializer.encode(addressManager),  '{"id":1337,"location":"Somewhere","owner":{"id":43}}');
+      expect(serializer.encode(addressEmployee), '{"id":1338,"location":"Somewhere else","owner":{"id":42}}');
+      expect(serializer.encode(manager),         '{"id":43,"name":"Alice Doo","address":{"id":1337}}');
+      expect(serializer.encode(employee),        '{"id":42,"name":"Bob Smith","address":{"id":1338},"manager":{"id":43}}');
+    });
+  });
 }

test/typed_json_test.dart

@@ -132,6 +132,25 @@ class M2 {
   String m2;
 }
 
+@referenceable
+@serializable
+class Employee {
+  @reference
+  int id;
+  String name;
+  Address address;
+  Employee manager;
+}
+
+@referenceable
+@serializable
+class Address {
+  @reference
+  int id;
+  String location;
+  Employee owner;
+}
+
 main() {
   var serializer = new Serializer.TypedJson();
 
@@ -382,8 +401,8 @@ main() {
       try {
         TypedDontWantToBeSerialize _ = serializer.decode('{"@type":"TypedDontWantToBeSerialize","foo":"bar"}');
       } catch (e) {
-       expect(true, e is String);
-       // expect("Cannot instantiate abstract class DontWantToBeSerialize: _url 'null' line null", e);
+        expect(true, e is String);
+        // expect("Cannot instantiate abstract class DontWantToBeSerialize: _url 'null' line null", e);
       }
     });
   });
@@ -463,4 +482,34 @@ main() {
       expect(mixin.m2, "M2");
     });
   });
+
+  group("Referenceable", () {
+    test("Serialize", () {
+      Address addressManager = new Address()
+        ..id       = 1337
+        ..location = "Somewhere";
+
+      Address addressEmployee = new Address()
+        ..id       = 1338
+        ..location = "Somewhere else";
+
+      Employee manager = new Employee()
+        ..id      = 43
+        ..name    = "Alice Doo"
+        ..address = addressManager;
+      addressManager.owner = manager;
+
+      Employee employee = new Employee()
+        ..id      = 42
+        ..name    = "Bob Smith"
+        ..address = addressEmployee
+        ..manager = manager;
+      addressEmployee.owner = employee;
+
+      expect(serializer.encode(addressManager),  '{"@type":"Address","id":1337,"location":"Somewhere","owner":{"@type":"Employee","id":43}}');
+      expect(serializer.encode(addressEmployee), '{"@type":"Address","id":1338,"location":"Somewhere else","owner":{"@type":"Employee","id":42}}');
+      expect(serializer.encode(manager),         '{"@type":"Employee","id":43,"name":"Alice Doo","address":{"@type":"Address","id":1337}}');
+      expect(serializer.encode(employee),        '{"@type":"Employee","id":42,"name":"Bob Smith","address":{"@type":"Address","id":1338},"manager":{"@type":"Employee","id":43}}');
+    });
+  });
 }