Respect the constructor param for classes w/ custom fromJson ctor

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.2.0+1
+
+* When serializing classes that implement their own `fromJson` constructor,
+  honor their constructor parameter type.
+
 ## 0.2.0
 
 * **BREAKING** Types are now segmented into their own libraries.

lib/src/type_helpers/json_helper.dart

@@ -28,10 +28,20 @@ class JsonHelper extends TypeHelper {
       return null;
     }
 
+    var classElement = targetType.element as ClassElement;
+    var fromJsonCtor =
+        classElement.constructors.firstWhere((ce) => ce.name == 'fromJson');
+    // TODO: should verify that this type is a valid JSON type...but for now...
+    var asCastType = fromJsonCtor.parameters.single.type;
+
+    var asCast = '';
+    if (!asCastType.isDynamic && !asCastType.isObject) {
+      asCast = ' as $asCastType';
+    }
+
     // TODO: the type could be imported from a library with a prefix!
     // github.com/dart-lang/json_serializable/issues/19
-    var result =
-        "new ${targetType.name}.fromJson($expression as Map<String, dynamic>)";
+    var result = "new ${targetType.name}.fromJson($expression$asCast)";
 
     if (nullable) {
       result = "$expression == null ? null : " + result;

pubspec.yaml

@@ -1,5 +1,5 @@
 name: json_serializable
-version: 0.2.0
+version: 0.2.0+1
 author: Dart Team <misc@dartlang.org>
 description: Generates utilities to aid in serializing to/from JSON.
 homepage: https://github.com/dart-lang/json_serializable

test/test_files/json_test_example.dart

@@ -34,6 +34,7 @@ class Order extends Object with _$OrderSerializerMixin {
   int count;
   bool isRushed;
   final UnmodifiableListView<Item> items;
+  Platform platform;
 
   int get price => items.fold(0, (total, item) => item.price + total);
 
@@ -69,3 +70,24 @@ class Item extends Object with _$ItemSerializerMixin {
 }
 
 bool _deepEquals(a, b) => const DeepCollectionEquality().equals(a, b);
+
+class Platform {
+  final String description;
+
+  static const Platform foo = const Platform._('foo');
+  static const Platform undefined = const Platform._('undefined');
+  const Platform._(this.description);
+
+  factory Platform.fromJson(String value) {
+    switch (value) {
+      case 'foo':
+        return foo;
+      case 'undefined':
+        return undefined;
+      default:
+        throw new ArgumentError.value(value, 'value', 'Not a supported value.');
+    }
+  }
+
+  String toJson() => description;
+}