Add @required annotations in constructor

angel_serialize_generator/lib/build_context.dart

@@ -34,7 +34,7 @@ Future<BuildContext> buildContext(
   autoSnakeCaseNames =
       annotation.peek('autoSnakeCaseNames')?.boolValue ?? autoSnakeCaseNames;
 
-  var ctx = new BuildContext(annotation,
+  var ctx = new BuildContext(annotation, clazz,
       originalClassName: clazz.name,
       sourceFilename: p.basename(buildStep.inputId.path),
       autoIdAndDateFields: autoIdAndDateFields,

angel_serialize_generator/lib/context.dart

@@ -32,10 +32,12 @@ class BuildContext {
 
   final ConstantReader annotation;
 
+  final ClassElement clazz;
+
   /// The name of the field that identifies data of this model type.
   String primaryKeyName = 'id';
 
-  BuildContext(this.annotation,
+  BuildContext(this.annotation, this.clazz,
       {this.originalClassName,
       this.sourceFilename,
       this.autoSnakeCaseNames,

angel_serialize_generator/lib/model.dart

@@ -100,6 +100,10 @@ class JsonModelGenerator extends GeneratorForAnnotation<Serializable> {
           else {
             b.type = convertTypeReference(field.type);
           }
+
+          if (ctx.requiredFields.containsKey(field.name)) {
+            b.annotations.add(new CodeExpression(new Code('required')));
+          }
         }));
       }
     }));

angel_serialize_generator/test/models/author.dart

@@ -3,6 +3,7 @@ library angel_serialize.test.models.author;
 import 'package:angel_framework/common.dart';
 import 'package:angel_serialize/angel_serialize.dart';
 import 'package:collection/collection.dart';
+import 'package:meta/meta.dart';
 import 'book.dart';
 
 part 'author.g.dart';
@@ -11,9 +12,14 @@ part 'author.serializer.g.dart';
 
 @serializable
 abstract class _Author extends Model {
+  @required
   String get name;
+
+  @required
   int get age;
+
   List<Book> get books;
+
   Book get newestBook;
 
   @exclude
@@ -34,7 +40,9 @@ abstract class _Bookmark extends Model {
   final Book book;
 
   List<int> get history;
+
   int get page;
+
   String get comment;
 
   _Bookmark(this.book);

angel_serialize_generator/test/models/author.g.dart

@@ -9,8 +9,8 @@ part of angel_serialize.test.models.author;
 class Author extends _Author {
   Author(
       {this.id,
-      this.name,
-      this.age,
+      @required this.name,
+      @required this.age,
       List<Book> books,
       this.newestBook,
       this.secret,