Check for required fields

angel_serialize_generator/lib/build_context.dart

@@ -4,6 +4,7 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/element.dart';
 import 'package:angel_serialize/angel_serialize.dart';
 import 'package:build/build.dart';
+import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
 import 'package:recase/recase.dart';
 import 'package:source_gen/source_gen.dart';
@@ -72,6 +73,18 @@ Future<BuildContext> buildContext(
         ctx.aliases[field.name] = new ReCase(field.name).snakeCase;
       }
 
+      // Check for @required
+      var required =
+          const TypeChecker.fromRuntime(Required).firstAnnotationOf(el);
+
+      if (required != null) {
+        var cr = new ConstantReader(required);
+        var reason = cr.peek('reason')?.stringValue ??
+            "Missing field '${ctx.resolveFieldName(field.name)}' on ${ctx
+                .modelClassName}.";
+        ctx.requiredFields[field.name] = reason;
+      }
+
       ctx.fields.add(field);
     }
   }

angel_serialize_generator/lib/context.dart

@@ -9,6 +9,9 @@ class BuildContext {
   ReCase _modelClassNameRecase;
   TypeReference _modelClassType;
 
+  /// A map of fields that are absolutely required, and error messages for when they are absent.
+  final Map<String, String> requiredFields = {};
+
   /// A map of field names to resolved names from `@Alias()` declarations.
   final Map<String, String> aliases = {};
 

angel_serialize_generator/pubspec.yaml

@@ -11,6 +11,7 @@ dependencies:
   code_buffer: ^1.0.0
   code_builder: ^3.0.0
   id: ^1.0.0
+  meta: ^1.0.0
   recase: ^1.0.0
   source_gen: ^0.7.0
 dev_dependencies: