Ignore field of entity b adding ignore annotation (#248)

floor_annotation/lib/floor_annotation.dart

@@ -6,6 +6,7 @@ export 'src/database.dart';
 export 'src/delete.dart';
 export 'src/entity.dart';
 export 'src/foreign_key.dart';
+export 'src/ignore.dart';
 export 'src/index.dart';
 export 'src/insert.dart';
 export 'src/on_conflict_strategy.dart';

floor_annotation/lib/src/ignore.dart

@@ -0,0 +1,7 @@
+class _Ignore {
+  const _Ignore();
+}
+
+/// Ignores the marked element from Floor's processing logic.
+/// It can only be applied to entity's fields.
+const ignore = _Ignore();

floor_generator/lib/processor/entity_processor.dart

@@ -274,6 +274,8 @@ class EntityProcessor extends Processor<Entity> {
 
 extension on FieldElement {
   bool shouldBeIncluded() {
-    return !(isStatic || displayName == 'hashCode');
+    final isIgnored = hasAnnotation(annotations.ignore.runtimeType);
+    final isHashCode = displayName == 'hashCode';
+    return !(isStatic || isHashCode || isIgnored);
   }
 }

floor_generator/test/processor/entity_processor_test.dart

@@ -229,6 +229,55 @@ void main() {
     });
   });
 
+  group('@Ignore', () {
+    test('ignore field not present in constructor', () async {
+      final classElement = await _createClassElement('''
+      @entity
+      class Person {
+        @primaryKey
+        final int id;
+      
+        final String name;
+        
+        @ignore
+        String foo;
+      
+        Person(this.id, this.name);
+      }
+    ''');
+
+      final actual = EntityProcessor(classElement)
+          .process()
+          .fields
+          .map((field) => field.name);
+
+      const expected = 'foo';
+      expect(actual, isNot(contains(expected)));
+    });
+
+    test('ignore field present in constructor', () async {
+      final classElement = await _createClassElement('''
+      @entity
+      class Person {
+        @primaryKey
+        final int id;
+      
+        final String name;
+        
+        @ignore
+        String foo;
+      
+        Person(this.id, this.name, [this.foo = 'foo']);
+      }
+    ''');
+
+      final actual = EntityProcessor(classElement).process().constructor;
+
+      const expected = "Person(row['id'] as int, row['name'] as String)";
+      expect(actual, equals(expected));
+    });
+  });
+
   group('foreign keys', () {
     test('foreign key holds correct values', () async {
       final classElements = await _createClassElements('''