Added cofig test for packed struct, fixed analysis warnings

Author: mannprerak2

test/code_generator_tests/code_generator_test.dart

@@ -3,7 +3,6 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:ffigen/src/code_generator.dart';
-import 'package:ffigen/src/strings.dart';
 import 'package:test/test.dart';
 import '../test_utils.dart';
 

test/config_tests/packed_struct_override_test.dart

@@ -0,0 +1,62 @@
+// Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:ffigen/ffigen.dart';
+import 'package:ffigen/src/code_generator.dart';
+import 'package:ffigen/src/strings.dart' as strings;
+import 'package:yaml/yaml.dart' as yaml;
+import 'package:test/test.dart';
+
+import '../test_utils.dart';
+
+late Library actual, expected;
+
+void main() {
+  group('packed_struct_override_test', () {
+    test('Invalid Packed Config values', () {
+      const baseYaml = '''${strings.name}: 'NativeLibrary'
+${strings.description}: 'Compiler Opts Test'
+${strings.output}: 'unused'
+${strings.headers}:
+  ${strings.entryPoints}:
+    - 'test/header_parser_tests/packed_structs.h'
+${strings.structs}:
+  ${strings.structPacking}:
+    ''';
+      expect(
+          () => Config.fromYaml(
+              yaml.loadYaml(baseYaml + "'.*': null") as yaml.YamlMap),
+          throwsA(TypeMatcher<FormatException>()));
+      expect(
+          () => Config.fromYaml(
+              yaml.loadYaml(baseYaml + "'.*': 3") as yaml.YamlMap),
+          throwsA(TypeMatcher<FormatException>()));
+      expect(
+          () => Config.fromYaml(
+              yaml.loadYaml(baseYaml + "'.*': 32") as yaml.YamlMap),
+          throwsA(TypeMatcher<FormatException>()));
+    });
+    test('Override values', () {
+      final config = Config.fromYaml(yaml.loadYaml('''
+${strings.name}: 'NativeLibrary'
+${strings.description}: 'Compiler Opts Test'
+${strings.output}: 'unused'
+${strings.headers}:
+  ${strings.entryPoints}:
+    - 'test/header_parser_tests/packed_structs.h'
+${strings.structs}:
+  ${strings.structPacking}:
+    'Normal.*': 1
+    'StructWithAttr': 2
+    'PackedAttr': none
+        ''') as yaml.YamlMap);
+
+      final library = parse(config);
+
+      expect((library.getBinding('NormalStruct1') as Struc).pack, 1);
+      expect((library.getBinding('StructWithAttr') as Struc).pack, 2);
+      expect((library.getBinding('PackedAttr') as Struc).pack, null);
+    });
+  });
+}