Default to new, null-aware element feature in Dart 3.8 (#1498)

Author: kevmoo

_test_yaml/test/src/build_config.g.dart

@@ -29,4 +29,5 @@ linter:
     - unnecessary_breaks
     - unnecessary_ignore
     - use_full_hex_values_for_flutter_colors
+    - use_null_aware_elements
     - use_string_buffers

analysis_options.yaml

@@ -1,6 +1,7 @@
 ## 6.9.6-wip
 
 - Move `package:collection` to a dev dependency.
+- Use new `null-aware element` feature in generated code.
 - Require Dart 3.8
 
 ## 6.9.5

example/lib/example.g.dart

@@ -14,6 +14,6 @@ const converterOrKeyInstructions = r'''
   https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonKey/fromJson.html
   https://pub.dev/documentation/json_annotation/latest/json_annotation/JsonKey/toJson.html''';
 
-/// This package generates code that uses case statements, which were introduced
-/// in Dart 3.0.
-const supportedLanguageConstraint = '^3.0.0';
+/// This package generates code that uses null-aware elements, which were
+/// introduced in Dart 3.8.
+const supportedLanguageConstraint = '^3.8.0';

json_serializable/CHANGELOG.md

@@ -6,7 +6,6 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:source_helper/source_helper.dart';
 
-import 'constants.dart';
 import 'enum_utils.dart';
 import 'helper_core.dart';
 import 'type_helpers/generic_factory_helper.dart';
@@ -109,10 +108,9 @@ mixin EncodeHelper implements HelperCore {
           final keyExpression = safeNameAccess(field);
           final valueExpression = _serializeField(field, access);
 
-          final keyValuePair = _canWriteJsonWithoutNullCheck(field)
-              ? '$keyExpression: $valueExpression'
-              : 'if ($valueExpression case final $generatedLocalVarName?) '
-                    '$keyExpression: $generatedLocalVarName';
+          final maybeQuestion = _canWriteJsonWithoutNullCheck(field) ? '' : '?';
+
+          final keyValuePair = '$keyExpression: $maybeQuestion$valueExpression';
           return '        $keyValuePair,\n';
         }),
       )

json_serializable/lib/src/constants.dart

@@ -32,7 +32,7 @@ void main() {
 
   group('language version', () {
     test('is less than required', () async {
-      const sdkLowerBound = '2.12.0';
+      const sdkLowerBound = '3.7.0';
       await _structurePackage(
         environment: const {'sdk': '^$sdkLowerBound'},
         dependencies: {'json_annotation': _annotationLowerBound},