[Annotation Only] Adding case insensitive to enum based on loading JsonEnum config

json_annotation/lib/src/enum_helpers.dart

@@ -4,6 +4,19 @@
 
 import 'json_key.dart';
 
+/// Compare an enum value against a source using case-insensitive.
+///
+/// Exposed only for code generated by `package:json_serializable`.
+/// Not meant to be used directly by user code.
+bool $enumCompareCaseInsensitive(String arg1, Object arg2) =>
+    arg2 is String && (arg1.toLowerCase() == arg2.toLowerCase());
+
+/// Compare an enum value against a source.
+///
+/// Exposed only for code generated by `package:json_serializable`.
+/// Not meant to be used directly by user code.
+bool $enumCompareStandard<V>(V arg1, Object arg2) => arg1 == arg2;
+
 /// Returns the key associated with value [source] from [enumValues], if one
 /// exists.
 ///
@@ -18,13 +31,16 @@ K? $enumDecodeNullable<K extends Enum, V>(
   Map<K, V> enumValues,
   Object? source, {
   Enum? unknownValue,
+  bool Function(V arg1, Object arg2)? comparator,
 }) {
   if (source == null) {
     return null;
   }
 
+  comparator ??= $enumCompareStandard;
+
   for (var entry in enumValues.entries) {
-    if (entry.value == source) {
+    if (comparator(entry.value, source)) {
       return entry.key;
     }
   }
@@ -65,6 +81,7 @@ K $enumDecode<K extends Enum, V>(
   Map<K, V> enumValues,
   Object? source, {
   K? unknownValue,
+  bool Function(V arg1, Object arg2)? comparator,
 }) {
   if (source == null) {
     throw ArgumentError(
@@ -73,8 +90,9 @@ K $enumDecode<K extends Enum, V>(
     );
   }
 
+  comparator ??= $enumCompareStandard;
   for (var entry in enumValues.entries) {
-    if (entry.value == source) {
+    if (comparator(entry.value, source)) {
       return entry.key;
     }
   }

json_annotation/lib/src/json_enum.dart

@@ -13,6 +13,7 @@ class JsonEnum {
   const JsonEnum({
     this.alwaysCreate = false,
     this.fieldRename = FieldRename.none,
+    this.caseInsensitive = false,
     this.valueField,
   });
 
@@ -36,6 +37,12 @@ class JsonEnum {
   /// for entries annotated with [JsonValue].
   final FieldRename fieldRename;
 
+  /// If `true`, enum comparison will be done using case-insensitive.
+  ///
+  /// The default, `false`, means enum comparison will be done using
+  /// case-sensitive.
+  final bool caseInsensitive;
+
   /// Specifies the field within an "enhanced enum" to use as the value
   /// to use for serialization.
   ///

json_annotation/lib/src/json_key.dart

@@ -149,19 +149,26 @@ class JsonKey {
   /// valid on a nullable enum field.
   final Enum? unknownEnumValue;
 
+  /// If true, enum will be parsed with case-insensitive.
+  /// Specifically, both values will be lower-cased and compared.
+  ///
+  /// Valid only on enum fields with a compatible enum value.
+  final bool caseInsensitive;
+
   /// Creates a new [JsonKey] instance.
   ///
   /// Only required when the default behavior is not desired.
   const JsonKey({
-    @Deprecated('Has no effect') bool? nullable,
+    @Deprecated('Has no effect')
+        bool? nullable,
     this.defaultValue,
     this.disallowNullValue,
     this.fromJson,
     @Deprecated(
       'Use `includeFromJson` and `includeToJson` with a value of `false` '
       'instead.',
     )
-    this.ignore,
+        this.ignore,
     this.includeFromJson,
     this.includeIfNull,
     this.includeToJson,
@@ -170,6 +177,7 @@ class JsonKey {
     this.required,
     this.toJson,
     this.unknownEnumValue,
+    this.caseInsensitive = false,
   });
 
   /// Sentinel value for use with [unknownEnumValue].