Support unknownEnumValue on Map values (#1093)

Author: t-beckmann

json_serializable/lib/src/json_key_utils.dart

@@ -162,11 +162,13 @@ KeyConfig _from(FieldElement element, ClassConfig classAnnotation) {
           targetEnumType = element.type;
         } else if (coreIterableTypeChecker.isAssignableFromType(element.type)) {
           targetEnumType = coreIterableGenericType(element.type);
+        } else if (coreMapTypeChecker.isAssignableFromType(element.type)) {
+          targetEnumType = coreMapGenericValueType(element.type);
         } else {
           throwUnsupported(
             element,
             '`$fieldName` can only be set on fields of type enum or on '
-            'Iterable, List, or Set instances of an enum type.',
+            'Iterable, List, Set or Map instances of an enum type.',
           );
         }
 

json_serializable/lib/src/shared_checkers.dart

@@ -19,6 +19,18 @@ const coreMapTypeChecker = TypeChecker.fromUrl('dart:core#Map');
 DartType coreIterableGenericType(DartType type) =>
     type.typeArgumentsOf(coreIterableTypeChecker)!.single;
 
+/// Returns the generic key type of the [Map] represented by [type].
+///
+/// If [type] does not extend [Map], an error is thrown.
+DartType coreMapGenericKeyType(DartType type) =>
+    type.typeArgumentsOf(coreMapTypeChecker)![0];
+
+/// Returns the generic value type of the [Map] represented by [type].
+///
+/// If [type] does not extend [Map], an error is thrown.
+DartType coreMapGenericValueType(DartType type) =>
+    type.typeArgumentsOf(coreMapTypeChecker)![1];
+
 /// A [TypeChecker] for [String], [bool] and [num].
 const simpleJsonTypeChecker = TypeChecker.any([
   coreStringTypeChecker,

json_serializable/test/json_serializable_test.dart

@@ -133,6 +133,8 @@ const _expectedAnnotatedTests = {
   'UnknownEnumValue',
   'UnknownEnumValueListWrongEnumType',
   'UnknownEnumValueListWrongType',
+  'UnknownEnumValueMapValueWrongEnumType',
+  'UnknownEnumValueMapValueWrongType',
   'UnknownEnumValueNotEnumField',
   'UnknownEnumValueWrongEnumType',
   'UnsupportedDateTimeField',

json_serializable/test/src/unknown_enum_value_test_input.dart

@@ -53,6 +53,28 @@ class UnknownEnumValueListWrongEnumType {
   late List<UnknownEnumValueItems> value;
 }
 
+@ShouldThrow(
+  'Error with `@JsonKey` on the `value` field. `unknownEnumValue` has type '
+  '`int`, but the provided unknownEnumValue is of type '
+  '`WrongEnumType`.',
+)
+@JsonSerializable()
+class UnknownEnumValueMapValueWrongType {
+  @JsonKey(unknownEnumValue: WrongEnumType.otherValue)
+  late Map<String, int> value;
+}
+
+@ShouldThrow(
+  'Error with `@JsonKey` on the `value` field. `unknownEnumValue` has type '
+  '`UnknownEnumValueItems`, but the provided unknownEnumValue is of type '
+  '`WrongEnumType`.',
+)
+@JsonSerializable()
+class UnknownEnumValueMapValueWrongEnumType {
+  @JsonKey(unknownEnumValue: WrongEnumType.otherValue)
+  late Map<String, UnknownEnumValueItems> value;
+}
+
 enum WrongEnumType { otherValue }
 
 @ShouldThrow(
@@ -68,7 +90,7 @@ class UnknownEnumValueWrongEnumType {
 
 @ShouldThrow(
   'Error with `@JsonKey` on the `value` field. `unknownEnumValue` can only be '
-  'set on fields of type enum or on Iterable, List, or Set instances of an '
+  'set on fields of type enum or on Iterable, List, Set or Map instances of an '
   'enum type.',
 )
 @JsonSerializable()