Converting object to an encodable object failed: Instance of '_CompactLinkedHashSet<String>'

[john916zhang]

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Issue Info

Platform Name: Flutter, Android
Platform Version: 1.20
Dio Version: 3.0.9

Issue Description and Steps

dio .post('$url/auth/local/register', data: {username, email, password}) .then((response) => print(response.data)) .catchError((error) => print(error));

`
DioError [DioErrorType.DEFAULT]: Converting object to an encodable object failed: Instance of '_CompactLinkedHashSet'
#0 _JsonStringifier.writeObject (dart:convert/json.dart:687:7)
#1 _JsonStringStringifier.printOn (dart:convert/json.dart:876:17)
#2 _JsonStringStringifier.stringify (dart:convert/json.dart:861:5)
#3 JsonEncoder.convert (dart:convert/json.dart:261:30)
#4 JsonCodec.encode (dart:convert/json.dart:171:45)
#5 DefaultTransformer.transformRequest (package:dio/src/transformer.dart:62:21)
#6 DioMixin._transformData (package:dio/src/dio.dart:1011:39)
#7 DioMixin._dispatchRequest (package:dio/src/dio.dart:918:26)
#8 DioMixin._request._interceptorWrapper... (package:dio/src/dio.dart:849:37)
#9 DioMixin.checkIfNeedEnqueue (package:dio/src/dio.dart:1117:22)
#10 DioMixin._request._interceptorWrapper.. (package:dio/src/dio.dart:846:22)
#11 new Future. (dart:async/future.dart:174:37)
#12 StackZoneSpecification._run (package:stack_trace/src/stack_zone_specification.dart:209:15)
#13 StackZoneSpecification._registerCallback. (package:stack_trace/src/stack_zone_specification.dart:119:48)
#14 _rootRun (dart:async/zone.dart:1182:47)
#15 _CustomZone.run (dart:async/zone.dart:1093:19)
#16 _CustomZone.runGuarded (dart:async/zone.dart:997:7)
#17 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:1037:23)
#18 StackZoneSpecification._run (package:stack_trace/src/stack_zone_specification.dart:209:15)
#19 StackZoneSpecification._registerCallback. (package:stack_trace/src/stack_zone_specification.dart:119:48)
#20 _rootRun (dart:async/zone.dart:1190:13)
#21 _CustomZone.run (dart:async/zone.dart:1093:19)
#22 _CustomZone.bindCallback. (dart:async/zone.dart:1021:23)
#23 Timer._createTimer. (dart:async-patch/timer_patch.dart:18:15)
#24 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:397:19)
#25 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:428:5)
#26 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)

`

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