Invalid argument(s), when response without the header: "content-type"

[laxian]

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Issue Info

Info	Value
Platform Name	ios / android
Platform Version	3.0.1
Dio Version	2.5.0 "macos_x64"
Android Studio / Xcode Version
Repro rate	100%

Issue Description and Steps

In my case, I tried to request a url with header "content-type: application/json",
I got response with code:401, while response headers do not contain "content-type",
then I got an exception

---

Exception has occurred.
DioError (DioError [DioErrorType.DEFAULT]: Invalid argument(s)
#0 _RegExp.matchAsPrefix (dart:core-patch/regexp_patch.dart:238:28)
#1 StringScanner.matches (package:string_scanner/src/string_scanner.dart:169:26)
#2 StringScanner.scan (package:string_scanner/src/string_scanner.dart:126:19)
#3 new MediaType.parse. (package:http_parser/src/media_type.dart:48:15)
#4 wrapFormatException (package:http_parser/src/utils.dart:13:16)
#5 new MediaType.parse (package:http_parser/src/media_type.dart:46:12)
#6 DefaultTransformer._isJsonMime (package:dio/src/transformer.dart:140:22)
#7 DefaultTransformer.transformResponse (package:dio/src/transformer.dart:129:9)

#8 DioMixin._dispatchRequest (package:dio/src/dio.dart:924:38)

#9 DioMixin._request._interceptorWrapper... (package:dio/src/dio.dart:828:37)
#10 DioMixin.checkIfNeedEnqueue (package:dio/src/dio.dart:1100:22)
#11 DioMixin._request._interceptorWrapper.. (package:dio/src/dio.dart:825:22)
#12 new Future. (dart:async/future.dart:176:37)
#13 _rootRun (dart:async/zone.dart:1120:38)
#14 _CustomZone.run (dart:async/zone.dart:1021:19)
#15 _CustomZone.runGuarded (dart:async/zone.dart:923:7)
#16 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:963:23)
#17 _rootRun (dart:async/zone.dart:1124:13)
#18 _CustomZone.run (dart:async/zone.dart:1021:19)
#19 _CustomZone.bindCallback. (dart:async/zone.dart:947:23)
#20 Timer._createTimer. (dart:async-patch/timer_patch.dart:21:15)
#21 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:382:19)
#22 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:416:5)
#23 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:172:12)
)

---

response headers:
HTTP/1.1 401
X-Application-Context gateway-service:test:8089
X-Foo 08011803-62de-4917-812c-1ebb2595faac
Transfer-Encoding chunked
Date Tue, 24 Sep 2019 06:57:25 GMT
Connection keep-alive

---

I found that exception here:

if (responseBody != null &&
        responseBody.isNotEmpty &&
        options.responseType == ResponseType.json &&
       
        //THIS LINE!!! the arg passed to _jsJsonMine is null
        _isJsonMime(response.headers[Headers.contentTypeHeader]?.first)) {
      if (jsonDecodeCallback != null) {
        return jsonDecodeCallback(responseBody);
      } else {
        return json.decode(responseBody);
      }
    }

I got exception because the RESPONSE HEADERS DO NOT CONTAIN "content-type".
Is it necessary?
Or it is a bug?

[stale]

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