OAuth with own nextcloud server fails silently

[Lattay]

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• [X] I have searched for similar issues (both open and closed) and cannot find a duplicate
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Describe the bug

When trying to connect to a Nextcloud server other than the official Saber one, the process goes normally, but when the procedure is done on the browser side nothing happen in the app.

I got this on android and with the flatpak version on linux, however the linux version let me run in a terminal and I get this exception:

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Deserializing to 'UsersGetCurrentUserResponseApplicationJson' failed due to: Deserializing to 'UsersGetCurrentUserResponseApplicationJson_Ocs' failed due to: Deserializing to 'UserDetails' failed due to: Tried to construct class "UserDetails" with null for non-nullable field "displayname".
#0      BuiltJsonSerializers._deserialize (package:built_value/src/built_json_serializers.dart:180)
#1      BuiltJsonSerializers.deserialize (package:built_value/src/built_json_serializers.dart:125)
#2      _deserialize (package:dynamite_runtime/src/client/response.dart:203)
#3      ResponseConverter.convert (package:dynamite_runtime/src/client/response.dart:143)
<asynchronous suspension>
#4      $UsersClient.getCurrentUser (package:nextcloud/src/api/provisioning_api.openapi.dart:3168)
<asynchronous suspension>
#5      NextcloudClientExtension.getUsername (package:saber/data/nextcloud/nextcloud_client_extension.dart:147)
<asynchronous suspension>
#6      _NcLoginStepState.startLoginFlow.<anonymous closure> (package:saber/components/nextcloud/nc_login_step.dart:54)
<asynchronous suspension>

To reproduce

1. In settings go to click on the account button
2. Fill the "other nextcloud server" field
3. Click connect
4. Follow the steps in the browser
5. At the end nothing happen

Expected behavior

Connection is validated.

Saber version

v0.24.3

Device

• Device: Samsung S8

• OS: Android 9

• Device: Linux laptop

• OS: Arch linux

Anything else?

The Nextcloud server is outdated, running 24.0.12. I don't have the possibility to update the server. If this project cannot support older servers it would be nice to have a mention of the minimum server requirement in the README.

[huste]

Same here on Android 9 with a Samsung Galaxy Note 8, Nextcloud 25.0.13. I treid with an app-token as well as with the default authentication method. Saber doesn't tell me anything why it fails.

[xxfogs]

Same issue on Samsung Galaxy A35, NextCloud 26.0.13

[xxfogs]

I've noticed something. If I remove TLS and use HTTP protocol instead, everything works just fine.

Perhaps the wrong protocol is being supplied in the OAuth requests?

[viktoriakeller]

I have the same issue on Mac and iOS (iPad, iPhone).