refactor: Connection error handling

lib/matrix_api.dart

@@ -30,6 +30,7 @@ export 'matrix_api/model/filter.dart';
 export 'matrix_api/model/keys_query_response.dart';
 export 'matrix_api/model/login_response.dart';
 export 'matrix_api/model/login_types.dart';
+export 'matrix_api/model/matrix_connection_exception.dart';
 export 'matrix_api/model/matrix_event.dart';
 export 'matrix_api/model/matrix_exception.dart';
 export 'matrix_api/model/matrix_keys.dart';

lib/matrix_api/matrix_api.dart

@@ -30,6 +30,7 @@ import 'model/filter.dart';
 import 'model/keys_query_response.dart';
 import 'model/login_response.dart';
 import 'model/login_types.dart';
+import 'model/matrix_connection_exception.dart';
 import 'model/matrix_event.dart';
 import 'model/matrix_exception.dart';
 import 'model/matrix_keys.dart';
@@ -190,6 +191,9 @@ class MatrixApi {
       } catch (_) {
         // No-OP
       }
+      if (resp.statusCode >= 500 && resp.statusCode < 600) {
+        throw Exception(respBody);
+      }
       var jsonString = String.fromCharCodes(respBody.runes);
       if (jsonString.startsWith('[') && jsonString.endsWith(']')) {
         jsonString = '\{"chunk":$jsonString\}';
@@ -197,18 +201,15 @@ class MatrixApi {
       jsonResp = jsonDecode(jsonString)
           as Map<String, dynamic>; // May throw FormatException
 
-      if (resp.statusCode >= 400 && resp.statusCode < 500) {
-        // The server has responsed with an matrix related error.
-        var exception = MatrixException(resp);
-
-        throw exception;
-      }
       _timeoutFactor = 1;
-    } on TimeoutException catch (_) {
+    } on TimeoutException catch (e, s) {
       _timeoutFactor *= 2;
-      rethrow;
-    } catch (_) {
-      rethrow;
+      throw MatrixConnectionException(e, s);
+    } catch (e, s) {
+      throw MatrixConnectionException(e, s);
+    }
+    if (resp.statusCode >= 400 && resp.statusCode < 500) {
+      throw MatrixException(resp);
     }
 
     return jsonResp;

lib/matrix_api/model/matrix_connection_exception.dart

@@ -0,0 +1,26 @@
+/*
+ *   Famedly Matrix SDK
+ *   Copyright (C) 2019, 2020 Famedly GmbH
+ *
+ *   This program is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU Affero General Public License as
+ *   published by the Free Software Foundation, either version 3 of the
+ *   License, or (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU Affero General Public License for more details.
+ *
+ *   You should have received a copy of the GNU Affero General Public License
+ *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+class MatrixConnectionException implements Exception {
+  final dynamic original;
+  final StackTrace stackTrace;
+  MatrixConnectionException(this.original, this.stackTrace);
+
+  @override
+  String toString() => original.toString();
+}

lib/src/client.dart

@@ -769,9 +769,12 @@ class Client extends MatrixApi {
         Logs.warning('The user has been logged out!');
         clear();
       }
+    } on MatrixConnectionException catch (e, s) {
+      Logs.warning('Synchronization connection failed: ${e.toString()}');
+      onSyncError.add(SdkError(exception: e, stackTrace: s));
     } catch (e, s) {
       if (!isLogged() || _disposed) return;
-      Logs.error('Error during processing events: ' + e.toString(), s);
+      Logs.error('Error during processing events: ${e.toString()}', s);
       onSyncError.add(SdkError(
           exception: e is Exception ? e : Exception(e), stackTrace: s));
     }

test/client_test.dart

@@ -78,7 +78,7 @@ void main() {
 
       try {
         await matrix.checkHomeserver('https://fakeserver.wrongaddress');
-      } on FormatException catch (exception) {
+      } on MatrixConnectionException catch (exception) {
         expect(exception != null, true);
       }
       await matrix.checkHomeserver('https://fakeserver.notexisting');