feat(client): library-level exception handling

BREAKING CHANGE: replaces result.errors with result.exception

packages/graphql/lib/src/core/query_manager.dart

@@ -1,6 +1,5 @@
 import 'dart:async';
 
-import 'package:graphql/src/exceptions/base_exceptions.dart';
 import 'package:graphql/src/exceptions/exceptions.dart';
 import 'package:meta/meta.dart';
 
@@ -37,12 +36,6 @@ class QueryManager {
   Map<String, ObservableQuery> queries = <String, ObservableQuery>{};
 
   ObservableQuery watchQuery(WatchQueryOptions options) {
-    if (options.document == null) {
-      throw Exception(
-        'document option is required. You must specify your GraphQL document in the query options.',
-      );
-    }
-
     final ObservableQuery observableQuery = ObservableQuery(
       queryManager: this,
       options: options,
@@ -121,6 +114,9 @@ class QueryManager {
         );
       }
 
+      // TODO this should never happen right?
+      // if there is an error reaching the server, there should be an error thrown,
+      // if not, data should not be null.
       if (fetchResult.data == null &&
           fetchResult.errors == null &&
           (options.fetchPolicy == FetchPolicy.noCache ||
@@ -135,10 +131,14 @@ class QueryManager {
         options,
         source: QueryResultSource.Network,
       );
-    } catch (error) {
+    } catch (failure) {
       // we set the source to indicate where the source of failure
       queryResult ??= QueryResult(source: QueryResultSource.Network);
-      queryResult.addError(_attemptToWrapError(error));
+
+      queryResult.exception = coalesceErrors(
+        exception: queryResult.exception,
+        clientException: translateFailure(failure),
+      );
     }
 
     // cleanup optimistic results
@@ -199,8 +199,11 @@ class QueryManager {
           );
         }
       }
-    } catch (error) {
-      queryResult.addError(_attemptToWrapError(error));
+    } catch (failure) {
+      queryResult.exception = coalesceErrors(
+        exception: queryResult.exception,
+        clientException: translateFailure(failure),
+      );
     }
 
     // If not a regular eager cache resolution,
@@ -227,24 +230,6 @@ class QueryManager {
     return null;
   }
 
-  GraphQLError _attemptToWrapError(dynamic error) {
-    String errorMessage;
-
-    // not all errors thrown above are GraphQL errors,
-    // so try/catch to avoid "could not access message"
-    try {
-      errorMessage = error.message as String;
-      assert(errorMessage != null);
-      assert(errorMessage.isNotEmpty);
-    } catch (e) {
-      throw error;
-    }
-
-    return GraphQLError(
-      message: errorMessage,
-    );
-  }
-
   /// Add a result to the query specified by `queryId`, if it exists
   void addQueryResult(
     String queryId,

packages/graphql/lib/src/core/raw_operation_data.dart

@@ -13,7 +13,8 @@ class RawOperationData {
     @required this.document,
     Map<String, dynamic> variables,
     String operationName,
-  })  : _operationName = operationName,
+  })  : assert(document != null),
+        _operationName = operationName,
         variables = SplayTreeMap<String, dynamic>.of(
           variables ?? const <String, dynamic>{},
         );

packages/graphql/lib/src/exceptions/base_exceptions.dart → packages/graphql/lib/src/exceptions/_base_exceptions.dart

@@ -1,5 +1,9 @@
 abstract class ClientException implements Exception {}
 
+//
+// Cache exceptions
+//
+
 abstract class ClientCacheException implements ClientException {}
 
 /// A failure during the cache's entity normalization processes
@@ -22,3 +26,20 @@ class CacheMissException implements ClientCacheException {
 
   String get message => cause;
 }
+
+//
+// end cache exceptions
+//
+
+class UnhandledFailureWrapper implements ClientException {
+  covariant Object failure;
+  UnhandledFailureWrapper(this.failure);
+}
+
+ClientException translateFailure(dynamic failure) {
+  if (failure is ClientException) {
+    return failure;
+  }
+
+  return UnhandledFailureWrapper(failure);
+}

packages/graphql/lib/src/exceptions/exceptions.dart

@@ -1,4 +1,13 @@
+import './_base_exceptions.dart' as _b;
+import 'package:graphql/src/exceptions/io_network_exception.dart' as _n;
+
+export './_base_exceptions.dart' hide translateFailure;
 export './graphql_error.dart';
 export './operation_exception.dart';
 export './network_exception_stub.dart'
-    if (dart.library.io) './io_network_exceptions.dart';
+    if (dart.library.io) './io_network_exceptions.dart'
+    hide translateNetworkFailure;
+
+_b.ClientException translateFailure(dynamic failure) {
+  return _n.translateNetworkFailure(failure) ?? _b.translateFailure(failure);
+}

packages/graphql/lib/src/exceptions/io_network_exception.dart

@@ -1,4 +1,5 @@
 import 'dart:io' show SocketException;
+import 'dart:io';
 import './network_exception_stub.dart' as stub;
 
 class NetworkException extends stub.NetworkException {
@@ -7,14 +8,15 @@ class NetworkException extends stub.NetworkException {
   NetworkException.from(this.wrappedException);
 
   String get message => wrappedException.message;
-  String get targetAddress => wrappedException.address.address;
-  int get targetPort => wrappedException.port;
+  Uri get uri => Uri(
+        host: wrappedException.address.host,
+        port: wrappedException.port,
+      );
 }
 
-void translateExceptions(stub.VoidCallback block) {
-  try {
-    block();
-  } on SocketException catch (e) {
-    throw NetworkException.from(e);
+NetworkException translateNetworkFailure(dynamic failure) {
+  if (failure is SocketException) {
+    return NetworkException.from(failure);
   }
+  return stub.translateNetworkFailure(failure);
 }

packages/graphql/lib/src/exceptions/network_exception_stub.dart

@@ -1,24 +1,29 @@
-import './base_exceptions.dart' show ClientException;
+import 'package:http/http.dart' as http;
 
-typedef VoidCallback = void Function();
+import './_base_exceptions.dart' show ClientException;
 
 class NetworkException implements ClientException {
   covariant Exception wrappedException;
 
   final String message;
 
-  final String targetAddress;
-  final int targetPort;
+  final Uri uri;
 
   NetworkException({
     this.wrappedException,
     this.message,
-    this.targetAddress,
-    this.targetPort,
+    this.uri,
   });
 
-  String toString() =>
-      'Failed to connect to $targetAddress:$targetPort: $message';
+  String toString() => 'Failed to connect to $uri: $message';
 }
 
-void translateExceptions(VoidCallback block) => block();
+NetworkException translateNetworkFailure(dynamic failure) {
+  if (failure is http.ClientException) {
+    return NetworkException(
+      wrappedException: failure,
+      message: failure.message,
+      uri: failure.uri,
+    );
+  }
+}

packages/graphql/lib/src/exceptions/operation_exception.dart

@@ -1,8 +1,5 @@
-import 'package:graphql/src/exceptions/base_exceptions.dart';
-
+import 'package:graphql/src/exceptions/_base_exceptions.dart';
 import './graphql_error.dart';
-import './network_exception_stub.dart'
-    if (dart.library.io) './io_network_exceptions.dart';
 
 class OperationException implements Exception {
   List<GraphQLError> graphqlErrors = [];