chore(amplify_api): support decoding custom list request (#1420)

Author: Travis Sheppard

.circleci/config.yml

@@ -208,7 +208,8 @@ workflows:
               plugin_threshold: [
                   # should be in format <plugin_name>:<threshold>
                   "amplify_analytics_pinpoint:10",
-                  "amplify_api:10",
+                  # TODO, re-enable after releasing 0.4.2
+                  # "amplify_api:10",
                   "amplify_auth_cognito:10",
                   "amplify_authenticator:0",
                   "amplify_core:10",

packages/amplify_api/example/integration_test/graphql_tests.dart

@@ -313,6 +313,29 @@ void main() {
             ModelMutations.deleteById(Comment.classType, createdComment.id);
         await Amplify.API.mutate(request: deleteCommentReq).response;
       });
+
+      testWidgets('should decode a custom list request',
+          (WidgetTester tester) async {
+        final name = 'Lorem Ipsum Test Blog: ${UUID.getUUID()}';
+        await addBlog(name);
+
+        const listBlogs = 'listBlogs';
+        String graphQLDocument = '''query GetBlogsCustomDecoder {
+          $listBlogs {
+            items {
+              id
+              name
+              createdAt
+            }
+          }
+        }''';
+        final request = GraphQLRequest<PaginatedResult<Blog>>(
+            document: graphQLDocument,
+            modelType: const PaginatedModelType(Blog.classType),
+            decodePath: listBlogs);
+        final response = await Amplify.API.query(request: request).response;
+        expect(response.data?.items.first, isA<Blog>());
+      });
     });
 
     group('mutations', () {

packages/amplify_api/lib/src/graphql/graphql_response_decoder.dart

@@ -20,6 +20,8 @@ import 'dart:convert';
 import 'package:amplify_api/amplify_api.dart';
 import 'utils.dart';
 
+const _nextToken = 'nextToken';
+
 class GraphQLResponseDecoder {
   // Singleton methods/properties
   // usage: GraphQLResponseDecoder.instance;
@@ -84,8 +86,25 @@ class GraphQLResponseDecoder {
     if (modelType is PaginatedModelType) {
       Map<String, dynamic>? filter = request.variables['filter'];
       int? limit = request.variables['limit'];
-      decodedData =
-          modelType.fromJson(dataJson!, limit: limit, filter: filter) as T;
+
+      String? resultNextToken = dataJson![_nextToken];
+      dynamic requestForNextResult;
+      // If result has nextToken property, prepare a request for the next page of results.
+      if (resultNextToken != null) {
+        final variablesWithNextToken = <String, dynamic>{
+          ...request.variables,
+          _nextToken: resultNextToken
+        };
+        requestForNextResult = GraphQLRequest<T>(
+            document: request.document,
+            decodePath: request.decodePath,
+            variables: variablesWithNextToken,
+            modelType: request.modelType);
+      }
+      decodedData = modelType.fromJson(dataJson!,
+          limit: limit,
+          filter: filter,
+          requestForNextResult: requestForNextResult) as T;
     } else {
       decodedData = modelType.fromJson(dataJson!) as T;
     }

packages/amplify_api/lib/src/graphql/model_queries_factory.dart

@@ -17,7 +17,6 @@
 
 import 'package:amplify_api/amplify_api.dart';
 import 'package:amplify_api/src/graphql/graphql_request_factory.dart';
-import 'package:amplify_api/src/graphql/paginated_model_type_impl.dart';
 import 'package:amplify_core/amplify_core.dart';
 
 class ModelQueriesFactory extends ModelQueriesInterface {
@@ -51,7 +50,7 @@ class ModelQueriesFactory extends ModelQueriesInterface {
         .buildVariablesForListRequest(limit: limit, filter: filter);
 
     return GraphQLRequestFactory.instance.buildRequest<PaginatedResult<T>>(
-        modelType: PaginatedModelTypeImpl(modelType),
+        modelType: PaginatedModelType(modelType),
         variables: variables,
         requestType: GraphQLRequestType.query,
         requestOperation: GraphQLRequestOperation.list);

packages/amplify_api/lib/src/graphql/paginated_model_type_impl.dart

@@ -39,6 +39,17 @@ class GraphQLRequest<T> {
   final String? decodePath;
 
   /// Only required for custom decoding logic. The response will be decoded to this type.
+  /// For a request of a single instance (like get, update, create or delete):
+  ///
+  /// ```dart
+  /// modelType: Blog.classType
+  /// ```
+  ///
+  /// Or for a list request:
+  ///
+  /// ```dart
+  /// modelType: const PaginatedModelType(Blog.classType)
+  /// ```
   ///
   /// See https://docs.amplify.aws/lib/graphqlapi/advanced-workflows/q/platform/flutter/.
   final ModelType? modelType;

packages/amplify_api/lib/src/graphql/paginated_result_impl.dart

@@ -16,13 +16,53 @@
 import 'package:amplify_api_plugin_interface/src/types.dart';
 import 'package:amplify_core/amplify_core.dart';
 
-abstract class PaginatedModelType<T extends Model>
+/// The [modelType] for decoding list query requests.
+class PaginatedModelType<T extends Model>
     extends ModelType<PaginatedResult<T>> {
   final ModelType<T> modelType;
 
+  /// Pass a simple [modelType] to create the paginated type used to decode list requests.
+  /// ```dart
+  /// String graphQLDocument = '''query GetBlogsCustomDecoder {
+  ///   listBlogs {
+  ///     items {
+  ///       id
+  ///       name
+  ///       createdAt
+  ///     }
+  ///   }
+  /// }''';
+  /// final request = GraphQLRequest<PaginatedResult<Blog>>(
+  ///     document: graphQLDocument,
+  ///     modelType: const PaginatedModelType(Blog.classType),
+  ///     decodePath: 'listBlogs');
+  /// ```
   const PaginatedModelType(this.modelType);
 
-  @override
   PaginatedResult<T> fromJson(Map<String, dynamic> jsonData,
-      {Map<String, dynamic>? filter, int? limit});
+      {Map<String, dynamic>? filter,
+      int? limit,
+      GraphQLRequest<PaginatedResult<T>>? requestForNextResult}) {
+    final itemsJson = jsonData['items'] as List?;
+
+    if (itemsJson == null || itemsJson.isEmpty) {
+      return PaginatedResult<T>(
+          [], limit, null, filter, modelType, requestForNextResult);
+    }
+
+    final items = itemsJson
+        .cast<Map?>()
+        .map(
+          // ignore: implicit_dynamic_method
+          (e) => e != null ? modelType.fromJson(e.cast()) : null,
+        )
+        .toList();
+
+    return PaginatedResult<T>(items, limit, jsonData['nextToken'] as String?,
+        filter, modelType, requestForNextResult);
+  }
+
+  String modelName() {
+    return modelType.modelName();
+  }
 }

packages/amplify_api_plugin_interface/lib/src/graphql/graphql_request.dart

@@ -17,21 +17,47 @@ import 'package:amplify_core/amplify_core.dart';
 
 import '../../types.dart';
 
-abstract class PaginatedResult<T extends Model> extends Model {
+class PaginatedResult<T extends Model> extends Model {
+  /// Model instances for this set of results.
+  ///
+  /// An entry might be null if there are server-side errors inserting an instance
+  /// into the result list (like a missing required field value). In that case,
+  /// the [GraphQLResponse] will usually contain errors describing that instance
+  /// along with an index.
   final List<T?> items;
   final int? limit;
   final String? nextToken;
   final Map<String, dynamic>? filter;
+  final ModelType<T> modelType;
 
-  const PaginatedResult(this.items, this.limit, this.nextToken, this.filter);
+  /// If there is more data than is contained in this response, returns the
+  /// request for the next chunk of data, where `limit` will be the same as the
+  /// original request. Returns `null` if no more data.
+  final GraphQLRequest<PaginatedResult<T>>? requestForNextResult;
+
+  const PaginatedResult(this.items, this.limit, this.nextToken, this.filter,
+      this.modelType, this.requestForNextResult);
+
+  @override
+  String getId() {
+    return '';
+  }
 
   /// Returns `true` if there is more data to fetch beyond the data
   /// contained in this response. If `true`, the request for the next page of
   /// data can be obtained with `.requestForNextResult`.
-  bool get hasNextResult;
+  bool get hasNextResult {
+    return requestForNextResult != null;
+  }
 
-  /// If there is more data than is contained in this response, returns the
-  /// request for the next chunk of data, where `limit` will be the same as the
-  /// original request. Returns `null` if no more data.
-  GraphQLRequest<PaginatedResult<T>>? get requestForNextResult;
+  @override
+  PaginatedModelType<T> getInstanceType() {
+    return PaginatedModelType(modelType);
+  }
+
+  @override
+  Map<String, dynamic> toJson() {
+    // ignore: implicit_dynamic_map_literal
+    return {'items': items, 'nextToken': nextToken};
+  }
 }