feat: pass context to gql links

packages/ferry/test/client/context_test.dart

@@ -0,0 +1,47 @@
+import 'package:ferry/ferry.dart';
+import 'package:ferry_test_graphql2/queries/__generated__/reviews.data.gql.dart';
+import 'package:ferry_test_graphql2/queries/__generated__/reviews.req.gql.dart';
+import 'package:gql_exec/gql_exec.dart';
+import 'package:test/test.dart';
+
+class _TestContextEntry implements ContextEntry {
+  final String test;
+  _TestContextEntry({required this.test});
+
+  @override
+  List<Object?> get fieldsForEquality => [test];
+}
+
+void main() {
+  test('passes context to links', () async {
+    // network response
+    final link = Link.function((request, [forward]) {
+      final contextTest = request.context.entry<_TestContextEntry>()!.test;
+      final data = GReviewsData((b) => b
+        ..reviews.addAll([
+          GReviewsData_reviews((b) => b
+            ..id = '1'
+            ..commentary = contextTest
+            ..stars = 5),
+        ])).toJson();
+
+      return Stream.value(Response(
+        errors: [],
+        data: data,
+        response: data,
+      ));
+    });
+
+    final client = Client(link: link);
+
+    final req = GReviewsReq((b) => b
+      ..vars.first = 3
+      ..vars.offset = 0
+      ..context =
+          Context.fromList([_TestContextEntry(test: 'some contextual value')]));
+
+    final result = await client.request(req).first;
+
+    expect(result.data!.reviews!.first!.commentary, 'some contextual value');
+  });
+}

packages/ferry_exec/lib/src/json_operation_request.dart

@@ -35,6 +35,9 @@ class JsonOperationRequest
   @override
   Request get execRequest => Request(operation: operation, variables: vars);
 
+  @override
+  final Context? context;
+
   JsonOperationRequest(
       {required this.operation,
       required this.fetchPolicy,
@@ -44,7 +47,8 @@ class JsonOperationRequest
       this.executeOnListen = true,
       required this.vars,
       this.updateResult,
-      this.optimisticResponse});
+      this.optimisticResponse,
+      this.context});
 
   @override
   Map<String, dynamic> parseData(Map<String, dynamic> json) => json;
@@ -93,15 +97,15 @@ class JsonOperationRequest
   JsonOperationRequest transformOperation(
       Operation Function(Operation) transform) {
     return JsonOperationRequest(
-      operation: transform(operation),
-      fetchPolicy: fetchPolicy,
-      vars: vars,
-      requestId: requestId,
-      updateCacheHandlerKey: updateCacheHandlerKey,
-      updateCacheHandlerContext: updateCacheHandlerContext,
-      executeOnListen: executeOnListen,
-      updateResult: updateResult,
-      optimisticResponse: optimisticResponse,
-    );
+        operation: transform(operation),
+        fetchPolicy: fetchPolicy,
+        vars: vars,
+        requestId: requestId,
+        updateCacheHandlerKey: updateCacheHandlerKey,
+        updateCacheHandlerContext: updateCacheHandlerContext,
+        executeOnListen: executeOnListen,
+        updateResult: updateResult,
+        optimisticResponse: optimisticResponse,
+        context: context);
   }
 }

packages/ferry_exec/lib/src/operation_request.dart

@@ -36,6 +36,9 @@ abstract interface class OperationRequest<TData, TVars> {
   /// controller when the stream returned by `request()` is listened to
   bool get executeOnListen;
 
+  /// The [Context] to be passed to links.
+  Context? get context;
+
   /// Parses data into a concrete type for the given operation
   ///
   /// This is a simple wrapper on the static fromJson method on the generated class.

packages/ferry_generator/lib/src/codegen/operation_req.dart

@@ -65,6 +65,10 @@ Class _buildOperationReqClass(
           ).call([], {
             'operation': refer('operation'),
             'variables': refer('vars').property('toJson').call([]),
+            'context': refer('context').ifNullThen(refer(
+              'Context',
+              'package:gql_exec/gql_exec.dart',
+            ).constInstance([])),
           }).code,
       ),
       Method(
@@ -147,6 +151,24 @@ Class _buildOperationReqClass(
           ..type = MethodType.getter
           ..name = 'executeOnListen',
       ),
+      Method(
+        (b) => b
+          ..annotations.addAll([
+            refer('override'),
+            refer('BuiltValueField', 'package:built_value/built_value.dart')
+                .call([], {
+              'serialize': refer('false'),
+            }),
+          ])
+          ..returns = TypeReference(
+            (b) => b
+              ..symbol = 'Context'
+              ..url = 'package:gql_exec/gql_exec.dart'
+              ..isNullable = true,
+          )
+          ..type = MethodType.getter
+          ..name = 'context',
+      ),
       Method(
         (b) => b
           ..annotations.add(refer('override'))