prints independent operation name

Author: vasilich6107

packages/graphql_codegen/lib/src/printer/base/operation.dart

@@ -6,12 +6,19 @@ import 'package:graphql_codegen/src/printer/clients/graphql.dart';
 import 'package:graphql_codegen/src/printer/clients/graphql_flutter.dart';
 import 'package:graphql_codegen/src/printer/context.dart';
 import 'package:graphql_codegen/src/config/config.dart';
+import 'package:graphql_codegen/src/printer/utils.dart';
 
 List<Spec> printOperationSpecs(PrintContext<ContextOperation> elementContext) {
   final context = elementContext.context;
   final operation = context.operation;
   final clients = context.config.clients;
+  final operationName = context.operation?.name;
+
+
   return [
+    if (context.config.setOperationName && operationName != null)
+      Code('const ${elementContext.namePrinter
+          .printOperationNameDefinition(context.path)} = ${literalString(operationName.value)};'),
     if (context.hasVariables) ...printVariableClasses(elementContext),
     printContext(elementContext),
     ...printContextExtension(elementContext),

packages/graphql_codegen/lib/src/printer/utils.dart

@@ -126,6 +126,9 @@ class NamePrinter {
   String printGraphQLFlutterClientOperationName(Name name) =>
       "${printName(name)}${separator}Widget";
 
+  String printOperationNameDefinition(Name name) =>
+      "operationName${printName(name)}";
+
   String printGraphQLFlutterClientMutationHookResultName(Name name) =>
       "${printName(name)}${separator}HookResult";
 

packages/graphql_codegen/test/assets/issue_191/mutation.graphql.dart

@@ -2,6 +2,8 @@ import 'dart:async';
 import 'package:gql/ast.dart';
 import 'package:graphql/client.dart' as graphql;
 
+const operationNameMutation$M = 'M';
+
 class Mutation$M {
   Mutation$M({
     this.bar,

packages/graphql_codegen/test/assets/issue_191/query.graphql.dart

@@ -2,6 +2,8 @@ import 'dart:async';
 import 'package:gql/ast.dart';
 import 'package:graphql/client.dart' as graphql;
 
+const operationNameQuery$Q = 'Q';
+
 class Query$Q {
   Query$Q({
     this.foo,

packages/graphql_codegen/test/assets/issue_191/subscription.graphql.dart

@@ -2,6 +2,8 @@ import 'dart:async';
 import 'package:gql/ast.dart';
 import 'package:graphql/client.dart' as graphql;
 
+const operationNameSubscription$S = 'S';
+
 class Subscription$S {
   Subscription$S({
     this.foo,