feat: Add extensions field to the subscribe message payload

PROTOCOL.md

@@ -72,6 +72,7 @@ interface SubscribeMessage {
     operationName?: string | null;
     query: string;
     variables?: Record<string, unknown> | null;
+    extensions?: Record<string, unknown> | null;
   };
 }
 ```

docs/interfaces/common.subscribepayload.md

@@ -8,12 +8,19 @@
 
 ### Properties
 
+- [extensions](common.subscribepayload.md#extensions)
 - [operationName](common.subscribepayload.md#operationname)
 - [query](common.subscribepayload.md#query)
 - [variables](common.subscribepayload.md#variables)
 
 ## Properties
 
+### extensions
+
+• `Optional` `Readonly` **extensions**: ``null`` \| *Record*<string, unknown\>
+
+___
+
 ### operationName
 
 • `Optional` `Readonly` **operationName**: ``null`` \| *string*

src/common.ts

@@ -94,6 +94,7 @@ export interface SubscribePayload {
   readonly operationName?: string | null;
   readonly query: string;
   readonly variables?: Record<string, unknown> | null;
+  readonly extensions?: Record<string, unknown> | null;
 }
 
 /** @category Common */
@@ -171,7 +172,11 @@ export function isMessage(val: unknown): val is Message {
           (!hasOwnProperty(val.payload, 'variables') ||
             val.payload.variables === undefined ||
             val.payload.variables === null ||
-            hasOwnObjectProperty(val.payload, 'variables'))
+            hasOwnObjectProperty(val.payload, 'variables')) &&
+          (!hasOwnProperty(val.payload, 'extensions') ||
+            val.payload.extensions === undefined ||
+            val.payload.extensions === null ||
+            hasOwnObjectProperty(val.payload, 'extensions'))
         );
       case MessageType.Next:
         return (

src/tests/client.ts

@@ -422,7 +422,7 @@ describe('query operation', () => {
     await sub.waitForComplete();
   });
 
-  it('should accept nullish value for `operationName` and `variables`', async () => {
+  it('should accept nullish value for `operationName`, `variables` and `extensions`', async () => {
     const { url } = await startTServer();
 
     const client = createClient({
@@ -441,13 +441,15 @@ describe('query operation', () => {
       operationName: undefined,
       query: 'query { getValue }',
       variables: undefined,
+      extensions: undefined,
     }).waitForComplete();
 
     // null
     await tsubscribe(client, {
       operationName: null,
       query: 'query { getValue }',
       variables: null,
+      extensions: null,
     }).waitForComplete();
   });
 });