fix: make sendError payload format respect WebSocket subprotocol

lib/subscription-connection.js

@@ -445,8 +445,11 @@ module.exports = class SubscriptionConnection {
 
   sendError (err, id) {
     const convertedError = toGraphQLError(err)
-    // Graphql over websocket spec requires that errors are wrapped in an array
-    this.sendMessage(this.protocolMessageTypes.GQL_ERROR, id, [convertedError])
+    // graphql-transport-ws requires errors wrapped in an array; the legacy
+    // subscriptions-transport-ws protocol (identified as 'graphql-ws') expects
+    // a single error object instead.
+    const payload = this.socket.protocol === 'graphql-ws' ? convertedError : [convertedError]
+    this.sendMessage(this.protocolMessageTypes.GQL_ERROR, id, payload)
   }
 
   async handleConnectionInitExtension (extension) {

test/query-depth.test.js

@@ -516,5 +516,6 @@ test('queryDepth - enforce depth limit for subscriptions over websocket', async
   const errorMessage = await waitForMessageType('error')
 
   t.assert.strictEqual(errorMessage.id, '1')
-  t.assert.match(errorMessage.payload[0].message, /Graphql validation error/)
+  // graphql-ws (subscriptions-transport-ws) sends a single error object, not an array
+  t.assert.match(errorMessage.payload.message, /Graphql validation error/)
 })

test/subscription-connection.test.js

@@ -943,3 +943,37 @@ test('should use default protocol when client does not specify a subprotocol', a
 
   ws.close()
 })
+
+test('sendError sends a plain object for graphql-ws protocol', async (t) => {
+  t.plan(2)
+  const messages = []
+  const sc = new SubscriptionConnection({
+    on () {},
+    close () {},
+    send (msg, cb) { messages.push(JSON.parse(msg)); cb() },
+    protocol: GRAPHQL_WS
+  }, {})
+
+  await sc.sendError(new Error('boom'), 1)
+
+  t.assert.strictEqual(messages.length, 1)
+  // legacy graphql-ws expects the payload to be a single error object, not an array
+  t.assert.ok(!Array.isArray(messages[0].payload), 'payload must not be an array for graphql-ws')
+})
+
+test('sendError wraps error in array for graphql-transport-ws protocol', async (t) => {
+  t.plan(2)
+  const messages = []
+  const sc = new SubscriptionConnection({
+    on () {},
+    close () {},
+    send (msg, cb) { messages.push(JSON.parse(msg)); cb() },
+    protocol: GRAPHQL_TRANSPORT_WS
+  }, {})
+
+  await sc.sendError(new Error('boom'), 1)
+
+  t.assert.strictEqual(messages.length, 1)
+  // graphql-transport-ws spec requires errors wrapped in an array
+  t.assert.ok(Array.isArray(messages[0].payload), 'payload must be an array for graphql-transport-ws')
+})

test/subscription-hooks.test.js

@@ -253,7 +253,8 @@ test('subscription - should handle preSubscriptionParsing hook errors', async t
     t.assert.deepEqual(data, {
       id: 1,
       type: 'error',
-      payload: [{ message: 'a preSubscriptionParsing error occurred' }]
+      // graphql-ws (subscriptions-transport-ws) expects a single error object, not an array
+      payload: { message: 'a preSubscriptionParsing error occurred' }
     })
   }
 })
@@ -303,7 +304,8 @@ test('subscription - should handle preSubscriptionExecution hook errors', async
     t.assert.deepEqual(data, {
       id: 1,
       type: 'error',
-      payload: [{ message: 'a preSubscriptionExecution error occurred' }]
+      // graphql-ws (subscriptions-transport-ws) expects a single error object, not an array
+      payload: { message: 'a preSubscriptionExecution error occurred' }
     })
   }
 })

test/subscription.test.js

@@ -1317,14 +1317,15 @@ test('subscription server sends correct error if execution throws', (t, done) =>
       const data = JSON.parse(chunk)
 
       if (data.id === 1 && data.type === 'error') {
+        // graphql-ws (subscriptions-transport-ws) expects a single error object, not an array
         t.assert.strictEqual(chunk, JSON.stringify({
           type: 'error',
           id: 1,
-          payload: [{
+          payload: {
             message: 'custom execution error',
             locations: [{ line: 3, column: 13 }],
             path: ['notificationAdded']
-          }]
+          }
         }))
 
         client.end()