Correctly handle reference types at the same path in the gateway

lib/gateway/make-resolver.js

@@ -397,8 +397,11 @@ function makeResolver ({ service, createOperation, transformData, isQuery, isRef
 
     if (isReference && !parent[fieldName]) return null
 
+    // Get the actual type as the returnType can be NonNull or List as well
+    const type = getNamedType(returnType)
+
     const queryId = generatePathKey(info.path).join('.')
-    const resolverKey = queryId.replace(/\d/g, '_IDX_')
+    const resolverKey = `${queryId.replace(/\d/g, '_IDX_')}.${type.toString()}`
     const { reply, __currentQuery, lruGatewayResolvers, pubsub } = context
 
     const cached = lruGatewayResolvers.get(`${__currentQuery}_${resolverKey}`)
@@ -407,9 +410,6 @@ function makeResolver ({ service, createOperation, transformData, isQuery, isRef
     let query
     let selections
 
-    // Get the actual type as the returnType can be NonNull or List as well
-    const type = getNamedType(returnType)
-
     if (cached) {
       variableNamesToDefine = cached.variableNamesToDefine
       query = cached.query

test/gateway/with-references-in-unions.js

@@ -0,0 +1,257 @@
+'use strict'
+
+const { test } = require('tap')
+const Fastify = require('fastify')
+const GQL = require('../..')
+
+async function createService (schema, resolvers = {}) {
+  const service = Fastify()
+  service.register(GQL, {
+    schema,
+    resolvers,
+    federationMetadata: true
+  })
+  await service.listen(0)
+
+  return [service, service.server.address().port]
+}
+
+const users = {
+  u1: {
+    id: 'u1',
+    name: 'Marie Curie',
+    fields: ['Physics', 'Chemistry']
+  },
+  u2: {
+    id: 'u2',
+    name: 'ALbert Einstein',
+    fields: ['Physics', 'Philosophy']
+  }
+}
+
+const messages = {
+  m1: {
+    id: 'm1',
+    message: 'Text Message.',
+    recipients: [{ id: 'u1' }]
+  },
+  m2: {
+    id: 'm2',
+    header: 'Email Header',
+    message: 'Email Message.',
+    recipients: [{ id: 'u2' }]
+  }
+}
+
+test('gateway handles reference types in unions at the same schema paths correctly', async (t) => {
+  t.plan(2)
+
+  const [messageService, messageServicePort] = await createService(
+    `
+    type Query @extends {
+      getMessages: [Message!]!
+    }
+
+    union Message = EmailMessage | TextMessage
+
+    type TextMessage {
+      id: ID!
+      message: String!
+      recipients: [TextMessageUser!]!
+    }
+
+    type EmailMessage {
+      id: ID!
+      message: String!
+      header: String!
+      recipients: [EmailMessageUser!]!
+    }
+
+    type TextMessageUser @extends @key(fields: "id") {
+      id: ID! @external
+    }
+
+    type EmailMessageUser @extends @key(fields: "id") {
+      id: ID! @external
+    }
+  `,
+    {
+      Query: {
+        getMessages: () => {
+          return Object.values(messages)
+        }
+      },
+      Message: {
+        resolveType: (message) => {
+          if ('header' in message) {
+            return 'EmailMessage'
+          }
+          return 'TextMessage'
+        }
+      }
+    }
+  )
+
+  const [userService, userServicePort] = await createService(
+    `
+    type TextMessageUser @key(fields: "id") {
+      id: ID!
+      name: String!
+      fields: [String!]!
+    }
+
+    type EmailMessageUser @key(fields: "id") {
+      id: ID!
+      name: String!
+      fields: [String!]!
+    }
+  `,
+    {
+      TextMessageUser: {
+        __resolveReference: (user) => {
+          return users[user.id]
+        }
+      },
+      EmailMessageUser: {
+        __resolveReference: (user) => {
+          return users[user.id]
+        }
+      }
+    }
+  )
+
+  const gateway = Fastify()
+  t.teardown(async () => {
+    await gateway.close()
+    await messageService.close()
+    await userService.close()
+  })
+  gateway.register(GQL, {
+    gateway: {
+      services: [
+        {
+          name: 'message',
+          url: `http://localhost:${messageServicePort}/graphql`
+        },
+        {
+          name: 'user',
+          url: `http://localhost:${userServicePort}/graphql`
+        }
+      ]
+    }
+  })
+
+  const query = `
+    query {
+      getMessages {
+        ... on TextMessage {
+          id
+          message
+          recipients {
+            id
+            name
+            fields
+          }
+        }
+        ... on EmailMessage {
+          id
+          header
+          message
+          recipients {
+            id
+            name
+            fields
+          }
+        }
+      }
+    }
+  `
+
+  // Not cached
+  {
+    const res = await gateway.inject({
+      method: 'POST',
+      headers: {
+        'content-type': 'application/json'
+      },
+      url: '/graphql',
+      body: JSON.stringify({
+        query
+      })
+    })
+
+    t.same(JSON.parse(res.body), {
+      data: {
+        getMessages: [
+          {
+            id: 'm1',
+            message: 'Text Message.',
+            recipients: [
+              {
+                id: 'u1',
+                name: 'Marie Curie',
+                fields: ['Physics', 'Chemistry']
+              }
+            ]
+          },
+          {
+            id: 'm2',
+            header: 'Email Header',
+            message: 'Email Message.',
+            recipients: [
+              {
+                id: 'u2',
+                name: 'ALbert Einstein',
+                fields: ['Physics', 'Philosophy']
+              }
+            ]
+          }
+        ]
+      }
+    })
+  }
+
+  // Cached
+  {
+    const res = await gateway.inject({
+      method: 'POST',
+      headers: {
+        'content-type': 'application/json'
+      },
+      url: '/graphql',
+      body: JSON.stringify({
+        query
+      })
+    })
+
+    t.same(JSON.parse(res.body), {
+      data: {
+        getMessages: [
+          {
+            id: 'm1',
+            message: 'Text Message.',
+            recipients: [
+              {
+                id: 'u1',
+                name: 'Marie Curie',
+                fields: ['Physics', 'Chemistry']
+              }
+            ]
+          },
+          {
+            id: 'm2',
+            header: 'Email Header',
+            message: 'Email Message.',
+            recipients: [
+              {
+                id: 'u2',
+                name: 'ALbert Einstein',
+                fields: ['Physics', 'Philosophy']
+              }
+            ]
+          }
+        ]
+      }
+    })
+  }
+})