Cleaning it all a bit before the call (didn't heavy test this)

server/src/createRemoteSchema.js

@@ -35,7 +35,14 @@ export const createRemoteSchema = async (uri) => {
 }
 
 export const createTransformedRemoteSchema = async (prefix, uri) => {
-  const schema = await createRemoteSchema(uri)
+  var schema
+  try {
+    schema = await createRemoteSchema(uri)
+  } catch (error) {
+    console.log(`An error occured while fetching ${prefix} schema :`)
+    console.log(error)
+    return false
+  }
   const transformedSchema = transformSchema(schema, [
     new RenameTypes((name) => prefix + capitalize(name)),
     new RenameRootFields((operation, name) => prefix + capitalize(name))

server/src/index.js

@@ -4,39 +4,33 @@ import 'dotenv/config'
 import { graphqlExpress, graphiqlExpress } from 'apollo-server-express'
 import { mergeSchemas } from 'graphql-tools'
 import { createTransformedRemoteSchema } from './createRemoteSchema'
+import { teams } from './links'
 
 async function run () {
   const transformedTeamsSchema = await createTransformedRemoteSchema('TeamsModule', process.env.TEAMS_API_URL)
   const transformedUsersSchema = await createTransformedRemoteSchema('UsersModule', process.env.USERS_API_URL)
   const transformedKeyVaultSchema = await createTransformedRemoteSchema('KeyVaultModule', process.env.KEYVAULT_API_URL)
 
-  const linkSchemaDefs =
-  `
-    extend type TeamsModuleTeam {
-      ownerUser: UsersModuleUser
+  var schemas = []
+  var resolvers = {}
+
+  if (transformedTeamsSchema) {
+    schemas.push(transformedTeamsSchema)
+    if (transformedUsersSchema) {
+      schemas.push(teams.linkSchemaDefs)
+      resolvers = Object.assign(resolvers, teams.resolver(transformedUsersSchema))
     }
-  `
+  }
+  if (transformedUsersSchema) {
+    schemas.push(transformedUsersSchema)
+  }
+  if (transformedKeyVaultSchema) {
+    schemas.push(transformedKeyVaultSchema)
+  }
 
   const schema = mergeSchemas({
-    schemas: [transformedTeamsSchema, transformedUsersSchema, transformedKeyVaultSchema, linkSchemaDefs],
-    resolvers: {
-      TeamsModuleTeam: {
-        ownerUser: {
-          fragment: `fragment UserFragment on TeamsModuleTeam{owner}`,
-          resolve (parent, args, context, info) {
-            const authId = parent.owner
-            return info.mergeInfo.delegateToSchema({
-              schema: transformedUsersSchema,
-              operation: 'query',
-              fieldName: 'UsersModuleUserByAuthId',
-              args: { authId },
-              context,
-              info
-            })
-          }
-        }
-      }
-    }
+    schemas,
+    resolvers
   })
 
   const app = express()

server/src/links/index.js

@@ -0,0 +1,3 @@
+import teams from './teams'
+
+export { teams }

server/src/links/teams.js

@@ -0,0 +1,27 @@
+export const linkSchemaDefs =
+  `
+    extend type TeamsModuleTeam {
+      ownerUser: UsersModuleUser
+    }
+  `
+
+export const resolver = (usersSchema) => ({
+  TeamsModuleTeam: {
+    ownerUser: {
+      fragment: `fragment UserFragment on TeamsModuleTeam{owner}`,
+      resolve (parent, args, context, info) {
+        const authId = parent.owner
+        return info.mergeInfo.delegateToSchema({
+          schema: usersSchema,
+          operation: 'query',
+          fieldName: 'UsersModuleUserByAuthId',
+          args: { authId },
+          context,
+          info
+        })
+      }
+    }
+  }
+})
+
+export default { resolver, linkSchemaDefs }