Keep requires directive in gateway schema (#756)

lib/federation.js

@@ -234,11 +234,13 @@ function addServiceResolver (schema, originalSchemaSDL) {
 
 function buildGatewaySchemaDirectives (schema) {
   // Remove service federation directives which should not be present in the gateway
-  const federationDirectiveNames = parse(BASE_FEDERATION_TYPES).definitions
+  const federationDirectiveNamesToRemove = parse(BASE_FEDERATION_TYPES).definitions
     .filter(definition => definition.kind === 'DirectiveDefinition')
+    // Keep `@requires` directive as it can be used in the gateway schema
+    .filter(definition => definition.name.value !== 'requires')
     .map(definition => definition.name.value)
   const directives = schema.getDirectives()
-    .filter(directive => !federationDirectiveNames.includes(directive.name))
+    .filter(directive => !federationDirectiveNamesToRemove.includes(directive.name))
 
   // De-duplicate custom directives
   const gatewayDirectives = []

test/gateway/custom-directives-with-batching.js

@@ -204,6 +204,7 @@ t.test('gateway with batching', t => {
       'skip',
       'deprecated',
       'specifiedBy',
+      'requires',
       'custom'
     ])
 

test/gateway/custom-directives.js

@@ -204,6 +204,7 @@ t.test('gateway', t => {
       'skip',
       'deprecated',
       'specifiedBy',
+      'requires',
       'custom'
     ])
 

test/gateway/pollingInterval.js

@@ -710,16 +710,6 @@ test('Polling schemas (should properly regenerate the schema when a downstream s
   })
   t.teardown(() => clock.uninstall())
   const oldSchema = `
-    directive @extends on INTERFACE | OBJECT
-
-    directive @external on FIELD_DEFINITION | OBJECT
-
-    directive @key(fields: String!) on INTERFACE | OBJECT
-
-    directive @provides(fields: String!) on FIELD_DEFINITION
-
-    directive @requires(fields: String!) on FIELD_DEFINITION
-
     type Query {
       me: User
     }
@@ -804,16 +794,6 @@ test('Polling schemas (should properly regenerate the schema when a downstream s
   })
 
   const refreshedSchema = `
-    directive @extends on INTERFACE | OBJECT
-
-    directive @external on FIELD_DEFINITION | OBJECT
-
-    directive @key(fields: String!) on INTERFACE | OBJECT
-
-    directive @provides(fields: String!) on FIELD_DEFINITION
-    
-    directive @requires(fields: String!) on FIELD_DEFINITION
-
     type User @key(fields: "id") {
       id: ID!
       lastName: String!

test/gateway/requires-directive.js

@@ -449,3 +449,80 @@ test('gateway handles @requires directive correctly apart of other directives',
     }
   })
 })
+
+test('gateway exposes @requires directive in list of directives', async (t) => {
+  const users = {
+    u1: {
+      id: 'u1',
+      name: 'John'
+    },
+    u2: {
+      id: 'u2',
+      name: 'Jane'
+    }
+  }
+
+  const userService = await createService(`
+    extend type Query {
+      me: User
+    }
+
+    type User @key(fields: "id") {
+      id: ID!
+      name: String!
+    }
+  `, {
+    Query: {
+      me: (root, args, context, info) => {
+        return users.u1
+      }
+    },
+    User: {
+      __resolveReference: (user, args, context, info) => {
+        return users[user.id]
+      }
+    }
+  })
+
+  const biographyService = await createService(`
+    type User @key(fields: "id") @extends {
+      id: ID! @external
+      name: String @external
+      biography: String @requires(fields: "id name")
+    }
+  `, {
+    User: {
+      biography (user) {
+        return `${user.name} with id ${user.id} test biography`
+      }
+    }
+  })
+
+  const { gateway, teardown } = await createGateway(biographyService, userService)
+  t.teardown(teardown)
+
+  const query = `
+    query IntrospectionQuery {
+      __schema {
+        directives {
+          name
+        }
+      }
+    } 
+  `
+  const res = await gatewayRequest(gateway, query)
+
+  t.same(JSON.parse(res.body), {
+    data: {
+      __schema: {
+        directives: [
+          { name: 'include' },
+          { name: 'skip' },
+          { name: 'deprecated' },
+          { name: 'specifiedBy' },
+          { name: 'requires' }
+        ]
+      }
+    }
+  })
+})