Update env vs code config behavior

gateway-js/src/__tests__/integration/configuration.test.ts

@@ -1,4 +1,5 @@
 import gql from 'graphql-tag';
+import mockedEnv from 'mocked-env';
 import { Logger } from 'apollo-server-types';
 import { ApolloGateway } from '../..';
 import {
@@ -187,3 +188,52 @@ describe('gateway startup errors', () => {
     `);
   });
 });
+
+describe('gateway config / env behavior', () => {
+  let gateway: ApolloGateway | null = null;
+  afterEach(async () => {
+    if (gateway) {
+      await gateway.stop();
+      gateway = null;
+    }
+  });
+
+  // TODO(trevor:cloudconfig): this behavior will be updated
+  describe('schema config delivery endpoint configuration', () => {
+    it('A code config overrides the env variable', async () => {
+      let cleanUp = mockedEnv({
+        APOLLO_SCHEMA_CONFIG_DELIVERY_ENDPOINT: 'env-config',
+      });
+
+      gateway = new ApolloGateway({
+        logger,
+        experimental_schemaConfigDeliveryEndpoint: 'code-config',
+      });
+
+      expect(gateway['experimental_schemaConfigDeliveryEndpoint']).toEqual(
+        'code-config',
+      );
+
+      gateway = null;
+      cleanUp();
+    });
+
+    it('A code config set to `null` takes precedence over an existing env variable', async () => {
+      let cleanUp = mockedEnv({
+        APOLLO_SCHEMA_CONFIG_DELIVERY_ENDPOINT: 'env-config',
+      });
+
+      gateway = new ApolloGateway({
+        logger,
+        experimental_schemaConfigDeliveryEndpoint: null,
+      });
+
+      expect(gateway['experimental_schemaConfigDeliveryEndpoint']).toEqual(
+        null,
+      );
+
+      gateway = null;
+      cleanUp();
+    });
+  });
+})

gateway-js/src/__tests__/integration/networkRequests.test.ts

@@ -124,22 +124,6 @@ it('Fetches CSDL from remote storage using a configured env variable', async ()
   cleanUp();
 });
 
-it('A configured env variable overrides the code configuration', async () => {
-  let cleanUp = mockedEnv({
-    APOLLO_SCHEMA_CONFIG_DELIVERY_ENDPOINT: 'env-override',
-  });
-
-  gateway = new ApolloGateway({
-    logger,
-    experimental_schemaConfigDeliveryEndpoint: 'code-config',
-  });
-
-  expect(gateway['experimental_schemaConfigDeliveryEndpoint']).toEqual('env-override');
-
-  gateway = null;
-  cleanUp();
-});
-
 it('Updates CSDL from remote storage', async () => {
   mockCsdlRequestSuccess();
   mockCsdlRequestSuccess(getTestingCsdl(fixturesWithUpdate), 'updatedId-5678');

gateway-js/src/config.ts

@@ -126,6 +126,13 @@ interface GatewayConfigBase {
   experimental_autoFragmentization?: boolean;
   fetcher?: typeof fetch;
   serviceHealthCheck?: boolean;
+  /**
+   * @deprecated This configuration option shouldn't be used unless by
+   *             recommendation from Apollo staff. This behavior will be
+   *             defaulted in a future release and this option will strictly be
+   *             used as an override.
+   */
+  experimental_schemaConfigDeliveryEndpoint?: null;
 }
 
 export interface RemoteGatewayConfig extends GatewayConfigBase {
@@ -138,8 +145,10 @@ export interface LegacyManagedGatewayConfig extends GatewayConfigBase {
   federationVersion?: number;
 }
 
+// This Omitted step is needed to "override"
+type Omitted = Omit<GatewayConfigBase, 'experimental_schemaConfigDeliveryEndpoint'>;
 // TODO(trevor:cloudconfig): This type becomes the only managed config
-export interface PrecomposedManagedGatewayConfig extends GatewayConfigBase {
+export interface PrecomposedManagedGatewayConfig extends Omitted {
   /**
    * @deprecated This configuration option shouldn't be used unless by
    *             recommendation from Apollo staff. This behavior will be
@@ -223,7 +232,10 @@ export function isManagedConfig(
 export function isPrecomposedManagedConfig(
   config: GatewayConfig,
 ): config is PrecomposedManagedGatewayConfig {
-  return 'experimental_schemaConfigDeliveryEndpoint' in config;
+  return (
+    'experimental_schemaConfigDeliveryEndpoint' in config &&
+    config.experimental_schemaConfigDeliveryEndpoint !== null
+  );
 }
 
 // A static config is one which loads synchronously on start and never updates

gateway-js/src/index.ts

@@ -215,21 +215,19 @@ export class ApolloGateway implements GraphQLService {
 
     this.experimental_pollInterval = config?.experimental_pollInterval;
 
-
     // Do not use this unless advised by Apollo staff to do so
+    // 1. If config is explicitly set to a `string` or `null` in code, use it
+    // 2. Else, if the env var is set, use that
+    // 3. Else, default to `null`
     this.experimental_schemaConfigDeliveryEndpoint =
-      process.env.APOLLO_SCHEMA_CONFIG_DELIVERY_ENDPOINT ?? null;
-
-    if (isPrecomposedManagedConfig(this.config)) {
-      // If the env was already set, it will maintain precedence here.
-      this.experimental_schemaConfigDeliveryEndpoint =
-        this.experimental_schemaConfigDeliveryEndpoint ??
-        this.config.experimental_schemaConfigDeliveryEndpoint ??
-        null;
-    }
+      isPrecomposedManagedConfig(this.config) ||
+      this.config.experimental_schemaConfigDeliveryEndpoint === null
+        ? // We know at this point the config is either string | null, but TS thinks it can also be undefined
+          (this.config.experimental_schemaConfigDeliveryEndpoint as string | null)
+        : process.env.APOLLO_SCHEMA_CONFIG_DELIVERY_ENDPOINT ?? null;
 
-      // Use the provided updater function if provided by the user, else default
     if (isManuallyManagedConfig(this.config)) {
+      // Use the provided updater function if provided by the user, else default
       if ('experimental_updateCsdl' in this.config) {
         this.updateServiceDefinitions = this.config.experimental_updateCsdl;
       } else if ('experimental_updateServiceDefinitions' in this.config) {