fix: cdk flags hint is shown before template payload (#785)

When a user runs `cdk synth`, they receive a message about their
unconfigured feature flags. This relocates the message to be displayed
after the CloudFormation templates, to make it more visible.

---
By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license

Author: vivian12300

packages/aws-cdk/lib/cli/cdk-toolkit.ts

@@ -1059,13 +1059,13 @@ export class CdkToolkit {
   ): Promise<any> {
     const stacks = await this.selectStacksForDiff(stackNames, exclusively, autoValidate);
 
-    await displayFlagsMessage(this.toolkit, this.props.cloudExecutable, this.ioHost.asIoHelper());
-
     // if we have a single stack, print it to STDOUT
     if (stacks.stackCount === 1) {
       if (!quiet) {
         await printSerializedObject(this.ioHost.asIoHelper(), obscureTemplate(stacks.firstStack.template), json ?? false);
       }
+
+      await displayFlagsMessage(this.toolkit, this.props.cloudExecutable);
       return undefined;
     }
 
@@ -1075,6 +1075,7 @@ export class CdkToolkit {
       `Supply a stack id (${stacks.stackArtifacts.map((s) => chalk.green(s.hierarchicalId)).join(', ')}) to display its template.`,
     );
 
+    await displayFlagsMessage(this.toolkit, this.props.cloudExecutable);
     return undefined;
   }
 
@@ -2111,14 +2112,13 @@ async function askUserConfirmation(
     }
   });
 }
-export async function displayFlagsMessage(toolkit: InternalToolkit, cloudExecutable: CloudExecutable,
-  ioHelper: IoHelper): Promise<void> {
+export async function displayFlagsMessage(toolkit: InternalToolkit, cloudExecutable: CloudExecutable): Promise<void> {
   let numUnconfigured = (await toolkit.flags(cloudExecutable))
     .filter(flag => !OBSOLETE_FLAGS.includes(flag.name))
     .filter(flag => flag.userValue === undefined).length;
 
   if (numUnconfigured > 0) {
-    await ioHelper.defaults.info(`You currently have ${numUnconfigured} unconfigured feature flags that may require attention to keep your application up-to-date. Run 'cdk flags' to learn more.`);
+    process.stderr.write(`You currently have ${numUnconfigured} unconfigured feature flag(s) that may require attention to keep your application up-to-date. Run 'cdk flags' to learn more.`);
   }
 }
 

packages/aws-cdk/test/cli/display-flags-message.test.ts

@@ -1,24 +1,20 @@
 import { Toolkit } from '@aws-cdk/toolkit-lib';
-import { asIoHelper } from '../../lib/api-private';
 import { displayFlagsMessage } from '../../lib/cli/cdk-toolkit';
-import { TestIoHost } from '../_helpers/io-host';
 
 describe('displayFlagsMessage', () => {
-  let ioHost: TestIoHost;
-  let ioHelper: any;
   let mockToolkit: jest.Mocked<Toolkit>;
   let mockCloudExecutable: any;
+  let stderrWriteSpy: jest.SpyInstance;
 
   beforeEach(() => {
-    ioHost = new TestIoHost();
-    ioHelper = asIoHelper(ioHost, 'synth');
     mockCloudExecutable = {};
 
     mockToolkit = {
       flags: jest.fn(),
     } as any;
 
     jest.spyOn(Toolkit.prototype, 'flags').mockImplementation(mockToolkit.flags);
+    stderrWriteSpy = jest.spyOn(process.stderr, 'write').mockImplementation(() => true);
   });
 
   afterEach(() => {
@@ -52,14 +48,11 @@ describe('displayFlagsMessage', () => {
 
     mockToolkit.flags.mockResolvedValue(mockFlagsData);
 
-    await displayFlagsMessage(mockToolkit as any, mockCloudExecutable, ioHelper);
+    await displayFlagsMessage(mockToolkit as any, mockCloudExecutable);
 
     expect(mockToolkit.flags).toHaveBeenCalledWith(mockCloudExecutable);
-    expect(ioHost.notifySpy).toHaveBeenCalledWith(
-      expect.objectContaining({
-        message: 'You currently have 1 unconfigured feature flags that may require attention to keep your application up-to-date. Run \'cdk flags\' to learn more.',
-        level: 'info',
-      }),
+    expect(stderrWriteSpy).toHaveBeenCalledWith(
+      'You currently have 1 unconfigured feature flag(s) that may require attention to keep your application up-to-date. Run \'cdk flags\' to learn more.',
     );
   });
   test('does not display a message when user has no unconfigured flags', async () => {
@@ -74,10 +67,10 @@ describe('displayFlagsMessage', () => {
     ];
     mockToolkit.flags.mockResolvedValue(mockFlagsData);
 
-    await displayFlagsMessage(mockToolkit as any, mockCloudExecutable, ioHelper);
+    await displayFlagsMessage(mockToolkit as any, mockCloudExecutable);
 
     expect(mockToolkit.flags).toHaveBeenCalledWith(mockCloudExecutable);
-    expect(ioHost.notifySpy).not.toHaveBeenCalled();
+    expect(stderrWriteSpy).not.toHaveBeenCalled();
   });
 });