fix(cli): cdk bootstrap cannot be used without supplying the --app ar…

…gument (aws#7970)

If a user supplied the `--app` argument, we select the environments from the
app. However, we did not have a check that precludes this selection when the
argument is not provided. We recently refactored this area in aws#7510

Closes aws#7906

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

@@ -346,9 +346,13 @@ export class CdkToolkit {
 
     const environments: cxapi.Environment[] = [
       ...environmentsFromDescriptors(environmentSpecs),
-      ...await globEnvironmentsFromStacks(await this.selectStacksForList([]), globSpecs, this.props.sdkProvider),
     ];
 
+    // If there is an '--app' argument, select the environments from the app.
+    if (this.props.cloudExecutable.hasApp) {
+      environments.push(...await globEnvironmentsFromStacks(await this.selectStacksForList([]), globSpecs, this.props.sdkProvider));
+    }
+
     await Promise.all(environments.map(async (environment) => {
       success(' ⏳  Bootstrapping environment %s...', colors.blue(environment.name));
       try {

packages/aws-cdk/test/cdk-toolkit.test.ts

@@ -99,6 +99,29 @@ describe('deploy', () => {
       }, expect.anything(), expect.anything());
       expect(mockBootstrapEnvironment).toHaveBeenCalledTimes(1);
     });
+
+    test('bootstrap can be invoked without the --app argument', async () => {
+      // GIVEN
+      cloudExecutable.configuration.settings.clear();
+      const mockSynthesize = jest.fn();
+      cloudExecutable.synthesize = mockSynthesize;
+
+      const toolkit = defaultToolkitSetup();
+
+      // WHEN
+      await toolkit.bootstrap(['aws://123456789012/west-pole'], undefined, undefined, false, false, {});
+
+      // THEN
+      expect(mockBootstrapEnvironment).toHaveBeenCalledWith({
+        account: '123456789012',
+        region: 'west-pole',
+        name: 'aws://123456789012/west-pole',
+      }, expect.anything(), expect.anything());
+      expect(mockBootstrapEnvironment).toHaveBeenCalledTimes(1);
+
+      expect(cloudExecutable.hasApp).toEqual(false);
+      expect(mockSynthesize).not.toHaveBeenCalled();
+    });
   });
 });