chore(migrate): only allow migrate on healthy stacks

packages/aws-cdk/lib/api/util/cloudformation/stack-status.ts

@@ -41,6 +41,11 @@ export class StackStatus {
     return !this.isNotFound && (this.name === 'CREATE_COMPLETE' || this.name === 'UPDATE_COMPLETE' || this.name === 'IMPORT_COMPLETE');
   }
 
+  get isRollbackSuccess(): boolean {
+    return this.name === 'ROLLBACK_COMPLETE'
+      || this.name === 'UPDATE_ROLLBACK_COMPLETE';
+  }
+
   public toString(): string {
     return this.name + (this.reason ? ` (${this.reason})` : '');
   }

packages/aws-cdk/lib/commands/migrate.ts

@@ -6,6 +6,7 @@ import { Environment, UNKNOWN_ACCOUNT, UNKNOWN_REGION } from '@aws-cdk/cx-api';
 import * as cdk_from_cfn from 'cdk-from-cfn';
 import { cliInit } from '../../lib/init';
 import { Mode, SdkProvider } from '../api';
+import { CloudFormationStack } from '../api/util/cloudformation';
 import { zipDirectory } from '../util/archive';
 
 const camelCase = require('camelcase');
@@ -112,9 +113,13 @@ export function readFromPath(inputPath?: string): string | undefined {
 export async function readFromStack(stackName: string, sdkProvider: SdkProvider, environment: Environment): Promise<string | undefined> {
   const cloudFormation = (await sdkProvider.forEnvironment(environment, Mode.ForReading)).sdk.cloudFormation();
 
-  return (await cloudFormation.getTemplate({
-    StackName: stackName,
-  }).promise()).TemplateBody;
+  const stack = await CloudFormationStack.lookup(cloudFormation, stackName);
+  if (stack.stackStatus.isDeploySuccess || stack.stackStatus.isRollbackSuccess) {
+    return JSON.stringify(await stack.template());
+  } else {
+    throw new Error(`Stack '${stackName}' in account ${environment.account} and region ${environment.region} has a status of '${stack.stackStatus.name}' due to '${stack.stackStatus.reason}'. The stack cannot be migrated until it is in a healthy state.`);
+  }
+  return;
 }
 
 /**

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

@@ -869,7 +869,7 @@ describe('synth', () => {
 
     test('migrate fails when neither --from-path or --from-stack are provided', async () => {
       const toolkit = defaultToolkitSetup();
-      await expect(() => toolkit.migrate({ stackName: 'no-source' })).rejects.toThrowError('Either `--from-path` or `--from-stack` must be used to provide the source of the CloudFormation template.');
+      await expect(() => toolkit.migrate({ stackName: 'no-source' })).rejects.toThrow('Either `--from-path` or `--from-stack` must be used to provide the source of the CloudFormation template.');
       expect(stderrMock.mock.calls[1][0]).toContain(' ❌  Migrate failed for `no-source`: Either `--from-path` or `--from-stack` must be used to provide the source of the CloudFormation template.');
     });
 
@@ -879,7 +879,7 @@ describe('synth', () => {
         stackName: 'no-source',
         fromPath: './here/template.yml',
         fromStack: true,
-      })).rejects.toThrowError('Only one of `--from-path` or `--from-stack` may be provided.');
+      })).rejects.toThrow('Only one of `--from-path` or `--from-stack` may be provided.');
       expect(stderrMock.mock.calls[1][0]).toContain(' ❌  Migrate failed for `no-source`: Only one of `--from-path` or `--from-stack` may be provided.');
     });
 
@@ -888,14 +888,14 @@ describe('synth', () => {
       await expect(() => toolkit.migrate({
         stackName: 'bad-local-source',
         fromPath: './here/template.yml',
-      })).rejects.toThrowError('\'./here/template.yml\' is not a valid path.');
+      })).rejects.toThrow('\'./here/template.yml\' is not a valid path.');
       expect(stderrMock.mock.calls[1][0]).toContain(' ❌  Migrate failed for `bad-local-source`: \'./here/template.yml\' is not a valid path.');
     });
 
     test('migrate fails when --from-stack is used and stack does not exist in account', async () => {
       const mockSdkProvider = new MockSdkProvider();
       mockSdkProvider.stubCloudFormation({
-        getTemplate(_request) {
+        describeStacks(_request) {
           throw new Error('Stack does not exist in this environment');
         },
       });

packages/aws-cdk/test/commands/migrate.test.ts

@@ -11,6 +11,7 @@ const exec = promisify(_exec);
 describe('Migrate Function Tests', () => {
   let sdkProvider: MockSdkProvider;
   let getTemplateMock: jest.Mock;
+  let describeStacksMock: jest.Mock;
   let cfnMocks: MockedObject<SyncHandlerSubsetOf<AWS.CloudFormation>>;
 
   const testResourcePath = [__dirname, 'test-resources'];
@@ -20,10 +21,11 @@ describe('Migrate Function Tests', () => {
   const validTemplatePath = path.join(...templatePath, 's3-template.json');
   const validTemplate = readFromPath(validTemplatePath)!;
 
-  beforeEach(() => {
+  beforeEach(async () => {
     sdkProvider = new MockSdkProvider();
     getTemplateMock = jest.fn();
-    cfnMocks = { getTemplate: getTemplateMock };
+    describeStacksMock = jest.fn();
+    cfnMocks = { getTemplate: getTemplateMock, describeStacks: describeStacksMock };
     sdkProvider.stubCloudFormation(cfnMocks as any);
   });
 
@@ -57,17 +59,40 @@ describe('Migrate Function Tests', () => {
   });
 
   test('readFromStack produces a string representation of the template retrieved from CloudFormation', async () => {
-    const template = fs.readFileSync(validTemplatePath);
-    getTemplateMock.mockImplementationOnce(() => ({
+    const template = fs.readFileSync(validTemplatePath, { encoding: 'utf-8' });
+    getTemplateMock.mockImplementation(() => ({
       TemplateBody: template,
     }));
 
-    expect(await readFromStack('this-one', sdkProvider, { account: 'num', region: 'here', name: 'hello-my-name-is-what...' })).toEqual(template);
+    describeStacksMock.mockImplementation(() => ({
+      Stacks: [
+        {
+          StackName: 'this-one',
+          StackStatus: 'CREATE_COMPLETE',
+        },
+      ],
+    }));
+
+    expect(await readFromStack('this-one', sdkProvider, { account: 'num', region: 'here', name: 'hello-my-name-is-what...' })).toEqual(JSON.stringify(JSON.parse(template)));
   });
 
   test('readFromStack throws error when no stack exists with the stack name in the account and region', async () => {
-    getTemplateMock.mockImplementationOnce(() => { throw new Error('No stack. This did not go well.'); });
-    await expect(() => readFromStack('that-one', sdkProvider, { account: 'num', region: 'here', name: 'hello-my-name-is-who...' })).rejects.toThrowError('No stack. This did not go well.');
+    describeStacksMock.mockImplementation(() => { throw new Error('No stack. This did not go well.'); });
+    await expect(() => readFromStack('that-one', sdkProvider, { account: 'num', region: 'here', name: 'hello-my-name-is-who...' })).rejects.toThrow('No stack. This did not go well.');
+  });
+
+  test('readFromStack throws error when stack exists but the status is not healthy', async () => {
+    describeStacksMock.mockImplementation(() => ({
+      Stacks: [
+        {
+          StackName: 'this-one',
+          StackStatus: 'CREATE_FAILED',
+          StackStatusReason: 'Something went wrong',
+        },
+      ],
+    }));
+
+    await expect(() => readFromStack('that-one', sdkProvider, { account: 'num', region: 'here', name: 'hello-my-name-is-chicka-chicka...' })).rejects.toThrow('Stack \'that-one\' in account num and region here has a status of \'CREATE_FAILED\' due to \'Something went wrong\'. The stack cannot be migrated until it is in a healthy state.');
   });
 
   test('setEnvironment sets account and region when provided', () => {