fix(cli): diff with changeset fails if deploy role cannot be assumed

packages/aws-cdk/lib/api/deployments.ts

@@ -265,6 +265,7 @@ export interface DestroyStackOptions {
 export interface StackExistsOptions {
   stack: cxapi.CloudFormationStackArtifact;
   deployName?: string;
+  tryLookupRole?: boolean;
 }
 
 export interface DeploymentsProps {
@@ -430,7 +431,12 @@ export class Deployments {
   }
 
   public async stackExists(options: StackExistsOptions): Promise<boolean> {
-    const { stackSdk } = await this.prepareSdkFor(options.stack, undefined, Mode.ForReading);
+    let stackSdk;
+    if (options.tryLookupRole) {
+      stackSdk = (await this.prepareSdkWithLookupOrDeployRole(options.stack)).stackSdk;
+    } else {
+      stackSdk = (await this.prepareSdkFor(options.stack, undefined, Mode.ForReading)).stackSdk;
+    }
     const stack = await CloudFormationStack.lookup(stackSdk.cloudFormation(), options.deployName ?? options.stack.stackName);
     return stack.exists;
   }

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

@@ -139,10 +139,19 @@ export class CdkToolkit {
       let changeSet = undefined;
 
       if (options.changeSet) {
-        const stackExists = await this.props.deployments.stackExists({
-          stack: stacks.firstStack,
-          deployName: stacks.firstStack.stackName,
-        });
+        let stackExists = false;
+        try {
+          stackExists = await this.props.deployments.stackExists({
+            stack: stacks.firstStack,
+            deployName: stacks.firstStack.stackName,
+            tryLookupRole: true,
+          });
+        } catch (e: any) {
+          debug(e.message);
+          stream.write('Checking if the stack exists before creating the changeset has failed, will base the diff on template differences (run again with -v to see the reason)\n');
+          stackExists = false;
+        }
+
         if (stackExists) {
           changeSet = await createDiffChangeSet({
             stack: stacks.firstStack,
@@ -154,7 +163,7 @@ export class CdkToolkit {
             stream,
           });
         } else {
-          debug(`the stack '${stacks.firstStack.stackName}' has not been deployed to CloudFormation, skipping changeset creation.`);
+          debug(`the stack '${stacks.firstStack.stackName}' has not been deployed to CloudFormation or describeStacks call failed, skipping changeset creation.`);
         }
       }
 
@@ -183,11 +192,21 @@ export class CdkToolkit {
         let changeSet = undefined;
 
         if (options.changeSet) {
-          // only perform this check if we're going to make a changeset. This check requires permissions that --no-changeset users might not have.
-          const stackExists = await this.props.deployments.stackExists({
-            stack: stack,
-            deployName: stack.stackName,
-          });
+
+          let stackExists = false;
+          try {
+            // only perform this check if we're going to make a changeset. This check requires permissions that --no-changeset users might not have.
+            stackExists = await this.props.deployments.stackExists({
+              stack,
+              deployName: stack.stackName,
+              tryLookupRole: true,
+            });
+          } catch (e: any) {
+            debug(e.message);
+            stream.write('Checking if the stack exists before creating the changeset has failed, will base the diff on template differences (run again with -v to see the reason)\n');
+            stackExists = false;
+          }
+
           if (stackExists) {
             changeSet = await createDiffChangeSet({
               stack,
@@ -200,7 +219,7 @@ export class CdkToolkit {
               stream,
             });
           } else {
-            debug(`the stack '${stack.stackName}' has not been deployed to CloudFormation, skipping changeset creation.`);
+            debug(`the stack '${stack.stackName}' has not been deployed to CloudFormation or describeStacks call failed, skipping changeset creation.`);
           }
         }
 

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

@@ -335,8 +335,86 @@ describe('non-nested stacks', () => {
     expect(buffer.data.trim()).not.toContain('There were no differences');
     expect(exitCode).toBe(0);
   });
+});
+
+describe('stack exists checks', () => {
+  beforeEach(() => {
+
+    jest.resetAllMocks();
+
+    cloudExecutable = new MockCloudExecutable({
+      stacks: [{
+        stackName: 'A',
+        template: { resource: 'A' },
+      },
+      {
+        stackName: 'B',
+        depends: ['A'],
+        template: { resource: 'B' },
+      },
+      {
+        stackName: 'C',
+        depends: ['A'],
+        template: { resource: 'C' },
+        metadata: {
+          '/resource': [
+            {
+              type: cxschema.ArtifactMetadataEntryType.ERROR,
+              data: 'this is an error',
+            },
+          ],
+        },
+      },
+      {
+        stackName: 'D',
+        template: { resource: 'D' },
+      }],
+    });
+
+    cloudFormation = instanceMockFrom(Deployments);
+
+    toolkit = new CdkToolkit({
+      cloudExecutable,
+      deployments: cloudFormation,
+      configuration: cloudExecutable.configuration,
+      sdkProvider: cloudExecutable.sdkProvider,
+    });
 
-  test('diff does not check for stack existence when --no-changeset is passed', async () => {
+    // Default implementations
+    cloudFormation.readCurrentTemplateWithNestedStacks.mockImplementation((stackArtifact: CloudFormationStackArtifact) => {
+      if (stackArtifact.stackName === 'D') {
+        return Promise.resolve({
+          deployedRootTemplate: { resource: 'D' },
+          nestedStacks: {},
+        });
+      }
+      return Promise.resolve({
+        deployedRootTemplate: {},
+        nestedStacks: {},
+      });
+    });
+    cloudFormation.deployStack.mockImplementation((options) => Promise.resolve({
+      noOp: true,
+      outputs: {},
+      stackArn: '',
+      stackArtifact: options.stack,
+    }));
+
+    jest.spyOn(cfn, 'createDiffChangeSet').mockImplementationOnce(async () => {
+      return {
+        Changes: [
+          {
+            ResourceChange: {
+              Action: 'Dummy',
+              LogicalResourceId: 'Object',
+            },
+          },
+        ],
+      };
+    });
+  });
+
+  test('diff does not check for stack existence when --no-change-set is passed', async () => {
     // GIVEN
     const buffer = new StringWritable();
 
@@ -353,6 +431,49 @@ describe('non-nested stacks', () => {
     expect(exitCode).toBe(0);
     expect(cloudFormation.stackExists).not.toHaveBeenCalled();
   });
+
+  test('diff falls back to classic diff when stack does not exist', async () => {
+    // GIVEN
+    const buffer = new StringWritable();
+    cloudFormation.stackExists = jest.fn().mockReturnValue(Promise.resolve(false));
+
+    // WHEN
+    const exitCode = await toolkit.diff({
+      stackNames: ['A', 'A'],
+      stream: buffer,
+      fail: false,
+      quiet: true,
+      changeSet: true,
+    });
+
+    // THEN
+    expect(exitCode).toBe(0);
+    expect(cloudFormation.stackExists).toHaveBeenCalled();
+    expect(cfn.createDiffChangeSet).not.toHaveBeenCalled();
+  });
+
+  test('diff falls back to classic diff when stackExists call fails', async () => {
+    // GIVEN
+    const buffer = new StringWritable();
+
+    cloudFormation.stackExists.mockImplementation(() => {
+      throw new Error('Fail fail fail');
+    });
+
+    // WHEN
+    const exitCode = await toolkit.diff({
+      stackNames: ['A', 'A'],
+      stream: buffer,
+      fail: false,
+      quiet: true,
+      changeSet: true,
+    });
+
+    // THEN
+    expect(exitCode).toBe(0);
+    expect(cloudFormation.stackExists).toHaveBeenCalled();
+    expect(cfn.createDiffChangeSet).not.toHaveBeenCalled();
+  });
 });
 
 describe('nested stacks', () => {