fix: deploy monitor count is off if there are > 100 changes (#20067)

The deployment monitor failed to account for the fact the
`DescribeChangeSet` operation returns a paginated output, and only
represents up to 100 changes per pages.

Since only the first page was considered, the progress bar would always
start with a value of 101 (or less), instead of the correct count.

This aggregates the `Changes` arrays from all pages of the change set
description so the count is correct.

Fixes #11805

----

### All Submissions:

* [X] Have you followed the guidelines in our [Contributing guide?](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md)

### Adding new Unconventional Dependencies:

* [ ] This PR adds new unconventional dependencies following the process described [here](https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md/#adding-new-unconventional-dependencies)

### New Features

* [ ] Have you added the new feature to an [integration test](https://github.com/aws/aws-cdk/blob/master/INTEGRATION_TESTS.md)?
	* [ ] Did you use `yarn integ` to deploy the infrastructure and generate the snapshot (i.e. `yarn integ` without `--dry-run`)?

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

packages/aws-cdk/lib/api/deploy-stack.ts

@@ -329,8 +329,12 @@ async function prepareAndExecuteChangeSet(
     Capabilities: ['CAPABILITY_IAM', 'CAPABILITY_NAMED_IAM', 'CAPABILITY_AUTO_EXPAND'],
     Tags: options.tags,
   }).promise();
+
+  const execute = options.execute ?? true;
+
   debug('Initiated creation of changeset: %s; waiting for it to finish creating...', changeSet.Id);
-  const changeSetDescription = await waitForChangeSet(cfn, deployName, changeSetName);
+  // Fetching all pages if we'll execute, so we can have the correct change count when monitoring.
+  const changeSetDescription = await waitForChangeSet(cfn, deployName, changeSetName, { fetchAll: execute });
 
   // Update termination protection only if it has changed.
   const terminationProtection = stackArtifact.terminationProtection ?? false;
@@ -352,7 +356,6 @@ async function prepareAndExecuteChangeSet(
     return { noOp: true, outputs: cloudFormationStack.outputs, stackArn: changeSet.StackId! };
   }
 
-  const execute = options.execute === undefined ? true : options.execute;
   if (execute) {
     debug('Initiating execution of changeset %s on stack %s', changeSet.Id, deployName);
 

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

@@ -170,14 +170,40 @@ export class CloudFormationStack {
 /**
  * Describe a changeset in CloudFormation, regardless of its current state.
  *
- * @param cfn       a CloudFormation client
- * @param stackName   the name of the Stack the ChangeSet belongs to
+ * @param cfn           a CloudFormation client
+ * @param stackName     the name of the Stack the ChangeSet belongs to
  * @param changeSetName the name of the ChangeSet
+ * @param fetchAll      if true, fetches all pages of the change set description.
  *
  * @returns       CloudFormation information about the ChangeSet
  */
-async function describeChangeSet(cfn: CloudFormation, stackName: string, changeSetName: string): Promise<CloudFormation.DescribeChangeSetOutput> {
+async function describeChangeSet(
+  cfn: CloudFormation,
+  stackName: string,
+  changeSetName: string,
+  { fetchAll }: { fetchAll: boolean },
+): Promise<CloudFormation.DescribeChangeSetOutput> {
   const response = await cfn.describeChangeSet({ StackName: stackName, ChangeSetName: changeSetName }).promise();
+
+  // If fetchAll is true, traverse all pages from the change set description.
+  while (fetchAll && response.NextToken != null) {
+    const nextPage = await cfn.describeChangeSet({
+      StackName: stackName,
+      ChangeSetName: response.ChangeSetId ?? changeSetName,
+      NextToken: response.NextToken,
+    }).promise();
+
+    // Consolidate the changes
+    if (nextPage.Changes != null) {
+      response.Changes = response.Changes != null
+        ? response.Changes.concat(nextPage.Changes)
+        : nextPage.Changes;
+    }
+
+    // Forward the new NextToken
+    response.NextToken = nextPage.NextToken;
+  }
+
   return response;
 }
 
@@ -207,17 +233,23 @@ async function waitFor<T>(valueProvider: () => Promise<T | null | undefined>, ti
  * Will return a changeset that is either ready to be executed or has no changes.
  * Will throw in other cases.
  *
- * @param cfn       a CloudFormation client
- * @param stackName   the name of the Stack that the ChangeSet belongs to
+ * @param cfn           a CloudFormation client
+ * @param stackName     the name of the Stack that the ChangeSet belongs to
  * @param changeSetName the name of the ChangeSet
+ * @param fetchAll      if true, fetches all pages of the ChangeSet before returning.
  *
  * @returns       the CloudFormation description of the ChangeSet
  */
 // eslint-disable-next-line max-len
-export async function waitForChangeSet(cfn: CloudFormation, stackName: string, changeSetName: string): Promise<CloudFormation.DescribeChangeSetOutput> {
+export async function waitForChangeSet(
+  cfn: CloudFormation,
+  stackName: string,
+  changeSetName: string,
+  { fetchAll }: { fetchAll: boolean },
+): Promise<CloudFormation.DescribeChangeSetOutput> {
   debug('Waiting for changeset %s on stack %s to finish creating...', changeSetName, stackName);
   const ret = await waitFor(async () => {
-    const description = await describeChangeSet(cfn, stackName, changeSetName);
+    const description = await describeChangeSet(cfn, stackName, changeSetName, { fetchAll });
     // The following doesn't use a switch because tsc will not allow fall-through, UNLESS it is allows
     // EVERYWHERE that uses this library directly or indirectly, which is undesirable.
     if (description.Status === 'CREATE_PENDING' || description.Status === 'CREATE_IN_PROGRESS') {
@@ -453,4 +485,4 @@ export class ParameterValues {
   }
 }
 
-export type ParameterChanges = boolean | 'ssm';
+export type ParameterChanges = boolean | 'ssm';