fix(core): cdk diff on large templates fails when passing in `toolk…

…itStackName` and `qualifier` (#31636)

Closes #29179 

### Reason for this change

If your account is bootstrapped with a custom `toolkitStackName` or `qualifier`, then running `cdk diff` does not work for large diff templates of over 50 KiB in size.

### Description of changes

The `toolkitStackName` was not passed down all the way through the `cdk diff` code path - this PR fixes the issue by adding the optional `toolkitStackName` property to the `DiffOptions` interface in `cdk-toolkit.ts` and passing that value all the way through the diff code path to the `uploadBodyParameterAndCreateChangeSet` function in `cloudformation.ts`, where the template asset is built and published.

### Description of how you validated changes

I created a CDK app locally and ran the commands (exactly following the reproduction steps from the original issue) using the CLI build from this PR and was able to successfully run `cdk diff` without needing to pass in the `--toolkit-stack-name` flag. 

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

packages/@aws-cdk-testing/cli-integ/lib/with-cdk-app.ts

@@ -258,6 +258,11 @@ interface CommonCdkBootstrapCommandOptions {
    * @default - none
    */
   readonly tags?: string;
+
+  /**
+   * @default - the default CDK qualifier
+   */
+  readonly qualifier?: string;
 }
 
 export interface CdkLegacyBootstrapCommandOptions extends CommonCdkBootstrapCommandOptions {
@@ -408,7 +413,7 @@ export class TestFixture extends ShellHelper {
     if (options.bootstrapBucketName) {
       args.push('--bootstrap-bucket-name', options.bootstrapBucketName);
     }
-    args.push('--qualifier', this.qualifier);
+    args.push('--qualifier', options.qualifier ?? this.qualifier);
     if (options.cfnExecutionPolicy) {
       args.push('--cloudformation-execution-policies', options.cfnExecutionPolicy);
     }

packages/@aws-cdk-testing/cli-integ/resources/cdk-apps/app/app.js

@@ -438,9 +438,17 @@ class IamRolesStack extends cdk.Stack {
     // Environment variabile is used to create a bunch of roles to test
     // that large diff templates are uploaded to S3 to create the changeset.
     for(let i = 1; i <= Number(process.env.NUMBER_OF_ROLES) ; i++) {
-      new iam.Role(this, `Role${i}`, {
+      const role = new iam.Role(this, `Role${i}`, {
         assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
       });
+      const cfnRole = role.node.defaultChild;
+
+      // For any extra IAM roles created, add a ton of metadata so that the template size is > 50 KiB.
+      if (i > 1) {
+        for(let i = 1; i <= 30 ; i++) {
+          cfnRole.addMetadata('a'.repeat(1000), 'v');
+        }
+      }
     }
   }
 }
@@ -792,6 +800,7 @@ switch (stackSet) {
 
     new LambdaStack(app, `${stackPrefix}-lambda`);
 
+    // This stack is used to test diff with large templates by creating a role with a ton of metadata
     new IamRolesStack(app, `${stackPrefix}-iam-roles`);
 
     if (process.env.ENABLE_VPC_TESTING == 'IMPORT') {

packages/@aws-cdk-testing/cli-integ/tests/cli-integ-tests/cli.integtest.ts

@@ -1034,18 +1034,18 @@ integTest(
 integTest(
   'cdk diff with large changeset does not fail',
   withDefaultFixture(async (fixture) => {
-    // GIVEN - small initial stack with only ane IAM role
+    // GIVEN - small initial stack with only one IAM role
     await fixture.cdkDeploy('iam-roles', {
       modEnv: {
         NUMBER_OF_ROLES: '1',
       },
     });
 
-    // WHEN - adding 200 roles to the same stack to create a large diff
+    // WHEN - adding an additional role with a ton of metadata to create a large diff
     const diff = await fixture.cdk(['diff', fixture.fullStackName('iam-roles')], {
       verbose: true,
       modEnv: {
-        NUMBER_OF_ROLES: '200',
+        NUMBER_OF_ROLES: '2',
       },
     });
 
@@ -1055,6 +1055,40 @@ integTest(
   }),
 );
 
+integTest('cdk diff with large changeset and custom toolkit stack name and qualifier does not fail', withoutBootstrap(async (fixture) => {
+  // Bootstrapping with custom toolkit stack name and qualifier
+  const qualifier = 'abc1111';
+  const toolkitStackName = 'custom-stack2';
+  await fixture.cdkBootstrapModern({
+    verbose: true,
+    toolkitStackName: toolkitStackName,
+    qualifier: qualifier,
+  });
+
+  // Deploying small initial stack with only one IAM role
+  await fixture.cdkDeploy('iam-roles', {
+    modEnv: {
+      NUMBER_OF_ROLES: '1',
+    },
+    options: [
+      '--toolkit-stack-name', toolkitStackName,
+      '--context', `@aws-cdk/core:bootstrapQualifier=${qualifier}`,
+    ],
+  });
+
+  // WHEN - adding a role with a ton of metadata to create a large diff
+  const diff = await fixture.cdk(['diff', '--toolkit-stack-name', toolkitStackName, '--context', `@aws-cdk/core:bootstrapQualifier=${qualifier}`, fixture.fullStackName('iam-roles')], {
+    verbose: true,
+    modEnv: {
+      NUMBER_OF_ROLES: '2',
+    },
+  });
+
+  // Assert that the CLI assumes the file publishing role:
+  expect(diff).toMatch(/Assuming role .*file-publishing-role/);
+  expect(diff).toContain('success: Published');
+}));
+
 integTest(
   'cdk diff --security-only successfully outputs sso-permission-set-without-managed-policy information',
   withDefaultFixture(async (fixture) => {

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

@@ -305,6 +305,7 @@ export type PrepareChangeSetOptions = {
   sdkProvider: SdkProvider;
   stream: NodeJS.WritableStream;
   parameters: { [name: string]: string | undefined };
+  toolkitStackName?: string;
   resourcesToImport?: ResourcesToImport;
 }
 
@@ -375,9 +376,11 @@ async function uploadBodyParameterAndCreateChangeSet(options: PrepareChangeSetOp
       for (const entry of file_entries) {
         await options.deployments.buildSingleAsset(artifact, assetManifest, entry, {
           stack: options.stack,
+          toolkitStackName: options.toolkitStackName,
         });
         await options.deployments.publishSingleAsset(assetManifest, entry, {
           stack: options.stack,
+          toolkitStackName: options.toolkitStackName,
         });
       }
     }

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

@@ -186,6 +186,7 @@ export class CdkToolkit {
               parameters: Object.assign({}, parameterMap['*'], parameterMap[stack.stackName]),
               resourcesToImport,
               stream,
+              toolkitStackName: options.toolkitStackName,
             });
           } else {
             debug(`the stack '${stack.stackName}' has not been deployed to CloudFormation or describeStacks call failed, skipping changeset creation.`);
@@ -1062,6 +1063,13 @@ export interface DiffOptions {
    */
   stackNames: string[];
 
+  /**
+   * Name of the toolkit stack, if not the default name
+   *
+   * @default 'CDKToolkit'
+   */
+  readonly toolkitStackName?: string;
+
   /**
    * Only select the given stack
    *

packages/aws-cdk/lib/cli.ts

@@ -505,6 +505,7 @@ export async function exec(args: string[], synthesizer?: Synthesizer): Promise<n
           compareAgainstProcessedTemplate: args.processed,
           quiet: args.quiet,
           changeSet: args['change-set'],
+          toolkitStackName: toolkitStackName,
         });
 
       case 'bootstrap':