fix(autoscaling): AutoScalingGroup requireImdsv2 with launchTemplate or mixedInstancesPolicy throws unclear error

[shinebleu]

Issue #27586

Fixes #27586

The above issue is already marked as closed, but there is some discussion in it about an additional edge case that this pull request fixes.

Reason for this change

When defining an AutoScalingGroup with both the requireImdsv2 prop and the launchTemplate prop, the error message is not clear about the problem.

    // example asg definition
    const asg = new AutoScalingGroup(this, "myasg", {
      vpc,
      launchTemplate: lt,
      requireImdsv2: true,
    });

TypeError: Cannot read properties of undefined (reading 'node')
    at AutoScalingGroupRequireImdsv2Aspect.visit (~/git/cdkApp2/node_modules/aws-cdk-lib/aws-autoscaling/lib/aspects/require-imdsv2-aspect.js:1:715)
    at recurse (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/private/synthesis.js:2:2236)
    at recurse (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/private/synthesis.js:2:2600)
    at recurse (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/private/synthesis.js:2:2600)
    at invokeAspects (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/private/synthesis.js:2:1860)
    at synthesize (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/private/synthesis.js:1:1473)
    at App.synth (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/stage.js:1:2382)
    at process.<anonymous> (~/git/cdkApp2/node_modules/aws-cdk-lib/core/lib/app.js:1:1767)
    at Object.onceWrapper (node:events:632:26)
    at process.emit (node:events:517:28)

It is not clear from the error that requireImdsv2 should be set in the provided launchTemplate itself rather than the AutoScalingGroup.

The error occurs because setting requireImdsv2 on the AutoScalingGroup adds the aspect AutoScalingGroupRequireImdsv2Aspect to it, which expects there to be a child node called either 'LaunchConfig' or 'LaunchTemplate' depending on a feature flag. This child node is only set in the AutoScalingGroup when neither launchTemplate nor mixedInstancesPolicy props are provided.

Description of changes

Add the requireImdsv2 prop to the verifyNoLaunchConfigPropIsGiven method, which throws errors when certains props are set at the same time as launchTemplate or mixedInstancesPolicy.

Description of how you validated changes

• Added a unit test
• Confirmed the new error message works in a sample cdk app

Error: Setting 'requireImdsv2' must not be set when 'launchTemplate' or 'mixedInstancesPolicy' is set
    at AutoScalingGroup.verifyNoLaunchConfigPropIsGiven (~/git/aws-cdk/packages/aws-cdk-lib/aws-autoscaling/lib/auto-scaling-group.ts:1762:13)
    at new AutoScalingGroup (~/git/aws-cdk/packages/aws-cdk-lib/aws-autoscaling/lib/auto-scaling-group.ts:1333:12)
    at new CdkAppStack (~/git/cdkApp/lib/cdk_app-stack.ts:31:17)
    at Object.<anonymous> (~/git/cdkApp/bin/cdk_app.ts:6:1)
    at Module._compile (node:internal/modules/cjs/loader:1256:14)
    at Module.m._compile (~/git/cdkApp/node_modules/ts-node/src/index.ts:1618:23)
    at Module._extensions..js (node:internal/modules/cjs/loader:1310:10)
    at Object.require.extensions.<computed> [as .ts] (~/git/cdkApp/node_modules/ts-node/src/index.ts:1621:12)
    at Module.load (node:internal/modules/cjs/loader:1119:32)
    at Function.Module._load (node:internal/modules/cjs/loader:960:12)

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

---

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

[aws-cdk-automation]

The pull request linter has failed. See the aws-cdk-automation comment below for failure reasons. If you believe this pull request should receive an exemption, please comment and provide a justification.

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[shinebleu]

Exemption Request on Fixes must contain a change to an integration test file and the resulting snapshot.: There is no behavioral change for when props are set correctly and cloud formation is produced. The only change is throwing a clearer error message where another, less clear error would otherwise be thrown anyway.

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: a59c87c
• Result: SUCCEEDED
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