feat(core): RemovalPolicies.of(scope)

[watany-dev]

Issue # (if applicable)

N/A - New feature proposal

Reason for this change

Currently, applying removal policies to multiple resources requires setting them individually or using Tags as a workaround. This change introduces a new RemovalPolicies module that provides a more intuitive and type-safe way to manage removal policies across multiple resources, similar to the existing Tags API.

Description of changes

Added a new RemovalPolicies module that provides:

• A similar interface to Tags.of() for managing removal policies

• Type-safe resource type specifications using CloudFormation resource type strings

• Ability to include or exclude specific resource types

• Convenient methods for common removal policies (destroy, retain, snapshot, retainOnUpdateOrDelete)

Example usage:

// Using CloudFormation resource type strings
RemovalPolicies.of(scope).retain({
  applyToResourceTypes: ['AWS::S3::Bucket', 'AWS::DynamoDB::Table']
});

const bucket = new s3.Bucket(scope, 'bucket')

// Using CDK resource classes (type-safe)
RemovalPolicies.of(scope).retain({
  applyToResourceTypes: [
       bucket.cfnResourceType,
       CfnTable.CFN_RESOURCE_TYPE_NAME,
  ]
});

// Mixed usage
RemovalPolicies.of(scope).retain({
  applyToResourceTypes: [bucket.cfnResourceType, 'AWS::DynamoDB::Table']
});

Description of how you validated changes

TBD

Checklist

[x] 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

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[go-to-k]

This feature is very helpful for me (or us)!

But I'm not sure if we should use an Enum-Like (Union-Like) class instead of an union type in order to generate a public interface for other languages using a jsii transformation, what do you think?

[watany-dev]

After much deliberation, I decided on string[]. because I thought it would work well enough.

RemovalPolicies.of(parent).retain({
  applyToResourceTypes: [
    'AWS::DynamoDB::Table',
    bucket.cfnResourceType, // 'AWS::S3::Bucket'
  ],
});

[go-to-k]

I'm OK! Could you please change the description (Type-safe resource type ...) and examples in this PR?

[watany-dev]

fixed.

[go-to-k]

We might want to fix that example as cfnResourceType appears to be a static method. (I often read the PR description to understand its feature, so correcting it would be more useful)

RemovalPolicies.of(scope).retain({
  applyToResourceTypes: [
       CfnBucket.cfnResourceType,
       CfnTable.cfnResourceType,
  ]
});

[watany-dev]

I have made the correct Usage.

[go-to-k]

Is this try/catch necessary? Are there any (bad) effects of not having it?
(IMO, I don't think we need this one.)

[watany-dev]

I thought about it, and it might not be necessary, so I removed it.

[go-to-k]

It would be good to add a property priority to RemovalPolicyProps? (ref: https://github.com/aws/aws-cdk/blob/v2.172.0/packages/aws-cdk-lib/core/lib/aspect.ts#L45)

(* The priority was introduced in v2.172.0: https://dev.to/aws-heroes/aws-cdk-aspects-specifications-have-changed-3i75.)

And the apply method will be changed like:

  public apply(policy: RemovalPolicy, props: RemovalPolicyProps = {}) {
    Aspects.of(this.scope).add(new RemovalPolicyAspect(policy, props), {
      priority: props.priority ?? AspectPriority.MUTATING,
    });
  }

Since the RemovalPolicy change is a kind of resource update, I think it is good that the default value should be MUTATING. (It is the same with the add and remove method of the Tags class.)

[go-to-k]

I've only seen halfway through, but I'll leave you with my comments so far.

[go-to-k]

Wouldn't it be difficult to maintain if all properties were listed on the README? (Because all of them are also in JSDoc...)

[go-to-k]

How about creating a custom construct that attaches a retain method? The following situation can be realized:

• Stack (with a destroy method)
  • Resource A: DESTROY
  • Resource B: DESTROY
  • RetainConstruct (with a retain method)
    • X: RETAIN

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