add-operator

name	add-operator
description	Add a new Operator (force-delete support for an AWS resource type that causes DELETE_FAILED, e.g. AWS::Athena::WorkGroup, AWS::IAM::User). Use when adding a new entry to the "Resource Types that can be forced to delete" table. Not for Preprocessors (deletion-protection checks, Lambda VPC detach, etc.) — use `add-preprocessor` for those.

Add a new Operator

You are adding force-delete support for a CloudFormation resource type that causes DELETE_FAILED. The Operator force-deletes the blocking sub-resources (e.g. emptying an S3 bucket, deleting ECR images, detaching IAM user dependencies) so CloudFormation can finish the stack delete.

Reference PR for the full diff shape: PR #569 (Athena WorkGroup).

Input

The user provides an AWS resource type, e.g. AWS::Athena::WorkGroup. Derive:

• Service name (lowercase, e.g. athena)
• Resource name (e.g. WorkGroup)
• AWS SDK v2 package: github.com/aws/aws-sdk-go-v2/service/<service>
• Client filename: pkg/client/<service>.go — if it already exists, extend the existing interface and struct rather than creating a new file (e.g. when adding AWS::IAM::User and iam.go is already there)
• Operator filename: internal/operation/<resource_type_snake>.go (e.g. athena_workgroup.go)
• Resource type constant name: PascalCase (e.g. AthenaWorkGroup)

Steps

1. internal/resourcetype/resourcetype.go — Add the constant to the const block and append it to the ResourceTypes slice. Keep it in the existing grouping (most go in the "For Force Deletion" group).

2. pkg/client/<service>.go — AWS SDK client wrapper.

   • Line 1 must be the //go:generate mockgen directive (mockgen requires this exact placement).
   • Define I<Service> interface and a <Service> struct that wraps the SDK client.
   • Public methods must wrap errors with ClientError (see how an existing client like pkg/client/ecr.go or pkg/client/athena.go does it).
   • If the file already exists, just add new methods to the existing interface + struct.
   • Keep these methods as thin SDK 1:1 wrappers. Composition (loops, parallel fan-out with errgroup, business logic that combines multiple SDK calls) belongs in the operation layer, not here. A method like "discover-and-delete in parallel" should live in internal/operation/, not in pkg/client/.

3. pkg/client/<service>_mock.go — Auto-generated. Do not edit by hand. Run make mockgen after step 2.

4. pkg/client/<service>_test.go — Tests use AWS SDK middleware mocks (NOT gomock). Inject a middleware.FinalizeMiddlewareFunc via config.WithAPIOptions. For paginated APIs, capture NextToken in an Initialize-stage middleware via middleware.WithStackValue and read it back via middleware.GetStackValue. See pkg/client/s3_test.go and pkg/client/backup_test.go.

5. internal/operation/<resource>.go — The Operator.

   • Implement IOperator. Add a compile-time assertion: var _ IOperator = (*<Resource>Operator)(nil).
   • Operations must be idempotent (check existence before deleting, or rely on a NotFound-tolerant client method).
   • Concurrency uses errgroup + semaphore.NewWeighted(runtime.NumCPU()).
   • Errors: return client errors as-is (already wrapped). Only wrap with ClientError for errors generated locally in the operation layer (e.g. ctx.Done(), validation).
   • Deletion model: the operator deletes the AWS resource itself directly via the SDK (and any blocking dependencies it owns). The CFN deletion loop in internal/operation/cloudformation_stack.go then passes every DELETE_FAILED LogicalResourceId as RetainResources on the next DeleteStack call, so CFN skips that resource on retry. Do not rely on CloudFormation to redelete the resource for you.
   • Cross-resource cleanup (advanced): an operator may also remove out-of-stack dependencies that block deletion (example: EC2SubnetOperator / EC2SecurityGroupOperator first remove orphan AWS Lambda VPC ENIs that AWS Lambda has not yet released, then delete the Subnet / SecurityGroup). When you do this, scope the dependency filter very tightly (e.g. status=available AND a description prefix) so you cannot accidentally touch unrelated resources. If two operators need the same cleanup (as Subnet and SecurityGroup do), put the shared helper as a package-level function in the operator file that owns the domain knowledge (here: internal/operation/lambda_function.go's cleanupOrphanLambdaENIsByFilter), not in pkg/client/.

6. internal/operation/<resource>_test.go — Tests use gomock (not middleware). Use the I<Service> mock generated in step 3.

7. internal/operation/operator_factory.go — Add Create<Resource>Operator() returning the new operator with its SDK client(s) initialised (use SDKRetryMaxAttempts and aws.RetryModeStandard like the existing factories).

8. internal/operation/operator_collection.go — Update 4 sites:

   1. Instantiate the operator in SetOperatorCollection() (<resource>Operator := c.operatorFactory.Create<Resource>Operator()).
   2. Add a case resourcetype.<Resource>: branch inside the switch over *resource.ResourceType that calls <resource>Operator.AddResource(&resource).
   3. Append the operator to the c.operators slice at the bottom of SetOperatorCollection().
   4. Add a row to supportedStackResourcesData in RaiseUnsupportedResourceError() describing what blocks deletion for this resource.

9. internal/operation/operator_collection_test.go — Update test cases to cover the new resource type.

10. go.mod / go.sum — go get github.com/aws/aws-sdk-go-v2/service/<service>, then go mod tidy so the dep ends up classified correctly (direct vs indirect).

11. README.md — Add a row to the "Resource Types that can be forced to delete" table (see the existing rows for tone and format).

12. E2E test — Two layouts are valid:

    (a) Extend e2e/full/ — preferred when the resource fits the existing combined test stack:

    1. e2e/full/cdk/lib/resource/<resource>.go — New<Resource>(scope, ...) constructor that creates the resource in a state that itself does not block deletion (e.g. IAM User with no attachments).
    2. e2e/full/cdk/cdk.go — Call the constructor in NewTestStack().
    3. e2e/full/deploy.go — After CDK deployment, attach the dependencies that do block deletion via SDK calls (e.g. upload S3 objects, push ECR images, attach IAM user policies). This is essential: if dependencies are inside the same stack, CloudFormation resolves the dependency order and the stack would delete cleanly, defeating the purpose of the test.
    4. e2e/full/go.mod — Add SDK service deps used by deploy.go.
    5. e2e/full/cdk/go.mod — Add CDK construct deps if used.
    6. e2e/full/README.md — Add the resource to the list.

    (b) Dedicated e2e/<scenario>/ directory — preferred when the failure mode requires special topology (VPC, Lambda@Edge) or out-of-band setup that would interfere with e2e/full/. Mirror an existing scenario such as e2e/preprocessor/ or e2e/vpc_lambda/. Required files:

    • cdk/cdk.go, cdk/cdk.json, cdk/lib/resource/<thing>.go, cdk/go.mod, cdk/go.sum
    • cdk/.gitignore (excluding at minimum cdk.context.json and cdk.out)
    • deploy.go, go.mod, go.sum, README.md
    • .gitignore at the e2e module root with /<basename> to ignore the binary go build ./... produces from deploy.go (the binary is named after the module's basename, e.g. e2e/vpc_lambda/vpc_lambda).
    • Add testgen_<scenario> and e2e_<scenario> targets to the root Makefile, plus matching lines under the / listings.

13. Verify locally:

    • make mockgen (regenerates the mock from step 3)
    • make test
    • make lint

Conventions reminder

• Code comments: minimal, in English.
• Test naming: Test[ReceiverType]_[MethodName] (e.g. TestEcr_DeleteRepository, TestS3BucketOperator_DeleteS3Bucket).
• All public-facing text (README rows, error messages, PR/commit) is English.
• Do not introduce a pkg/client/<service>.go if one already exists for that AWS service — extend it.