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kcc-direct-brownfield-types-implementer

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Guides the implementation of KRM types and CRD scaffolding for migrating existing resources to "direct" controllers.

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Source SKILL.md: https://github.com/GoogleCloudPlatform/k8s-config-connector/blob/HEAD/.gemini/skills/kcc-direct-brownfield-types-implementer/SKILL.md

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KCC Direct Brownfield Types Implementer

This skill provides the mandatory standards for creating the initial KRM types (_types.go) and generation scripts (generate.sh) when migrating an existing (brownfield) resource to the direct controller approach.

Workflow

1. Configure generate.sh

Create or update apis/<service>/v1alpha1/generate.sh. Use a versioned proto source path to ensure stability.

#!/bin/bash
set -o errexit
set -o nounset
set -o pipefail

REPO_ROOT="$(git rev-parse --show-toplevel)"
cd ${REPO_ROOT}/dev/tools/controllerbuilder

# Use the pinned SHA from apis/git.versions or a specific override
PROTO_SHA="<sha>" 
PROTO_OUT="${REPO_ROOT}/.build/googleapis-${PROTO_SHA}.pb"

./generate-proto.sh ${PROTO_SHA} ${PROTO_OUT}

go run . generate-types \
    --service <proto.package> \
    --api-version <service>.cnrm.cloud.google.com/v1alpha1 \
    --resource <Kind>:<ProtoMessage> \
    --proto-source-path ${PROTO_OUT}

2. Standards for _types.go

After running the generator, verify the _types.go file meets these requirements:

  • Copyright: Must be // Copyright 2026 Google LLC.
  • CRD Labels: Include exactly these labels in the type definition: 
    // +kubebuilder:metadata:labels="cnrm.cloud.google.com/managed-by-kcc=true"
// +kubebuilder:metadata:labels="cnrm.cloud.google.com/system=true"
// +kubebuilder:metadata:labels="cnrm.cloud.google.com/stability-level=alpha"
  • Proto Mapping: Ensure +kcc:proto tags are present on the Spec and ObservedState structs to link them to the GCP API definitions.
  • Status Fields: status.observedGeneration must be an *int64.
  • Use Existing References: ALWAYS reuse existing resource reference structures that live in apis/refs/ instead of hand-coding or defining duplicate types.
    • For example, ProjectRef (which lives in apis/refs/v1beta1/project_ref.go) and other resource reference types should be imported from github.com/GoogleCloudPlatform/k8s-config-connector/apis/refs/v1beta1 rather than being defined locally in <kind>_types.go.
  • Strict Schema Compatibility: At the initial stage of creating a direct Go type for an existing resource (transitioning from Terraform/DCL), the Go type should be strictly schema-compatible with the existing CRD definition.
    • Do NOT add new fields like externalRef or observedState under Status yet.
    • Run dev/tasks/diff-crds to verify schema compatibility and ensure no unintended new fields are introduced.

3. Fuzzers

  • Create a fuzzer for the mapper to verify that round-trip conversions (FromProto and ToProto) are lossless and correct.
  • See the kcc-direct-controller-implementer skill for details on implementing fuzzers.

4. Registration

  • Ensure the new Kind is registered in apis/<service>/v1alpha1/register.go.
  • Run dev/tasks/generate-crds and verify the YAML appears in config/crds/resources/.