Create Mapper Fuzzer

Skill: Create Mapper and Fuzzer for Direct Controller

Overview

This skill guides an automated agent through the process to implement the Mapper and Fuzzer for KCC direct resources. The goal is to ensure all KRM fields correctly map to GCP fields (Protobuf or OpenAPI) and that this mapping is validated via a lossless round-trip fuzz test.

Workflow: The Mapper

The generate-mapper tool is greedy and attempts to map everything. You must use an iterative feedback loop to identify where it fails.

1. Audit and Generate

To generate the mappers without touching type definitions or rebuilding CRDs, you must run the generate-mapper tool directly.

First, locate the generate.sh script for the resource (e.g., apis/<service>/<version>/generate.sh).

Check if the generate-mapper command is already present in the script.

• If it exists: Copy the exact arguments and run it from dev/tools/controllerbuilder.
• If it does NOT exist: You must construct the command based on the generate-types command found in the script, append it to generate.sh so it is saved for the future, and then run it.

The command you construct (and append to generate.sh) will look like this:

go run . generate-mapper \
  --service <copy-from-generate-types> \
  --api-version <copy-from-generate-types> \
  --include-skipped-output

(Run this constructed command from inside dev/tools/controllerbuilder)

Identify Failures during Generation:

• Panics (klog.Fatalf): The generator will crash if it encounters an unhandled Protobuf/OpenAPI type. Note the struct and field mentioned in the panic; you must hand-code the mapper for that struct in <kind>_mapper.go.
• Missing Fields: Grep the output file mapper.generated.go for // MISSING:. This indicates the tool couldn't find a matching KRM field. If the field should be supported, hand-code the mapping. If it is intentionally unsupported for now, it must be explicitly ignored in the fuzzer (see below).

2. Build and Fix

Run the compiler to find type signature mismatches:

go build ./pkg/controller/direct/...

Common Compilation Errors and Fixes:

• Type Mismatches: If the proto uses int32 but KRM uses int64, the generated code (out.Field = in.Field) will fail. You must hand-code the mapping in <kind>_mapper.go with an explicit cast: out.Field = int64(in.Field).
• Resource References: The generator cannot resolve KCC *Ref types (e.g., ComputeNetworkRef). These MUST be hand-coded to map to/from their string representations in the Protobuf/API.
• Enums: If KRM uses strings for enums but the proto expects integers, hand-code the translation.

The Golden Rule: When you define a mapping function (e.g., KindSpec_FromProto) in <kind>_mapper.go, the generator will detect it and skip generating that specific function in mapper.generated.go.

Workflow: The Fuzzer

Once the code compiles, you must prove the mapping is lossless using KCC's fuzztesting framework.

1. Delegate to the create-fuzzer Skill

To create and configure the fuzzer file, you should adopt the create-fuzzer skill's workflow. Please read and follow the detailed instructions for fuzzer implementation from: .gemini/skills/create-fuzzer/skill.md

That skill will guide you through:

• Creating the <kind>_fuzzer.go file (handling both Protobuf and OpenAPI variants).
• Categorizing fields correctly (f.SpecField, f.StatusField, f.Unimplemented_Identity, etc.).
• Registering the direct package in pkg/controller/direct/register/register.go (CRITICAL).

2. Run and Debug the Fuzzer

After following the create-fuzzer instructions, run the fuzz test centrally:

go test -v -count=1 -timeout=20m ./pkg/fuzztesting/fuzztests/...

CRITICAL / DO NOT: Never create any individual unit test files (such as *_fuzzer_test.go) for specific fuzzers inside direct controller directories. All fuzzers are executed via the central fuzz testing suite (pkg/fuzztesting/fuzztests/...).

If it fails with a diff:

• Analyze the diff to see which field lost data.
• If the data loss is in a supported field, fix your mapping logic in <kind>_mapper.go.
• If the field isn't meant to be supported yet, add it to Unimplemented_NotYetTriaged as instructed in the fuzzer skill.

Acceptance Criteria

1. go build ./pkg/controller/direct/... succeeds.
2. go test -v -count=1 -timeout=20m ./pkg/fuzztesting/fuzztests/... passes flawlessly.
3. Any // MISSING: comments remaining in mapper.generated.go correspond to fields that are intentionally unsupported and explicitly ignored in the fuzzer configuration.
4. The package is registered in pkg/controller/direct/register/register.go.