Kube API Linter

Kube API Linter (KAL) is a Golang based linter for Kubernetes API types. It checks for common mistakes and enforces best practices. The rules implemented by the Kube API Linter, are based on the Kubernetes API Conventions.

Kube API Linter is aimed at being an assistant to API review, by catching the mechanical elements of API review, and allowing reviewers to focus on the more complex aspects of API design.

Installation

Kube API Linter ships as a standalone binary, golangci-lint plugin, and a golangci-lint module.

Standalone binary

The binary version of Kube API Linter can be built with make build or a standard go build command.

go build -o ./bin ./cmd/golangci-lint-kube-api-linter 

The binary builds a custom version of golangci-lint with Kube API Linter included as a module. See Golangci-lint Moduule for details on configuration of the module under linter-settings.

Golangci-lint Module

To install the golangci-lint module, first you must have golangci-lint installed. If you do not have golangci-lint installed, review the golangci-lint install guide.

You will need to create a .custom-gcl.yml file to describe the custom linters you want to run. The following is an example of a .custom-gcl.yml file:

version:  v1.64.8
name: golangci-kube-api-linter
destination: ./bin
plugins:
- module: 'sigs.k8s.io/kube-api-linter'
  version: 'v0.0.0' # Replace with the latest version

Once you have created the custom configuration file, you can run the following command to build the custom golangci-kal binary:

golangci-lint custom

The output binary will be a combination of the initial golangci-lint binary and the Kube API linter plugin. This means that you can use any of the standard golangci-lint configuration or flags to run the binary, but may also include the Kube API Linter rules.

If you wish to only use the Kube API Linter rules, you can configure your .golangci.yml file to only run the Kube API Linter:

linters-settings:
  custom:
    kubeapilinter:
      type: "module"
      description: Kube API LInter lints Kube like APIs based on API conventions and best practices.
      settings:
        linters: {}
        lintersConfig: {}
linters:
  disable-all: true
  enable:
    - kubeapilinter

# To only run Kube API Linter on specific path
issues:
  exclude-rules:
    - path-except: "api/*"
      linters:
        - kubeapilinter

If you wish to only run selected linters you can do so by specifying the linters you want to enable in the linters section:

linters-settings:
  custom:
    kubeapilinter:
      type: "module"
      settings:
        linters:
          disable:
            - "*"
          enable:
            - requiredfields
            - statusoptional
            - statussubresource

The settings for Kube API Linter are based on the GolangCIConfig struct and allow for finer control over the linter rules.

If you wish to use the Kube API Linter in conjunction with other linters, you can enable the Kube API Linter in the .golangci.yml file by ensuring that kubeapilinter is in the linters.enabled list. To provide further configuration, add the custom.kubeapilinter section to your linter-settings as per the example above.

Where fixes are available within a rule, these can be applied automatically with the --fix flag.

golangci-kube-api-linter run path/to/api/types --fix

Golangci-lint Plugin

The Kube API Linter can also be used as a plugin for golangci-lint. To do this, you will need to install the golangci-lint binary and then install the Kube API Linter plugin.

More information about golangci-lint plugins can be found in the golangci-lint plugin documentation.

go build -buildmode=plugin -o bin/kube-api-linter.so sigs.k8s.io/kube-api-linter/pkg/plugin

This will create a kube-api-linter.so file in the bin directory.

The golangci-lint configuration is similar to the module configuration, however, you will need to specify the plugin path instead.

linters-settings:
  custom:
    kubeapilinter:
      path: "bin/kube-api-linter.so"
      description: Kube API LInter lints Kube like APIs based on API conventions and best practices.
      original-url: sigs.k8s.io/kube-api-linter
      settings:
        linters: {}
        lintersConfig: {}

The rest of the configuration is the same as the module configuration, except the standard golangci-lint binary is invoked, rather than a custom binary.

VSCode integration

Since VSCode already integrates with golangci-lint via the Go extension, you can use the golangci-kal binary as a linter in VSCode. If your project authors are already using VSCode and have the configuration to lint their code when saving, this can be a seamless integration.

Ensure that your project setup includes building the golangci-kube-api-linter binary, and then configure the go.lintTool and go.alternateTools settings in your project .vscode/settings.json file.

{
    "go.lintTool": "golangci-lint",
    "go.alternateTools": {
        "golangci-lint": "${workspaceFolder}/bin/golangci-kube-api-linter",
    }
}

Alternatively, you can also replace the binary with a script that runs the golangci-kube-api-linter binary, allowing for customisation or automatic copmilation of the project should it not already exist.

{
    "go.lintTool": "golangci-lint",
    "go.alternateTools": {
        "golangci-lint": "${workspaceFolder}/hack/golangci-lint.sh",
    }
}

Contributing

New linters can be added by following the New Linter guide.

Linters

For a complete list of available linters and their configuration options, see docs/linters.md.

License

KAL is licensed under the Apache License, Version 2.0. See LICENSE for the full license text.