crd-to-sample-yaml or cty ( city )

Generate a sample YAML file from a CRD definition.

Dynamic CRD Parsing on the frontend

CRD Testing using CTY

For more information about how to use cty for helm-like unit testing your CRD schemas, please follow the How to test CRDs with CTY Readme.

Getting started

• Prerequisites: Go installed on your machine. (Check out this link for details: https://go.dev/doc/install)
• Clone the repository
• Execute make build to build the binary

Now you can simply run:

cty generate crd -c delivery.krok.app_krokcommands

Optionally, define a URL at which a CRD is located:

cty generate crd -u https://raw.githubusercontent.com/kubernetes-sigs/cluster-api-provider-aws/main/config/crd/bases/infrastructure.cluster.x-k8s.io_awsclusters.yaml

cty does not support authentication modes, therefore the CRD needs to be publicly accessible.

This will result in a file similar to this:

apiVersion: delivery.krok.app/v1alpha1
kind: KrokCommand
metadata: {}
spec:
  commandHasOutputToWrite: true
  dependencies: ["string"]
  enabled: true
  image: string
  platforms: ["string"]
  readInputFromSecret:
    name: string
    namespace: string
  schedule: string
status: {}

A single file will be created containing all versions in the CRD delimited by ---.

Optionally, you can provide the flag -s which will output the generated content to stdout.

HTML output

It's possible to generate a pre-rendered HTML based output for self-hosting what the website produces online.

To get an HTML output provide the format flag like this:

cty generate crd -c delivery.krok.app_krokcommands --comments --format html

In case of multiple CRD files being parsed using a folder target, the CRDs will be listed in collapsed drop-down menus where their KIND is the title.

Minimal required CRD sample

It's possible to generate a sample YAML for a CRD that will make the CRD validation pass. Meaning, it will only contain samples for fields that are actually required. All other fields will be ignored.

For example, a CRD having a single required field with an example and the rest being optional would generate something like this:

apiVersion: delivery.krok.app/v1alpha1
kind: KrokCommand
spec:
  image: "krok-hook/slack-notification:v0.0.1"

To run cty with minimal required fields, pass in --minimal to the command like this:

cty generate crd -c delivery.krok.app_krokcommands --comments --minimal --format html

Folder source

To parse multiple CRDs in a single folder, just pass in the whole folder like this:

cty generate crd -r folder

Any other flag will work as before.

Schema Generation

cty also provides a way to generate a JSON Schema out of a CRD. Simply use:

cty generate schema -c sample-crd/delivery.krok.app_krokcommands.yaml

to target a single file. Or

cty generate schema -r sample-crd

to target a folder.

CRD Types

ANY kind of type can be used, not just CustomResourceDefinitions as long as they provide the following structure:

# top level spec field
spec:
  names:
    kind: # this should be the kind of the generated object
  group: # the group of the generated object
  # optional version field 
  versions:
    - name: v1alpha1
      # OpenAPI schema (like the one used by Kubernetes CRDs). Determines what fields
      # the XR (and claim) will have. Will be automatically extended by crossplane.
      # See https://kubernetes.io/docs/tasks/extend-kubernetes/custom-resources/custom-resource-definitions/
      # for full CRD documentation and guide on how to write OpenAPI schemas
      schema:
        openAPIV3Schema:
  # optional validation field describing all versions
  validation:
    openAPIV3Schema:

If these fields are respected, the apiVersion or the kind of the resource doesn't matter. It's all unstructured in the background.

WASM frontend

There is a WASM based frontend that can be started by navigating into the wasm folder and running the following make target:

make run

This will start a front-end that can be used to paste in and parse CRDs.

Shareable Link

It's possible to provide a link that can be shared using a url parameter like this:

https://crdtoyaml.com/share?url=https://raw.githubusercontent.com/Skarlso/crd-to-sample-yaml/main/sample-crd/infrastructure.cluster.x-k8s.io_awsclusters.yaml

Will load the content, or display an appropriate error message.

Comments

Comments can be added to each line of the generated YAML content where descriptions are available. This looks something like this:

# APIVersion defines the versioned schema of this representation of an object. Servers should convert recognized schemas to the latest internal value, and may reject unrecognized values. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#resources
apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
# Kind is a string value representing the REST resource this object represents. Servers may infer this from the endpoint the client submits requests to. Cannot be updated. In CamelCase. More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#types-kinds
kind: AWSCluster
metadata: {}
# AWSClusterSpec defines the desired state of an EC2-based Kubernetes cluster.
spec:
  # AdditionalTags is an optional set of tags to add to AWS resources managed by the AWS provider, in addition to the ones added by default.
  additionalTags: {}
  # Bastion contains options to configure the bastion host.
  bastion:
  ...

To add comments simply run cty with:

cty generate -c sample-crd/infrastructure.cluster.x-k8s.io_awsclusters.yaml --comments

The frontend also has a checkbox to add comments to the generated yaml output.

Templated CRDs

It's possible to provide a templated CRD like this one for flux: Helm Controller.

It contains template definition like:

{{- if and .Values.installCRDs .Values.helmController.create }}

These are trimmed so that the CRD parses correctly. Any values that might be in-lined are replaced with replaced. This is done to avoid trying to parse a breaking yaml.

Things like this:

kind: CustomResourceDefinition
metadata:
  annotations:
    controller-gen.kubebuilder.io/version: v0.15.0
  labels:
    app.kubernetes.io/component: helm-controller
    app.kubernetes.io/instance: {{ .Release.Namespace }}
    app.kubernetes.io/managed-by: {{ .Release.Service }}
    app.kubernetes.io/part-of: flux
    app.kubernetes.io/version: {{ .Chart.AppVersion }}
    helm.sh/chart: '{{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}'
  name: helmreleases.helm.toolkit.fluxcd.io

Where some templated value isn't escaped with ' will create an invalid YAML that fails to parse.

Showcase

Parsed Yaml output on the website: