How to recursively print #Defs with Go API

[cueckoo]

Originally opened by @verdverm in cuelang/cue#579

I'm attempting to print the following definition with all sub-definitions expanded as well, using the GoAPI

input:

import (
  appsV1 "k8s.io/api/apps/v1"
)

#deploy: appsV1.#DeploymentSpec

code:

...
                syn := val.Syntax(
                        cue.Final(),
                        cue.Raw(),
                        cue.Schema(),
                        cue.Attributes(false),
                        cue.Concrete(false),
                        cue.Definitions(true),
                        cue.Docs(true),
                        cue.Hidden(true),
                        cue.Optional(true),
                        cue.ResolveReferences(true),
                )
                out, err := format.Node(
                        syn,
                        format.TabIndent(false),
                        format.UseSpaces(2),
                        format.Simplify(),
                )
                if err != nil {
                        fmt.Println("Print Err:", err)
                        continue
                }

                fmt.Println(string(out))
...

result:

import metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"

#deploy: {
  // Number of desired pods. This is a pointer to distinguish between explicit
  // zero and not specified. Defaults to 1.
  // +optional
  replicas?: null | int & >=-2147483648 & <=2147483647

  // Label selector for pods. Existing ReplicaSets whose pods are
  // selected by this will be the ones affected by this deployment.
  // It must match the pod template's labels.
  selector?: null | metav1.#LabelSelector

  // Template describes the pods that will be created.
  template: {
    // Standard object's metadata.
    // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#metadata
    // +optional
    metadata?: metav1.#ObjectMeta

    // Specification of the desired behavior of the pod.
    // More info: https://git.k8s.io/community/contributors/devel/sig-architecture/api-conventions.md#spec-and-status
    // +optional
    spec?: #PodSpec
  }

  // The deployment strategy to use to replace existing pods with new ones.
  // +optional
  // +patchStrategy=retainKeys
  strategy?: #DeploymentStrategy

  // Minimum number of seconds for which a newly created pod should be ready
  // without any of its container crashing, for it to be considered available.
  // Defaults to 0 (pod will be considered available as soon as it is ready)
  // +optional
  minReadySeconds?: >=-2147483648 & <=2147483647 & int

  // The number of old ReplicaSets to retain to allow rollback.
  // This is a pointer to distinguish between explicit zero and not specified.
  // Defaults to 10.
  // +optional
  revisionHistoryLimit?: null | int & >=-2147483648 & <=2147483647

  // Indicates that the deployment is paused.
  // +optional
  paused?: bool

  // The maximum time in seconds for a deployment to make progress before it
  // is considered to be failed. The deployment controller will continue to
  // process failed deployments and a condition with a ProgressDeadlineExceeded
  // reason will be surfaced in the deployment status. Note that progress will
  // not be estimated during the time a deployment is paused. Defaults to 600s.
  progressDeadlineSeconds?: null | int & >=-2147483648 & <=2147483647
}

How can I get fields to expand as well?

Example fields:

• deploy.selector?: null | metav1.#LabelSelector
• deploy.template.spec?: #PodSpec
• deploy.strategy?: #DeploymentStrategy

[cueckoo]

Original reply by @jlongtine in cuelang/cue#579 (comment)

@verdverm Have you tried Evaling val first?

[cueckoo]

Original reply by @verdverm in cuelang/cue#579 (comment)

no difference

cue eval / def don't seem to support printing the nested defs either

[cueckoo]

Original reply by @mpvl in cuelang/cue#579 (comment)

Like with bugs, it is always good to be very explicit about what you saw (you did) and what you expected to see. What do you mean with "expand fields as well"?

Please note that the options specify both schema and final, which are a bit conflicting. In general, it is quite tricky to print in mixed mode, as it is prone to introducing infinite cycles. Furthermore, a CUE evaluation result has no references. The values still contain references to the original conjuncts, but they, in turn, do not have evaluated values. This strict separation has cleaned things up considerably, actually.

So if you want something custom you could do what Joel suggests, using Eval (in the API) and manage your own cycle handling and decision on what to expand and what not.

In the future I intend to have a separate package for creating CUE ast values from cue.Values that perhaps allows more control over this. The Syntax API hasn't really held up with the development of CUE. In general, cue.Value should be much simpler with separate packages doing the bulk of the work.