Improve clusterctl's --list-variables output

[wfernandes]

User Story

As a developer/user/operator I would like to see more details when I list the variables of a template yaml using clusterctl so that I know what values will be used and what values I need to specify.

Detailed Description
Currently, This is the output of a clusterctl command with --list-variables:

$ clusterctl config cluster foo -i aws:v0.5.4 --list-variables
Using configuration File="/Users/wfernandes/.cluster-api/clusterctl.yaml"
Fetching File="cluster-template.yaml" Provider="infrastructure-aws" Version="v0.5.4"
Variables:
  - AWS_CONTROL_PLANE_MACHINE_TYPE
  - AWS_NODE_MACHINE_TYPE
  - AWS_REGION
  - AWS_SSH_KEY_NAME
  - CLUSTER_NAME
  - CONTROL_PLANE_MACHINE_COUNT
  - KUBERNETES_VERSION
  - WORKER_MACHINE_COUNT

This is great. But now that we have support for default values ${VAR:=defaultValue} it would be nice to also view the default values that may be specified in the template.

Anything else you would like to add:
Extra bonus: It would also be nice to know which variables I may need to yet specify. That is, out of these variables, AWS_CONTROL_PLANE_MACHINE_TYPE, AWS_NODE_MACHINE_TYPE, AWS_SSH_KEY_NAME I may only have setup AWS_SSH_KEY_NAME in my clusterctl.yaml config.

A suggestion could be simply to display a table format such that the blank/empty values are the ones that may be required.
This way we could gain insight into what default values are being used and also what values are missing that I may still need to configure.

VARIABLE	VALUE
AWS_REGION	us-east1
AWS_CONTROL_PLANE_MACHINE_TYPE
AWS_NODE_MACHINE_TYPE
AWS_SSH_KEY_NAME	my-ssh-key

/kind feature
/area clusterctl

[vincepri]

/milestone v0.3.x

[vincepri]

/milestone v0.4.0

[prankul88]

@wfernandes Hi, I would like to work on this.

/assign

[fabriziopandini]

Thanks @prankul88 !
/lifecycle active

[fejta-bot]

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/lifecycle stale

[fabriziopandini]

/remove-lifecycle stale

[vincepri]

@prankul88 Are you still interested in tackling this issue?

[prankul88]

@vincepri Yes, had left it due to some issues. Would like to give it a shot once this week.

[prankul88]

@wfernandes Hi, I wanted a suggestion from you, if you can help. To fetch the default values from the template should I prefer making a separate function (Eg, func DefaultValues) and use it here or rather make Variables a map instead of a string to allow it to store default values.

I am facing some doubt on how to fetch the "Param" from envsubst package after traversing. Working on it..

[wfernandes]

@prankul88 Changing the Variables() []string definition would mean a change in the interface and which is not ideal but it may not be a non-blocker for v0.4.x since the main clusterctl API wouldn't be affected (I think).

I suggest moving towards the first option for now and see what the reviewers think. Some points to also think about is ensuring the list of variables is ordered so it's easier for users to look at. That is, iterating through a map is unordered and it could be difficult for users to see a different ordered list every time they print out the list.

FYI, I'm currently no longer on this project and won't be involved in further PR reviews. I suggest reaching out to other maintainers/reviewers (e.g. @fabriziopandini) to get their opinion.

Again, thanks for working on this 🙂

[prankul88]

@wfernandes Thanks for the feedback !! :)

[fabriziopandini]

@prankul88 are you working to this issue?
@CecileRobertMichon recently filed with an interesting variation of this request. do you mind if I close this issue in favour of the new one?

[CecileRobertMichon]

Ah sorry, I searched for existing issues but didn't see this issue before opening mine. I'm fine with copying my proposal here as a comment too if we want to keep history.

[CecileRobertMichon]

/close

[k8s-ci-robot]

@CecileRobertMichon: Closing this issue.

In response to this:

/close

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