✨ default a LeaderElectionID

[mengqiy]

kubernetes-sigs/controller-runtime#446 removed the defaulting for LeaderElectionID.
It makes sense for controller-runtime. But kubebuilder should still be able to scaffold a project that work out-of-box.
So we will give users some instructions to update it in code comment.

[k8s-ci-robot]

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[mengqiy]

This PR is a prerequisite for #1391.

[Adirio]

v1 didn't support leader election, did it?

Minor comment

[Adirio]

I would create a unique string from domain and repo, adding some hashing too. Something like "{{ .Domain }}/{{ hash .Repo }}". WDYT?

hash could be something as simple as this example:

import (
	"fmt"
	"hash/fnv"
)

var hasher = fnv.New32a()

func hash(s string) string {
	hasher.Write([]byte(s))
	defer hasher.Reset()

	return fmt.Sprintf("%x", hasher.Sum(nil))
}

[mengqiy]

I guess I need to change file.Template a bit to make it more flexible to pass the additional FuncMap around.

type Template interface {
	Builder
	// GetBody returns the template body
	GetBody() string
	// SetTemplateDefaults sets the default values for templates
	SetTemplateDefaults() error
	// GetFuncMap allow each template to provide its own FuncMap.
	GetFuncMap() template.FuncMap
}

EDIT: Not sure if this way is the best. Still trying to find a clean way to do it.

[Adirio]

In that case, I would go for:

type CustomTemplate interface {
	Template
	GetFuncMap() template.FuncMap
}

This way only those that need it have to implement it.

But we could also implement it by having a HashedRepo field, set it in the SetTemplateDefaults, and then use it like "{{ .Domain }}/{{ .HashedRepo }}".

[mengqiy]

@Adirio Any thoughts on current implementation?

[Adirio]

The only NIT would be adding the Template to the UseCustomFuncMap

[mengqiy]

@Adirio v1 doesn't support leader election.

[mengqiy]

PTAL

[Adirio]

LGTM

[mengqiy]

/assign @estroz

[estroz]

/lgtm