🏃 Homogenize commands through Scaffolder interface

[Adirio]

Description

This PR defines a Scaffolder interface with a single method:

type Scaffolder interface {
	Scaffold()
}

This interface is used as the API between the cmd and the pkg/scaffold packages. This allows to provide a clearer limit between the two packages, as previously the limit was not clear and logic that should be placed in pkg/scaffold could be found in cmd (e.g., webhook scaffolding was being done directly in cmd).

Additionally the option structs for each command has also been homogenized. An unexported interface has been used for this purpose:

type commandOptions interface {
	// bindFlags binds the command flags to the fields in the options struct
	bindFlags(command *cobra.Command)

	// The following steps define a generic logic to follow when developing new commands. Some steps may be no-ops.
	// - Step 1: load the config failing if expected but not found or if not expected but found
	loadConfig() (*config.Config, error)
	// - Step 2: verify that the command can be run (e.g., go version, project version, arguments, ...)
	validate(*config.Config) error
	// - Step 3: create the Scaffolder instance
	scaffolder(*config.Config) (scaffold.Scaffolder, error)
	// - Step 4: call the Scaffold method of the Scaffolder instance
	// Doesn't need any method
	// - Step 5: finish the command execution
	postScaffold(*config.Config) error
}
}

The logic flow described for the run method has been used for every command. In some cases, some steps are simply no-ops, like the 5th step for the edit command.

Motivation

This PR is one of the main contributors to #1218.

[k8s-ci-robot]

Hi @Adirio. Thanks for your PR.

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[DirectXMan12]

/ok-to-test

[DirectXMan12]

Generally looks good. Is there any way that we can put the steps into an interface / helper so we don't have to repeat them in every run method?

[Adirio]

Is there any way that we can put the steps into an interface / helper so we don't have to repeat them in every run method?

@DirectXMan12 Something like the following?

type commandOptions interface {
	bindFlags(cmd *cobra.Command)
	loadConfig() (*Config, error)
	validate(*config.Config) error
	scaffolder(*config.Config) (Scaffolder, error)
	postScaffold(*config.Config) error
}

func run(options commandOptions) error {
	// Step 1: load config
	config, err := options.loadConfig()
	if err != nil {
		return err
	}

	// Step 2: validate
	if err := options.validate(config); err != nil {
		return err
	}

	// Step 3: create scaffolder
	scaffolder, err := options.scaffolder(config)
	if err != nil {
		return err
	}

	// Step 4: scaffold
	if err := scaffolder.Scaffold(); err != nil {
		return err
	}

	// Step 5: finish
	if err := options.postScaffold(); err != nil {
		return err
	}
}

[Adirio]

Didn't expect the golden test to check file permission, but it does.

[Adirio]

@DirectXMan12 I made a separate commit with the helper as I described here.

[DirectXMan12]

looks good once it's rebased

[mengqiy]

one nit.
Other bits LGTM.

[mengqiy]

This is a great refactor! Thanks for working on this.

[mengqiy]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Adirio, mengqiy

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