[Scaffold enhancement] File interface

[Adirio]

Context

Current situation

The current File interface is as follows:

kubebuilder/pkg/scaffold/input/input.go

Lines 141 to 145 in 03f70fb

	// File is a scaffoldable file
	type File interface {
	// GetInput returns the Input for creating a scaffold file
	GetInput() (Input, error)
	}

The single method is not descriptive enough and does different tasks:

1. Sets default values
2. Returns a non-descriptive Input struct which contains:
   • Two fields needed to prepare the template: Path and TemplateBody
   • Several other fileds that are not used

Note: the Input struct also works as a parent class for mostly all File-implementing structs so that they can be injected some data from the scaffold. By mostly I mean all except the PROJECT file, which is an special-cased yaml file which doesn't have an embedded Input.

GetInput usage

I have tracked GetInput usages.

pkg/scaffold/project.go

Lines 101 and 106 for v1, 192 and 197 for v2:

kubebuilder/pkg/scaffold/project.go

Line 101 in 03f70fb

projectInput, err := p.Project.GetInput()

kubebuilder/pkg/scaffold/project.go

Line 106 in 03f70fb

bpInput, err := p.Boilerplate.GetInput()

kubebuilder/pkg/scaffold/project.go

Line 192 in 03f70fb

projectInput, err := p.Project.GetInput()

kubebuilder/pkg/scaffold/project.go

Line 197 in 03f70fb

bpInput, err := p.Boilerplate.GetInput()

The created variables are used in lines 113 and 127 for v1, and 204 and 218 for v2:

kubebuilder/pkg/scaffold/project.go

Line 113 in 03f70fb

input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},

kubebuilder/pkg/scaffold/project.go

Line 127 in 03f70fb

input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},

kubebuilder/pkg/scaffold/project.go

Line 204 in 03f70fb

input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},

kubebuilder/pkg/scaffold/project.go

Line 218 in 03f70fb

input.Options{ProjectPath: projectInput.Path, BoilerplatePath: bpInput.Path},

Only the path is needed. Setting the default values (which is also done by GetInput) is not needed here except for the path itself.

pkg/scaffold/scaffold.go

Line 229:

kubebuilder/pkg/scaffold/scaffold.go

Line 229 in 03f70fb

i, err := e.GetInput()

Which is later used in line 235 and 238:

kubebuilder/pkg/scaffold/scaffold.go

Line 235 in 03f70fb

Path: i.Path,

kubebuilder/pkg/scaffold/scaffold.go

Line 238 in 03f70fb

if b, err := s.doTemplate(i, e); err != nil {

The usage in doTemplate are in lines 278, 291 and 292:

kubebuilder/pkg/scaffold/scaffold.go

Line 278 in 03f70fb

temp, err := newTemplate(e).Parse(i.TemplateBody)

kubebuilder/pkg/scaffold/scaffold.go

Lines 291 to 292 in 03f70fb

	if filepath.Ext(i.Path) == ".go" {
	b, err = imports.Process(i.Path, b, nil)

The path is needed in lines 235, 291 and 292. The template body is needed in line 278. The side-effect of setting the default values is important here as the files are used to execute the templates in line 284:

kubebuilder/pkg/scaffold/scaffold.go

Line 284 in 03f70fb

err = temp.Execute(out, e)

pkg/scaffold/project/project_test.go

Line 49:

kubebuilder/pkg/scaffold/project/project_test.go

Lines 48 to 52 in 03f70fb

	It("should skip writing boilerplate if the file exists", func() {
	i, err := (&project.Boilerplate{}).GetInput()
	Expect(err).NotTo(HaveOccurred())
	Expect(i.IfExistsAction).To(Equal(input.Skip))
	})

It is used to set the default values.

Proposal

A new interface is proposed:

type File interface {
	GetPath() string
	GetTemplateBody() string
	SetDefaults() error
}

Method usage

• GetPath would be used in lines 113, 127, 204 and 218 of pkg/scaffold/project.go and in lines 235, 291 and 292 of pkg/scaffold/scaffold.go.
• GetTemplateBody would be used in line 278 of pkg/scaffold/scaffold.go.
• SetDefaults would be called before line 284 of pkg/scaffold/scaffold.go and in line 49 of pkg/scaffold/project/project_test.go.
• All the GetInput calls with their error handlings could be removed.

This feature is part of a bigger change tracked in #1218

/kind feature