add IfNotExistsAction to machinery for optional file handling

Author: aman4433

pkg/machinery/file.go

@@ -30,6 +30,17 @@ const (
 	OverwriteFile
 )
 
+// IfNotExistsAction determines what to do if a file to be updated does not exist
+type IfNotExistsAction int
+
+const (
+	// ErrorIfNotExist returns an error and stops processing (default behavior)
+	ErrorIfNotExist IfNotExistsAction = iota
+
+	// IgnoreFile skips the file and logs a message if it does not exist
+	IgnoreFile
+)
+
 // File describes a file that will be written
 type File struct {
 	// Path is the file to write
@@ -40,4 +51,7 @@ type File struct {
 
 	// IfExistsAction determines what to do if the file exists
 	IfExistsAction IfExistsAction
+
+	// IfNotExistsAction determines what to do if the file is missing (optional updates only)
+	IfNotExistsAction IfNotExistsAction
 }

pkg/machinery/interfaces.go

@@ -59,6 +59,11 @@ type Inserter interface {
 	GetCodeFragments() CodeFragmentsMap
 }
 
+// HasIfNotExistsAction allows a template to define an action if the file is missing
+type HasIfNotExistsAction interface {
+	GetIfNotExistsAction() IfNotExistsAction
+}
+
 // HasDomain allows the domain to be used on a template
 type HasDomain interface {
 	// InjectDomain sets the template domain

pkg/machinery/mixins.go

@@ -153,3 +153,14 @@ func (m *ResourceMixin) InjectResource(res *resource.Resource) {
 		m.Resource = res
 	}
 }
+
+// IfNotExistsActionMixin provides file builders with an if-not-exists-action field
+type IfNotExistsActionMixin struct {
+	// IfNotExistsAction determines what to do if the file does not exist
+	IfNotExistsAction IfNotExistsAction
+}
+
+// GetIfNotExistsAction implements Inserter
+func (m *IfNotExistsActionMixin) GetIfNotExistsAction() IfNotExistsAction {
+	return m.IfNotExistsAction
+}

pkg/machinery/scaffold.go

@@ -237,13 +237,13 @@ func doTemplate(t Template) ([]byte, error) {
 func (s Scaffold) updateFileModel(i Inserter, models map[string]*File) error {
 	m, err := s.loadPreviousModel(i, models)
 	if err != nil {
-		// TODO(kubebuilder/issues/4960): Create Machinery implementation to allow defining IfNotExistsAction
-		// If the file path starts with test/, warn and skip
-		// Workaround to allow projects be backwards compatible with previous versions
-		if strings.HasPrefix(i.GetPath(), "test/") {
-			log.Warnf("Skipping missing test file: %s", i.GetPath())
-			log.Warn("The code fragments will not be inserted.")
-			return nil
+		if os.IsNotExist(err) {
+			if withOptionalBehavior, ok := i.(HasIfNotExistsAction); ok &&
+				withOptionalBehavior.GetIfNotExistsAction() == IgnoreFile {
+				log.Warnf("Skipping missing file: %s", i.GetPath())
+				log.Warn("The code fragments will not be inserted.")
+				return nil
+			}
 		}
 		return fmt.Errorf("failed to load previous model for %s: %w", i.GetPath(), err)
 	}

pkg/plugins/golang/v4/scaffolds/internal/templates/webhooks/webhook_test_template.go

@@ -34,6 +34,7 @@ type WebhookTest struct {
 	machinery.MultiGroupMixin
 	machinery.BoilerplateMixin
 	machinery.ResourceMixin
+	machinery.IfNotExistsActionMixin
 
 	Force bool
 
@@ -78,7 +79,10 @@ func (f *WebhookTest) SetTemplateDefaults() error {
 
 	if f.Force {
 		f.IfExistsAction = machinery.OverwriteFile
+	} else {
+		f.IfExistsAction = machinery.Error
 	}
+	f.IfNotExistsAction = machinery.IgnoreFile
 
 	return nil
 }