refactor generator

refactor funcs out of generator

staging/src/k8s.io/kubectl/pkg/explain/v2/explain.go

@@ -43,7 +43,7 @@ func PrintModelDescription(
 
 // Factored out for testability
 func printModelDescriptionWithGenerator(
-	generator *generator,
+	generator Generator,
 	fieldsPath []string,
 	w io.Writer,
 	client openapi.Client,

staging/src/k8s.io/kubectl/pkg/explain/v2/funcs.go

@@ -0,0 +1,40 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package v2
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"reflect"
+	"strings"
+	"text/template"
+
+	"github.com/go-openapi/jsonreference"
+	"k8s.io/kubectl/pkg/util/term"
+)
+
+func WithBuiltinTemplateFuncs(tmpl *template.Template) *template.Template {
+	return tmpl.Funcs(map[string]interface{}{
+		"toJson": func(obj any) (string, error) {
+			res, err := json.Marshal(obj)
+			return string(res), err
+		},
+	})
+}
+

staging/src/k8s.io/kubectl/pkg/explain/v2/generator.go

@@ -17,7 +17,6 @@ limitations under the License.
 package v2
 
 import (
-	"encoding/json"
 	"fmt"
 	"io"
 	"text/template"
@@ -25,6 +24,26 @@ import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
 )
 
+type Generator interface {
+	AddTemplate(name string, contents string) error
+
+	Render(
+		// Template to use for rendering
+		templateName string,
+		// Self-Contained OpenAPI Document Containing all schemas used by $ref
+		// Only OpenAPI V3 documents are supported
+		document map[string]interface{},
+		// Resource within OpenAPI document for which to render explain schema
+		gvr schema.GroupVersionResource,
+		// Field path of child of resource to focus output onto
+		fieldSelector []string,
+		// Boolean indicating whether the fields should be rendered recursively/deeply
+		recursive bool,
+		// Output writer
+		writer io.Writer,
+	) error
+}
+
 type TemplateContext struct {
 	GVR       schema.GroupVersionResource
 	Document  map[string]interface{}
@@ -36,22 +55,14 @@ type generator struct {
 	templates map[string]*template.Template
 }
 
-func NewGenerator() *generator {
+func NewGenerator() Generator {
 	return &generator{
 		templates: make(map[string]*template.Template),
 	}
 }
 
 func (g *generator) AddTemplate(name string, contents string) error {
-	compiled, err := template.
+	compiled, err := WithBuiltinTemplateFuncs(template.New(name)).Parse(contents)
-		New(name).
-		Funcs(map[string]interface{}{
-			"toJson": func(obj any) (string, error) {
-				res, err := json.Marshal(obj)
-				return string(res), err
-			},
-		}).
-		Parse(contents)
 
 	if err != nil {
 		return err