feat: Allow using kubectl built-in kustomize when separate kustomize binary is missing

kubectl_kustomize_test.go

@@ -0,0 +1,109 @@
+package chartify
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestKubectlKustomize tests behavior when kubectl kustomize is explicitly configured
+// via KustomizeBin("kubectl kustomize"). The automatic fallback selection is tested
+// in TestKustomizeBin.
+func TestKubectlKustomize(t *testing.T) {
+	t.Run("KustomizeBuild succeeds with kubectl kustomize option", func(t *testing.T) {
+		if _, err := exec.LookPath("kubectl"); err != nil {
+			t.Skip("kubectl binary not found in PATH")
+		}
+
+		tmpDir := t.TempDir()
+		srcDir := t.TempDir()
+
+		kustomizationContent := `apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+- deployment.yaml
+`
+		deploymentContent := `apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: test
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: test
+  template:
+    metadata:
+      labels:
+        app: test
+    spec:
+      containers:
+      - name: test
+        image: test:latest
+`
+
+		templatesDir := filepath.Join(tmpDir, "templates")
+		require.NoError(t, os.MkdirAll(templatesDir, 0755))
+
+		require.NoError(t, os.WriteFile(filepath.Join(srcDir, "kustomization.yaml"), []byte(kustomizationContent), 0644))
+		require.NoError(t, os.WriteFile(filepath.Join(srcDir, "deployment.yaml"), []byte(deploymentContent), 0644))
+
+		r := New(KustomizeBin("kubectl kustomize"))
+
+		outputFile, err := r.KustomizeBuild(srcDir, tmpDir)
+		require.NoError(t, err)
+		require.FileExists(t, outputFile)
+	})
+
+	t.Run("edit commands not supported with kubectl kustomize", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		srcDir := t.TempDir()
+
+		kustomizationContent := `apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+resources:
+- deployment.yaml
+`
+		deploymentContent := `apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: test
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: test
+  template:
+    metadata:
+      labels:
+        app: test
+    spec:
+      containers:
+      - name: test
+        image: test:latest
+`
+
+		templatesDir := filepath.Join(tmpDir, "templates")
+		valuesDir := t.TempDir()
+		valuesFile := filepath.Join(valuesDir, "values.yaml")
+		valuesContent := `images:
+- name: test
+  newName: newtest
+  newTag: v2
+`
+
+		require.NoError(t, os.MkdirAll(templatesDir, 0755))
+		require.NoError(t, os.WriteFile(filepath.Join(srcDir, "kustomization.yaml"), []byte(kustomizationContent), 0644))
+		require.NoError(t, os.WriteFile(filepath.Join(srcDir, "deployment.yaml"), []byte(deploymentContent), 0644))
+		require.NoError(t, os.WriteFile(valuesFile, []byte(valuesContent), 0644))
+
+		r := New(KustomizeBin("kubectl kustomize"))
+
+		_, err := r.KustomizeBuild(srcDir, tmpDir, &KustomizeBuildOpts{ValuesFiles: []string{valuesFile}})
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "setting images via kustomizeOpts.Images is not supported when using 'kubectl kustomize'")
+	})
+}

kustomize.go

@@ -110,6 +110,9 @@ func (r *Runner) KustomizeBuild(srcDir string, tempDir string, opts ...Kustomize
 	}
 
 	if len(kustomizeOpts.Images) > 0 {
+		if r.isUsingKubectlKustomize() {
+			return "", fmt.Errorf("setting images via kustomizeOpts.Images is not supported when using 'kubectl kustomize'. Please set images directly in your kustomization.yaml file")
+		}
 		args := []string{"edit", "set", "image"}
 		for _, image := range kustomizeOpts.Images {
 			args = append(args, image.String())
@@ -120,27 +123,40 @@ func (r *Runner) KustomizeBuild(srcDir string, tempDir string, opts ...Kustomize
 		}
 	}
 	if kustomizeOpts.NamePrefix != "" {
+		if r.isUsingKubectlKustomize() {
+			return "", fmt.Errorf("setting namePrefix via kustomizeOpts.NamePrefix is not supported when using 'kubectl kustomize'. Please set namePrefix directly in your kustomization.yaml file")
+		}
 		_, err := r.runInDir(tempDir, r.kustomizeBin(), "edit", "set", "nameprefix", kustomizeOpts.NamePrefix)
 		if err != nil {
 			fmt.Println(err)
 			return "", err
 		}
 	}
 	if kustomizeOpts.NameSuffix != "" {
+		if r.isUsingKubectlKustomize() {
+			return "", fmt.Errorf("setting nameSuffix via kustomizeOpts.NameSuffix is not supported when using 'kubectl kustomize'. Please set nameSuffix directly in your kustomization.yaml file")
+		}
 		// "--" is there to avoid `namesuffix -acme` to fail due to `-a` being considered as a flag
 		_, err := r.runInDir(tempDir, r.kustomizeBin(), "edit", "set", "namesuffix", "--", kustomizeOpts.NameSuffix)
 		if err != nil {
 			return "", err
 		}
 	}
 	if kustomizeOpts.Namespace != "" {
+		if r.isUsingKubectlKustomize() {
+			return "", fmt.Errorf("setting namespace via kustomizeOpts.Namespace is not supported when using 'kubectl kustomize'. Please set namespace directly in your kustomization.yaml file")
+		}
 		_, err := r.runInDir(tempDir, r.kustomizeBin(), "edit", "set", "namespace", kustomizeOpts.Namespace)
 		if err != nil {
 			return "", err
 		}
 	}
 	outputFile := filepath.Join(tempDir, "templates", "kustomized.yaml")
-	kustomizeArgs := []string{"-o", outputFile, "build"}
+	kustomizeArgs := []string{"-o", outputFile}
+
+	if !r.isUsingKubectlKustomize() {
+		kustomizeArgs = append(kustomizeArgs, "build")
+	}
 
 	if u.EnableAlphaPlugins {
 		f, err := r.kustomizeEnableAlphaPluginsFlag()
@@ -190,10 +206,18 @@ func (r *Runner) kustomizeVersion() (*semver.Version, error) {
 	return version, nil
 }
 
+// isUsingKubectlKustomize checks if we're using kubectl's built-in kustomize
+func (r *Runner) isUsingKubectlKustomize() bool {
+	return r.kustomizeBin() == "kubectl kustomize"
+}
+
 // kustomizeEnableAlphaPluginsFlag returns the kustomize binary alpha plugin argument.
 // Above Kustomize v3, it is `--enable-alpha-plugins`.
 // Below Kustomize v3 (including v3), it is `--enable_alpha_plugins`.
 func (r *Runner) kustomizeEnableAlphaPluginsFlag() (string, error) {
+	if r.isUsingKubectlKustomize() {
+		return "--enable-alpha-plugins", nil
+	}
 	version, err := r.kustomizeVersion()
 	if err != nil {
 		return "", err
@@ -209,6 +233,9 @@ func (r *Runner) kustomizeEnableAlphaPluginsFlag() (string, error) {
 // Above Kustomize v3, it is `--load-restrictor=LoadRestrictionsNone`.
 // Below Kustomize v3 (including v3), it is `--load_restrictor=none`.
 func (r *Runner) kustomizeLoadRestrictionsNoneFlag() (string, error) {
+	if r.isUsingKubectlKustomize() {
+		return "--load-restrictor=LoadRestrictionsNone", nil
+	}
 	version, err := r.kustomizeVersion()
 	if err != nil {
 		return "", err

patch.go

@@ -181,9 +181,13 @@ resources:
 
 	renderedFileName := "all.patched.yaml"
 	renderedFile := filepath.Join(tempDir, renderedFileName)
-	r.Logf("Generating %s", renderedFile)
+	r.Logf("Generating %s", renderedFileName)
 
-	kustomizeArgs := []string{"build", tempDir, "--output", renderedFile}
+	kustomizeArgs := []string{"--output", renderedFile}
+
+	if !r.isUsingKubectlKustomize() {
+		kustomizeArgs = append([]string{"build", tempDir}, kustomizeArgs...)
+	}
 
 	if u.EnableAlphaPlugins {
 		f, err := r.kustomizeEnableAlphaPluginsFlag()

runner.go

@@ -108,6 +108,15 @@ func (r *Runner) kustomizeBin() string {
 	if r.KustomizeBinary != "" {
 		return r.KustomizeBinary
 	}
+	if env := os.Getenv("KUSTOMIZE_BIN"); env != "" {
+		return env
+	}
+	if _, err := exec.LookPath("kustomize"); err == nil {
+		return "kustomize"
+	}
+	if _, err := exec.LookPath("kubectl"); err == nil {
+		return "kubectl kustomize"
+	}
 	return "kustomize"
 }
 
@@ -140,7 +149,7 @@ func (r *Runner) runBytes(envs map[string]string, dir, cmd string, args ...strin
 
 	name := nameArgs[0]
 
-	if len(nameArgs) > 2 {
+	if len(nameArgs) > 1 {
 		a := append([]string{}, nameArgs[1:]...)
 		a = append(a, args...)
 
@@ -154,10 +163,10 @@ func (r *Runner) runBytes(envs map[string]string, dir, cmd string, args ...strin
 		wrappedErr := fmt.Errorf(`%w
 
 COMMAND:
-%s
+ %s
 
 OUTPUT:
-%s`,
+ %s`,
 			err,
 			indent(c, "  "),
 			indent(string(errBytes), "  "),

util_test.go

@@ -1,9 +1,12 @@
 package chartify
 
 import (
+	"os"
+	"path/filepath"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
 )
 
 func TestCreateFlagChain(t *testing.T) {
@@ -107,3 +110,91 @@ func TestFindSemVerInfo(t *testing.T) {
 		})
 	}
 }
+
+func TestKustomizeBin(t *testing.T) {
+	t.Run("KustomizeBinary option is set", func(t *testing.T) {
+		r := New(KustomizeBin("/custom/kustomize"))
+		got := r.kustomizeBin()
+		want := "/custom/kustomize"
+		if got != want {
+			t.Errorf("kustomizeBin() = %v, want %v", got, want)
+		}
+	})
+
+	t.Run("KUSTOMIZE_BIN environment variable", func(t *testing.T) {
+		if _, ok := os.LookupEnv("KUSTOMIZE_BIN"); ok {
+			t.Skip("KUSTOMIZE_BIN environment variable is already set")
+		}
+		os.Setenv("KUSTOMIZE_BIN", "/custom/kustomize")
+		defer os.Unsetenv("KUSTOMIZE_BIN")
+		r := New()
+		got := r.kustomizeBin()
+		want := "/custom/kustomize"
+		if got != want {
+			t.Errorf("kustomizeBin() = %v, want %v", got, want)
+		}
+	})
+
+	t.Run("fallback to kubectl kustomize when kustomize not found", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		binDir := filepath.Join(tmpDir, "bin")
+		require.NoError(t, os.MkdirAll(binDir, 0755))
+
+		kubectlPath := filepath.Join(binDir, "kubectl")
+		kubectlContent := []byte("#!/bin/sh\necho 'kubectl version'\n")
+		require.NoError(t, os.WriteFile(kubectlPath, kubectlContent, 0755))
+
+		origPath := os.Getenv("PATH")
+		defer os.Setenv("PATH", origPath)
+		os.Setenv("PATH", binDir)
+
+		r := New()
+		got := r.kustomizeBin()
+		want := "kubectl kustomize"
+		if got != want {
+			t.Errorf("kustomizeBin() = %v, want %v", got, want)
+		}
+	})
+
+	t.Run("use kustomize when both kustomize and kubectl exist in PATH", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		binDir := filepath.Join(tmpDir, "bin")
+		require.NoError(t, os.MkdirAll(binDir, 0755))
+
+		kustomizePath := filepath.Join(binDir, "kustomize")
+		kustomizeContent := []byte("#!/bin/sh\necho 'kustomize version'\n")
+		require.NoError(t, os.WriteFile(kustomizePath, kustomizeContent, 0755))
+
+		kubectlPath := filepath.Join(binDir, "kubectl")
+		kubectlContent := []byte("#!/bin/sh\necho 'kubectl version'\n")
+		require.NoError(t, os.WriteFile(kubectlPath, kubectlContent, 0755))
+
+		origPath := os.Getenv("PATH")
+		defer os.Setenv("PATH", origPath)
+		os.Setenv("PATH", binDir)
+
+		r := New()
+		got := r.kustomizeBin()
+		want := "kustomize"
+		if got != want {
+			t.Errorf("kustomizeBin() = %v, want %v", got, want)
+		}
+	})
+
+	t.Run("return kustomize as fallback when neither kustomize nor kubectl exist", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		binDir := filepath.Join(tmpDir, "bin")
+		require.NoError(t, os.MkdirAll(binDir, 0755))
+
+		origPath := os.Getenv("PATH")
+		defer os.Setenv("PATH", origPath)
+		os.Setenv("PATH", binDir)
+
+		r := New()
+		got := r.kustomizeBin()
+		want := "kustomize"
+		if got != want {
+			t.Errorf("kustomizeBin() = %v, want %v", got, want)
+		}
+	})
+}