feat(understackctl): deploy check uses kustomize build to validate

go/understackctl/cmd/deploy/check.go

@@ -3,12 +3,23 @@ package deploy
 import (
 	"fmt"
 	"os"
+	"os/exec"
 	"path/filepath"
+	"strings"
 
 	"github.com/charmbracelet/log"
 	"github.com/spf13/cobra"
 )
 
+// kustomizeBuildArgs mirrors the kustomize.buildOptions configured in
+// components/argocd/values.yaml so local validation matches ArgoCD's behaviour.
+var kustomizeBuildArgs = []string{
+	"--enable-alpha-plugins",
+	"--enable-exec",
+	"--enable-helm",
+	"--load-restrictor", "LoadRestrictionsNone",
+}
+
 func newCmdDeployCheck() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "check <cluster-name>",
@@ -36,7 +47,14 @@ func runDeployCheck(clusterName string) error {
 		return nil
 	}
 
+	kustomizePath, err := exec.LookPath("kustomize")
+	if err != nil {
+		log.Warn("kustomize not found in PATH, skipping kustomization.yaml validation")
+		kustomizePath = ""
+	}
+
 	missing := []string{}
+	var kustomizeErrors []string
 
 	for _, comp := range components {
 		compDir := filepath.Join(clusterName, comp.Name)
@@ -52,6 +70,16 @@ func runDeployCheck(clusterName string) error {
 			kustomPath := filepath.Join(compDir, "kustomization.yaml")
 			if _, err := os.Stat(kustomPath); os.IsNotExist(err) {
 				missing = append(missing, kustomPath)
+				continue
+			}
+
+			if kustomizePath != "" {
+				args := append(append([]string{"build"}, kustomizeBuildArgs...), compDir)
+				out, err := exec.Command(kustomizePath, args...).CombinedOutput()
+				if err != nil {
+					kustomizeErrors = append(kustomizeErrors,
+						fmt.Sprintf("%s: %s", kustomPath, strings.TrimSpace(string(out))))
+				}
 			}
 		}
 	}
@@ -61,7 +89,17 @@ func runDeployCheck(clusterName string) error {
 		for _, path := range missing {
 			log.Errorf("  - %s", path)
 		}
-		return fmt.Errorf("validation failed: %d missing files", len(missing))
+	}
+
+	if len(kustomizeErrors) > 0 {
+		log.Error("kustomize build failures:")
+		for _, msg := range kustomizeErrors {
+			log.Errorf("  - %s", msg)
+		}
+	}
+
+	if total := len(missing) + len(kustomizeErrors); total > 0 {
+		return fmt.Errorf("validation failed: %d error(s)", total)
 	}
 
 	log.Infof("All %d components validated successfully", len(components))

go/understackctl/cmd/deploy/deploy_test.go

@@ -284,7 +284,7 @@ func TestDeployCheck(t *testing.T) {
 	kustomPath := filepath.Join(keystoneDir, "kustomization.yaml")
 	valuesPath := filepath.Join(keystoneDir, "values.yaml")
 
-	if err := os.WriteFile(kustomPath, []byte("test"), 0644); err != nil {
+	if err := os.WriteFile(kustomPath, []byte(kustomizationContent), 0644); err != nil {
 		t.Fatalf("failed to write kustomization.yaml: %v", err)
 	}