fix: nomos default kubeconfig path (#1028)

Work around a controller-runtime quirk that was causing nomos not
to have a default KUBECONFIG value.

cmd/nomos/nomos.go

@@ -29,7 +29,9 @@ import (
 	"kpt.dev/configsync/cmd/nomos/version"
 	"kpt.dev/configsync/cmd/nomos/vet"
 	"kpt.dev/configsync/pkg/api/configmanagement"
+	"kpt.dev/configsync/pkg/client/restconfig"
 	pkgversion "kpt.dev/configsync/pkg/version"
+	"sigs.k8s.io/controller-runtime/pkg/client/config"
 )
 
 var (
@@ -57,6 +59,20 @@ func main() {
 	// Register klog flags
 	klog.InitFlags(fs)
 
+	// Work around the controller-runtime init registering a --kubeconfig flag
+	// with no default value. Use the same default as kubectl instead.
+	// https://github.com/kubernetes-sigs/controller-runtime/blob/v0.16.3/pkg/client/config/config.go#L44
+	if f := fs.Lookup(config.KubeconfigFlagName); f != nil {
+		// Change the default value & usage.
+		// This path should be expected because import inits load first.
+		defaultKubeConfigPath, err := restconfig.KubeConfigPath()
+		if err != nil {
+			klog.Fatal(err)
+		}
+		f.DefValue = defaultKubeConfigPath
+		f.Usage = "Path to the client config file."
+	}
+
 	// Cobra uses the pflag lib, instead of the go flag lib.
 	// So re-register all go flags as global (aka persistent) pflags.
 	rootCmd.PersistentFlags().AddGoFlagSet(fs)

pkg/client/restconfig/config.go

@@ -40,15 +40,15 @@ func defaultGetCurrentUser() (*user.User, error) {
 	return user.Current()
 }
 
-// newConfigPath returns the correct kubeconfig file path to use, depending on
-// the current user settings and the runtime environment.
-func newConfigPath() (string, error) {
-	// First try the KUBECONFIG variable.
+// KubeConfigPath returns the path to the kubeconfig:
+// 1. ${KUBECONFIG}, if non-empty
+// 2. ${userCurrentTestHook.HomeDir}/.kube/config, if userCurrentTestHook is set
+// 3. ${HOME}/.kube/config
+func KubeConfigPath() (string, error) {
 	envPath := os.Getenv("KUBECONFIG")
 	if envPath != "" {
 		return envPath, nil
 	}
-	// Try the current user.
 	curentUser, err := userCurrentTestHook()
 	if err != nil {
 		return "", errors.Wrapf(err, "failed to get current user")
@@ -60,7 +60,7 @@ func newConfigPath() (string, error) {
 // newRawConfigWithRules returns a clientcmdapi.Config from a configuration file whose path is
 // provided by newConfigPath, and the clientcmd.ClientConfigLoadingRules associated with it
 func newRawConfigWithRules() (*clientcmdapi.Config, *clientcmd.ClientConfigLoadingRules, error) {
-	configPath, err := newConfigPath()
+	configPath, err := KubeConfigPath()
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "while getting config path")
 	}

pkg/client/restconfig/restconfig.go

@@ -38,7 +38,7 @@ const DefaultTimeout = 15 * time.Second
 func NewRestConfig(timeout time.Duration) (*rest.Config, error) {
 	var cfg *rest.Config
 	// Detect kubectl config file
-	path, err := newConfigPath()
+	path, err := KubeConfigPath()
 	if err != nil {
 		// Build from k8s downward API
 		cfg, err = NewFromInClusterConfig()