Config consumers should be able to recognize an empty config

For UX, it would be better if we presented an error for validation that
is "this config is empty" rather than the inaccurate "no server name" or
"no context name" errors. Returns a typed error.

pkg/client/unversioned/clientcmd/api/helpers.go

@@ -31,6 +31,14 @@ func init() {
 	redactedBytes = []byte(string(sDec))
 }
 
+// IsConfigEmpty returns true if the config is empty.
+func IsConfigEmpty(config *Config) bool {
+	return len(config.AuthInfos) == 0 && len(config.Clusters) == 0 && len(config.Contexts) == 0 &&
+		len(config.CurrentContext) == 0 &&
+		len(config.Preferences.Extensions) == 0 && !config.Preferences.Colors &&
+		len(config.Extensions) == 0
+}
+
 // MinifyConfig read the current context and uses that to keep only the relevant pieces of config
 // This is useful for making secrets based on kubeconfig files
 func MinifyConfig(config *Config) error {

pkg/client/unversioned/clientcmd/api/types.go

@@ -24,6 +24,7 @@ import (
 // Top level config objects and all values required for proper functioning are not "omitempty".  Any truly optional piece of config is allowed to be omitted.
 
 // Config holds the information needed to build connect to remote kubernetes clusters as a given user
+// IMPORTANT if you add fields to this struct, please update IsConfigEmpty()
 type Config struct {
 	// Legacy field from pkg/api/types.go TypeMeta.
 	// TODO(jlowdermilk): remove this after eliminating downstream dependencies.
@@ -44,6 +45,7 @@ type Config struct {
 	Extensions map[string]*runtime.EmbeddedObject `json:"extensions,omitempty"`
 }
 
+// IMPORTANT if you add fields to this struct, please update IsConfigEmpty()
 type Preferences struct {
 	Colors bool `json:"colors,omitempty"`
 	// Extensions holds additional information. This is useful for extenders so that reads and writes don't clobber unknown fields

pkg/client/unversioned/clientcmd/client_config.go

@@ -233,7 +233,11 @@ func (config DirectClientConfig) ConfirmUsable() error {
 	validationErrors := make([]error, 0)
 	validationErrors = append(validationErrors, validateAuthInfo(config.getAuthInfoName(), config.getAuthInfo())...)
 	validationErrors = append(validationErrors, validateClusterInfo(config.getClusterName(), config.getCluster())...)
-
+	// when direct client config is specified, and our only error is that no server is defined, we should
+	// return a standard "no config" error
+	if len(validationErrors) == 1 && validationErrors[0] == ErrEmptyCluster {
+		return newErrConfigurationInvalid([]error{ErrEmptyConfig})
+	}
 	return newErrConfigurationInvalid(validationErrors)
 }
 

pkg/client/unversioned/clientcmd/validation.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"os"
+	"reflect"
 	"strings"
 
 	clientcmdapi "k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api"
@@ -27,7 +28,12 @@ import (
 	"k8s.io/kubernetes/pkg/util/validation"
 )
 
-var ErrNoContext = errors.New("no context chosen")
+var (
+	ErrNoContext   = errors.New("no context chosen")
+	ErrEmptyConfig = errors.New("no configuration has been provided")
+	// message is for consistency with old behavior
+	ErrEmptyCluster = errors.New("cluster has no server defined")
+)
 
 type errContextNotFound struct {
 	ContextName string
@@ -49,6 +55,16 @@ func IsContextNotFound(err error) bool {
 	return strings.Contains(err.Error(), "context was not found for specified context")
 }
 
+// IsEmptyConfig returns true if the provided error indicates the provided configuration
+// is empty.
+func IsEmptyConfig(err error) bool {
+	switch t := err.(type) {
+	case errConfigurationInvalid:
+		return len(t) == 1 && t[0] == ErrEmptyConfig
+	}
+	return err == ErrEmptyConfig
+}
+
 // errConfigurationInvalid is a set of errors indicating the configuration is invalid.
 type errConfigurationInvalid []error
 
@@ -88,6 +104,10 @@ func IsConfigurationInvalid(err error) bool {
 func Validate(config clientcmdapi.Config) error {
 	validationErrors := make([]error, 0)
 
+	if clientcmdapi.IsConfigEmpty(&config) {
+		return newErrConfigurationInvalid([]error{ErrEmptyConfig})
+	}
+
 	if len(config.CurrentContext) != 0 {
 		if _, exists := config.Contexts[config.CurrentContext]; !exists {
 			validationErrors = append(validationErrors, &errContextNotFound{config.CurrentContext})
@@ -114,6 +134,10 @@ func Validate(config clientcmdapi.Config) error {
 func ConfirmUsable(config clientcmdapi.Config, passedContextName string) error {
 	validationErrors := make([]error, 0)
 
+	if clientcmdapi.IsConfigEmpty(&config) {
+		return newErrConfigurationInvalid([]error{ErrEmptyConfig})
+	}
+
 	var contextName string
 	if len(passedContextName) != 0 {
 		contextName = passedContextName
@@ -143,6 +167,10 @@ func ConfirmUsable(config clientcmdapi.Config, passedContextName string) error {
 func validateClusterInfo(clusterName string, clusterInfo clientcmdapi.Cluster) []error {
 	validationErrors := make([]error, 0)
 
+	if reflect.DeepEqual(clientcmdapi.Cluster{}, clusterInfo) {
+		return []error{ErrEmptyCluster}
+	}
+
 	if len(clusterInfo.Server) == 0 {
 		if len(clusterName) == 0 {
 			validationErrors = append(validationErrors, fmt.Errorf("default cluster has no server defined"))

pkg/client/unversioned/clientcmd/validation_test.go

@@ -87,7 +87,7 @@ func TestConfirmUsableEmptyConfig(t *testing.T) {
 	config := clientcmdapi.NewConfig()
 	test := configValidationTest{
 		config:                 config,
-		expectedErrorSubstring: []string{"no context chosen"},
+		expectedErrorSubstring: []string{"invalid configuration: no configuration has been provided"},
 	}
 
 	test.testConfirmUsable("", t)
@@ -96,7 +96,7 @@ func TestConfirmUsableMissingConfig(t *testing.T) {
 	config := clientcmdapi.NewConfig()
 	test := configValidationTest{
 		config:                 config,
-		expectedErrorSubstring: []string{"context was not found for"},
+		expectedErrorSubstring: []string{"invalid configuration: no configuration has been provided"},
 	}
 
 	test.testConfirmUsable("not-here", t)
@@ -104,7 +104,8 @@ func TestConfirmUsableMissingConfig(t *testing.T) {
 func TestValidateEmptyConfig(t *testing.T) {
 	config := clientcmdapi.NewConfig()
 	test := configValidationTest{
-		config: config,
+		config:                 config,
+		expectedErrorSubstring: []string{"invalid configuration: no configuration has been provided"},
 	}
 
 	test.testConfig(t)
@@ -132,6 +133,18 @@ func TestIsContextNotFound(t *testing.T) {
 	}
 }
 
+func TestIsEmptyConfig(t *testing.T) {
+	config := clientcmdapi.NewConfig()
+
+	err := Validate(*config)
+	if !IsEmptyConfig(err) {
+		t.Errorf("Expected context not found, but got %v", err)
+	}
+	if !IsConfigurationInvalid(err) {
+		t.Errorf("Expected configuration invalid, but got %v", err)
+	}
+}
+
 func TestIsConfigurationInvalid(t *testing.T) {
 	if newErrConfigurationInvalid([]error{}) != nil {
 		t.Errorf("unexpected error")
@@ -177,7 +190,7 @@ func TestValidateEmptyClusterInfo(t *testing.T) {
 	config.Clusters["empty"] = &clientcmdapi.Cluster{}
 	test := configValidationTest{
 		config:                 config,
-		expectedErrorSubstring: []string{"no server found for"},
+		expectedErrorSubstring: []string{"cluster has no server defined"},
 	}
 
 	test.testCluster("empty", t)

pkg/client/unversioned/helper.go

@@ -327,6 +327,11 @@ func NewOrDie(c *Config) *Client {
 // running inside a pod running on kuberenetes. It will return an error if
 // called from a process not running in a kubernetes environment.
 func InClusterConfig() (*Config, error) {
+	host, port := os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT")
+	if len(host) == 0 || len(port) == 0 {
+		return nil, fmt.Errorf("unable to load in-cluster configuration, KUBERNETES_SERVICE_HOST and KUBERNETES_SERVICE_PORT must be defined")
+	}
+
 	token, err := ioutil.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/" + api.ServiceAccountTokenKey)
 	if err != nil {
 		return nil, err
@@ -341,7 +346,7 @@ func InClusterConfig() (*Config, error) {
 
 	return &Config{
 		// TODO: switch to using cluster DNS.
-		Host:            "https://" + net.JoinHostPort(os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT")),
+		Host:            "https://" + net.JoinHostPort(host, port),
 		BearerToken:     string(token),
 		TLSClientConfig: tlsClientConfig,
 	}, nil