Allow in-cluster config for oc

Because we set the default env value to empty, we can't use the default
in cluster config for 'oc' (when you run inside a container, oc works).
It's really important for container integration scenarios that oc uses
the service account token by default, just like kubeconfig.

hack/test-cmd.sh

@@ -187,7 +187,7 @@ atomic-enterprise start \
 	"${NODE_CONFIG_DIR}/node-config.yaml"
 
 # test client not configured
-[ "$(oc get services 2>&1 | grep 'Error in configuration')" ]
+[ "$(oc get services 2>&1 | grep 'No configuration file found, please login')" ]
 
 # Set KUBERNETES_MASTER for oc from now on
 export KUBERNETES_MASTER="${API_SCHEME}://${API_HOST}:${API_PORT}"

pkg/cmd/util/clientcmd/factory.go

@@ -3,6 +3,8 @@ package clientcmd
 import (
 	"errors"
 	"fmt"
+	"os"
+	"reflect"
 	"sort"
 	"strconv"
 	"time"
@@ -13,6 +15,7 @@ import (
 	"k8s.io/kubernetes/pkg/api/meta"
 	kclient "k8s.io/kubernetes/pkg/client/unversioned"
 	kclientcmd "k8s.io/kubernetes/pkg/client/unversioned/clientcmd"
+	kclientcmdapi "k8s.io/kubernetes/pkg/client/unversioned/clientcmd/api"
 	"k8s.io/kubernetes/pkg/fields"
 	"k8s.io/kubernetes/pkg/kubectl"
 	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
@@ -33,24 +36,73 @@ import (
 	routegen "github.com/openshift/origin/pkg/route/generator"
 )
 
+// defaultClusterConfigURL is a local name that is used to identify when the client config
+// is unspecified.
+const defaultClusterConfigURL = "https://localhost:8443"
+
 // New creates a default Factory for commands that should share identical server
 // connection behavior. Most commands should use this method to get a factory.
 func New(flags *pflag.FlagSet) *Factory {
-	// Override global default to "" so we force the client to ask for user input
 	// TODO refactor this upstream:
 	// DefaultCluster should not be a global
 	// A call to ClientConfig() should always return the best clientCfg possible
 	// even if an error was returned, and let the caller decide what to do
-	kclientcmd.DefaultCluster.Server = ""
+	kclientcmd.DefaultCluster.Server = defaultClusterConfigURL
 
 	// TODO: there should be two client configs, one for OpenShift, and one for Kubernetes
 	clientConfig := DefaultClientConfig(flags)
+	clientConfig = defaultingClientConfig{clientConfig}
 	f := NewFactory(clientConfig)
 	f.BindFlags(flags)
 
 	return f
 }
 
+// defaultingClientConfig detects whether the provided config is the default, and if
+// so returns an error that indicates the user should set up their config.
+type defaultingClientConfig struct {
+	nested kclientcmd.ClientConfig
+}
+
+// RawConfig calls the nested method
+func (c defaultingClientConfig) RawConfig() (kclientcmdapi.Config, error) {
+	return c.nested.RawConfig()
+}
+
+// Namespace calls the nested method
+func (c defaultingClientConfig) Namespace() (string, bool, error) {
+	return c.nested.Namespace()
+}
+
+// ClientConfig returns a complete client config
+func (c defaultingClientConfig) ClientConfig() (*kclient.Config, error) {
+	cfg, err := c.nested.ClientConfig()
+	if err != nil {
+		return nil, err
+	}
+	if isDefaultConfig(cfg) {
+		return nil, fmt.Errorf(`No configuration file found, please login or point to an existing file:
+
+  1. Via the command-line flag --config
+  2. Via the KUBECONFIG environment variable
+  3. In your home directory as ~/.kube/config
+
+To view or setup config directly use the 'config' command.`)
+	}
+	return cfg, nil
+}
+
+func isDefaultConfig(cfg *kclient.Config) bool {
+	if len(os.Getenv("KUBERNETES_MASTER")) > 0 {
+		return false
+	}
+	defaultConfig, err := kclientcmd.DefaultClientConfig.ClientConfig()
+	if err != nil {
+		return false
+	}
+	return reflect.DeepEqual(cfg, defaultConfig)
+}
+
 // Factory provides common options for OpenShift commands
 type Factory struct {
 	*cmdutil.Factory