Add support for -u/--unset

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

cmd/kubectx/flags.go

@@ -18,6 +18,9 @@ type SwitchOp struct {
 	Target string // '-' for back and forth, or NAME
 }
 
+// UnsetOp indicates intention to remove current-context preference.
+type UnsetOp struct{}
+
 // UnknownOp indicates an unsupported flag.
 type UnknownOp struct{ Args []string }
 
@@ -36,6 +39,9 @@ func parseArgs(argv []string) Op {
 		if v == "--current" || v == "-c" {
 			return CurrentOp{}
 		}
+		if v == "--unset" || v == "-u" {
+			return UnsetOp{}
+		}
 
 		if strings.HasPrefix(v, "-") && v != "-" {
 			return UnknownOp{argv}

cmd/kubectx/flags_test.go

@@ -30,6 +30,12 @@ func Test_parseArgs_new(t *testing.T) {
 		{name: "current long form",
 			args: []string{"--current"},
 			want: CurrentOp{}},
+		{name: "unset shorthand",
+			args: []string{"-u"},
+			want: UnsetOp{}},
+		{name: "unset long form",
+			args: []string{"--unset"},
+			want: UnsetOp{}},
 		{name: "switch by name",
 			args: []string{"foo"},
 			want: SwitchOp{Target: "foo"}},

cmd/kubectx/kubeconfig_raw.go

@@ -0,0 +1,52 @@
+package main
+
+import (
+	"io"
+	"os"
+
+	"github.com/pkg/errors"
+	"gopkg.in/yaml.v3"
+)
+
+func parseKubeconfigRaw(r io.Reader) (*yaml.Node, error) {
+	var v yaml.Node
+	if err := yaml.NewDecoder(r).Decode(&v); err != nil {
+		return nil, err
+	}
+	return v.Content[0], nil
+}
+
+func saveKubeconfigRaw(w io.Writer, rootNode *yaml.Node) error {
+	enc := yaml.NewEncoder(w)
+	enc.SetIndent(2)
+	return enc.Encode(rootNode)
+}
+
+func openKubeconfig() (f *os.File, rootNode *yaml.Node, err error) {
+	cfgPath, err := kubeconfigPath()
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "cannot determine kubeconfig path")
+	}
+	f, err = os.OpenFile(cfgPath, os.O_RDWR, 0)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "failed to open file")
+	}
+
+	kc, err := parseKubeconfigRaw(f)
+	if err != nil {
+		f.Close()
+		return nil, nil, errors.Wrap(err, "yaml parse error")
+	}
+	return f, kc, nil
+}
+
+// resetFile deletes contents of a file and sets the seek
+// position to 0.
+func resetFile(f *os.File) error {
+	if err := f.Truncate(0); err != nil {
+		return errors.Wrap(err, "failed to truncate")
+	}
+
+	_, err := f.Seek(0, 0)
+	return errors.Wrap(err, "failed to seek")
+}

cmd/kubectx/main.go

@@ -22,6 +22,11 @@ func main() {
 			printError(err.Error())
 			os.Exit(1)
 		}
+	case UnsetOp:
+		if err := unsetContext(); err != nil {
+			printError(err.Error())
+			os.Exit(1)
+		}
 	case ListOp:
 		if err := printListContexts(os.Stdout); err != nil {
 			printError(err.Error())

cmd/kubectx/switch.go

@@ -1,9 +1,6 @@
 package main
 
 import (
-	"io"
-	"os"
-
 	"github.com/pkg/errors"
 	"gopkg.in/yaml.v3"
 )
@@ -15,21 +12,12 @@ func switchContext(name string) (string, error) {
 		return "", errors.Wrap(err, "failed to determine state file")
 	}
 
-	cfgPath, err := kubeconfigPath()
+	f, kc, err := openKubeconfig()
 	if err != nil {
-		return "", errors.Wrap(err, "cannot determine kubeconfig path")
-	}
-	f, err := os.OpenFile(cfgPath, os.O_RDWR, 0)
-	if err != nil {
-		return "", errors.Wrap(err, "failed to open file")
+		return "", err
 	}
 	defer f.Close()
 
-	kc, err := parseKubeconfigRaw(f)
-	if err != nil {
-		return "", errors.Wrap(err, "yaml parse error")
-	}
-
 	prev := getCurrentContext(kc)
 
 	// TODO: add a check to ensure user can't switch to non-existing context.
@@ -41,12 +29,8 @@ func switchContext(name string) (string, error) {
 		return "", err
 	}
 
-	if err := f.Truncate(0); err != nil {
-		return "", errors.Wrap(err, "failed to truncate")
-	}
-
-	if _, err := f.Seek(0, 0); err != nil {
-		return "", errors.Wrap(err, "failed to seek")
+	if err := resetFile(f); err != nil {
+		return "", err
 	}
 
 	if err := saveKubeconfigRaw(f, kc); err != nil {
@@ -153,17 +137,3 @@ func modifyCurrentContext(rootNode *yaml.Node, name string) error {
 	rootNode.Content = append(rootNode.Content, keyNode, valueNode)
 	return nil
 }
-
-func parseKubeconfigRaw(r io.Reader) (*yaml.Node, error) {
-	var v yaml.Node
-	if err := yaml.NewDecoder(r).Decode(&v); err != nil {
-		return nil, err
-	}
-	return v.Content[0], nil
-}
-
-func saveKubeconfigRaw(w io.Writer, rootNode *yaml.Node) error {
-	enc := yaml.NewEncoder(w)
-	enc.SetIndent(2)
-	return enc.Encode(rootNode)
-}

cmd/kubectx/unset.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"github.com/pkg/errors"
+	"gopkg.in/yaml.v3"
+)
+
+func unsetContext() error {
+	f, rootNode, err := openKubeconfig()
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := modifyDocToUnsetContext(rootNode); err != nil {
+		return errors.Wrap(err, "error while modifying current-context")
+	}
+	if err := resetFile(f); err != nil {
+		return err
+	}
+	if err := saveKubeconfigRaw(f, rootNode); err != nil {
+		return errors.Wrap(err, "failed to save kubeconfig file after modification")
+	}
+	return nil
+}
+
+func modifyDocToUnsetContext(rootNode *yaml.Node) error {
+	if rootNode.Kind != yaml.MappingNode {
+		return errors.New("kubeconfig file is not a map document")
+	}
+	curCtxValNode := valueOf(rootNode, "current-context")
+	curCtxValNode.Value = ""
+	return nil
+}