Support for -d (deleting contexts)

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

cmd/kubectx/delete.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/pkg/errors"
+	"gopkg.in/yaml.v3"
+)
+
+// deleteContexts deletes context entries one by one.
+func deleteContexts(w io.Writer, ctxs []string) error {
+	for _, ctx := range ctxs {
+		// TODO inefficency here. we open/write/close the same file many times.
+		deletedName, wasActiveContext, err := deleteContext(ctx)
+		if err != nil {
+			return errors.Wrapf(err, "error deleting context %q", ctx)
+		}
+		if wasActiveContext {
+			// TODO we don't always run as kubectx (sometimes "kubectl ctx")
+			printWarning("You deleted the current context. use \"kubectx\" to select a different one.")
+		}
+		fmt.Fprintf(w, "deleted context %q\n", deletedName) // TODO write with printSuccess (i.e. green)
+	}
+	return nil
+}
+
+// deleteContext deletes a context entry by NAME or current-context
+// indicated by ".".
+func deleteContext(name string) (deleteName string, wasActiveContext bool, err error) {
+	f, rootNode, err := openKubeconfig()
+	if err != nil {
+		return "", false, err
+	}
+	defer f.Close()
+
+	cur := getCurrentContext(rootNode)
+
+	// resolve "." to a real name
+	if name == "." {
+		wasActiveContext = true
+		name = cur
+	}
+
+	if !checkContextExists(rootNode, name) {
+		return "", false, errors.New("context does not exist")
+	}
+
+	if err := modifyDocToDeleteContext(rootNode, name); err != nil {
+		return "", false, errors.Wrap(err, "failed to modify yaml doc")
+	}
+
+	if err := resetFile(f); err != nil {
+		return "", false, err
+	}
+	return name, wasActiveContext, errors.Wrap(saveKubeconfigRaw(f, rootNode), "failed to save kubeconfig file")
+}
+
+func modifyDocToDeleteContext(rootNode *yaml.Node, deleteName string) error {
+	if rootNode.Kind != yaml.MappingNode {
+		return errors.New("root node was not a mapping node")
+	}
+	contexts := valueOf(rootNode, "contexts")
+	if contexts == nil {
+		return errors.New("there are no contexts in kubeconfig")
+	}
+	if contexts.Kind != yaml.SequenceNode {
+		return errors.New("'contexts' key is not a sequence")
+	}
+
+	i := -1
+	for j, ctxNode := range contexts.Content {
+		nameNode := valueOf(ctxNode, "name")
+		if nameNode != nil && nameNode.Kind == yaml.ScalarNode && nameNode.Value == deleteName {
+			i = j
+			break
+		}
+	}
+	if i >= 0 {
+		copy(contexts.Content[i:], contexts.Content[i+1:])
+		contexts.Content[len(contexts.Content)-1] = nil
+		contexts.Content = contexts.Content[:len(contexts.Content)-1]
+	}
+	return nil
+}

cmd/kubectx/flags.go

@@ -21,6 +21,11 @@ type SwitchOp struct {
 // UnsetOp indicates intention to remove current-context preference.
 type UnsetOp struct{}
 
+// DeleteOp indicates intention to delete contexts.
+type DeleteOp struct {
+	Contexts []string // NAME or '.' to indicate current-context.
+}
+
 // UnknownOp indicates an unsupported flag.
 type UnknownOp struct{ Args []string }
 
@@ -31,6 +36,11 @@ func parseArgs(argv []string) Op {
 		return ListOp{}
 	}
 
+	if argv[0] == "-d" {
+		ctxs := argv[1:]
+		return DeleteOp{ctxs}
+	}
+
 	if len(argv) == 1 {
 		v := argv[0]
 		if v == "--help" || v == "-h" {

cmd/kubectx/flags_test.go

@@ -42,6 +42,15 @@ func Test_parseArgs_new(t *testing.T) {
 		{name: "switch by swap",
 			args: []string{"-"},
 			want: SwitchOp{Target: "-"}},
+		{name: "delete - without contexts",
+			args: []string{"-d"},
+			want: DeleteOp{[]string{}}},
+		{name: "delete - current context",
+			args: []string{"-d", "."},
+			want: DeleteOp{[]string{"."}}},
+		{name: "delete - multiple contexts",
+			args: []string{"-d", ".", "a", "b"},
+			want: DeleteOp{[]string{".", "a", "b"}}},
 		{name: "unrecognized flag",
 			args: []string{"-x"},
 			want: UnknownOp{Args: []string{"-x"}}},

cmd/kubectx/main.go

@@ -32,6 +32,11 @@ func main() {
 			printError(err.Error())
 			os.Exit(1)
 		}
+	case DeleteOp:
+		if err := deleteContexts(os.Stderr, v.Contexts); err != nil {
+			printError(err.Error())
+			os.Exit(1)
+		}
 	case SwitchOp:
 		var newCtx string
 		var err error
@@ -57,3 +62,7 @@ func main() {
 func printError(format string, args ...interface{}) {
 	fmt.Fprintf(os.Stderr, color.RedString("error: ")+format+"\n", args...)
 }
+
+func printWarning(format string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, color.YellowString("warning: ")+format+"\n", args...)
+}