Implement list (via exec kubectl), clearer color settings

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

cmd/kubectx/list.go

@@ -34,11 +34,7 @@ func (_ ListOp) Run(stdout, stderr io.Writer) error {
 	// TODO support KUBECTX_CURRENT_BGCOLOR
 
 	currentColor := color.New(color.FgGreen, color.Bold)
-	if v := printer.UseColors(); v != nil && *v {
-		currentColor.EnableColor()
-	} else if v != nil && !*v {
-		currentColor.DisableColor()
-	}
+	printer.EnableOrDisableColor(currentColor)
 
 	cur := kc.GetCurrentContext()
 	for _, c := range ctxs {

cmd/kubens/list.go

@@ -1,11 +1,80 @@
 package main
 
 import (
+	"bytes"
+	"fmt"
 	"io"
+	"os"
+	"os/exec"
+	"strings"
+
+	"github.com/fatih/color"
+	"github.com/pkg/errors"
+
+	"github.com/ahmetb/kubectx/internal/cmdutil"
+	"github.com/ahmetb/kubectx/internal/kubeconfig"
+	"github.com/ahmetb/kubectx/internal/printer"
 )
 
 type ListOp struct{}
 
 func (op ListOp) Run(stdout, stderr io.Writer) error {
-	panic("implement me")
+	kc := new(kubeconfig.Kubeconfig).WithLoader(cmdutil.DefaultLoader)
+	defer kc.Close()
+	if err := kc.Parse(); err != nil {
+		if cmdutil.IsNotFoundErr(err) {
+			printer.Warning(stderr, "kubeconfig file not found")
+			return nil
+		}
+		return errors.Wrap(err, "kubeconfig error")
+	}
+
+	ctx := kc.GetCurrentContext()
+	if ctx == "" {
+		return errors.New("current-context is not set")
+	}
+	curNs, err := kc.NamespaceOfContext(ctx)
+	if err != nil {
+		return errors.Wrap(err, "cannot read current namespace")
+	}
+
+	kubectl, err := findKubectl()
+	if err != nil {
+		return err
+	}
+	ns, err := queryNamespaces(kubectl)
+	if err != nil {
+		return err
+	}
+
+	currentColor := color.New(color.FgGreen, color.Bold)
+	printer.EnableOrDisableColor(currentColor)
+
+	for _, c := range ns {
+		s := c
+		if c == curNs {
+			s = currentColor.Sprint(c)
+		}
+		fmt.Fprintf(stdout, "%s\n", s)
+	}
+	return nil
+}
+
+func findKubectl() (string, error) {
+	if v := os.Getenv("KUBECTL"); v != "" {
+		return v, nil
+	}
+	v, err := exec.LookPath("kubectl")
+	return v, errors.Wrap(err, "kubectl not found, needed for kubens")
+}
+
+func queryNamespaces(kubectl string) ([]string, error) {
+	var b bytes.Buffer
+	cmd := exec.Command(kubectl, "get", "namespaces", `-o=jsonpath={range .items[*].metadata.name}{@}{"\n"}{end}`)
+	cmd.Env = os.Environ()
+	cmd.Stdout, cmd.Stderr = &b, &b
+	if err := cmd.Run(); err != nil {
+		return nil, errors.Wrapf(err, "failed to query namespaces: %v", b.String())
+	}
+	return strings.Split(strings.TrimSpace(b.String()), "\n"), nil
 }

internal/printer/color.go

@@ -3,13 +3,15 @@ package printer
 import (
 	"os"
 
+	"github.com/fatih/color"
+
 	"github.com/ahmetb/kubectx/internal/env"
 )
 
-// UseColors returns true if colors are force-enabled,
+// useColors returns true if colors are force-enabled,
 // false if colors are disabled, or nil for default behavior
 // which is determined based on factors like if stdout is tty.
-func UseColors() *bool {
+func useColors() *bool {
 	tr, fa := true, false
 	if os.Getenv(env.EnvForceColor) != "" {
 		return &tr
@@ -18,3 +20,13 @@ func UseColors() *bool {
 	}
 	return nil
 }
+
+// EnableOrDisableColor determines if color should be force-enabled or force-disabled
+// or left untouched based on environment configuration.
+func EnableOrDisableColor(c *color.Color) {
+	if v := useColors(); v != nil && *v {
+		c.EnableColor()
+	} else if v != nil && !*v {
+		c.DisableColor()
+	}
+}

internal/printer/color_test.go

@@ -16,16 +16,16 @@ func Test_useColors_forceColors(t *testing.T) {
 	defer testutil.WithEnvVar("_KUBECTX_FORCE_COLOR", "1")()
 	defer testutil.WithEnvVar("NO_COLOR", "1")()
 
-	if v := UseColors(); !cmp.Equal(v, &tr) {
-		t.Fatalf("expected UseColors() = true; got = %v", v)
+	if v := useColors(); !cmp.Equal(v, &tr) {
+		t.Fatalf("expected useColors() = true; got = %v", v)
 	}
 }
 
 func Test_useColors_disableColors(t *testing.T) {
 	defer testutil.WithEnvVar("NO_COLOR", "1")()
 
-	if v := UseColors(); !cmp.Equal(v, &fa) {
-		t.Fatalf("expected UseColors() = false; got = %v", v)
+	if v := useColors(); !cmp.Equal(v, &fa) {
+		t.Fatalf("expected useColors() = false; got = %v", v)
 	}
 }
 
@@ -33,7 +33,7 @@ func Test_useColors_default(t *testing.T) {
 	defer testutil.WithEnvVar("NO_COLOR", "")()
 	defer testutil.WithEnvVar("_KUBECTX_FORCE_COLOR", "")()
 
-	if v := UseColors(); v != nil {
-		t.Fatalf("expected UseColors() = nil; got=%v", *v)
+	if v := useColors(); v != nil {
+		t.Fatalf("expected useColors() = nil; got=%v", *v)
 	}
 }

internal/printer/printer.go

@@ -14,7 +14,7 @@ var (
 )
 
 func init() {
-	colors := UseColors()
+	colors := useColors()
 	if colors == nil {
 		return
 	}