feat: enable kubectl segment to read kubeconfig

This extends the kubectl segment to optionally not rely on the
kubectl command and instead to directly parse kubeconfig files like
kubectl does. This is meant as a performance optimization similar
to how the git segment can determine the current branch itself
without calling to git. Especially on Windows and in the presence
other factors slowing process creation like like AntiVirus this
can make shells using the segment considerably more responsive.

The functionality is enabled using the new parse_kubeconfig prop.
It defaults to false to prevent breaking existing users in case
there are any unanticipated behavioral changes.

Additionally the new template properties Cluster and User were
added as they are easily available and helpful in kubectl
setups with more elaborate configuration.

docs/docs/segment-kubectl.md

@@ -29,11 +29,15 @@ Display the currently active Kubernetes context name and namespace name.
 - template: `string` - A go [text/template][go-text-template] template extended with [sprig][sprig] utilizing the
 properties below - defaults to `{{.Context}}{{if .Namespace}} :: {{.Namespace}}{{end}}`
 - display_error: `boolean` - show the error context when failing to retrieve the kubectl information - defaults to `false`
+- parse_kubeconfig: `boolean` - parse kubeconfig files instead of calling out to kubectl to improve
+performance - defaults to `false`
 
 ## Template Properties
 
 - `.Context`: `string` - the current kubectl context
-- `.Namespace`: `string` - the current kubectl namespace
+- `.Namespace`: `string` - the current kubectl context namespace
+- `.User`: `string` - the current kubectl context user
+- `.Cluster`: `string` - the current kubectl context cluster
 
 ## Tips
 

src/go.mod

@@ -35,6 +35,8 @@ require (
 	howett.net/plist v0.0.0-20201203080718-1454fab16a06 // indirect
 )
 
+require gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b
+
 require (
 	github.com/Masterminds/goutils v1.1.1 // indirect
 	github.com/Masterminds/semver/v3 v3.1.1 // indirect
@@ -54,7 +56,6 @@ require (
 	github.com/tklauser/numcpus v0.3.0 // indirect
 	github.com/xo/terminfo v0.0.0-20210125001918-ca9a967f8778 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
 )
 
 replace github.com/distatus/battery v0.10.0 => github.com/JanDeDobbeleer/battery v0.10.0-2

src/segment_kubectl.go

@@ -1,14 +1,34 @@
 package main
 
 import (
+	"path/filepath"
 	"strings"
+
+	"gopkg.in/yaml.v3"
 )
 
+// Whether to use kubectl or read kubeconfig ourselves
+const ParseKubeConfig Property = "parse_kubeconfig"
+
 type kubectl struct {
 	props   properties
 	env     environmentInfo
 	Context string
-	Namespace string
+	KubeConfigContext
+}
+
+type KubeConfigContext struct {
+	Cluster   string `yaml:"cluster"`
+	User      string `yaml:"user"`
+	Namespace string `yaml:"namespace"`
+}
+
+type KubeConfig struct {
+	CurrentContext string `yaml:"current-context"`
+	Contexts       []struct {
+		Context KubeConfigContext `yaml:"context"`
+		Name    string            `yaml:"name"`
+	} `yaml:"contexts"`
 }
 
 func (k *kubectl) string() string {
@@ -31,15 +51,69 @@ func (k *kubectl) init(props properties, env environmentInfo) {
 }
 
 func (k *kubectl) enabled() bool {
+	parseKubeConfig := k.props.getBool(ParseKubeConfig, false)
+	if parseKubeConfig {
+		return k.doParseKubeConfig()
+	}
+	return k.doCallKubectl()
+}
+
+func (k *kubectl) doParseKubeConfig() bool {
+	// Follow kubectl search rules (see https://kubernetes.io/docs/concepts/configuration/organize-cluster-access-kubeconfig/#the-kubeconfig-environment-variable)
+	// TL;DR: KUBECONFIG can contain a list of files. If it's empty ~/.kube/config is used. First file in list wins when merging keys.
+	kubeconfigs := filepath.SplitList(k.env.getenv("KUBECONFIG"))
+	if len(kubeconfigs) == 0 {
+		kubeconfigs = []string{filepath.Join(k.env.homeDir(), ".kube/config")}
+	}
+	contexts := make(map[string]KubeConfigContext)
+	k.Context = ""
+	for _, kubeconfig := range kubeconfigs {
+		if len(kubeconfig) == 0 {
+			continue
+		}
+
+		content := k.env.getFileContent(kubeconfig)
+
+		var config KubeConfig
+		err := yaml.Unmarshal([]byte(content), &config)
+		if err != nil {
+			continue
+		}
+
+		for _, context := range config.Contexts {
+			if _, exists := contexts[context.Name]; !exists {
+				contexts[context.Name] = context.Context
+			}
+		}
+
+		if len(k.Context) == 0 {
+			k.Context = config.CurrentContext
+		}
+
+		context, exists := contexts[k.Context]
+		if exists {
+			k.KubeConfigContext = context
+			return true
+		}
+	}
+
+	displayError := k.props.getBool(DisplayError, false)
+	if !displayError {
+		return false
+	}
+	k.setError("KUBECONFIG ERR")
+	return true
+}
+
+func (k *kubectl) doCallKubectl() bool {
 	cmd := "kubectl"
 	if !k.env.hasCommand(cmd) {
 		return false
 	}
-	result, err := k.env.runCommand(cmd, "config", "view", "--minify", "--output", "jsonpath={..current-context},{..namespace}")
+	result, err := k.env.runCommand(cmd, "config", "view", "--minify", "--output", "jsonpath={..current-context},{..namespace},{..context.user},{..context.cluster}")
 	displayError := k.props.getBool(DisplayError, false)
 	if err != nil && displayError {
-		k.Context = "KUBECTL ERR"
+		k.setError("KUBECTL ERR")
-		k.Namespace = k.Context
 		return true
 	}
 	if err != nil {
@@ -49,5 +123,16 @@ func (k *kubectl) enabled() bool {
 	values := strings.Split(result, ",")
 	k.Context = values[0]
 	k.Namespace = values[1]
-	return k.Context != ""
+	k.User = values[2]
+	k.Cluster = values[3]
+	return len(k.Context) > 0
+}
+
+func (k *kubectl) setError(message string) {
+	if len(k.Context) == 0 {
+		k.Context = message
+	}
+	k.Namespace = message
+	k.User = message
+	k.Cluster = message
 }

src/segment_kubectl_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -9,16 +10,23 @@ import (
 type kubectlArgs struct {
 	kubectlExists       bool
 	kubectlErr          bool
+	kubeconfig          string
+	parseKubeConfig     bool
 	template            string
 	displayError        bool
-	context       string
+	kubectlOutContext   string
-	namespace     string
+	kubectlOutNamespace string
+	kubectlOutUser      string
+	kubectlOutCluster   string
+	files               map[string]string
 }
 
+const testKubectlAllInfoTemplate = "{{.Context}} :: {{.Namespace}} :: {{.User}} :: {{.Cluster}}"
+
 func bootStrapKubectlTest(args *kubectlArgs) *kubectl {
 	env := new(MockedEnvironment)
 	env.On("hasCommand", "kubectl").Return(args.kubectlExists)
-	kubectlOut := args.context + "," + args.namespace
+	kubectlOut := args.kubectlOutContext + "," + args.kubectlOutNamespace + "," + args.kubectlOutUser + "," + args.kubectlOutCluster
 	var kubectlErr error
 	if args.kubectlErr {
 		kubectlErr = &commandError{
@@ -26,12 +34,21 @@ func bootStrapKubectlTest(args *kubectlArgs) *kubectl {
 			exitCode: 1,
 		}
 	}
-	env.On("runCommand", "kubectl", []string{"config", "view", "--minify", "--output", "jsonpath={..current-context},{..namespace}"}).Return(kubectlOut, kubectlErr)
+	env.On("runCommand", "kubectl",
+		[]string{"config", "view", "--minify", "--output", "jsonpath={..current-context},{..namespace},{..context.user},{..context.cluster}"}).Return(kubectlOut, kubectlErr)
+
+	env.On("getenv", "KUBECONFIG").Return(args.kubeconfig)
+	for path, content := range args.files {
+		env.On("getFileContent", path).Return(content)
+	}
+	env.On("homeDir", nil).Return("testhome")
+
 	k := &kubectl{
 		env: env,
 		props: map[Property]interface{}{
 			SegmentTemplate: args.template,
 			DisplayError:    args.displayError,
+			ParseKubeConfig: args.parseKubeConfig,
 		},
 	}
 	return k
@@ -39,24 +56,47 @@ func bootStrapKubectlTest(args *kubectlArgs) *kubectl {
 
 func TestKubectlSegment(t *testing.T) {
 	standardTemplate := "{{.Context}}{{if .Namespace}} :: {{.Namespace}}{{end}}"
+	lsep := string(filepath.ListSeparator)
+
 	cases := []struct {
 		Case            string
 		Template        string
 		DisplayError    bool
 		KubectlExists   bool
+		Kubeconfig      string
+		ParseKubeConfig bool
 		Context         string
 		Namespace       string
+		User            string
+		Cluster         string
 		KubectlErr      bool
 		ExpectedEnabled bool
 		ExpectedString  string
+		Files           map[string]string
 	}{
 		{Case: "disabled", Template: standardTemplate, KubectlExists: false, Context: "aaa", Namespace: "bbb", ExpectedString: "", ExpectedEnabled: false},
 		{Case: "normal", Template: standardTemplate, KubectlExists: true, Context: "aaa", Namespace: "bbb", ExpectedString: "aaa :: bbb", ExpectedEnabled: true},
+		{Case: "all information", Template: testKubectlAllInfoTemplate, KubectlExists: true, Context: "aaa", Namespace: "bbb", User: "ccc", Cluster: "ddd",
+			ExpectedString: "aaa :: bbb :: ccc :: ddd", ExpectedEnabled: true},
 		{Case: "no namespace", Template: standardTemplate, KubectlExists: true, Context: "aaa", Namespace: "", ExpectedString: "aaa", ExpectedEnabled: true},
 		{Case: "kubectl error", Template: standardTemplate, DisplayError: true, KubectlExists: true, Context: "aaa", Namespace: "bbb", KubectlErr: true,
 			ExpectedString: "KUBECTL ERR :: KUBECTL ERR", ExpectedEnabled: true},
-		{Case: "kubectl error hidden", Template: standardTemplate, DisplayError: false, KubectlExists: true, Context: "aaa", Namespace: "bbb", KubectlErr: true,
+		{Case: "kubectl error hidden", Template: standardTemplate, DisplayError: false, KubectlExists: true, Context: "aaa", Namespace: "bbb", KubectlErr: true, ExpectedEnabled: false},
-			ExpectedString: "", ExpectedEnabled: false},
+		{Case: "kubeconfig home", Template: testKubectlAllInfoTemplate, ParseKubeConfig: true, Files: testKubeConfigFiles, ExpectedString: "aaa :: bbb :: ccc :: ddd",
+			ExpectedEnabled: true},
+		{Case: "kubeconfig multiple current marker first", Template: testKubectlAllInfoTemplate, ParseKubeConfig: true,
+			Kubeconfig: "" + lsep + "currentcontextmarker" + lsep + "contextdefinition" + lsep + "contextredefinition",
+			Files:      testKubeConfigFiles, ExpectedString: "ctx :: ns :: usr :: cl", ExpectedEnabled: true},
+		{Case: "kubeconfig multiple context first", Template: testKubectlAllInfoTemplate, ParseKubeConfig: true,
+			Kubeconfig: "contextdefinition" + lsep + "contextredefinition" + lsep + "currentcontextmarker" + lsep,
+			Files:      testKubeConfigFiles, ExpectedString: "ctx :: ns :: usr :: cl", ExpectedEnabled: true},
+		{Case: "kubeconfig error hidden", Template: testKubectlAllInfoTemplate, ParseKubeConfig: true, Kubeconfig: "invalid", Files: testKubeConfigFiles, ExpectedEnabled: false},
+		{Case: "kubeconfig error", Template: testKubectlAllInfoTemplate, ParseKubeConfig: true,
+			Kubeconfig: "invalid", Files: testKubeConfigFiles, DisplayError: true,
+			ExpectedString: "KUBECONFIG ERR :: KUBECONFIG ERR :: KUBECONFIG ERR :: KUBECONFIG ERR", ExpectedEnabled: true},
+		{Case: "kubeconfig incomplete", Template: testKubectlAllInfoTemplate, ParseKubeConfig: true,
+			Kubeconfig: "currentcontextmarker" + lsep + "contextdefinitionincomplete",
+			Files:      testKubeConfigFiles, ExpectedString: "ctx ::  ::  :: ", ExpectedEnabled: true},
 	}
 
 	for _, tc := range cases {
@@ -64,12 +104,60 @@ func TestKubectlSegment(t *testing.T) {
 			kubectlExists:       tc.KubectlExists,
 			template:            tc.Template,
 			displayError:        tc.DisplayError,
-			context:       tc.Context,
+			kubectlOutContext:   tc.Context,
-			namespace:     tc.Namespace,
+			kubectlOutNamespace: tc.Namespace,
+			kubectlOutUser:      tc.User,
+			kubectlOutCluster:   tc.Cluster,
 			kubectlErr:          tc.KubectlErr,
+			parseKubeConfig:     tc.ParseKubeConfig,
+			files:               tc.Files,
+			kubeconfig:          tc.Kubeconfig,
 		}
 		kubectl := bootStrapKubectlTest(args)
 		assert.Equal(t, tc.ExpectedEnabled, kubectl.enabled(), tc.Case)
+		if tc.ExpectedEnabled {
 			assert.Equal(t, tc.ExpectedString, kubectl.string(), tc.Case)
 		}
 	}
+}
+
+var testKubeConfigFiles = map[string]string{
+	filepath.Join("testhome", ".kube/config"): `
+apiVersion: v1
+contexts:
+  - context:
+      cluster: ddd
+      user: ccc
+      namespace: bbb
+    name: aaa
+current-context: aaa
+`,
+	"contextdefinition": `
+apiVersion: v1
+contexts:
+  - context:
+      cluster: cl
+      user: usr
+      namespace: ns
+    name: ctx
+`,
+	"currentcontextmarker": `
+apiVersion: v1
+current-context: ctx
+`,
+	"invalid": "this is not yaml",
+	"contextdefinitionincomplete": `
+apiVersion: v1
+contexts:
+  - name: ctx
+`,
+	"contextredefinition": `
+apiVersion: v1
+contexts:
+  - context:
+      cluster: wrongcl
+      user: wrongu
+      namespace: wrongns
+    name: ctx
+`,
+}

themes/schema.json

@@ -866,6 +866,12 @@
                     "title": "Display Error",
                     "description": "Show the error context when failing to retrieve the kubectl information",
                     "default": false
+                  },
+                  "parse_kubeconfig": {
+                    "type": "boolean",
+                    "title": "Parse kubeconfig",
+                    "description": "Parse kubeconfig files instead of calling out to kubectl to improve performance.",
+                    "default": false
                   }
                 }
               }