feat(template): introduce --validate

This feature flag allows `helm template` to be used against a live cluster. Some charts need CRDs to be applied to the cluster before calling `helm install`. This allows users to validate their templates will render with those resources set.

Signed-off-by: Matthew Fisher <matt.fisher@microsoft.com>

cmd/helm/root.go

@@ -172,6 +172,7 @@ func newRootCmd(actionConfig *action.Configuration, out io.Writer, args []string
 		newReleaseTestCmd(actionConfig, out),
 		newRollbackCmd(actionConfig, out),
 		newStatusCmd(actionConfig, out),
+		newTemplateCmd(actionConfig, out),
 		newUninstallCmd(actionConfig, out),
 		newUpgradeCmd(actionConfig, out),
 
@@ -179,7 +180,6 @@ func newRootCmd(actionConfig *action.Configuration, out io.Writer, args []string
 		newHomeCmd(out),
 		newInitCmd(out),
 		newPluginCmd(out),
-		newTemplateCmd(out),
 		newVersionCmd(out),
 
 		// Hidden documentation generator command: 'helm docs'

cmd/helm/template.go

@@ -19,18 +19,12 @@ package main
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
 	"strings"
 
 	"github.com/spf13/cobra"
-	"github.com/spf13/pflag"
 
 	"helm.sh/helm/cmd/helm/require"
 	"helm.sh/helm/pkg/action"
-	"helm.sh/helm/pkg/chartutil"
-	kubefake "helm.sh/helm/pkg/kube/fake"
-	"helm.sh/helm/pkg/storage"
-	"helm.sh/helm/pkg/storage/driver"
 )
 
 const templateDesc = `
@@ -42,18 +36,9 @@ of the server-side testing of chart validity (e.g. whether an API is supported)
 is done.
 `
 
-func newTemplateCmd(out io.Writer) *cobra.Command {
-	customConfig := &action.Configuration{
-		// Add mock objects in here so it doesn't use Kube API server
-		Releases:     storage.Init(driver.NewMemory()),
-		KubeClient:   &kubefake.PrintingKubeClient{Out: ioutil.Discard},
-		Capabilities: chartutil.DefaultCapabilities,
-		Log: func(format string, v ...interface{}) {
-			fmt.Fprintf(out, format, v...)
-		},
-	}
-
-	client := action.NewInstall(customConfig)
+func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
+	var validate bool
+	client := action.NewInstall(cfg)
 
 	cmd := &cobra.Command{
 		Use:   "template [NAME] [CHART]",
@@ -64,6 +49,7 @@ func newTemplateCmd(out io.Writer) *cobra.Command {
 			client.DryRun = true
 			client.ReleaseName = "RELEASE-NAME"
 			client.Replace = true // Skip the name check
+			client.ClientOnly = !validate
 			rel, err := runInstall(args, client, out)
 			if err != nil {
 				return err
@@ -73,12 +59,10 @@ func newTemplateCmd(out io.Writer) *cobra.Command {
 		},
 	}
 
-	addInstallFlags(cmd.Flags(), client)
-	addTemplateFlags(cmd.Flags(), client)
+	f := cmd.Flags()
+	addInstallFlags(f, client)
+	f.StringVar(&client.OutputDir, "output-dir", "", "writes the executed templates to files in output-dir instead of stdout")
+	f.BoolVar(&validate, "validate", false, "establish a connection to Kubernetes for schema validation")
 
 	return cmd
 }
-
-func addTemplateFlags(f *pflag.FlagSet, client *action.Install) {
-	f.StringVar(&client.OutputDir, "output-dir", "", "writes the executed templates to files in output-dir instead of stdout")
-}

pkg/action/install.go

@@ -41,9 +41,12 @@ import (
 	"helm.sh/helm/pkg/engine"
 	"helm.sh/helm/pkg/getter"
 	"helm.sh/helm/pkg/hooks"
+	kubefake "helm.sh/helm/pkg/kube/fake"
 	"helm.sh/helm/pkg/release"
 	"helm.sh/helm/pkg/releaseutil"
 	"helm.sh/helm/pkg/repo"
+	"helm.sh/helm/pkg/storage"
+	"helm.sh/helm/pkg/storage/driver"
 	"helm.sh/helm/pkg/strvals"
 	"helm.sh/helm/pkg/version"
 )
@@ -70,6 +73,7 @@ type Install struct {
 	ChartPathOptions
 	ValueOptions
 
+	ClientOnly       bool
 	DryRun           bool
 	DisableHooks     bool
 	Replace          bool
@@ -119,6 +123,14 @@ func (i *Install) Run(chrt *chart.Chart) (*release.Release, error) {
 		return nil, err
 	}
 
+	if i.ClientOnly {
+		// Add mock objects in here so it doesn't use Kube API server
+		// NOTE(bacongobbler): used for `helm template`
+		i.cfg.Capabilities = chartutil.DefaultCapabilities
+		i.cfg.KubeClient = &kubefake.PrintingKubeClient{Out: ioutil.Discard}
+		i.cfg.Releases = storage.Init(driver.NewMemory())
+	}
+
 	// Make sure if Atomic is set, that wait is set as well. This makes it so
 	// the user doesn't have to specify both
 	i.Wait = i.Wait || i.Atomic

pkg/action/install_test.go

@@ -29,9 +29,10 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"helm.sh/helm/internal/test"
+	"helm.sh/helm/pkg/chartutil"
+	kubefake "helm.sh/helm/pkg/kube/fake"
 	"helm.sh/helm/pkg/release"
 	"helm.sh/helm/pkg/storage/driver"
-	kubefake "helm.sh/helm/pkg/kube/fake"
 )
 
 type nameTemplateTestCase struct {
@@ -74,6 +75,16 @@ func TestInstallRelease(t *testing.T) {
 	is.Equal(rel.Info.Description, "Install complete")
 }
 
+func TestInstallReleaseClientOnly(t *testing.T) {
+	is := assert.New(t)
+	instAction := installAction(t)
+	instAction.ClientOnly = true
+	instAction.Run(buildChart()) // disregard output
+
+	is.Equal(instAction.cfg.Capabilities, chartutil.DefaultCapabilities)
+	is.Equal(instAction.cfg.KubeClient, &kubefake.PrintingKubeClient{Out: ioutil.Discard})
+}
+
 func TestInstallRelease_NoName(t *testing.T) {
 	instAction := installAction(t)
 	instAction.ReleaseName = ""