feat(helm): add ability for --dry-run to do lookup functions

When a helm command is run with the --dry-run flag, it will try to connect to the cluster
if the value is 'server' to be able to render lookup functions.
Closes #8137

Signed-off-by: Tapas Kapadia <tapaskapadia10@gmail.com>

cmd/helm/install.go

@@ -154,7 +154,8 @@ func newInstallCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 
 func addInstallFlags(cmd *cobra.Command, f *pflag.FlagSet, client *action.Install, valueOpts *values.Options) {
 	f.BoolVar(&client.CreateNamespace, "create-namespace", false, "create the release namespace if not present")
-	f.BoolVar(&client.DryRun, "dry-run", false, "simulate an install")
+	f.StringVar(&client.DryRun, "dry-run", "none", "simulate an install. If --dry-run is set with no option being specified or as 'client', it will not attempt cluster connections. Setting option as 'server' allows attempting cluster connections.")
+	f.Lookup("dry-run").NoOptDefVal = "client"
 	f.BoolVar(&client.Force, "force", false, "force resource updates through a replacement strategy")
 	f.BoolVar(&client.DisableHooks, "no-hooks", false, "prevent hooks from running during install")
 	f.BoolVar(&client.Replace, "replace", false, "re-use the given name, only if that name is a deleted release which remains in the history. This is unsafe in production")
@@ -261,6 +262,11 @@ func runInstall(args []string, client *action.Install, valueOpts *values.Options
 
 	client.Namespace = settings.Namespace()
 
+	// validate dry-run flag value is one of the allowed values
+	if err := validateDryRunFlag(client); err != nil {
+		return nil, err
+	}
+
 	// Create context and prepare the handle of SIGTERM
 	ctx := context.Background()
 	ctx, cancel := context.WithCancel(ctx)
@@ -301,3 +307,19 @@ func compInstall(args []string, toComplete string, client *action.Install) ([]st
 	}
 	return nil, cobra.ShellCompDirectiveNoFileComp
 }
+
+func validateDryRunFlag(client *action.Install) error {
+	// validate dry-run flag value with set of allowed value
+	allowedDryRunValues := []string{"false", "true", "none", "client", "server"}
+	isAllowed := false
+	for _, v := range allowedDryRunValues {
+		if client.DryRun == v {
+			isAllowed = true
+			break
+		}
+	}
+	if !isAllowed {
+		return errors.New("Invalid dry-run flag. Flag must one of the following: false, true, none, client, sever")
+	} 
+	return nil
+}

cmd/helm/template.go

@@ -73,7 +73,7 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 				client.KubeVersion = parsedKubeVersion
 			}
 
-			client.DryRun = true
+			client.DryRun = "client"
 			client.ReleaseName = "release-name"
 			client.Replace = true // Skip the name check
 			client.ClientOnly = !validate

cmd/helm/upgrade.go

@@ -120,6 +120,11 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 					instClient.Description = client.Description
 					instClient.DependencyUpdate = client.DependencyUpdate
 
+					// validate dry-run flag value is one of the allowed values
+					if err := validateDryRunFlag(instClient); err != nil {
+						return err
+					}
+
 					rel, err := runInstall(args, instClient, valueOpts, out)
 					if err != nil {
 						return err
@@ -214,7 +219,8 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 	f.BoolVar(&createNamespace, "create-namespace", false, "if --install is set, create the release namespace if not present")
 	f.BoolVarP(&client.Install, "install", "i", false, "if a release by this name doesn't already exist, run an install")
 	f.BoolVar(&client.Devel, "devel", false, "use development versions, too. Equivalent to version '>0.0.0-0'. If --version is set, this is ignored")
-	f.BoolVar(&client.DryRun, "dry-run", false, "simulate an upgrade")
+	f.StringVar(&client.DryRun, "dry-run", "none", "simulate an install. If --dry-run is set with no option being specified or as 'client', it will not attempt cluster connections. Setting option as 'server' allows attempting cluster connections.")
+	f.Lookup("dry-run").NoOptDefVal = "client"
 	f.BoolVar(&client.Recreate, "recreate-pods", false, "performs pods restart for the resource if applicable")
 	f.MarkDeprecated("recreate-pods", "functionality will no longer be updated. Consult the documentation for other methods to recreate pods")
 	f.BoolVar(&client.Force, "force", false, "force resource updates through a replacement strategy")

pkg/action/action.go

@@ -102,7 +102,7 @@ type Configuration struct {
 // TODO: This function is badly in need of a refactor.
 // TODO: As part of the refactor the duplicate code in cmd/helm/template.go should be removed
 //       This code has to do with writing files to disk.
-func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, interactWithRemote bool) ([]*release.Hook, *bytes.Buffer, string, error) {
+func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun string) ([]*release.Hook, *bytes.Buffer, string, error) {
 	hs := []*release.Hook{}
 	b := bytes.NewBuffer(nil)
 
@@ -121,11 +121,11 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 	var err2 error
 
 	// A `helm template`  should not talk to the remote cluster. However, commands
-	// with `--dry-run` should be able to try to connect to the cluster.
+	// with `--dry-run` with the value of false, none, or sever should try to connect to the cluster.
 	// This enables the ability to render 'lookup' functions.
 	// It may break in interesting and exotic ways because other data (e.g. discovery)
 	// is mocked.
-	if interactWithRemote && cfg.RESTClientGetter != nil {
+	if (dryRun == "server" ||  dryRun == "none" || dryRun == "false") && cfg.RESTClientGetter != nil {
 		restConfig, err := cfg.RESTClientGetter.ToRESTConfig()
 		if err != nil {
 			return hs, b, "", err

pkg/action/install.go

@@ -71,7 +71,7 @@ type Install struct {
 	ClientOnly               bool
 	Force                    bool
 	CreateNamespace          bool
-	DryRun                   bool
+	DryRun                   string
 	DisableHooks             bool
 	Replace                  bool
 	Wait                     bool
@@ -128,6 +128,8 @@ type ChartPathOptions struct {
 func NewInstall(cfg *Configuration) *Install {
 	in := &Install{
 		cfg: cfg,
+		// Set default value of DryRun for before flags are binded (tests)
+		DryRun: "none",
 	}
 	in.ChartPathOptions.registryClient = cfg.RegistryClient
 
@@ -207,7 +209,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	// contacts the upstream server and builds the capabilities object.
 	if crds := chrt.CRDObjects(); !i.ClientOnly && !i.SkipCRDs && len(crds) > 0 {
 		// On dry run, bail here
-		if i.DryRun {
+		if i.DryRun != "none" && i.DryRun != "false" {
 			i.cfg.Log("WARNING: This chart or one of its subcharts contains CRDs. Rendering may fail or contain inaccuracies.")
 		} else if err := i.installCRDs(crds); err != nil {
 			return nil, err
@@ -241,7 +243,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	}
 
 	// special case for helm template --is-upgrade
-	isUpgrade := i.IsUpgrade && i.DryRun
+	isUpgrade := i.IsUpgrade && (i.DryRun != "none" && i.DryRun != "false") 
 	options := chartutil.ReleaseOptions{
 		Name:      i.ReleaseName,
 		Namespace: i.Namespace,
@@ -261,8 +263,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	// as they both set the Install.DryRun field to `true`. The `--dry-run` flag should be able
 	// to connect to remote for the lookup function. `helm template` is the only command that
 	// Install.APIVersions field will not be nil.
-	interactWithRemote := !i.DryRun || i.APIVersions == nil
-	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, interactWithRemote)
+	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun)
 	// Even for errors, attach this if available
 	if manifestDoc != nil {
 		rel.Manifest = manifestDoc.String()
@@ -303,7 +304,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	}
 
 	// Bail out here if it is a dry run
-	if i.DryRun {
+	if i.DryRun != "none" && i.DryRun != "false" {
 		rel.Info.Description = "Dry run complete"
 		return rel, nil
 	}
@@ -472,7 +473,8 @@ func (i *Install) availableName() error {
 	if err := chartutil.ValidateReleaseName(start); err != nil {
 		return errors.Wrapf(err, "release name %q", start)
 	}
-	if i.DryRun {
+	// On dry run, bail here
+	if i.DryRun != "none" && i.DryRun != "false" {
 		return nil
 	}
 

pkg/action/install_test.go

@@ -234,7 +234,7 @@ func TestInstallRelease_WithChartAndDependencyAllNotes(t *testing.T) {
 func TestInstallRelease_DryRun(t *testing.T) {
 	is := assert.New(t)
 	instAction := installAction(t)
-	instAction.DryRun = true
+	instAction.DryRun = "true"
 	vals := map[string]interface{}{}
 	res, err := instAction.Run(buildChart(withSampleTemplates()), vals)
 	if err != nil {
@@ -258,7 +258,7 @@ func TestInstallRelease_DryRun(t *testing.T) {
 func TestInstallRelease_DryRun_Lookup(t *testing.T) {
 	is := assert.New(t)
 	instAction := installAction(t)
-	instAction.DryRun = true
+	instAction.DryRun = "true"
 	vals := map[string]interface{}{}
 
 	mockChart := buildChart(withSampleTemplates())
@@ -278,7 +278,7 @@ func TestInstallRelease_DryRun_Lookup(t *testing.T) {
 func TestInstallReleaseIncorrectTemplate_DryRun(t *testing.T) {
 	is := assert.New(t)
 	instAction := installAction(t)
-	instAction.DryRun = true
+	instAction.DryRun = "true"
 	vals := map[string]interface{}{}
 	_, err := instAction.Run(buildChart(withSampleIncludingIncorrectTemplates()), vals)
 	expectedErr := "\"hello/templates/incorrect\" at <.Values.bad.doh>: nil pointer evaluating interface {}.doh"

pkg/action/upgrade.go

@@ -70,8 +70,7 @@ type Upgrade struct {
 	// DisableHooks disables hook processing if set to true.
 	DisableHooks bool
 	// DryRun controls whether the operation is prepared, but not executed.
-	// If `true`, the upgrade is prepared but not performed.
-	DryRun bool
+	DryRun string
 	// Force will, if set to `true`, ignore certain warnings and perform the upgrade anyway.
 	//
 	// This should be used with caution.
@@ -114,6 +113,8 @@ type resultMessage struct {
 func NewUpgrade(cfg *Configuration) *Upgrade {
 	up := &Upgrade{
 		cfg: cfg,
+		// Set default value of DryRun for before flags are binded (tests)
+		DryRun: "none",
 	}
 	up.ChartPathOptions.registryClient = cfg.RegistryClient
 
@@ -152,8 +153,8 @@ func (u *Upgrade) RunWithContext(ctx context.Context, name string, chart *chart.
 	if err != nil {
 		return res, err
 	}
-
-	if !u.DryRun {
+	// Do not update for dry runs
+	if u.DryRun == "none" || u.DryRun == "false"  {
 		u.cfg.Log("updating status for upgraded release for %s", name)
 		if err := u.cfg.Releases.Update(upgradedRelease); err != nil {
 			return res, err
@@ -230,8 +231,8 @@ func (u *Upgrade) prepareUpgrade(name string, chart *chart.Chart, vals map[strin
 	if err != nil {
 		return nil, nil, err
 	}
-	// Interacts with cluster if possible
-	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, true)
+
+	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -309,7 +310,8 @@ func (u *Upgrade) performUpgrade(ctx context.Context, originalRelease, upgradedR
 		return nil
 	})
 
-	if u.DryRun {
+	// Run if it is a dry run
+	if u.DryRun != "none" && u.DryRun != "false" {
 		u.cfg.Log("dry run for %s", upgradedRelease.Name)
 		if len(u.Description) > 0 {
 			upgradedRelease.Info.Description = u.Description