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

@@ -263,7 +263,7 @@ 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 {
+	if err := validateDryRunFlag(client.DryRun); err != nil {
 		return nil, err
 	}
 
@@ -308,12 +308,12 @@ func compInstall(args []string, toComplete string, client *action.Install) ([]st
 	return nil, cobra.ShellCompDirectiveNoFileComp
 }
 
-func validateDryRunFlag(client *action.Install) error {
+func validateDryRunFlag(dryRunFlagValue string) 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 {
+		if dryRunFlagValue == v {
 			isAllowed = true
 			break
 		}

cmd/helm/upgrade.go

@@ -120,11 +120,6 @@ 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
@@ -144,6 +139,10 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 			if err != nil {
 				return err
 			}
+			// validate dry-run flag value is one of the allowed values
+			if err := validateDryRunFlag(client.DryRun); err != nil {
+				return err
+			}
 
 			p := getter.All(settings)
 			vals, err := valueOpts.MergeValues(p)

pkg/action/action.go

@@ -125,7 +125,7 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 	// 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 (dryRun == "server" ||  dryRun == "none" || dryRun == "false") && 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

@@ -243,7 +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 != "none" && i.DryRun != "false") 
+	isUpgrade := i.IsUpgrade && (i.DryRun != "none" && i.DryRun != "false")
 	options := chartutil.ReleaseOptions{
 		Name:      i.ReleaseName,
 		Namespace: i.Namespace,

pkg/action/upgrade.go

@@ -154,7 +154,7 @@ func (u *Upgrade) RunWithContext(ctx context.Context, name string, chart *chart.
 		return res, err
 	}
 	// Do not update for dry runs
-	if u.DryRun == "none" || u.DryRun == "false"  {
+	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