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

cmd/helm/install.go

@@ -142,6 +142,9 @@ func newInstallCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 			}
 			client.SetRegistryClient(registryClient)
 
+			if client.DryRunOption == "unchanged" {
+				client.DryRunOption = "none"
+			}
 			rel, err := runInstall(args, client, valueOpts, out)
 			if err != nil {
 				return errors.Wrap(err, "INSTALLATION FAILED")
@@ -160,7 +163,8 @@ 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.DryRunOption, "dry-run", "unchanged", "simulate an install. If --dry-run is set with no option being specified or as '--dry-run=client', it will not attempt cluster connections. Setting '--dry-run=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")
@@ -268,6 +272,11 @@ func runInstall(args []string, client *action.Install, valueOpts *values.Options
 
 	client.Namespace = settings.Namespace()
 
+	// Validate DryRunOption member is one of the allowed values
+	if err := validateDryRunOptionFlag(client.DryRunOption); err != nil {
+		return nil, err
+	}
+
 	// Create context and prepare the handle of SIGTERM
 	ctx := context.Background()
 	ctx, cancel := context.WithCancel(ctx)
@@ -308,3 +317,19 @@ func compInstall(args []string, toComplete string, client *action.Install) ([]st
 	}
 	return nil, cobra.ShellCompDirectiveNoFileComp
 }
+
+func validateDryRunOptionFlag(dryRunOptionFlagValue string) error {
+	// Validate dry-run flag value with a set of allowed value
+	allowedDryRunValues := []string{"false", "true", "none", "client", "server"}
+	isAllowed := false
+	for _, v := range allowedDryRunValues {
+		if dryRunOptionFlagValue == v {
+			isAllowed = true
+			break
+		}
+	}
+	if !isAllowed {
+		return errors.New("Invalid dry-run flag. Flag must one of the following: false, true, none, client, server")
+	}
+	return nil
+}

cmd/helm/template.go

@@ -79,6 +79,9 @@ func newTemplateCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 			}
 			client.SetRegistryClient(registryClient)
 
+			if client.DryRunOption == "unchanged" {
+				client.DryRunOption = "true"
+			}
 			client.DryRun = true
 			client.ReleaseName = "release-name"
 			client.Replace = true // Skip the name check

cmd/helm/upgrade.go

@@ -96,6 +96,9 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 			}
 			client.SetRegistryClient(registryClient)
 
+			if client.DryRunOption == "unchanged" {
+				client.DryRunOption = "none"
+			}
 			// Fixes #7002 - Support reading values from STDIN for `upgrade` command
 			// Must load values AFTER determining if we have to call install so that values loaded from stdin are are not read twice
 			if client.Install {
@@ -112,6 +115,7 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 					instClient.ChartPathOptions = client.ChartPathOptions
 					instClient.Force = client.Force
 					instClient.DryRun = client.DryRun
+					instClient.DryRunOption = client.DryRunOption
 					instClient.DisableHooks = client.DisableHooks
 					instClient.SkipCRDs = client.SkipCRDs
 					instClient.Timeout = client.Timeout
@@ -146,6 +150,10 @@ 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 := validateDryRunOptionFlag(client.DryRunOption); err != nil {
+				return err
+			}
 
 			p := getter.All(settings)
 			vals, err := valueOpts.MergeValues(p)
@@ -221,7 +229,8 @@ 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.DryRunOption, "dry-run", "unchanged", "simulate an install. If --dry-run is set with no option being specified or as '--dry-run=client', it will not attempt cluster connections. Setting '--dry-run=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

@@ -103,7 +103,7 @@ type Configuration struct {
 // 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, dryRun, enableDNS 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, interactWithRemote, enableDNS bool) ([]*release.Hook, *bytes.Buffer, string, error) {
 	hs := []*release.Hook{}
 	b := bytes.NewBuffer(nil)
 
@@ -121,12 +121,10 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 	var files map[string]string
 	var err2 error
 
-	// A `helm template` or `helm install --dry-run` should not talk to the remote cluster.
-	// It will break in interesting and exotic ways because other data (e.g. discovery)
-	// is mocked. It is not up to the template author to decide when the user wants to
-	// connect to the cluster. So when the user says to dry run, respect the user's
-	// wishes and do not connect to the cluster.
-	if !dryRun && cfg.RESTClientGetter != nil {
+	// A `helm template` should not talk to the remote cluster. However, commands with the flag
+	//`--dry-run` with the value of `false`, `none`, or `server` should try to interact with the cluster.
+	// It may break in interesting and exotic ways because other data (e.g. discovery) is mocked.
+	if interactWithRemote && cfg.RESTClientGetter != nil {
 		restConfig, err := cfg.RESTClientGetter.ToRESTConfig()
 		if err != nil {
 			return hs, b, "", err

pkg/action/install.go

@@ -73,6 +73,7 @@ type Install struct {
 	Force                    bool
 	CreateNamespace          bool
 	DryRun                   bool
+	DryRunOption             string
 	DisableHooks             bool
 	Replace                  bool
 	Wait                     bool
@@ -227,6 +228,16 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 		return nil, err
 	}
 
+	// Determine dry run behavior
+	if i.DryRun || i.DryRunOption == "client" || i.DryRunOption == "server" || i.DryRunOption == "true" {
+		i.DryRun = true
+	}
+
+	var interactWithRemote bool
+	if !i.DryRun || i.DryRunOption == "server" || i.DryRunOption == "none" || i.DryRunOption == "false" {
+		interactWithRemote = true
+	}
+
 	// Pre-install anything in the crd/ directory. We do this before Helm
 	// contacts the upstream server and builds the capabilities object.
 	if crds := chrt.CRDObjects(); !i.ClientOnly && !i.SkipCRDs && len(crds) > 0 {
@@ -281,7 +292,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	rel := i.createRelease(chrt, vals)
 
 	var manifestDoc *bytes.Buffer
-	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, i.EnableDNS)
+	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, i.EnableDNS)
 	// Even for errors, attach this if available
 	if manifestDoc != nil {
 		rel.Manifest = manifestDoc.String()
@@ -491,6 +502,7 @@ func (i *Install) availableName() error {
 	if err := chartutil.ValidateReleaseName(start); err != nil {
 		return errors.Wrapf(err, "release name %q", start)
 	}
+	// On dry run, bail here
 	if i.DryRun {
 		return nil
 	}

pkg/action/install_test.go

@@ -254,7 +254,7 @@ func TestInstallRelease_DryRun(t *testing.T) {
 	is.Equal(res.Info.Description, "Dry run complete")
 }
 
-// Regression test for #7955: Lookup must not connect to Kubernetes on a dry-run.
+// Regression test for #7955
 func TestInstallRelease_DryRun_Lookup(t *testing.T) {
 	is := assert.New(t)
 	instAction := installAction(t)

pkg/action/upgrade.go

@@ -71,8 +71,9 @@ 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
+	// DryRunOption controls whether the operation is prepared, but not executed with options on whether or not to interact with the remote cluster.
+	DryRunOption string
 	// Force will, if set to `true`, ignore certain warnings and perform the upgrade anyway.
 	//
 	// This should be used with caution.
@@ -147,6 +148,12 @@ func (u *Upgrade) RunWithContext(ctx context.Context, name string, chart *chart.
 	if err := chartutil.ValidateReleaseName(name); err != nil {
 		return nil, errors.Errorf("release name is invalid: %s", name)
 	}
+
+	// Determine dry run behavior
+	if u.DryRun || u.DryRunOption == "client" || u.DryRunOption == "server" || u.DryRunOption == "true" {
+		u.DryRun = true
+	}
+
 	u.cfg.Log("preparing upgrade for %s", name)
 	currentRelease, upgradedRelease, err := u.prepareUpgrade(name, chart, vals)
 	if err != nil {
@@ -161,6 +168,7 @@ func (u *Upgrade) RunWithContext(ctx context.Context, name string, chart *chart.
 		return res, err
 	}
 
+	// Do not update for dry runs
 	if !u.DryRun {
 		u.cfg.Log("updating status for upgraded release for %s", name)
 		if err := u.cfg.Releases.Update(upgradedRelease); err != nil {
@@ -239,7 +247,13 @@ func (u *Upgrade) prepareUpgrade(name string, chart *chart.Chart, vals map[strin
 		return nil, nil, err
 	}
 
-	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun, u.EnableDNS)
+	// Determine whether or not to interact with remote
+	var interactWithRemote bool
+	if !u.DryRun || u.DryRunOption == "server" {
+		interactWithRemote = true
+	}
+
+	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, interactWithRemote, u.EnableDNS)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -317,6 +331,7 @@ func (u *Upgrade) performUpgrade(ctx context.Context, originalRelease, upgradedR
 		return nil
 	})
 
+	// Run if it is a dry run
 	if u.DryRun {
 		u.cfg.Log("dry run for %s", upgradedRelease.Name)
 		if len(u.Description) > 0 {