feat: show live output from the Helm binary (#286)

* feat: show live output from the Helm binary

Signed-off-by: Rodrigo Fior Kuntzer <rodrigo@miro.com>

* fixup! Merge branch 'main' into enable-live-output

Signed-off-by: Yusuke Kuoka <ykuoka@gmail.com>

.github/workflows/ci.yaml

@@ -52,16 +52,32 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        helm-version:
+       include:
-          - v3.4.2
+         # We intend to support 2 helm minor version at a time.
-          - v3.5.4
+         # What's why we include only 2 helm minor versions in this matrix.
-          - v3.6.3
+         # See https://github.com/helmfile/helmfile/pull/286#issuecomment-1250161182 for more context.
-          - v3.7.2
+         - helm-version: v3.8.2
-          - v3.8.2
+           plugin-secrets-version: 3.15.0
-          - v3.9.4
+           extra-helmfile-flags:
-        plugin-secrets-version:
+         - helm-version: v3.8.2
-          - 3.15.0
+           # We assume that the helm-secrets plugin is supposed to
-          - 4.0.0
+           # work with the two most recent helm minor versions.
+           # Once it turned out to be not practically true,
+           # we will mark this combination as failable,
+           # and instruct users to upgrade helm and helm-secrets at once.
+           plugin-secrets-version: 4.0.0
+           extra-helmfile-flags:
+         - helm-version: v3.9.4
+           plugin-secrets-version: 3.15.0
+           extra-helmfile-flags:
+         - helm-version: v3.9.4
+           plugin-secrets-version: 4.0.0
+           extra-helmfile-flags:
+         # In case you need to test some optional helmfile features,
+         # enable it via extra-helmfile-flags below.
+         - helm-version: v3.9.4
+           plugin-secrets-version: 4.0.0
+           extra-helmfile-flags: "--enable-live-output"
     steps:
     - uses: actions/checkout@v2
     - name: Cache libraries
@@ -102,4 +118,5 @@ jobs:
         HELM_SECRETS_VERSION: ${{ matrix.plugin-secrets-version }}
         HELMFILE_HELM3: 1
         TERM: xterm
+        EXTRA_HELMFILE_FLAGS: ${{ matrix.extra-helmfile-flags }}
       run: make integration

cmd/root.go

@@ -122,6 +122,8 @@ A release must match all labels in a group in order to be used. Multiple groups
 "--selector tier=frontend,tier!=proxy --selector tier=backend" will match all frontend, non-proxy releases AND all backend releases.
 The name of a release can be used as a label: "--selector name=myrelease"`)
 	fs.BoolVar(&globalOptions.AllowNoMatchingRelease, "allow-no-matching-release", false, `Do not exit with an error code if the provided selector has no matching releases.`)
+	fs.BoolVar(&globalOptions.EnableLiveOutput, "enable-live-output", globalOptions.EnableLiveOutput, `Show live output from the Helm binary Stdout/Stderr into Helmfile own Stdout/Stderr.
+	It only applies for the Helm CLI commands, Stdout/Stderr for Hooks are still displayed only when it's execution finishes.`)
 	// avoid 'pflag: help requested' error (#251)
 	fs.BoolP("help", "h", false, "help for helmfile")
 }

pkg/app/app.go

@@ -28,6 +28,7 @@ import (
 type App struct {
 	OverrideKubeContext string
 	OverrideHelmBinary  string
+	EnableLiveOutput    bool
 
 	Logger      *zap.SugaredLogger
 	Env         string
@@ -64,6 +65,7 @@ func New(conf ConfigProvider) *App {
 	return Init(&App{
 		OverrideKubeContext: conf.KubeContext(),
 		OverrideHelmBinary:  conf.HelmBinary(),
+		EnableLiveOutput:    conf.EnableLiveOutput(),
 		Logger:              conf.Logger(),
 		Env:                 conf.Env(),
 		Namespace:           conf.Namespace(),
@@ -84,6 +86,10 @@ func Init(app *App) *App {
 		panic(fmt.Sprintf("Failed to initialize vals runtime: %v", err))
 	}
 
+	if app.EnableLiveOutput {
+		app.Logger.Info("Live output is enabled")
+	}
+
 	return app
 }
 
@@ -213,6 +219,9 @@ func (a *App) Template(c TemplateConfigProvider) error {
 	return a.ForEachState(func(run *Run) (ok bool, errs []error) {
 		includeCRDs := c.IncludeCRDs()
 
+		// Live output should never be enabled for the "template" subcommand to avoid breaking `helmfile template | kubectl apply -f -`
+		run.helm.SetEnableLiveOutput(false)
+
 		// `helm template` in helm v2 does not support local chart.
 		// So, we set forceDownload=true for helm v2 only
 		prepErr := run.withPreparedCharts("template", state.ChartPrepareOptions{
@@ -717,6 +726,7 @@ func (a *App) loadDesiredStateFromYaml(file string, opts ...LoadOpts) (*state.He
 
 		overrideKubeContext: a.OverrideKubeContext,
 		overrideHelmBinary:  a.OverrideHelmBinary,
+		enableLiveOutput:    a.EnableLiveOutput,
 		getHelm:             a.getHelm,
 		valsRuntime:         a.valsRuntime,
 	}
@@ -755,7 +765,7 @@ func (a *App) getHelm(st *state.HelmState) helmexec.Interface {
 	key := createHelmKey(bin, kubectx)
 
 	if _, ok := a.helms[key]; !ok {
-		a.helms[key] = helmexec.New(bin, a.Logger, kubectx, &helmexec.ShellRunner{
+		a.helms[key] = helmexec.New(bin, a.EnableLiveOutput, a.Logger, kubectx, &helmexec.ShellRunner{
 			Logger: a.Logger,
 		})
 	}

pkg/app/app_test.go

@@ -2488,12 +2488,12 @@ func (mock *mockRunner) ExecuteStdIn(cmd string, args []string, env map[string]s
 	return []byte{}, nil
 }
 
-func (mock *mockRunner) Execute(cmd string, args []string, env map[string]string) ([]byte, error) {
+func (mock *mockRunner) Execute(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
 	return []byte{}, nil
 }
 
 func MockExecer(logger *zap.SugaredLogger, kubeContext string) helmexec.Interface {
-	execer := helmexec.New("helm", logger, kubeContext, &mockRunner{})
+	execer := helmexec.New("helm", false, logger, kubeContext, &mockRunner{})
 	return execer
 }
 
@@ -2538,6 +2538,8 @@ func (helm *mockHelmExec) SetExtraArgs(args ...string) {
 }
 func (helm *mockHelmExec) SetHelmBinary(bin string) {
 }
+func (helm *mockHelmExec) SetEnableLiveOutput(enableLiveOutput bool) {
+}
 func (helm *mockHelmExec) AddRepo(name, repository, cafile, certfile, keyfile, username, password string, managed string, passCredentials string, skipTLSVerify string) error {
 	helm.repos = append(helm.repos, mockRepo{Name: name})
 	return nil

pkg/app/config.go

@@ -5,6 +5,7 @@ import "go.uber.org/zap"
 type ConfigProvider interface {
 	Args() string
 	HelmBinary() string
+	EnableLiveOutput() bool
 
 	FileOrDir() string
 	KubeContext() string

pkg/app/desired_state_file_loader.go

@@ -24,6 +24,7 @@ const (
 type desiredStateLoader struct {
 	overrideKubeContext string
 	overrideHelmBinary  string
+	enableLiveOutput    bool
 
 	env       string
 	namespace string
@@ -162,7 +163,7 @@ func (ld *desiredStateLoader) loadFileWithOverrides(inheritedEnv, overrodeEnv *e
 }
 
 func (a *desiredStateLoader) underlying() *state.StateCreator {
-	c := state.NewCreator(a.logger, a.fs, a.valsRuntime, a.getHelm, a.overrideHelmBinary, a.remote)
+	c := state.NewCreator(a.logger, a.fs, a.valsRuntime, a.getHelm, a.overrideHelmBinary, a.remote, a.enableLiveOutput)
 	c.LoadFile = a.loadFile
 	return c
 }

pkg/app/mocks_test.go

@@ -46,6 +46,9 @@ func (helm *noCallHelmExec) SetExtraArgs(args ...string) {
 func (helm *noCallHelmExec) SetHelmBinary(bin string) {
 	helm.doPanic()
 }
+func (helm *noCallHelmExec) SetEnableLiveOutput(enableLiveOutput bool) {
+	helm.doPanic()
+}
 func (helm *noCallHelmExec) AddRepo(name, repository, cafile, certfile, keyfile, username, password string, managed string, passCredentials string, skipTLSVerify string) error {
 	helm.doPanic()
 	return nil

pkg/config/global.go

@@ -44,6 +44,8 @@ type GlobalOptions struct {
 	AllowNoMatchingRelease bool
 	// logger is the logger to use.
 	logger *zap.SugaredLogger
+	// EnableLiveOutput enables live output from the Helm binary stdout/stderr into Helmfile own stdout/stderr
+	EnableLiveOutput bool
 }
 
 // Logger returns the logger to use.
@@ -120,6 +122,11 @@ func (g *GlobalImpl) StateValuesFiles() []string {
 	return g.GlobalOptions.StateValuesFile
 }
 
+// EnableLiveOutput return when to pipe the stdout and stderr from Helm live to the helmfile stdout
+func (g *GlobalImpl) EnableLiveOutput() bool {
+	return g.GlobalOptions.EnableLiveOutput
+}
+
 // Logger returns the logger
 func (g *GlobalImpl) Logger() *zap.SugaredLogger {
 	return g.GlobalOptions.logger

pkg/event/bus.go

@@ -118,7 +118,7 @@ func (bus *Bus) Trigger(evt string, evtErr error, context map[string]interface{}
 			}
 		}
 
-		bytes, err := bus.Runner.Execute(command, args, map[string]string{})
+		bytes, err := bus.Runner.Execute(command, args, map[string]string{}, false)
 		bus.Logger.Debugf("hook[%s]: %s\n", name, string(bytes))
 		if hook.ShowLogs {
 			prefix := fmt.Sprintf("\nhook[%s] logs | ", evt)

pkg/event/bus_test.go

@@ -19,7 +19,7 @@ func (r *runner) ExecuteStdIn(cmd string, args []string, env map[string]string,
 	return []byte(""), nil
 }
 
-func (r *runner) Execute(cmd string, args []string, env map[string]string) ([]byte, error) {
+func (r *runner) Execute(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
 	if cmd == "ng" {
 		return nil, fmt.Errorf("cmd failed due to invalid cmd: %s", cmd)
 	}

pkg/exectest/helm.go

@@ -89,6 +89,8 @@ func (helm *Helm) SetExtraArgs(args ...string) {
 }
 func (helm *Helm) SetHelmBinary(bin string) {
 }
+func (helm *Helm) SetEnableLiveOutput(enableLiveOutput bool) {
+}
 func (helm *Helm) AddRepo(name, repository, cafile, certfile, keyfile, username, password string, managed string, passCredentials string, skipTLSVerify string) error {
 	helm.Repo = []string{name, repository, cafile, certfile, keyfile, username, password, managed, passCredentials, skipTLSVerify}
 	return nil

pkg/helmexec/exec.go

@@ -28,6 +28,7 @@ type decryptedSecret struct {
 
 type execer struct {
 	helmBinary           string
+	enableLiveOutput     bool
 	version              semver.Version
 	runner               Runner
 	logger               *zap.SugaredLogger
@@ -78,7 +79,7 @@ func parseHelmVersion(versionStr string) (semver.Version, error) {
 
 func getHelmVersion(helmBinary string, runner Runner) (semver.Version, error) {
 	// Autodetect from `helm version`
-	outBytes, err := runner.Execute(helmBinary, []string{"version", "--client", "--short"}, nil)
+	outBytes, err := runner.Execute(helmBinary, []string{"version", "--client", "--short"}, nil, false)
 	if err != nil {
 		return semver.Version{}, fmt.Errorf("error determining helm version: %w", err)
 	}
@@ -110,7 +111,7 @@ func redactedURL(chart string) string {
 
 // New for running helm commands
 // nolint: golint
-func New(helmBinary string, logger *zap.SugaredLogger, kubeContext string, runner Runner) *execer {
+func New(helmBinary string, enableLiveOutput bool, logger *zap.SugaredLogger, kubeContext string, runner Runner) *execer {
 	// TODO: proper error handling
 	version, err := getHelmVersion(helmBinary, runner)
 	if err != nil {
@@ -118,6 +119,7 @@ func New(helmBinary string, logger *zap.SugaredLogger, kubeContext string, runne
 	}
 	return &execer{
 		helmBinary:       helmBinary,
+		enableLiveOutput: enableLiveOutput,
 		version:          version,
 		logger:           logger,
 		kubeContext:      kubeContext,
@@ -134,6 +136,10 @@ func (helm *execer) SetHelmBinary(bin string) {
 	helm.helmBinary = bin
 }
 
+func (helm *execer) SetEnableLiveOutput(enableLiveOutput bool) {
+	helm.enableLiveOutput = enableLiveOutput
+}
+
 func (helm *execer) AddRepo(name, repository, cafile, certfile, keyfile, username, password string, managed string, passCredentials string, skipTLSVerify string) error {
 	var args []string
 	var out []byte
@@ -174,7 +180,7 @@ func (helm *execer) AddRepo(name, repository, cafile, certfile, keyfile, usernam
 			args = append(args, "--insecure-skip-tls-verify")
 		}
 		helm.logger.Infof("Adding repo %v %v", name, repository)
-		out, err = helm.exec(args, map[string]string{})
+		out, err = helm.exec(args, map[string]string{}, nil)
 	default:
 		helm.logger.Errorf("ERROR: unknown type '%v' for repository %v", managed, name)
 		out = nil
@@ -186,7 +192,7 @@ func (helm *execer) AddRepo(name, repository, cafile, certfile, keyfile, usernam
 
 func (helm *execer) UpdateRepo() error {
 	helm.logger.Info("Updating repo")
-	out, err := helm.exec([]string{"repo", "update"}, map[string]string{})
+	out, err := helm.exec([]string{"repo", "update"}, map[string]string{}, nil)
 	helm.info(out)
 	return err
 }
@@ -210,14 +216,14 @@ func (helm *execer) RegistryLogin(repository string, username string, password s
 
 func (helm *execer) BuildDeps(name, chart string) error {
 	helm.logger.Infof("Building dependency release=%v, chart=%v", name, chart)
-	out, err := helm.exec([]string{"dependency", "build", chart}, map[string]string{})
+	out, err := helm.exec([]string{"dependency", "build", chart}, map[string]string{}, nil)
 	helm.info(out)
 	return err
 }
 
 func (helm *execer) UpdateDeps(chart string) error {
 	helm.logger.Infof("Updating dependency %v", chart)
-	out, err := helm.exec([]string{"dependency", "update", chart}, map[string]string{})
+	out, err := helm.exec([]string{"dependency", "update", chart}, map[string]string{}, nil)
 	helm.info(out)
 	return err
 }
@@ -233,7 +239,7 @@ func (helm *execer) SyncRelease(context HelmContext, name, chart string, flags .
 		env["HELM_TILLER_HISTORY_MAX"] = strconv.Itoa(context.HistoryMax)
 	}
 
-	out, err := helm.exec(append(append(preArgs, "upgrade", "--install", "--reset-values", name, chart), flags...), env)
+	out, err := helm.exec(append(append(preArgs, "upgrade", "--install", "--reset-values", name, chart), flags...), env, nil)
 	helm.write(nil, out)
 	return err
 }
@@ -242,7 +248,7 @@ func (helm *execer) ReleaseStatus(context HelmContext, name string, flags ...str
 	helm.logger.Infof("Getting status %v", name)
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
-	out, err := helm.exec(append(append(preArgs, "status", name), flags...), env)
+	out, err := helm.exec(append(append(preArgs, "status", name), flags...), env, nil)
 	helm.write(nil, out)
 	return err
 }
@@ -258,7 +264,8 @@ func (helm *execer) List(context HelmContext, filter string, flags ...string) (s
 		args = []string{"list", filter}
 	}
 
-	out, err := helm.exec(append(append(preArgs, args...), flags...), env)
+	enableLiveOutput := false
+	out, err := helm.exec(append(append(preArgs, args...), flags...), env, &enableLiveOutput)
 	// In v2 we have been expecting `helm list FILTER` prints nothing.
 	// In v3 helm still prints the header like `NAME	NAMESPACE	REVISION	UPDATED	STATUS	CHART	APP VERSION`,
 	// which confuses helmfile's existing logic that treats any non-empty output from `helm list` is considered as the indication
@@ -308,7 +315,8 @@ func (helm *execer) DecryptSecret(context HelmContext, name string, flags ...str
 		if pluginVersion.Major() > 3 {
 			secretArg = "decrypt"
 		}
-		secretBytes, err := helm.exec(append(append(preArgs, "secrets", secretArg, absPath), flags...), env)
+		enableLiveOutput := false
+		secretBytes, err := helm.exec(append(append(preArgs, "secrets", secretArg, absPath), flags...), env, &enableLiveOutput)
 		if err != nil {
 			secret.err = err
 			return "", err
@@ -370,7 +378,7 @@ func (helm *execer) TemplateRelease(name string, chart string, flags ...string)
 		args = []string{"template", chart, "--name", name}
 	}
 
-	out, err := helm.exec(append(args, flags...), map[string]string{})
+	out, err := helm.exec(append(args, flags...), map[string]string{}, nil)
 
 	var outputToFile bool
 
@@ -407,7 +415,12 @@ func (helm *execer) DiffRelease(context HelmContext, name, chart string, suppres
 	}
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
-	out, err := helm.exec(append(append(preArgs, "diff", "upgrade", "--reset-values", "--allow-unreleased", name, chart), flags...), env)
+	var overrideEnableLiveOutput *bool = nil
+	if suppressDiff {
+		enableLiveOutput := false
+		overrideEnableLiveOutput = &enableLiveOutput
+	}
+	out, err := helm.exec(append(append(preArgs, "diff", "upgrade", "--reset-values", "--allow-unreleased", name, chart), flags...), env, overrideEnableLiveOutput)
 	// Do our best to write STDOUT only when diff existed
 	// Unfortunately, this works only when you run helmfile with `--detailed-exitcode`
 	detailedExitcodeEnabled := false
@@ -433,14 +446,14 @@ func (helm *execer) DiffRelease(context HelmContext, name, chart string, suppres
 
 func (helm *execer) Lint(name, chart string, flags ...string) error {
 	helm.logger.Infof("Linting release=%v, chart=%v", name, chart)
-	out, err := helm.exec(append([]string{"lint", chart}, flags...), map[string]string{})
+	out, err := helm.exec(append([]string{"lint", chart}, flags...), map[string]string{}, nil)
 	helm.write(nil, out)
 	return err
 }
 
 func (helm *execer) Fetch(chart string, flags ...string) error {
 	helm.logger.Infof("Fetching %v", redactedURL(chart))
-	out, err := helm.exec(append([]string{"fetch", chart}, flags...), map[string]string{})
+	out, err := helm.exec(append([]string{"fetch", chart}, flags...), map[string]string{}, nil)
 	helm.info(out)
 	return err
 }
@@ -463,7 +476,7 @@ func (helm *execer) ChartPull(chart string, flags ...string) error {
 	} else {
 		helmArgs = []string{"chart", "pull", chart}
 	}
-	out, err := helm.exec(append(helmArgs, flags...), map[string]string{"HELM_EXPERIMENTAL_OCI": "1"})
+	out, err := helm.exec(append(helmArgs, flags...), map[string]string{"HELM_EXPERIMENTAL_OCI": "1"}, nil)
 	helm.info(out)
 	return err
 }
@@ -478,7 +491,7 @@ func (helm *execer) ChartExport(chart string, path string, flags ...string) erro
 	} else {
 		helmArgs = []string{"chart", "export", chart}
 	}
-	out, err := helm.exec(append(append(helmArgs, "--destination", path), flags...), map[string]string{"HELM_EXPERIMENTAL_OCI": "1"})
+	out, err := helm.exec(append(append(helmArgs, "--destination", path), flags...), map[string]string{"HELM_EXPERIMENTAL_OCI": "1"}, nil)
 	helm.info(out)
 	return err
 }
@@ -487,7 +500,7 @@ func (helm *execer) DeleteRelease(context HelmContext, name string, flags ...str
 	helm.logger.Infof("Deleting %v", name)
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
-	out, err := helm.exec(append(append(preArgs, "delete", name), flags...), env)
+	out, err := helm.exec(append(append(preArgs, "delete", name), flags...), env, nil)
 	helm.write(nil, out)
 	return err
 }
@@ -497,12 +510,12 @@ func (helm *execer) TestRelease(context HelmContext, name string, flags ...strin
 	preArgs := context.GetTillerlessArgs(helm)
 	env := context.getTillerlessEnv()
 	args := []string{"test", name}
-	out, err := helm.exec(append(append(preArgs, args...), flags...), env)
+	out, err := helm.exec(append(append(preArgs, args...), flags...), env, nil)
 	helm.write(nil, out)
 	return err
 }
 
-func (helm *execer) exec(args []string, env map[string]string) ([]byte, error) {
+func (helm *execer) exec(args []string, env map[string]string, overrideEnableLiveOutput *bool) ([]byte, error) {
 	cmdargs := args
 	if len(helm.extra) > 0 {
 		cmdargs = append(cmdargs, helm.extra...)
@@ -512,7 +525,11 @@ func (helm *execer) exec(args []string, env map[string]string) ([]byte, error) {
 	}
 	cmd := fmt.Sprintf("exec: %s %s", helm.helmBinary, strings.Join(cmdargs, " "))
 	helm.logger.Debug(cmd)
-	outBytes, err := helm.runner.Execute(helm.helmBinary, cmdargs, env)
+	enableLiveOutput := helm.enableLiveOutput
+	if overrideEnableLiveOutput != nil {
+		enableLiveOutput = *overrideEnableLiveOutput
+	}
+	outBytes, err := helm.runner.Execute(helm.helmBinary, cmdargs, env, enableLiveOutput)
 	return outBytes, err
 }
 
@@ -534,7 +551,7 @@ func (helm *execer) azcli(name string) ([]byte, error) {
 	cmdargs := append(strings.Split("acr helm repo add --name", " "), name)
 	cmd := fmt.Sprintf("exec: az %s", strings.Join(cmdargs, " "))
 	helm.logger.Debug(cmd)
-	outBytes, err := helm.runner.Execute("az", cmdargs, map[string]string{})
+	outBytes, err := helm.runner.Execute("az", cmdargs, map[string]string{}, false)
 	helm.logger.Debugf("%s: %s", cmd, outBytes)
 	return outBytes, err
 }

pkg/helmexec/exec_test.go

@@ -29,13 +29,13 @@ func (mock *mockRunner) ExecuteStdIn(cmd string, args []string, env map[string]s
 	return mock.output, mock.err
 }
 
-func (mock *mockRunner) Execute(cmd string, args []string, env map[string]string) ([]byte, error) {
+func (mock *mockRunner) Execute(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
 	return mock.output, mock.err
 }
 
 // nolint: golint
 func MockExecer(logger *zap.SugaredLogger, kubeContext string) *execer {
-	execer := New("helm", logger, kubeContext, &mockRunner{})
+	execer := New("helm", false, logger, kubeContext, &mockRunner{})
 	return execer
 }
 
@@ -82,6 +82,17 @@ func Test_SetHelmBinary(t *testing.T) {
 	}
 }
 
+func Test_SetEnableLiveOutput(t *testing.T) {
+	helm := MockExecer(NewLogger(os.Stdout, "info"), "dev")
+	if helm.enableLiveOutput {
+		t.Error("helmexec.enableLiveOutput should not be enabled by default")
+	}
+	helm.SetEnableLiveOutput(true)
+	if !helm.enableLiveOutput {
+		t.Errorf("helmexec.SetEnableLiveOutput() - actual = %t expect = true", helm.enableLiveOutput)
+	}
+}
+
 func Test_AddRepo_Helm_3_3_2(t *testing.T) {
 	var buffer bytes.Buffer
 	logger := NewLogger(&buffer, "debug")
@@ -582,7 +593,7 @@ func Test_exec(t *testing.T) {
 	logger := NewLogger(&buffer, "debug")
 	helm := MockExecer(logger, "")
 	env := map[string]string{}
-	_, err := helm.exec([]string{"version"}, env)
+	_, err := helm.exec([]string{"version"}, env, nil)
 	expected := `exec: helm version
 `
 	if err != nil {
@@ -593,14 +604,14 @@ func Test_exec(t *testing.T) {
 	}
 
 	helm = MockExecer(logger, "dev")
-	ret, _ := helm.exec([]string{"diff"}, env)
+	ret, _ := helm.exec([]string{"diff"}, env, nil)
 	if len(ret) != 0 {
 		t.Error("helmexec.exec() - expected empty return value")
 	}
 
 	buffer.Reset()
 	helm = MockExecer(logger, "dev")
-	_, err = helm.exec([]string{"diff", "release", "chart", "--timeout 10", "--wait", "--wait-for-jobs"}, env)
+	_, err = helm.exec([]string{"diff", "release", "chart", "--timeout 10", "--wait", "--wait-for-jobs"}, env, nil)
 	expected = `exec: helm --kube-context dev diff release chart --timeout 10 --wait --wait-for-jobs
 `
 	if err != nil {
@@ -611,7 +622,7 @@ func Test_exec(t *testing.T) {
 	}
 
 	buffer.Reset()
-	_, err = helm.exec([]string{"version"}, env)
+	_, err = helm.exec([]string{"version"}, env, nil)
 	expected = `exec: helm --kube-context dev version
 `
 	if err != nil {
@@ -623,7 +634,7 @@ func Test_exec(t *testing.T) {
 
 	buffer.Reset()
 	helm.SetExtraArgs("foo")
-	_, err = helm.exec([]string{"version"}, env)
+	_, err = helm.exec([]string{"version"}, env, nil)
 	expected = `exec: helm --kube-context dev version foo
 `
 	if err != nil {
@@ -636,7 +647,7 @@ func Test_exec(t *testing.T) {
 	buffer.Reset()
 	helm = MockExecer(logger, "")
 	helm.SetHelmBinary("overwritten")
-	_, err = helm.exec([]string{"version"}, env)
+	_, err = helm.exec([]string{"version"}, env, nil)
 	expected = `exec: overwritten version
 `
 	if err != nil {
@@ -896,20 +907,20 @@ exec: helm --kube-context dev template https://example_user:example_password@rep
 
 func Test_IsHelm3(t *testing.T) {
 	helm2Runner := mockRunner{output: []byte("Client: v2.16.0+ge13bc94\n")}
-	helm := New("helm", NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
+	helm := New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
 	if helm.IsHelm3() {
 		t.Error("helmexec.IsHelm3() - Detected Helm 3 with Helm 2 version")
 	}
 
 	helm3Runner := mockRunner{output: []byte("v3.0.0+ge29ce2a\n")}
-	helm = New("helm", NewLogger(os.Stdout, "info"), "dev", &helm3Runner)
+	helm = New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm3Runner)
 	if !helm.IsHelm3() {
 		t.Error("helmexec.IsHelm3() - Failed to detect Helm 3")
 	}
 
 	t.Setenv(envvar.Helm3, "1")
 	helm2Runner = mockRunner{output: []byte("Client: v2.16.0+ge13bc94\n")}
-	helm = New("helm", NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
+	helm = New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
 	if !helm.IsHelm3() {
 		t.Errorf("helmexec.IsHelm3() - Helm3 not detected when %s is set", envvar.Helm3)
 	}
@@ -940,14 +951,14 @@ func Test_GetPluginVersion(t *testing.T) {
 
 func Test_GetVersion(t *testing.T) {
 	helm2Runner := mockRunner{output: []byte("Client: v2.16.1+ge13bc94\n")}
-	helm := New("helm", NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
+	helm := New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
 	ver := helm.GetVersion()
 	if ver.Major != 2 || ver.Minor != 16 || ver.Patch != 1 {
 		t.Errorf("helmexec.GetVersion - did not detect correct Helm2 version; it was: %+v", ver)
 	}
 
 	helm3Runner := mockRunner{output: []byte("v3.2.4+ge29ce2a\n")}
-	helm = New("helm", NewLogger(os.Stdout, "info"), "dev", &helm3Runner)
+	helm = New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm3Runner)
 	ver = helm.GetVersion()
 	if ver.Major != 3 || ver.Minor != 2 || ver.Patch != 4 {
 		t.Errorf("helmexec.GetVersion - did not detect correct Helm3 version; it was: %+v", ver)
@@ -956,7 +967,7 @@ func Test_GetVersion(t *testing.T) {
 
 func Test_IsVersionAtLeast(t *testing.T) {
 	helm2Runner := mockRunner{output: []byte("Client: v2.16.1+ge13bc94\n")}
-	helm := New("helm", NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
+	helm := New("helm", false, NewLogger(os.Stdout, "info"), "dev", &helm2Runner)
 	if !helm.IsVersionAtLeast("2.1.0") {
 		t.Error("helmexec.IsVersionAtLeast - 2.16.1 not atleast 2.1")
 	}

pkg/helmexec/helmexec.go

@@ -11,6 +11,7 @@ type Version struct {
 type Interface interface {
 	SetExtraArgs(args ...string)
 	SetHelmBinary(bin string)
+	SetEnableLiveOutput(enableLiveOutput bool)
 
 	AddRepo(name, repository, cafile, certfile, keyfile, username, password string, managed string, passCredentials string, skipTLSVerify string) error
 	UpdateRepo() error

pkg/helmexec/runner.go

@@ -1,6 +1,7 @@
 package helmexec
 
 import (
+	"bufio"
 	"bytes"
 	"errors"
 	"fmt"
@@ -16,7 +17,7 @@ import (
 
 // Runner interface for shell commands
 type Runner interface {
-	Execute(cmd string, args []string, env map[string]string) ([]byte, error)
+	Execute(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error)
 	ExecuteStdIn(cmd string, args []string, env map[string]string, stdin io.Reader) ([]byte, error)
 }
 
@@ -28,13 +29,18 @@ type ShellRunner struct {
 }
 
 // Execute a shell command
-func (shell ShellRunner) Execute(cmd string, args []string, env map[string]string) ([]byte, error) {
+func (shell ShellRunner) Execute(cmd string, args []string, env map[string]string, enableLiveOutput bool) ([]byte, error) {
 	preparedCmd := exec.Command(cmd, args...)
 	preparedCmd.Dir = shell.Dir
 	preparedCmd.Env = mergeEnv(os.Environ(), env)
+
+	if !enableLiveOutput {
 		return Output(preparedCmd, &logWriterGenerator{
 			log: shell.Logger,
 		})
+	} else {
+		return LiveOutput(preparedCmd, os.Stdout)
+	}
 }
 
 // Execute a shell command
@@ -94,6 +100,43 @@ func Output(c *exec.Cmd, logWriterGenerators ...*logWriterGenerator) ([]byte, er
 	return stdout.Bytes(), err
 }
 
+func LiveOutput(c *exec.Cmd, stdout io.Writer) ([]byte, error) {
+	reader, writer := io.Pipe()
+	scannerStopped := make(chan struct{})
+
+	go func() {
+		defer close(scannerStopped)
+		scanner := bufio.NewScanner(reader)
+		for scanner.Scan() {
+			fmt.Fprintln(stdout, scanner.Text())
+		}
+	}()
+
+	c.Stdout = writer
+	c.Stderr = writer
+	err := c.Start()
+	if err == nil {
+		err = c.Wait()
+		_ = writer.Close()
+		<-scannerStopped
+	}
+
+	if err != nil {
+		switch ee := err.(type) {
+		case *exec.ExitError:
+			// Propagate any non-zero exit status from the external command, rather than throwing it away,
+			// so that helmfile could return its own exit code accordingly
+			waitStatus := ee.Sys().(syscall.WaitStatus)
+			exitStatus := waitStatus.ExitStatus()
+			err = newExitError(c.Path, c.Args, exitStatus, ee, "", "")
+		default:
+			panic(fmt.Sprintf("unexpected error: %v", err))
+		}
+	}
+
+	return nil, err
+}
+
 func mergeEnv(orig []string, new map[string]string) []string {
 	wanted := env2map(orig)
 	for k, v := range new {

pkg/helmexec/runner_test.go

@@ -0,0 +1,88 @@
+package helmexec
+
+import (
+	"bytes"
+	"os/exec"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+func TestShellRunner_Execute(t *testing.T) {
+	tests := []struct {
+		name             string
+		want             []byte
+		stdoutWant       string
+		enableLiveOutput bool
+	}{
+		{
+			name:             "echo_template_no_live_output",
+			want:             []byte("template\n"),
+			enableLiveOutput: false,
+		},
+		{
+			name:             "echo_template_enable_live_output",
+			want:             nil,
+			enableLiveOutput: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			var buffer bytes.Buffer
+			shell := ShellRunner{
+				Logger: NewLogger(&buffer, "debug"),
+			}
+			got, err := shell.Execute("echo", strings.Split("template", " "), map[string]string{}, tt.enableLiveOutput)
+
+			if err != nil {
+				t.Errorf("Execute() has produced an error = %v", err)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("ExecuteStdIn() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLiveOutput(t *testing.T) {
+	tests := []struct {
+		name    string
+		cmd     *exec.Cmd
+		wantW   string
+		wantErr bool
+	}{
+		{
+			name:    "echo_template",
+			cmd:     exec.Command("echo", "template"),
+			wantW:   "template\n",
+			wantErr: false,
+		},
+		{
+			name: "helm_template",
+			cmd:  exec.Command("helm", "template"),
+			wantW: `Error: "helm template" requires at least 1 argument
+
+Usage:  helm template [NAME] [CHART] [flags]
+`,
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			w := &bytes.Buffer{}
+			got, err := LiveOutput(tt.cmd, w)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("LiveOutput() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if gotW := w.String(); gotW != tt.wantW {
+				t.Errorf("LiveOutput() gotW = %v, want %v", gotW, tt.wantW)
+			}
+			if got != nil {
+				t.Errorf("LiveOutput() got unespected %v", got)
+			}
+		})
+	}
+}

pkg/state/create.go

@@ -55,10 +55,12 @@ type StateCreator struct {
 
 	overrideHelmBinary string
 
+	enableLiveOutput bool
+
 	remote *remote.Remote
 }
 
-func NewCreator(logger *zap.SugaredLogger, fs *filesystem.FileSystem, valsRuntime vals.Evaluator, getHelm func(*HelmState) helmexec.Interface, overrideHelmBinary string, remote *remote.Remote) *StateCreator {
+func NewCreator(logger *zap.SugaredLogger, fs *filesystem.FileSystem, valsRuntime vals.Evaluator, getHelm func(*HelmState) helmexec.Interface, overrideHelmBinary string, remote *remote.Remote, enableLiveOutput bool) *StateCreator {
 	return &StateCreator{
 		logger: logger,
 
@@ -68,6 +70,7 @@ func NewCreator(logger *zap.SugaredLogger, fs *filesystem.FileSystem, valsRuntim
 		getHelm:     getHelm,
 
 		overrideHelmBinary: overrideHelmBinary,
+		enableLiveOutput:   enableLiveOutput,
 
 		remote: remote,
 	}

pkg/state/create_test.go

@@ -65,6 +65,10 @@ type stateTestEnv struct {
 }
 
 func (testEnv stateTestEnv) MustLoadState(t *testing.T, file, envName string) *HelmState {
+	return testEnv.MustLoadStateWithEnableLiveOutput(t, file, envName, false)
+}
+
+func (testEnv stateTestEnv) MustLoadStateWithEnableLiveOutput(t *testing.T, file, envName string, enableLiveOutput bool) *HelmState {
 	t.Helper()
 
 	testFs := testhelper.NewTestFs(testEnv.Files)
@@ -79,7 +83,7 @@ func (testEnv stateTestEnv) MustLoadState(t *testing.T, file, envName string) *H
 	}
 
 	r := remote.NewRemote(logger, testFs.Cwd, testFs.ToFileSystem())
-	state, err := NewCreator(logger, testFs.ToFileSystem(), nil, nil, "", r).
+	state, err := NewCreator(logger, testFs.ToFileSystem(), nil, nil, "", r, enableLiveOutput).
 		ParseAndLoad([]byte(yamlContent), filepath.Dir(file), file, envName, true, nil)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -149,7 +153,7 @@ releaseNamespace: mynamespace
 	env := environment.Environment{
 		Name: "production",
 	}
-	state, err := NewCreator(logger, testFs.ToFileSystem(), nil, nil, "", r).
+	state, err := NewCreator(logger, testFs.ToFileSystem(), nil, nil, "", r, false).
 		ParseAndLoad(yamlContent, filepath.Dir(yamlFile), yamlFile, "production", true, &env)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
@@ -236,7 +240,7 @@ overrideNamespace: myns
 	testFs.Cwd = "/example/path/to"
 
 	r := remote.NewRemote(logger, testFs.Cwd, testFs.ToFileSystem())
-	state, err := NewCreator(logger, testFs.ToFileSystem(), nil, nil, "", r).
+	state, err := NewCreator(logger, testFs.ToFileSystem(), nil, nil, "", r, false).
 		ParseAndLoad(yamlContent, filepath.Dir(yamlFile), yamlFile, "production", true, nil)
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)

test/e2e/template/helmfile/testdata/snapshot/chart_need_enable_live_output/config.yaml

@@ -0,0 +1,7 @@
+localChartRepoServer:
+  enabled: true
+  port: 18080
+chartifyTempDir: temp1
+helmfileArgs:
+- --enable-live-output
+- template

test/e2e/template/helmfile/testdata/snapshot/chart_need_enable_live_output/input.yaml

@@ -0,0 +1,31 @@
+repositories:
+- name: myrepo
+  url: http://localhost:18080/
+
+releases:
+- name: foo
+  chart: ../../charts/raw
+  values:
+  - templates:
+    - |
+      apiVersion: v1
+      kind: ConfigMap
+      metadata:
+        name: {{`{{ .Release.Name }}`}}-1
+        namespace: {{`{{ .Release.Namespace }}`}}
+      data:
+        foo: FOO
+    dep:
+      templates:
+      - |
+        apiVersion: v1
+        kind: ConfigMap
+        metadata:
+          name: {{`{{ .Release.Name }}`}}-2
+          namespace: {{`{{ .Release.Namespace }}`}}
+        data:
+          bar: BAR
+  dependencies:
+  - alias: dep
+    chart: myrepo/raw
+    version: 0.1.0

test/e2e/template/helmfile/testdata/snapshot/chart_need_enable_live_output/output.yaml

@@ -0,0 +1,27 @@
+Live output is enabled
+Adding repo myrepo http://localhost:18080/
+"myrepo" has been added to your repositories
+
+Building dependency release=foo, chart=$WD/temp1/foo
+Templating release=foo, chart=$WD/temp1/foo
+---
+# Source: raw/templates/charts/dep/templates/resources.yaml
+# Source: raw/charts/dep/templates/resources.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: foo-2
+  namespace: default
+data:
+  bar: BAR
+---
+# Source: raw/templates/resources.yaml
+# Source: raw/templates/resources.yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: foo-1
+  namespace: default
+data:
+  foo: FOO
+

test/integration/run.sh

@@ -17,7 +17,7 @@ if [[ ! -d "${dir}" ]]; then dir="${PWD}"; fi
 # GLOBALS -----------------------------------------------------------------------------------------------------------
 
 test_ns="helmfile-tests-$(date +"%Y%m%d-%H%M%S")"
-helmfile="./helmfile --namespace=${test_ns}"
+helmfile="./helmfile ${EXTRA_HELMFILE_FLAGS} --namespace=${test_ns}"
 helm="helm --kube-context=minikube"
 kubectl="kubectl --context=minikube --namespace=${test_ns}"
 helm_dir="${PWD}/${dir}/.helm"