Merge pull request #4070 from adamreese/dev-v3-arg-validation

ref(cmd): refactor argument validation

cmd/helm/create.go

@@ -21,9 +21,9 @@ import (
 	"io"
 	"path/filepath"
 
-	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 	"k8s.io/helm/pkg/hapi/chart"
 )
@@ -60,10 +60,8 @@ func newCreateCmd(out io.Writer) *cobra.Command {
 		Use:   "create NAME",
 		Short: "create a new chart with the given name",
 		Long:  createDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errors.New("the name of the new chart is required")
-			}
 			o.name = args[0]
 			return o.run(out)
 		},

cmd/helm/delete.go

@@ -20,9 +20,9 @@ import (
 	"fmt"
 	"io"
 
-	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm"
 )
 
@@ -50,15 +50,13 @@ func newDeleteCmd(c helm.Interface, out io.Writer) *cobra.Command {
 	o := &deleteOptions{client: c}
 
 	cmd := &cobra.Command{
-		Use:        "delete [flags] RELEASE_NAME [...]",
+		Use:        "delete RELEASE_NAME [...]",
 		Aliases:    []string{"del"},
 		SuggestFor: []string{"remove", "rm"},
 		Short:      "given a release name, delete the release from Kubernetes",
 		Long:       deleteDesc,
+		Args:       require.MinimumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errors.New("command 'delete' requires a release name")
-			}
 			o.client = ensureHelmClient(o.client, false)
 
 			for i := 0; i < len(args); i++ {

cmd/helm/dependency.go

@@ -25,6 +25,7 @@ import (
 	"github.com/gosuri/uitable"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 )
 
@@ -93,6 +94,7 @@ func newDependencyCmd(out io.Writer) *cobra.Command {
 		Aliases: []string{"dep", "dependencies"},
 		Short:   "manage a chart's dependencies",
 		Long:    dependencyDesc,
+		Args:    require.NoArgs,
 	}
 
 	cmd.AddCommand(newDependencyListCmd(out))
@@ -112,10 +114,11 @@ func newDependencyListCmd(out io.Writer) *cobra.Command {
 	}
 
 	cmd := &cobra.Command{
-		Use:     "list [flags] CHART",
+		Use:     "list CHART",
 		Aliases: []string{"ls"},
 		Short:   "list the dependencies for the given chart",
 		Long:    dependencyListDesc,
+		Args:    require.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if len(args) > 0 {
 				o.chartpath = filepath.Clean(args[0])

cmd/helm/dependency_build.go

@@ -20,6 +20,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/downloader"
 	"k8s.io/helm/pkg/getter"
 )
@@ -48,9 +49,10 @@ func newDependencyBuildCmd(out io.Writer) *cobra.Command {
 	}
 
 	cmd := &cobra.Command{
-		Use:   "build [flags] CHART",
+		Use:   "build CHART",
 		Short: "rebuild the charts/ directory based on the requirements.lock file",
 		Long:  dependencyBuildDesc,
+		Args:  require.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if len(args) > 0 {
 				o.chartpath = args[0]

cmd/helm/dependency_update.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/downloader"
 	"k8s.io/helm/pkg/getter"
 	"k8s.io/helm/pkg/helm/helmpath"
@@ -60,10 +61,11 @@ func newDependencyUpdateCmd(out io.Writer) *cobra.Command {
 	}
 
 	cmd := &cobra.Command{
-		Use:     "update [flags] CHART",
+		Use:     "update CHART",
 		Aliases: []string{"up"},
 		Short:   "update charts/ based on the contents of requirements.yaml",
 		Long:    dependencyUpDesc,
+		Args:    require.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if len(args) > 0 {
 				o.chartpath = filepath.Clean(args[0])

cmd/helm/docs.go

@@ -22,6 +22,8 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 	"github.com/spf13/cobra/doc"
+
+	"k8s.io/helm/cmd/helm/require"
 )
 
 const docsDesc = `
@@ -51,6 +53,7 @@ func newDocsCmd(out io.Writer) *cobra.Command {
 		Short:  "Generate documentation as markdown or man pages",
 		Long:   docsDesc,
 		Hidden: true,
+		Args:   require.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o.topCmd = cmd.Root()
 			return o.run(out)

cmd/helm/fetch.go

@@ -26,6 +26,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 	"k8s.io/helm/pkg/downloader"
 	"k8s.io/helm/pkg/getter"
@@ -70,14 +71,11 @@ func newFetchCmd(out io.Writer) *cobra.Command {
 	o := &fetchOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "fetch [flags] [chart URL | repo/chartname] [...]",
+		Use:   "fetch [chart URL | repo/chartname] [...]",
 		Short: "download a chart from a repository and (optionally) unpack it in local directory",
 		Long:  fetchDesc,
+		Args:  require.MinimumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errors.Errorf("need at least one argument, url or repo/name of the chart")
-			}
-
 			if o.version == "" && o.devel {
 				debug("setting version to >0.0.0-0")
 				o.version = ">0.0.0-0"

cmd/helm/get.go

@@ -19,9 +19,9 @@ package main
 import (
 	"io"
 
-	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm"
 )
 
@@ -38,8 +38,6 @@ By default, this prints a human readable collection of information about the
 chart, the supplied values, and the generated manifest file.
 `
 
-var errReleaseRequired = errors.New("release name is required")
-
 type getOptions struct {
 	version int // --revision
 
@@ -52,13 +50,11 @@ func newGetCmd(client helm.Interface, out io.Writer) *cobra.Command {
 	o := &getOptions{client: client}
 
 	cmd := &cobra.Command{
-		Use:   "get [flags] RELEASE_NAME",
+		Use:   "get RELEASE_NAME",
 		Short: "download a named release",
 		Long:  getHelp,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errReleaseRequired
-			}
 			o.release = args[0]
 			o.client = ensureHelmClient(o.client, false)
 			return o.run(out)

cmd/helm/get_hooks.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm"
 )
 
@@ -41,13 +42,11 @@ func newGetHooksCmd(client helm.Interface, out io.Writer) *cobra.Command {
 	o := &getHooksOptions{client: client}
 
 	cmd := &cobra.Command{
-		Use:   "hooks [flags] RELEASE_NAME",
+		Use:   "hooks RELEASE_NAME",
 		Short: "download all hooks for a named release",
 		Long:  getHooksHelp,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errReleaseRequired
-			}
 			o.release = args[0]
 			o.client = ensureHelmClient(o.client, false)
 			return o.run(out)

cmd/helm/get_manifest.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm"
 )
 
@@ -45,13 +46,11 @@ func newGetManifestCmd(client helm.Interface, out io.Writer) *cobra.Command {
 	o := &getManifestOptions{client: client}
 
 	cmd := &cobra.Command{
-		Use:   "manifest [flags] RELEASE_NAME",
+		Use:   "manifest RELEASE_NAME",
 		Short: "download the manifest for a named release",
 		Long:  getManifestHelp,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errReleaseRequired
-			}
 			o.release = args[0]
 			o.client = ensureHelmClient(o.client, false)
 			return o.run(out)

cmd/helm/get_values.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 	"k8s.io/helm/pkg/helm"
 )
@@ -43,13 +44,11 @@ func newGetValuesCmd(client helm.Interface, out io.Writer) *cobra.Command {
 	o := &getValuesOptions{client: client}
 
 	cmd := &cobra.Command{
-		Use:   "values [flags] RELEASE_NAME",
+		Use:   "values RELEASE_NAME",
 		Short: "download the values file for a named release",
 		Long:  getValuesHelp,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errReleaseRequired
-			}
 			o.release = args[0]
 			o.client = ensureHelmClient(o.client, false)
 			return o.run(out)

cmd/helm/helm.go

@@ -20,10 +20,8 @@ import (
 	"fmt"
 	"log"
 	"os"
-	"strings"
 	"sync"
 
-	"github.com/pkg/errors"
 	// Import to initialize client auth plugins.
 	_ "k8s.io/client-go/plugin/pkg/client/auth"
 	"k8s.io/client-go/tools/clientcmd"
@@ -59,18 +57,6 @@ func main() {
 	}
 }
 
-func checkArgsLength(argsReceived int, requiredArgs ...string) error {
-	expectedNum := len(requiredArgs)
-	if argsReceived != expectedNum {
-		arg := "arguments"
-		if expectedNum == 1 {
-			arg = "argument"
-		}
-		return errors.Errorf("this command needs %v %s: %s", expectedNum, arg, strings.Join(requiredArgs, ", "))
-	}
-	return nil
-}
-
 // ensureHelmClient returns a new helm client impl. if h is not nil.
 func ensureHelmClient(h helm.Interface, allNamespaces bool) helm.Interface {
 	if h != nil {

cmd/helm/history.go

@@ -26,6 +26,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/hapi/chart"
 	"k8s.io/helm/pkg/hapi/release"
 	"k8s.io/helm/pkg/helm"
@@ -71,14 +72,12 @@ func newHistoryCmd(c helm.Interface, out io.Writer) *cobra.Command {
 	o := &historyOptions{client: c}
 
 	cmd := &cobra.Command{
-		Use:     "history [flags] RELEASE_NAME",
+		Use:     "history RELEASE_NAME",
 		Long:    historyHelp,
 		Short:   "fetch release history",
 		Aliases: []string{"hist"},
+		Args:    require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errReleaseRequired
-			}
 			o.client = ensureHelmClient(o.client, false)
 			o.release = args[0]
 			return o.run(out)

cmd/helm/home.go

@@ -21,6 +21,8 @@ import (
 	"io"
 
 	"github.com/spf13/cobra"
+
+	"k8s.io/helm/cmd/helm/require"
 )
 
 var longHomeHelp = `
@@ -33,6 +35,7 @@ func newHomeCmd(out io.Writer) *cobra.Command {
 		Use:   "home",
 		Short: "displays the location of HELM_HOME",
 		Long:  longHomeHelp,
+		Args:  require.NoArgs,
 		Run: func(cmd *cobra.Command, args []string) {
 			h := settings.Home
 			fmt.Fprintln(out, h)

cmd/helm/init.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/getter"
 	"k8s.io/helm/pkg/helm/helmpath"
 	"k8s.io/helm/pkg/repo"
@@ -52,10 +53,8 @@ func newInitCmd(out io.Writer) *cobra.Command {
 		Use:   "init",
 		Short: "initialize Helm client",
 		Long:  initDesc,
+		Args:  require.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) != 0 {
-				return errors.New("this command does not accept arguments")
-			}
 			o.home = settings.Home
 			return o.run(out)
 		},

cmd/helm/inspect.go

@@ -24,6 +24,7 @@ import (
 	"github.com/ghodss/yaml"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 	"k8s.io/helm/pkg/hapi/chart"
 )
@@ -80,10 +81,8 @@ func newInspectCmd(out io.Writer) *cobra.Command {
 		Use:   "inspect [CHART]",
 		Short: "inspect a chart",
 		Long:  inspectDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "chart name"); err != nil {
-				return err
-			}
 			cp, err := locateChartPath(o.repoURL, o.username, o.password, args[0], o.version, o.verify, o.keyring,
 				o.certFile, o.keyFile, o.caFile)
 			if err != nil {
@@ -98,11 +97,9 @@ func newInspectCmd(out io.Writer) *cobra.Command {
 		Use:   "values [CHART]",
 		Short: "shows inspect values",
 		Long:  inspectValuesDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o.output = valuesOnly
-			if err := checkArgsLength(len(args), "chart name"); err != nil {
-				return err
-			}
 			cp, err := locateChartPath(o.repoURL, o.username, o.password, args[0], o.version, o.verify, o.keyring,
 				o.certFile, o.keyFile, o.caFile)
 			if err != nil {
@@ -117,11 +114,9 @@ func newInspectCmd(out io.Writer) *cobra.Command {
 		Use:   "chart [CHART]",
 		Short: "shows inspect chart",
 		Long:  inspectChartDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o.output = chartOnly
-			if err := checkArgsLength(len(args), "chart name"); err != nil {
-				return err
-			}
 			cp, err := locateChartPath(o.repoURL, o.username, o.password, args[0], o.version, o.verify, o.keyring,
 				o.certFile, o.keyFile, o.caFile)
 			if err != nil {
@@ -136,11 +131,9 @@ func newInspectCmd(out io.Writer) *cobra.Command {
 		Use:   "readme [CHART]",
 		Short: "shows inspect readme",
 		Long:  readmeChartDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o.output = readmeOnly
-			if err := checkArgsLength(len(args), "chart name"); err != nil {
-				return err
-			}
 			cp, err := locateChartPath(o.repoURL, o.username, o.password, args[0], o.version, o.verify, o.keyring,
 				o.certFile, o.keyFile, o.caFile)
 			if err != nil {

cmd/helm/install.go

@@ -32,6 +32,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 	"k8s.io/helm/pkg/downloader"
 	"k8s.io/helm/pkg/getter"
@@ -155,11 +156,8 @@ func newInstallCmd(c helm.Interface, out io.Writer) *cobra.Command {
 		Use:   "install [CHART]",
 		Short: "install a chart archive",
 		Long:  installDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "chart name"); err != nil {
-				return err
-			}
-
 			debug("Original chart version: %q", o.version)
 			if o.version == "" && o.devel {
 				debug("setting version to >0.0.0-0")

cmd/helm/lint.go

@@ -55,7 +55,7 @@ func newLintCmd(out io.Writer) *cobra.Command {
 	o := &lintOptions{paths: []string{"."}}
 
 	cmd := &cobra.Command{
-		Use:   "lint [flags] PATH",
+		Use:   "lint PATH",
 		Short: "examines a chart for possible issues",
 		Long:  longLintHelp,
 		RunE: func(cmd *cobra.Command, args []string) error {

cmd/helm/list.go

@@ -24,6 +24,7 @@ import (
 	"github.com/gosuri/uitable"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/hapi"
 	"k8s.io/helm/pkg/hapi/release"
 	"k8s.io/helm/pkg/helm"
@@ -83,10 +84,11 @@ func newListCmd(client helm.Interface, out io.Writer) *cobra.Command {
 	o := &listOptions{client: client}
 
 	cmd := &cobra.Command{
-		Use:     "list [flags] [FILTER]",
+		Use:     "list [FILTER]",
 		Short:   "list releases",
 		Long:    listHelp,
 		Aliases: []string{"ls"},
+		Args:    require.MaximumNArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			if len(args) > 0 {
 				o.filter = strings.Join(args, " ")

cmd/helm/package.go

@@ -71,7 +71,7 @@ func newPackageCmd(out io.Writer) *cobra.Command {
 	o := &packageOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "package [flags] [CHART_PATH] [...]",
+		Use:   "package [CHART_PATH] [...]",
 		Short: "package a chart directory into a chart archive",
 		Long:  packageDesc,
 		RunE: func(cmd *cobra.Command, args []string) error {

cmd/helm/plugin_install.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"io"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm/helmpath"
 	"k8s.io/helm/pkg/plugin"
 	"k8s.io/helm/pkg/plugin/installer"
@@ -45,6 +46,7 @@ func newPluginInstallCmd(out io.Writer) *cobra.Command {
 		Use:   "install [options] <path|url>...",
 		Short: "install one or more Helm plugins",
 		Long:  pluginInstallDesc,
+		Args:  require.ExactArgs(1),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
 			return o.complete(args)
 		},
@@ -57,9 +59,6 @@ func newPluginInstallCmd(out io.Writer) *cobra.Command {
 }
 
 func (o *pluginInstallOptions) complete(args []string) error {
-	if err := checkArgsLength(len(args), "plugin"); err != nil {
-		return err
-	}
 	o.source = args[0]
 	o.home = settings.Home
 	return nil

cmd/helm/release_testing.go

@@ -23,6 +23,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/hapi/release"
 	"k8s.io/helm/pkg/helm"
 )
@@ -48,11 +49,8 @@ func newReleaseTestCmd(c helm.Interface, out io.Writer) *cobra.Command {
 		Use:   "test [RELEASE]",
 		Short: "test a release",
 		Long:  releaseTestDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "release name"); err != nil {
-				return err
-			}
-
 			o.name = args[0]
 			o.client = ensureHelmClient(o.client, false)
 			return o.run(out)

cmd/helm/repo.go

@@ -20,6 +20,8 @@ import (
 	"io"
 
 	"github.com/spf13/cobra"
+
+	"k8s.io/helm/cmd/helm/require"
 )
 
 var repoHelm = `
@@ -32,9 +34,10 @@ Example usage:
 
 func newRepoCmd(out io.Writer) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "repo [FLAGS] add|remove|list|index|update [ARGS]",
+		Use:   "repo add|remove|list|index|update [ARGS]",
 		Short: "add, list, remove, update, and index chart repositories",
 		Long:  repoHelm,
+		Args:  require.NoArgs,
 	}
 
 	cmd.AddCommand(newRepoAddCmd(out))

cmd/helm/repo_add.go

@@ -23,6 +23,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/getter"
 	"k8s.io/helm/pkg/helm/helmpath"
 	"k8s.io/helm/pkg/repo"
@@ -45,13 +46,10 @@ func newRepoAddCmd(out io.Writer) *cobra.Command {
 	o := &repoAddOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "add [flags] [NAME] [URL]",
+		Use:   "add [NAME] [URL]",
 		Short: "add a chart repository",
+		Args:  require.ExactArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "name for the chart repository", "the url of the chart repository"); err != nil {
-				return err
-			}
-
 			o.name = args[0]
 			o.url = args[1]
 			o.home = settings.Home

cmd/helm/repo_index.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/repo"
 )
 
@@ -48,16 +49,12 @@ func newRepoIndexCmd(out io.Writer) *cobra.Command {
 	o := &repoIndexOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "index [flags] [DIR]",
+		Use:   "index [DIR]",
 		Short: "generate an index file given a directory containing packaged charts",
 		Long:  repoIndexDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "path to a directory"); err != nil {
-				return err
-			}
-
 			o.dir = args[0]
-
 			return o.run(out)
 		},
 	}

cmd/helm/repo_list.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm/helmpath"
 	"k8s.io/helm/pkg/repo"
 )
@@ -36,8 +37,9 @@ func newRepoListCmd(out io.Writer) *cobra.Command {
 	o := &repoListOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "list [flags]",
+		Use:   "list",
 		Short: "list chart repositories",
+		Args:  require.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o.home = settings.Home
 			return o.run(out)

cmd/helm/repo_remove.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm/helmpath"
 	"k8s.io/helm/pkg/repo"
 )
@@ -37,13 +38,11 @@ func newRepoRemoveCmd(out io.Writer) *cobra.Command {
 	o := &repoRemoveOptions{}
 
 	cmd := &cobra.Command{
-		Use:     "remove [flags] [NAME]",
+		Use:     "remove [NAME]",
 		Aliases: []string{"rm"},
 		Short:   "remove a chart repository",
+		Args:    require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "name of chart repository"); err != nil {
-				return err
-			}
 			o.name = args[0]
 			o.home = settings.Home
 

cmd/helm/repo_update.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/getter"
 	"k8s.io/helm/pkg/helm/helmpath"
 	"k8s.io/helm/pkg/repo"
@@ -52,6 +53,7 @@ func newRepoUpdateCmd(out io.Writer) *cobra.Command {
 		Aliases: []string{"up"},
 		Short:   "update information of available charts locally from chart repositories",
 		Long:    updateDesc,
+		Args:    require.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			o.home = settings.Home
 			return o.run(out)

cmd/helm/require/args.go

@@ -0,0 +1,88 @@
+/*
+Copyright 2018 The Kubernetes Authors All rights reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package require
+
+import (
+	"github.com/pkg/errors"
+	"github.com/spf13/cobra"
+)
+
+// NoArgs returns an error if any args are included.
+func NoArgs(cmd *cobra.Command, args []string) error {
+	if len(args) > 0 {
+		return errors.Errorf(
+			"%q accepts no arguments\n\nUsage:  %s",
+			cmd.CommandPath(),
+			cmd.UseLine(),
+		)
+	}
+	return nil
+}
+
+// ExactArgs returns an error if there are not exactly n args.
+func ExactArgs(n int) cobra.PositionalArgs {
+	return func(cmd *cobra.Command, args []string) error {
+		if len(args) != n {
+			return errors.Errorf(
+				"%q requires %d %s\n\nUsage:  %s",
+				cmd.CommandPath(),
+				n,
+				pluralize("argument", n),
+				cmd.UseLine(),
+			)
+		}
+		return nil
+	}
+}
+
+// MaximumNArgs returns an error if there are more than N args.
+func MaximumNArgs(n int) cobra.PositionalArgs {
+	return func(cmd *cobra.Command, args []string) error {
+		if len(args) > n {
+			return errors.Errorf(
+				"%q accepts at most %d %s\n\nUsage:  %s",
+				cmd.CommandPath(),
+				n,
+				pluralize("argument", n),
+				cmd.UseLine(),
+			)
+		}
+		return nil
+	}
+}
+
+// MinimumNArgs returns an error if there is not at least N args.
+func MinimumNArgs(n int) cobra.PositionalArgs {
+	return func(cmd *cobra.Command, args []string) error {
+		if len(args) < n {
+			return errors.Errorf(
+				"%q requires at least %d %s\n\nUsage:  %s",
+				cmd.CommandPath(),
+				n,
+				pluralize("argument", n),
+				cmd.UseLine(),
+			)
+		}
+		return nil
+	}
+}
+
+func pluralize(word string, n int) string {
+	if n == 1 {
+		return word
+	}
+	return word + "s"
+}

cmd/helm/require/args_test.go

@@ -0,0 +1,91 @@
+/*
+Copyright 2018 The Kubernetes Authors All rights reserved.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package require
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strings"
+	"testing"
+
+	"github.com/spf13/cobra"
+)
+
+func TestArgs(t *testing.T) {
+	runTestCases(t, []testCase{{
+		validateFunc: NoArgs,
+	}, {
+		args:         []string{"one"},
+		validateFunc: NoArgs,
+		wantError:    `"root" accepts no arguments`,
+	}, {
+		args:         []string{"one"},
+		validateFunc: ExactArgs(1),
+	}, {
+		validateFunc: ExactArgs(1),
+		wantError:    `"root" requires 1 argument`,
+	}, {
+		validateFunc: ExactArgs(2),
+		wantError:    `"root" requires 2 arguments`,
+	}, {
+		args:         []string{"one"},
+		validateFunc: MaximumNArgs(1),
+	}, {
+		args:         []string{"one", "two"},
+		validateFunc: MaximumNArgs(1),
+		wantError:    `"root" accepts at most 1 argument`,
+	}, {
+		validateFunc: MinimumNArgs(1),
+		wantError:    `"root" requires at least 1 argument`,
+	}, {
+		args:         []string{"one", "two"},
+		validateFunc: MinimumNArgs(1),
+	}})
+}
+
+type testCase struct {
+	args         []string
+	validateFunc cobra.PositionalArgs
+	wantError    string
+}
+
+func runTestCases(t *testing.T, testCases []testCase) {
+	for i, tc := range testCases {
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			cmd := &cobra.Command{
+				Use:  "root",
+				Run:  func(*cobra.Command, []string) {},
+				Args: tc.validateFunc,
+			}
+			cmd.SetArgs(tc.args)
+			cmd.SetOutput(ioutil.Discard)
+
+			err := cmd.Execute()
+			if tc.wantError == "" {
+				if err != nil {
+					t.Fatalf("unexpected error, got '%v'", err)
+				}
+				return
+			}
+			if !strings.Contains(err.Error(), tc.wantError) {
+				t.Fatalf("unexpected error \n\nWANT:\n%q\n\nGOT:\n%q\n", tc.wantError, err)
+			}
+			if !strings.Contains(err.Error(), "Usage:") {
+				t.Fatalf("unexpected error: want Usage string\n\nGOT:\n%q\n", err)
+			}
+		})
+	}
+}

cmd/helm/rollback.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm"
 )
 
@@ -51,14 +52,11 @@ func newRollbackCmd(c helm.Interface, out io.Writer) *cobra.Command {
 	o := &rollbackOptions{client: c}
 
 	cmd := &cobra.Command{
-		Use:   "rollback [flags] [RELEASE] [REVISION]",
+		Use:   "rollback [RELEASE] [REVISION]",
 		Short: "roll back a release to a previous revision",
 		Long:  rollbackDesc,
+		Args:  require.ExactArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "release name", "revision number"); err != nil {
-				return err
-			}
-
 			o.name = args[0]
 
 			v64, err := strconv.ParseInt(args[1], 10, 32)

cmd/helm/root.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/helm"
 )
 
@@ -51,6 +52,7 @@ func newRootCmd(c helm.Interface, out io.Writer, args []string) *cobra.Command {
 		Short:        "The Helm package manager for Kubernetes.",
 		Long:         globalUsage,
 		SilenceUsage: true,
+		Args:         require.NoArgs,
 	}
 	flags := cmd.PersistentFlags()
 

cmd/helm/status.go

@@ -29,6 +29,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/hapi"
 	"k8s.io/helm/pkg/hapi/release"
 	"k8s.io/helm/pkg/helm"
@@ -56,13 +57,11 @@ func newStatusCmd(client helm.Interface, out io.Writer) *cobra.Command {
 	o := &statusOptions{client: client}
 
 	cmd := &cobra.Command{
-		Use:   "status [flags] RELEASE_NAME",
+		Use:   "status RELEASE_NAME",
 		Short: "displays the status of the named release",
 		Long:  statusHelp,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errReleaseRequired
-			}
 			o.release = args[0]
 			o.client = ensureHelmClient(o.client, false)
 			return o.run(out)

cmd/helm/template.go

@@ -77,7 +77,7 @@ func newTemplateCmd(out io.Writer) *cobra.Command {
 	o := &templateOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "template [flags] CHART",
+		Use:   "template CHART",
 		Short: fmt.Sprintf("locally render templates"),
 		Long:  templateDesc,
 		RunE: func(cmd *cobra.Command, args []string) error {

cmd/helm/testdata/output/delete-no-args.txt

@@ -1 +1,3 @@
-Error: command 'delete' requires a release name
+Error: "helm delete" requires at least 1 argument
+
+Usage:  helm delete RELEASE_NAME [...] [flags]

cmd/helm/testdata/output/get-hooks-no-args.txt

@@ -1 +1,3 @@
-Error: release name is required
+Error: "helm get hooks" requires 1 argument
+
+Usage:  helm get hooks RELEASE_NAME [flags]

cmd/helm/testdata/output/get-manifest-no-args.txt

@@ -1 +1,3 @@
-Error: release name is required
+Error: "helm get manifest" requires 1 argument
+
+Usage:  helm get manifest RELEASE_NAME [flags]

cmd/helm/testdata/output/get-no-args.txt

@@ -1 +1,3 @@
-Error: release name is required
+Error: "helm get" requires 1 argument
+
+Usage:  helm get RELEASE_NAME [flags]

cmd/helm/testdata/output/get-values-args.txt

@@ -1 +1,3 @@
-Error: release name is required
+Error: "helm get values" requires 1 argument
+
+Usage:  helm get values RELEASE_NAME [flags]

cmd/helm/testdata/output/install-no-args.txt

@@ -1 +1,3 @@
-Error: this command needs 1 argument: chart name
+Error: "helm install" requires 1 argument
+
+Usage:  helm install [CHART] [flags]

cmd/helm/testdata/output/rollback-no-args.txt

@@ -1 +1,3 @@
-Error: this command needs 2 arguments: release name, revision number
+Error: "helm rollback" requires 2 arguments
+
+Usage:  helm rollback [RELEASE] [REVISION] [flags]

cmd/helm/testdata/output/upgrade-with-missing-dependencies.txt

@@ -1 +1,3 @@
-Error: this command needs 2 arguments: release name, chart path
+Error: "helm upgrade" requires 2 arguments
+
+Usage:  helm upgrade [RELEASE] [CHART] [flags]

cmd/helm/upgrade.go

@@ -24,6 +24,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/chartutil"
 	"k8s.io/helm/pkg/helm"
 	"k8s.io/helm/pkg/storage/driver"
@@ -90,11 +91,8 @@ func newUpgradeCmd(client helm.Interface, out io.Writer) *cobra.Command {
 		Use:   "upgrade [RELEASE] [CHART]",
 		Short: "upgrade a release",
 		Long:  upgradeDesc,
+		Args:  require.ExactArgs(2),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if err := checkArgsLength(len(args), "release name", "chart path"); err != nil {
-				return err
-			}
-
 			if o.version == "" && o.devel {
 				debug("setting version to >0.0.0-0")
 				o.version = ">0.0.0-0"

cmd/helm/verify.go

@@ -18,9 +18,9 @@ package main
 import (
 	"io"
 
-	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/downloader"
 )
 
@@ -44,13 +44,11 @@ func newVerifyCmd(out io.Writer) *cobra.Command {
 	o := &verifyOptions{}
 
 	cmd := &cobra.Command{
-		Use:   "verify [flags] PATH",
+		Use:   "verify PATH",
 		Short: "verify that a chart at the given path has been signed and is valid",
 		Long:  verifyDesc,
+		Args:  require.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if len(args) == 0 {
-				return errors.New("a path to a package file is required")
-			}
 			o.chartfile = args[0]
 			return o.run(out)
 		},

cmd/helm/verify_test.go

@@ -41,7 +41,7 @@ func TestVerifyCmd(t *testing.T) {
 		{
 			name:      "verify requires a chart",
 			cmd:       "verify",
-			expect:    "a path to a package file is required",
+			expect:    "\"helm verify\" requires 1 argument\n\nUsage:  helm verify PATH [flags]",
 			wantError: true,
 		},
 		{

cmd/helm/version.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/helm/cmd/helm/require"
 	"k8s.io/helm/pkg/version"
 )
 
@@ -52,6 +53,7 @@ func newVersionCmd(out io.Writer) *cobra.Command {
 		Use:   "version",
 		Short: "print the client version information",
 		Long:  versionDesc,
+		Args:  require.NoArgs,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return o.run(out)
 		},