Don't allow non flag arguments by default.

pkg/cli/commands.go

@@ -3,7 +3,6 @@
 package cli
 
 import (
-	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -17,6 +16,8 @@ type Command struct {
 	Resources     []ResourceLoader
 	Run           func([]string) error
 	Hidden        bool
+	// AllowArg if not set, disallows any argument that is not a known command or a sub-command.
+	AllowArg    bool
 	subCommands []*Command
 }
 
@@ -40,13 +41,17 @@ func Execute(cmd *Command) error {
 }
 
 func execute(cmd *Command, args []string, root bool) error {
+	// Calls command without args.
 	if len(args) == 1 {
-		if err := run(cmd, args); err != nil {
+		if err := run(cmd, args[1:]); err != nil {
 			return fmt.Errorf("command %s error: %v", args[0], err)
 		}
 		return nil
 	}
 
+	// Special case: if the command is the top level one,
+	// and the first arg (`args[1]`) is not the command name or a known sub-command,
+	// then we run the top level command itself.
 	if root && cmd.Name != args[1] && !contains(cmd.subCommands, args[1]) {
 		if err := run(cmd, args[1:]); err != nil {
 			return fmt.Errorf("command %s error: %v", filepath.Base(args[0]), err)
@@ -54,6 +59,7 @@ func execute(cmd *Command, args []string, root bool) error {
 		return nil
 	}
 
+	// Calls command by its name.
 	if len(args) >= 2 && cmd.Name == args[1] {
 		if err := run(cmd, args[2:]); err != nil {
 			return fmt.Errorf("command %s error: %v", cmd.Name, err)
@@ -61,6 +67,7 @@ func execute(cmd *Command, args []string, root bool) error {
 		return nil
 	}
 
+	// No sub-command, calls the current command.
 	if len(cmd.subCommands) == 0 {
 		if err := run(cmd, args[1:]); err != nil {
 			return fmt.Errorf("command %s error: %v", cmd.Name, err)
@@ -68,6 +75,7 @@ func execute(cmd *Command, args []string, root bool) error {
 		return nil
 	}
 
+	// Trying to find the sub-command.
 	for _, subCmd := range cmd.subCommands {
 		if len(args) >= 2 && subCmd.Name == args[1] {
 			return execute(subCmd, args[1:], false)
@@ -84,7 +92,12 @@ func run(cmd *Command, args []string) error {
 
 	if cmd.Run == nil {
 		_ = PrintHelp(os.Stdout, cmd)
-		return errors.New("command not found")
+		return fmt.Errorf("command %s is not runnable", cmd.Name)
+	}
+
+	if len(args) > 0 && !isFlag(args[0]) && !cmd.AllowArg {
+		_ = PrintHelp(os.Stdout, cmd)
+		return fmt.Errorf("command not found: %v", args)
 	}
 
 	if cmd.Configuration == nil {
@@ -113,3 +126,7 @@ func contains(cmds []*Command, name string) bool {
 
 	return false
 }
+
+func isFlag(arg string) bool {
+	return len(arg) > 0 && arg[1] == '-'
+}

pkg/cli/commands_test.go

@@ -86,6 +86,23 @@ func Test_execute(t *testing.T) {
 			},
 			expected: expected{result: "root"},
 		},
+		{
+			desc: "root command, with argument, command not found",
+			args: []string{"", "echo"},
+			command: func() *Command {
+				return &Command{
+					Name:          "root",
+					Description:   "This is a test",
+					Configuration: nil,
+					Run: func(_ []string) error {
+						called = "root"
+						return nil
+					},
+				}
+
+			},
+			expected: expected{error: true},
+		},
 		{
 			desc: "one sub command",
 			args: []string{"", "sub1"},
@@ -114,6 +131,34 @@ func Test_execute(t *testing.T) {
 			},
 			expected: expected{result: "sub1"},
 		},
+		{
+			desc: "one sub command, with argument, command not found",
+			args: []string{"", "sub1", "echo"},
+			command: func() *Command {
+				rootCmd := &Command{
+					Name:          "test",
+					Description:   "This is a test",
+					Configuration: nil,
+					Run: func(_ []string) error {
+						called += "root"
+						return nil
+					},
+				}
+
+				_ = rootCmd.AddCommand(&Command{
+					Name:          "sub1",
+					Description:   "sub1",
+					Configuration: nil,
+					Run: func(_ []string) error {
+						called += "sub1"
+						return nil
+					},
+				})
+
+				return rootCmd
+			},
+			expected: expected{error: true},
+		},
 		{
 			desc: "two sub commands",
 			args: []string{"", "sub2"},
@@ -376,6 +421,7 @@ func Test_execute(t *testing.T) {
 					Name:          "sub1",
 					Description:   "sub1",
 					Configuration: nil,
+					AllowArg:      true,
 					Run: func(args []string) error {
 						called += "sub1-" + strings.Join(args, "-")
 						return nil
@@ -394,6 +440,7 @@ func Test_execute(t *testing.T) {
 					Name:          "root",
 					Description:   "This is a test",
 					Configuration: nil,
+					AllowArg:      true,
 					Run: func(args []string) error {
 						called += "root-" + strings.Join(args, "-")
 						return nil