Make command suggestion messages configurable

args.go

@@ -33,7 +33,7 @@ func legacyArgs(cmd *Command, args []string) error {
 
 	// root command with subcommands, do subcommand checking.
 	if !cmd.HasParent() && len(args) > 0 {
-		return fmt.Errorf("unknown command %q for %q%s", args[0], cmd.CommandPath(), cmd.findSuggestions(args[0]))
+		return fmt.Errorf("unknown command %q for %q%s", args[0], cmd.CommandPath(), cmd.SuggestFunc(args[0]))
 	}
 	return nil
 }
@@ -58,7 +58,7 @@ func OnlyValidArgs(cmd *Command, args []string) error {
 		}
 		for _, v := range args {
 			if !stringInSlice(v, validArgs) {
-				return fmt.Errorf("invalid argument %q for %q%s", v, cmd.CommandPath(), cmd.findSuggestions(args[0]))
+				return fmt.Errorf("invalid argument %q for %q%s", v, cmd.CommandPath(), cmd.SuggestFunc(args[0]))
 			}
 		}
 	}

command.go

@@ -180,6 +180,8 @@ type Command struct {
 	helpCommand *Command
 	// helpCommandGroupID is the group id for the helpCommand
 	helpCommandGroupID string
+	// suggestFunc is suggest func defined by the user.
+	suggestFunc func(string) string
 
 	// completionCommandGroupID is the group id for the completion command
 	completionCommandGroupID string
@@ -340,6 +342,10 @@ func (c *Command) SetHelpCommandGroupID(groupID string) {
 	c.helpCommandGroupID = groupID
 }
 
+func (c *Command) SetSuggestFunc(f func(string) string) {
+	c.suggestFunc = f
+}
+
 // SetCompletionCommandGroupID sets the group id of the completion command.
 func (c *Command) SetCompletionCommandGroupID(groupID string) {
 	// completionCommandGroupID is used if no completion command is defined by the user
@@ -477,6 +483,37 @@ func (c *Command) Help() error {
 	return nil
 }
 
+// SuggestFunc returns suggestions for the provided typedName using either
+// the function set by SetSuggestFunc for this command, parent's or a default one.
+// When searching for a parent's function, it recursively checks towards the root
+// and returns the first one found. If none found, uses direct parent's default.
+func (c *Command) SuggestFunc(typedName string) string {
+	if c.DisableSuggestions {
+		return ""
+	}
+	if c.suggestFunc != nil {
+		return c.suggestFunc(typedName)
+	}
+	if c.HasParent() {
+		var getParentFunc func(*Command) func(string) string
+		getParentFunc = func(parent *Command) func(string) string {
+			if parent.suggestFunc != nil {
+				return parent.suggestFunc
+			}
+			if !parent.HasParent() {
+				return nil
+			}
+			return getParentFunc(parent.Parent())
+		}
+		parentFunc := getParentFunc(c.Parent())
+		if parentFunc != nil {
+			return parentFunc(typedName)
+		}
+		return c.Parent().findSuggestions(typedName)
+	}
+	return c.findSuggestions(typedName)
+}
+
 // UsageString returns usage string.
 func (c *Command) UsageString() string {
 	// Storing normal writers

command_test.go

@@ -1393,6 +1393,126 @@ func TestSuggestions(t *testing.T) {
 	}
 }
 
+func TestCustomSuggestions(t *testing.T) {
+	rootCmd := &Command{Use: "root", Run: emptyRun}
+	timesCmd := &Command{Use: "times", Run: emptyRun}
+	rootCmd.AddCommand(timesCmd)
+
+	var expected, output string
+
+	expected = ""
+	output, _ = executeCommand(rootCmd, "times")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	expected = fmt.Sprintf("Error: unknown command \"%s\" for \"root\"\n\nDid you mean this?\n\t%s\n\nRun 'root --help' for usage.\n", "time", "times")
+	output, _ = executeCommand(rootCmd, "time")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	rootCmd.DisableSuggestions = true
+
+	expected = fmt.Sprintf("Error: unknown command \"%s\" for \"root\"\nRun 'root --help' for usage.\n", "time")
+	output, _ = executeCommand(rootCmd, "time")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	rootCmd.DisableSuggestions = false
+	rootCmd.SetSuggestFunc(func(typedName string) string {
+		return "\nSome custom suggestion.\n"
+	})
+
+	expected = fmt.Sprintf("Error: unknown command \"%s\" for \"root\"\nSome custom suggestion.\n\nRun 'root --help' for usage.\n", "time")
+	output, _ = executeCommand(rootCmd, "time")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+}
+
+func TestCustomSuggestions_OnlyValidArgs(t *testing.T) {
+	validArgs := []string{"a"}
+	rootCmd := &Command{Use: "root", Args: OnlyValidArgs, Run: emptyRun, ValidArgs: validArgs}
+	grandparentCmd := &Command{Use: "grandparent", Args: OnlyValidArgs, Run: emptyRun, ValidArgs: validArgs}
+	parentCmd := &Command{Use: "parent", Args: OnlyValidArgs, Run: emptyRun, ValidArgs: validArgs}
+	timesCmd := &Command{Use: "times", Run: emptyRun}
+	parentCmd.AddCommand(timesCmd)
+	grandparentCmd.AddCommand(parentCmd)
+	rootCmd.AddCommand(grandparentCmd)
+
+	var expected, output string
+
+	// No typos.
+	expected = ""
+	output, _ = executeCommand(rootCmd, "grandparent")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	expected = ""
+	output, _ = executeCommand(rootCmd, "grandparent", "parent")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	expected = ""
+	output, _ = executeCommand(rootCmd, "grandparent", "parent", "times")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	// 1st level typo.
+	expected = "Error: invalid argument \"grandparen\" for \"root\"\n\nDid you mean this?\n\tgrandparent\n\nUsage:\n  root [flags]\n  root [command]\n\nAvailable Commands:\n  completion  Generate the autocompletion script for the specified shell\n  grandparent \n  help        Help about any command\n\nFlags:\n  -h, --help   help for root\n\nUse \"root [command] --help\" for more information about a command.\n\n"
+	output, _ = executeCommand(rootCmd, "grandparen")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	// 2nd level typo.
+	expected = "Error: invalid argument \"paren\" for \"root grandparent\"\nUsage:\n  root grandparent [flags]\n  root grandparent [command]\n\nAvailable Commands:\n  parent      \n\nFlags:\n  -h, --help   help for grandparent\n\nUse \"root grandparent [command] --help\" for more information about a command.\n\n"
+	output, _ = executeCommand(rootCmd, "grandparent", "paren")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	// 3rd level typo.
+	expected = "Error: invalid argument \"time\" for \"root grandparent parent\"\nUsage:\n  root grandparent parent [flags]\n  root grandparent parent [command]\n\nAvailable Commands:\n  times       \n\nFlags:\n  -h, --help   help for parent\n\nUse \"root grandparent parent [command] --help\" for more information about a command.\n\n"
+	output, _ = executeCommand(rootCmd, "grandparent", "parent", "time")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	// Custom suggestion on root function.
+	rootCmd.SetSuggestFunc(func(typedName string) string {
+		return "\nRoot custom suggestion.\n"
+	})
+
+	expected = "Error: invalid argument \"grandparen\" for \"root\"\nRoot custom suggestion.\n\nUsage:\n  root [flags]\n  root [command]\n\nAvailable Commands:\n  completion  Generate the autocompletion script for the specified shell\n  grandparent \n  help        Help about any command\n\nFlags:\n  -h, --help   help for root\n\nUse \"root [command] --help\" for more information about a command.\n\n"
+	output, _ = executeCommand(rootCmd, "grandparen")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	expected = "Error: invalid argument \"time\" for \"root grandparent parent\"\nRoot custom suggestion.\n\nUsage:\n  root grandparent parent [flags]\n  root grandparent parent [command]\n\nAvailable Commands:\n  times       \n\nFlags:\n  -h, --help   help for parent\n\nUse \"root grandparent parent [command] --help\" for more information about a command.\n\n"
+	output, _ = executeCommand(rootCmd, "grandparent", "parent", "time")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+
+	// Custom suggestion on parent function (kept root's to make sure this one is prioritised).
+	parentCmd.SetSuggestFunc(func(typedName string) string {
+		return "\nParent custom suggestion.\n"
+	})
+
+	expected = "Error: invalid argument \"time\" for \"root grandparent parent\"\nParent custom suggestion.\n\nUsage:\n  root grandparent parent [flags]\n  root grandparent parent [command]\n\nAvailable Commands:\n  times       \n\nFlags:\n  -h, --help   help for parent\n\nUse \"root grandparent parent [command] --help\" for more information about a command.\n\n"
+	output, _ = executeCommand(rootCmd, "grandparent", "parent", "time")
+	if output != expected {
+		t.Errorf("\nExpected:\n %q\nGot:\n %q", expected, output)
+	}
+}
+
 func TestCaseInsensitive(t *testing.T) {
 	rootCmd := &Command{Use: "root", Run: emptyRun}
 	childCmd := &Command{Use: "child", Run: emptyRun, Aliases: []string{"alternative"}}