cli: improvements to help and error messages (#6375)

examples/cli.v

@@ -12,6 +12,7 @@ fn main() {
 	mut greet_cmd := Command{
 		name: 'greet'
 		description: 'Prints greeting in different languages.'
+		usage: '<name>'
 		required_args: 1
 		pre_execute: greet_pre_func
 		execute: greet_func
@@ -44,13 +45,13 @@ fn greet_func(cmd Command) {
 	name := cmd.args[0]
 	for _ in 0 .. times {
 		match language {
-			'english' {
+			'english', 'en' {
 				println('Welcome $name')
 			}
-			'german' {
+			'german', 'de' {
 				println('Willkommen $name')
 			}
-			'dutch' {
+			'dutch', 'nl' {
 				println('Welkom $name')
 			}
 			else {

vlib/cli/command.v

@@ -269,7 +269,7 @@ fn (cmds []Command) get(name string) ?Command {
 			return cmd
 		}
 	}
-	return error('Command `$name` not found')
+	return error('Command `$name` not found in $cmds')
 }
 
 fn (cmds []Command) contains(name string) bool {

vlib/cli/flag.v

@@ -26,7 +26,7 @@ pub fn (flags []Flag) get_all_found() []Flag {
 
 pub fn (flag Flag) get_bool() ?bool {
 	if flag.flag != .bool {
-		return error('Invalid flag type')
+		return error('$flag.name: Invalid flag type `$flag.flag`, expected `bool`')
 	}
 	return flag.value == 'true'
 }
@@ -45,7 +45,7 @@ pub fn (flags []Flag) get_bool_or(name string, or_value bool) bool {
 
 pub fn (flag Flag) get_int() ?int {
 	if flag.flag != .int {
-		return error('Invalid flag type')
+		return error('$flag.name: Invalid flag type `$flag.flag`, expected `int`')
 	}
 	return flag.value.int()
 }
@@ -64,7 +64,7 @@ pub fn (flags []Flag) get_int_or(name string, or_value int) int {
 
 pub fn (flag Flag) get_float() ?f64 {
 	if flag.flag != .float {
-		return error('Invalid flag type')
+		return error('$flag.name: Invalid flag type `$flag.flag`, expected `float`')
 	}
 	return flag.value.f64()
 }
@@ -83,7 +83,7 @@ pub fn (flags []Flag) get_float_or(name string, or_value f64) f64 {
 
 pub fn (flag Flag) get_string() ?string {
 	if flag.flag != .string {
-		return error('Invalid flag type')
+		return error('$flag.name: Invalid flag type `$flag.flag`, expected `string`')
 	}
 	return flag.value
 }
@@ -159,7 +159,7 @@ fn (flags []Flag) get(name string) ?Flag {
 			return flag
 		}
 	}
-	return error('Flag `$name` not found')
+	return error('Flag `$name` not found in $flags')
 }
 
 fn (flags []Flag) contains(name string) bool {

vlib/cli/help.v

@@ -63,15 +63,16 @@ fn (cmd Command) help_message() string {
 	if cmd.commands.len > 0 {
 		help += ' [commands]'
 	}
+	if cmd.usage.len > 0 {
+		help += ' $cmd.usage'
+	} else {
 		for i in 0 .. cmd.required_args {
 			help += ' <arg$i>'
 		}
-	if cmd.usage.len > 0 {
-		help += ' $cmd.usage'
 	}
-	help += '\n\n'
+	help += '\n'
 	if cmd.description != '' {
-		help += '$cmd.description\n\n'
+		help += '\n$cmd.description\n'
 	}
 	mut abbrev_len := 0
 	mut name_len := min_description_indent_len
@@ -92,7 +93,7 @@ fn (cmd Command) help_message() string {
 		}
 	}
 	if cmd.flags.len > 0 {
-		help += 'Flags:\n'
+		help += '\nFlags:\n'
 		for flag in cmd.flags {
 			mut flag_name := ''
 			if flag.abbrev != '' && cmd.flags.have_abbrev() {
@@ -113,17 +114,15 @@ fn (cmd Command) help_message() string {
 			help += '$base_indent$flag_name$description_indent' + pretty_description(flag.description +
 				required, base_indent_len + name_len) + '\n'
 		}
-		help += '\n'
 	}
 	if cmd.commands.len > 0 {
-		help += 'Commands:\n'
+		help += '\nCommands:\n'
 		for command in cmd.commands {
 			base_indent := ' '.repeat(base_indent_len)
 			description_indent := ' '.repeat(name_len - command.name.len)
 			help += '$base_indent$command.name$description_indent' + pretty_description(command.description, name_len) +
 				'\n'
 		}
-		help += '\n'
 	}
 	return help
 }