flag: add optional value description to string parameters

vlib/flag/flag.v

@@ -400,19 +400,39 @@ pub fn (mut fs FlagParser) float(name string, abbr u8, fdefault f64, usage strin
 	return value
 }
 
+@[params]
+pub struct FlagConfig {
+pub:
+	val_desc string // descriptive string for an argument
+}
+
 // string_multi returns all string values, associated with the flag named `name`.
 // When no values for that flag are found, it returns an empty array.
 // This version supports abbreviations.
-pub fn (mut fs FlagParser) string_multi(name string, abbr u8, usage string) []string {
-	fs.add_flag(name, abbr, usage, '<multiple strings>')
+// This version supports a custom value description.
+pub fn (mut fs FlagParser) string_multi(name string, abbr u8, usage string, c FlagConfig) []string {
+	val_desc := if c.val_desc == '' {
+		'<multiple strings>'
+	} else {
+		c.val_desc
+	}
+
+	fs.add_flag(name, abbr, usage, val_desc)
 	return fs.parse_value(name, abbr)
 }
 
 // string_opt returns an option with the string value, associated with the flag in `name`.
 // When the flag is not given by the user, it returns an error.
 // This version supports abbreviations.
-pub fn (mut fs FlagParser) string_opt(name string, abbr u8, usage string) !string {
-	fs.add_flag(name, abbr, usage, '<string>')
+// This version supports a custom value description.
+pub fn (mut fs FlagParser) string_opt(name string, abbr u8, usage string, c FlagConfig) !string {
+	val_desc := if c.val_desc == '' {
+		'<string>'
+	} else {
+		c.val_desc
+	}
+
+	fs.add_flag(name, abbr, usage, val_desc)
 	parsed := fs.parse_value(name, abbr)
 	if parsed.len == 0 {
 		return error("parameter '${name}' not provided")
@@ -424,8 +444,9 @@ pub fn (mut fs FlagParser) string_opt(name string, abbr u8, usage string) !strin
 // If that flag is given as an option, then its parsed value is returned as a string.
 // When it is not, it returns the default string value in `sdefault`.
 // This version supports abbreviations.
-pub fn (mut fs FlagParser) string(name string, abbr u8, sdefault string, usage string) string {
-	value := fs.string_opt(name, abbr, usage) or { return sdefault }
+// This version supports a custom value description.
+pub fn (mut fs FlagParser) string(name string, abbr u8, sdefault string, usage string, c FlagConfig) string {
+	value := fs.string_opt(name, abbr, usage, c) or { return sdefault }
 	return value
 }
 

vlib/flag/flag_test.v

@@ -194,6 +194,24 @@ fn test_if_no_options_given_usage_message_does_not_contain_options() {
 	assert !fp.usage().contains('Options:')
 }
 
+fn test_default_val_descriptions_for_strings() {
+	mut fp := flag.new_flag_parser([])
+	fp.string_multi('a_string', `a`, '')
+	fp.string('a_string', `s`, '', '')
+
+	assert fp.usage().contains('<multiple strings>')
+	assert fp.usage().contains('<string>')
+}
+
+fn test_custom_val_descriptions_for_strings() {
+	mut fp := flag.new_flag_parser([])
+	fp.string_multi('a_string', `a`, '', val_desc: '<multi custom>')
+	fp.string('a_string', `s`, '', '', val_desc: '<custom>')
+
+	assert fp.usage().contains('<multi custom>')
+	assert fp.usage().contains('<custom>')
+}
+
 fn test_free_args_could_be_limited() {
 	mut fp1 := flag.new_flag_parser(['a', 'b', 'c'])
 	fp1.limit_free_args(1, 4)!