v/vlib/flag/flag.v

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module flag
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// data object storing information about a defined flag
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pub struct Flag {
pub:
name string // name as it appears on command line
abbr byte // shortcut
usage string // help message
val_desc string // something like '<arg>' that appears in usage,
// and also the default value, when the flag is not given
}
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struct UnkownFlagError {
Error
flag string
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}
fn (err UnkownFlagError) msg() string {
return 'Unknown flag `$err.flag`'
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}
struct ArgsCountError {
Error
got int
want int
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}
fn (err ArgsCountError) msg() string {
if err.want == 0 {
return 'Expected no arguments, but got $err.got'
} else if err.got > err.want {
return 'Expected at most $err.want arguments, but got $err.got'
} else {
return 'Expected at least $err.want arguments, but got $err.got'
}
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}
// free frees the resources associated with a given Flag
// It is called automatically when -autofree is used.
// It should be called manually in functions that use Flags,
// and are marked with [manualfree]. After you call .free() on
// a Flag instance, you should NOT use that instance any more.
[unsafe]
fn (mut f Flag) free() {
unsafe {
f.name.free()
f.usage.free()
f.val_desc.free()
}
}
// str returns a string representation of the given Flag
pub fn (f Flag) str() string {
return '' + ' flag:\n' + ' name: $f.name\n' +
' abbr: `$f.abbr.ascii_str()`\n' + ' usag: $f.usage\n' +
' desc: $f.val_desc'
}
// str returns a string representation of the given array of Flags
pub fn (af []Flag) str() string {
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mut res := []string{}
res << '\n []Flag = ['
for f in af {
res << f.str()
}
res << ' ]'
return res.join('\n')
}
// FlagParser is the heart of the `flag` module.
// That structure is created with `mut parser := flag.new_flag_parser(os.args)`,
// The returned instance can be further customised by calling various methods,
// for specifying the accepted options and their values. The user should finally
// call `rest := parser.finalize() ?` to get the rest of the non optional arguments
// (if there are any left).
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pub struct FlagParser {
pub:
original_args []string // the original arguments to be parsed
idx_dashdash int // the index of a `--`, -1 if there is not any
all_after_dashdash []string // all options after `--` are ignored, and will be passed to the application unmodified
pub mut:
usage_examples []string // when set, --help will print:
// Usage: $appname $usage_examples[0]`
// or: $appname $usage_examples[1]`
// etc
default_help_label string = 'display this help and exit'
default_version_label string = 'output version information and exit'
args []string // the current list of processed args
max_free_args int
flags []Flag // registered flags
application_name string
application_version string
application_description string
min_free_args int
args_description string
allow_unknown_args bool // whether passing undescribed arguments is allowed
footers []string // when set, --help will display all the collected footers at the bottom.
}
// free frees the resources allocated for the given FlagParser instance.
// It should be called manually in functions that use it, and that are
// marked with `[manualfree]`, otherwise, it is called automatically
// in programs, compiled with `-autofree`. NB: you should NOT use the
// instance over which you have called .free() for anything after the call.
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[unsafe]
fn (mut f FlagParser) free() {
unsafe {
for a in f.args {
a.free()
}
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f.args.free()
//
for flag in f.flags {
flag.free()
}
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f.flags.free()
//
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f.application_name.free()
f.application_version.free()
f.application_description.free()
f.args_description.free()
}
}
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pub const (
// used for formating usage message
space = ' '
underline = '-----------------------------------------------'
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max_args_number = 4048
)
// new_flag_parser - create a new flag parser for the given args
pub fn new_flag_parser(args []string) &FlagParser {
original_args := args.clone()
idx_dashdash := args.index('--')
mut all_before_dashdash := args.clone()
mut all_after_dashdash := []string{}
if idx_dashdash >= 0 {
all_before_dashdash.trim(idx_dashdash)
if idx_dashdash < original_args.len {
all_after_dashdash = original_args[idx_dashdash + 1..]
}
}
return &FlagParser{
original_args: original_args
idx_dashdash: idx_dashdash
all_after_dashdash: all_after_dashdash
args: all_before_dashdash
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max_free_args: flag.max_args_number
}
}
// usage_example - add an usage example
// All examples will be listed in the help screen.
// If you do not give any examples, then a default usage
// will be shown, based on whether the application takes
// options and expects additional parameters.
pub fn (mut fs FlagParser) usage_example(example string) {
fs.usage_examples << example
}
// add_footer - add a footnote, that will be shown
// at the bottom of the help screen.
pub fn (mut fs FlagParser) footer(footer string) {
fs.footers << footer
}
// change the application name to be used in 'usage' output
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pub fn (mut fs FlagParser) application(name string) {
fs.application_name = name
}
// change the application version to be used in 'usage' output
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pub fn (mut fs FlagParser) version(vers string) {
fs.application_version = vers
}
// description appends to the application description lines, shown
// in the help/usage screen
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pub fn (mut fs FlagParser) description(desc string) {
if fs.application_description.len == 0 {
fs.application_description = desc
} else {
fs.application_description += '\n$desc'
}
}
// in most cases you do not need the first argv for flag parsing
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pub fn (mut fs FlagParser) skip_executable() {
fs.args.delete(0)
}
// allow_unknown_args - if your program has sub commands, that have
// their own arguments, you can call .allow_unknown_args(), so that
// the subcommand arguments (which generally are not known to your
// parent program), will not cause the validation in .finalize() to fail.
pub fn (mut fs FlagParser) allow_unknown_args() {
fs.allow_unknown_args = true
}
// private helper to register a flag
// This version supports abbreviations.
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fn (mut fs FlagParser) add_flag(name string, abbr byte, usage string, desc string) {
fs.flags << Flag{
name: name
abbr: abbr
usage: usage
val_desc: desc
}
}
// private: general parsing a single argument
// - search args for existence
// if true
// extract the defined value as string
// else
// return an (dummy) error -> argument is not defined
//
// - the name, usage are registered
// - found arguments and corresponding values are removed from args list
[manualfree]
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fn (mut fs FlagParser) parse_value(longhand string, shorthand byte) []string {
full := '--$longhand'
defer {
unsafe { full.free() }
}
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mut found_entries := []string{}
mut to_delete := []int{}
defer {
unsafe { to_delete.free() }
}
mut should_skip_one := false
for i, arg in fs.args {
if should_skip_one {
should_skip_one = false
continue
}
if arg.len == 0 || arg[0] != `-` {
continue
}
if (arg.len == 2 && arg[0] == `-` && arg[1] == shorthand) || arg == full {
if i + 1 >= fs.args.len {
return []
}
nextarg := fs.args[i + 1]
if nextarg.len > 2 {
nextarg_rest := nextarg[..2]
if nextarg_rest == '--' {
// It could be end of input (--) or another argument (--abc).
// Both are invalid so die.
unsafe { nextarg_rest.free() }
return []
}
unsafe { nextarg_rest.free() }
}
found_entries << fs.args[i + 1]
to_delete << i
to_delete << i + 1
should_skip_one = true
continue
}
if arg.len > full.len + 1 && arg[..full.len + 1] == '$full=' {
found_entries << arg[full.len + 1..]
to_delete << i
continue
}
}
for i, del in to_delete {
// i entrys are deleted so it's shifted left i times.
fs.args.delete(del - i)
}
return found_entries
}
// special parsing for bool values
// see also: parse_value
//
// special: it is allowed to define bool flags without value
// -> '--flag' is parsed as true
// -> '--flag' is equal to '--flag=true'
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fn (mut fs FlagParser) parse_bool_value(longhand string, shorthand byte) ?string {
{
full := '--$longhand'
for i, arg in fs.args {
if arg.len == 0 {
continue
}
if arg[0] != `-` {
continue
}
if (arg.len == 2 && arg[0] == `-` && arg[1] == shorthand) || arg == full {
if fs.args.len > i + 1 && (fs.args[i + 1] in ['true', 'false']) {
val := fs.args[i + 1]
fs.args.delete(i + 1)
fs.args.delete(i)
return val
} else {
fs.args.delete(i)
return 'true'
}
}
if arg.len > full.len + 1 && arg[..full.len + 1] == '$full=' {
// Flag abc=true
val := arg[full.len + 1..]
fs.args.delete(i)
return val
}
if arg.len > 1 && arg[0] == `-` && arg[1] != `-` && arg.index_byte(shorthand) != -1 {
// -abc is equivalent to -a -b -c
return 'true'
}
}
}
return error("parameter '$longhand' not found")
}
// bool_opt returns an option with the bool value of the given command line flag, named `name`.
// It returns an error, when the flag is not given by the user.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) bool_opt(name string, abbr byte, usage string) ?bool {
mut res := false
{
fs.add_flag(name, abbr, usage, '<bool>')
parsed := fs.parse_bool_value(name, abbr) or {
return error("parameter '$name' not provided")
}
res = parsed == 'true'
}
return res
}
// bool defines and parses a string flag/option named `name`.
// If that flag is given by the user, then it returns its parsed bool value.
// When it is not, it returns the default value in `bdefault`.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) bool(name string, abbr byte, bdefault bool, usage string) bool {
value := fs.bool_opt(name, abbr, usage) or { return bdefault }
return value
}
// int_multi returns all values associated with the provided flag in `name`.
// When that flag has no values, it returns an empty array.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) int_multi(name string, abbr byte, usage string) []int {
fs.add_flag(name, abbr, usage, '<multiple ints>')
parsed := fs.parse_value(name, abbr)
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mut value := []int{}
for val in parsed {
value << val.int()
}
return value
}
// int_opt returns an option with the integer value, associated with the flag in `name`.
// When the flag is not given by the user, it returns an error.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) int_opt(name string, abbr byte, usage string) ?int {
mut res := 0
{
fs.add_flag(name, abbr, usage, '<int>')
parsed := fs.parse_value(name, abbr)
if parsed.len == 0 {
return error("parameter '$name' not provided")
}
parsed0 := parsed[0]
res = parsed0.int()
}
return res
}
// int defines and parses an integer flag, named `name`.
// When the flag is given by the user, it returns its parsed integer value.
// When it is not, it returns the integer value in `idefault`.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) int(name string, abbr byte, idefault int, usage string) int {
value := fs.int_opt(name, abbr, usage) or { return idefault }
return value
}
// float_multi returns all floating point values, associated with the flag named `name`.
// When no values for that flag are found, it returns an empty array.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) float_multi(name string, abbr byte, usage string) []f64 {
fs.add_flag(name, abbr, usage, '<multiple floats>')
parsed := fs.parse_value(name, abbr)
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mut value := []f64{}
for val in parsed {
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value << val.f64()
}
return value
}
// float_opt returns an option with the floating point value, associated with the flag in `name`.
// When the flag is not given by the user, it returns an error.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) float_opt(name string, abbr byte, usage string) ?f64 {
mut res := 0.0
{
fs.add_flag(name, abbr, usage, '<float>')
parsed := fs.parse_value(name, abbr)
if parsed.len == 0 {
return error("parameter '$name' not provided")
}
res = parsed[0].f64()
}
return res
}
// float defines and parses a floating point flag, named `name`.
// When the flag is given by the user, it returns its parsed floating point value.
// When it is not, it returns the value in `fdefault`.
// This version supports abbreviations.
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pub fn (mut fs FlagParser) float(name string, abbr byte, fdefault f64, usage string) f64 {
value := fs.float_opt(name, abbr, usage) or { return fdefault }
return value
}
// 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.
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pub fn (mut fs FlagParser) string_multi(name string, abbr byte, usage string) []string {
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fs.add_flag(name, abbr, usage, '<multiple strings>')
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.
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pub fn (mut fs FlagParser) string_opt(name string, abbr byte, usage string) ?string {
mut res := ''
{
fs.add_flag(name, abbr, usage, '<string>')
parsed := fs.parse_value(name, abbr)
if parsed.len == 0 {
return error("parameter '$name' not provided")
}
res = parsed[0]
}
return res
}
// string defines and parses a string flag/option, named `name`.
// 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.
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pub fn (mut fs FlagParser) string(name string, abbr byte, sdefault string, usage string) string {
value := fs.string_opt(name, abbr, usage) or { return sdefault }
return value
}
// limit_free_args_to_at_least restricts the list of free arguments (non options) to be
// at least `n` in length. If the user gives less free arguments to the program,
// the parser will return an error.
pub fn (mut fs FlagParser) limit_free_args_to_at_least(n int) ? {
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if n > flag.max_args_number {
return error('flag.limit_free_args_to_at_least expect n to be smaller than $flag.max_args_number')
}
if n <= 0 {
return error('flag.limit_free_args_to_at_least expect n to be a positive number')
}
fs.min_free_args = n
}
// limit_free_args_to_exactly restricts the list of free arguments (non options) to be
// at exactly `n` in length. If the user gives more or less free arguments to the program,
// the parser will return an error.
pub fn (mut fs FlagParser) limit_free_args_to_exactly(n int) ? {
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if n > flag.max_args_number {
return error('flag.limit_free_args_to_exactly expect n to be smaller than $flag.max_args_number')
}
if n < 0 {
return error('flag.limit_free_args_to_exactly expect n to be a non negative number')
}
fs.min_free_args = n
fs.max_free_args = n
}
// limit_free_args restricts the list of free arguments (non options) to be between
// `min` and `max` in length. If the user gives more or less free arguments to the program,
// the parser will return an error.
pub fn (mut fs FlagParser) limit_free_args(min int, max int) ? {
if min > max {
return error('flag.limit_free_args expect min < max, got $min >= $max')
}
fs.min_free_args = min
fs.max_free_args = max
}
// arguments_description sets the description field of the parser.
// This field is usually shown when the `--help` option is given to the program.
pub fn (mut fs FlagParser) arguments_description(description string) {
fs.args_description = description
}
// usage returns a nicely formatted usage screen, containing all the
// possible options, as well as the description for the program.
// That screen is usually shown when the `--help` option is given to the program.
pub fn (fs FlagParser) usage() string {
positive_min_arg := (fs.min_free_args > 0)
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positive_max_arg := (fs.max_free_args > 0 && fs.max_free_args != flag.max_args_number)
no_arguments := (fs.min_free_args == 0 && fs.max_free_args == 0)
mut adesc := if fs.args_description.len > 0 { fs.args_description } else { '[ARGS]' }
if no_arguments {
adesc = ''
}
mut use := []string{}
if fs.application_version != '' {
use << '$fs.application_name $fs.application_version'
use << '$flag.underline'
}
if fs.usage_examples.len == 0 {
use << 'Usage: $fs.application_name [options] $adesc'
} else {
for i, example in fs.usage_examples {
if i == 0 {
use << 'Usage: $fs.application_name $example'
} else {
use << ' or: $fs.application_name $example'
}
}
}
use << ''
if fs.application_description != '' {
use << 'Description: $fs.application_description'
use << ''
}
// show a message about the [ARGS]:
if positive_min_arg || positive_max_arg || no_arguments {
if no_arguments {
use << 'This application does not expect any arguments'
use << ''
} else {
mut s := []string{}
if positive_min_arg {
s << 'at least $fs.min_free_args'
}
if positive_max_arg {
s << 'at most $fs.max_free_args'
}
if positive_min_arg && positive_max_arg && fs.min_free_args == fs.max_free_args {
s = ['exactly $fs.min_free_args']
}
sargs := s.join(' and ')
use << 'The arguments should be $sargs in number.'
use << ''
}
}
if fs.flags.len > 0 {
use << 'Options:'
for f in fs.flags {
mut onames := []string{}
if f.abbr != 0 {
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onames << '-$f.abbr.ascii_str()'
}
if f.name != '' {
if !f.val_desc.contains('<bool>') {
onames << '--$f.name $f.val_desc'
} else {
onames << '--$f.name'
}
}
option_names := ' ' + onames.join(', ')
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mut xspace := ''
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if option_names.len > flag.space.len - 2 {
xspace = '\n$flag.space'
} else {
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xspace = flag.space[option_names.len..]
}
fdesc := '$option_names$xspace$f.usage'
use << fdesc
}
}
for footer in fs.footers {
use << footer
}
return use.join('\n').replace('- ,', ' ')
}
// find_existing_flag looks up the given flag by name, and returns
// it, if it was found in the FlagParser. If it was not, it returns an error.
fn (mut fs FlagParser) find_existing_flag(fname string) ?Flag {
for f in fs.flags {
if f.name == fname {
return f
}
}
return error('no such flag')
}
// handle_builtin_options handles the default behaviour of the very frequently
// given options: `--help` and `--version`.
// You can change/customise that, by defining your own options with these names.
fn (mut fs FlagParser) handle_builtin_options() {
mut show_version := false
mut show_help := false
fs.find_existing_flag('help') or {
show_help = fs.bool('help', `h`, false, fs.default_help_label)
}
fs.find_existing_flag('version') or {
show_version = fs.bool('version', 0, false, fs.default_version_label)
}
if show_help {
println(fs.usage())
exit(0)
}
if show_version {
println('$fs.application_name $fs.application_version')
exit(0)
}
}
// finalize - return all remaining arguments (non options).
// Call .finalize() after all arguments are defined.
// The remaining arguments are returned in the same order they are
// defined on the command line. If additional flags are found, i.e.
// (things starting with '--' or '-'), it returns an error.
pub fn (mut fs FlagParser) finalize() ?[]string {
fs.handle_builtin_options()
mut remaining := fs.args.clone()
if !fs.allow_unknown_args {
for a in remaining {
if (a.len >= 2 && a[..2] == '--') || (a.len == 2 && a[0] == `-`) {
return IError(&UnkownFlagError{
flag: a
})
}
}
}
if remaining.len < fs.min_free_args && fs.min_free_args > 0 {
return IError(&ArgsCountError{
want: fs.min_free_args
got: remaining.len
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})
}
if remaining.len > fs.max_free_args && fs.max_free_args > 0 {
return IError(&ArgsCountError{
want: fs.max_free_args
got: remaining.len
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})
}
if remaining.len > 0 && fs.max_free_args == 0 && fs.min_free_args == 0 {
return IError(&ArgsCountError{
want: 0
got: remaining.len
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})
}
remaining << fs.all_after_dashdash
return remaining
}
// remaining_parameters will return all remaining parameters.
// Call .remaining_parameters() *AFTER* you have defined all options
// that your program needs. remaining_parameters will also print any
// parsing errors and stop the program. Use .finalize() instead, if
// you want more control over the error handling.
pub fn (mut fs FlagParser) remaining_parameters() []string {
return fs.finalize() or {
eprintln(err.msg())
println(fs.usage())
exit(1)
}
}