Please complete the following tasks
Rust Version
rustc 1.56.0 (09c42c458 2021-10-18)
Clap Version
master
Minimal reproducible code
use clap::Parser;
#[derive(Parser, Debug)]
struct Opt {
#[clap(short,long)]
foo: Option<Option<String>>,
input: String,
}
fn main() {
let opt = Opt::parse();
println!("{:?}", opt);
}Steps to reproduce the bug with the above code
or
Actual Behaviour
error: The following required arguments were not provided:
<INPUT>
USAGE:
clap-test --foo <FOO> <INPUT>
For more information try --help
Expected Behaviour
Opt { foo: Some(None), input: "input" }
Additional Context
There needs to be some special handling of options with optional arguments.
Optional option-arguments are bad
First of all, users really need to be discouraged (if we ever add some lint-like feature, e.g. #[clap(enable-warnings)).
POSIX says:
Option-arguments should not be optional.
Solaris says:
Option-arguments cannot be optional.
Parsing
I know some people have a preference for -f OptArg over -fOptArg, but if the option-argument is optional, then only the latter is correct. If there is a space, it means the optional argument is not there.
From POSIX.1-2017 - Ch. 12: Utility Conventions:
a conforming application shall place any option-argument for that option directly adjacent to the option in the same argument string, without intervening <blank> characters
If the utility receives an argument containing only the option, it shall behave as specified in its description for an omitted option-argument; it shall not treat the next argument (if any) as the option-argument for that option.
Same thing with the long option, which is a GNU extension.
From GNU C Library Reference Manual - Ch. 25.1.1: Program Argument Syntax Conventions:
To specify an argument for a long option, write --name=value. This syntax enables a long option to accept an argument that is itself optional.
See this SO question about how getopt handles this: getopt does not parse optional arguments to parameters.
In clap terms, these are saying we should only allow
--long--long=value-s-svalue
In contrast, clap supports
- Default:
--long--long=value--long value-s-s value-s=value-svalue
requires_equals(true)
--long--long=value-s-s=value
Debug Output
[ clap::build::app] App::_do_parse
[ clap::build::app] App::_build
[ clap::build::app] App::_propagate:clap-test
[ clap::build::app] App::_check_help_and_version
[ clap::build::app] App::_check_help_and_version: Removing generated version
[ clap::build::app] App::_propagate_global_args:clap-test
[ clap::build::app] App::_derive_display_order:clap-test
[clap::build::app::debug_asserts] App::_debug_asserts
[clap::build::arg::debug_asserts] Arg::_debug_asserts:help
[clap::build::arg::debug_asserts] Arg::_debug_asserts:foo
[clap::build::arg::debug_asserts] Arg::_debug_asserts:input
[ clap::parse::parser] Parser::get_matches_with
[ clap::parse::parser] Parser::_build
[ clap::parse::parser] Parser::_verify_positionals
[ clap::parse::parser] Parser::get_matches_with: Begin parsing 'RawOsStr("-f")' ([45, 102])
[ clap::parse::parser] Parser::get_matches_with: Positional counter...1
[ clap::parse::parser] Parser::get_matches_with: Low index multiples...false
[ clap::parse::parser] Parser::possible_subcommand: arg=RawOsStr("-f")
[ clap::parse::parser] Parser::get_matches_with: sc=None
[ clap::parse::parser] Parser::parse_short_arg: short_arg=RawOsStr("f")
[ clap::parse::parser] Parser::parse_short_arg:iter:f
[ clap::parse::parser] Parser::parse_short_arg:iter:f: cur_idx:=1
[ clap::parse::parser] Parser::parse_short_arg:iter:f: Found valid opt or flag
[ clap::parse::parser] Parser::parse_short_arg:iter:f: val=RawOsStr("") (bytes), val=[] (ascii), short_arg=RawOsStr("f")
[ clap::parse::parser] Parser::parse_opt; opt=foo, val=None
[ clap::parse::parser] Parser::parse_opt; opt.settings=ArgFlags(TAKES_VAL)
[ clap::parse::parser] Parser::parse_opt; Checking for val...
[ clap::parse::parser] Parser::parse_opt: More arg vals required...
[ clap::parse::arg_matcher] ArgMatcher::inc_occurrence_of: arg=foo
[ clap::build::app] App::groups_for_arg: id=foo
[ clap::build::app] App::groups_for_arg: id=foo
[ clap::parse::parser] Parser::get_matches_with: After parse_short_arg Opt(foo)
[ clap::parse::parser] Parser::get_matches_with: Begin parsing 'RawOsStr("input")' ([105, 110, 112, 117, 116])
[ clap::parse::parser] Parser::get_matches_with: Positional counter...1
[ clap::parse::parser] Parser::get_matches_with: Low index multiples...false
[ clap::parse::parser] Parser::add_val_to_arg; arg=foo, val=RawOsStr("input")
[ clap::parse::parser] Parser::add_val_to_arg; trailing_values=false, DontDelimTrailingVals=false
[ clap::parse::parser] Parser::add_single_val_to_arg: adding val..."input"
[ clap::parse::parser] Parser::add_single_val_to_arg: cur_idx:=2
[ clap::build::app] App::groups_for_arg: id=foo
[ clap::parse::arg_matcher] ArgMatcher::needs_more_vals: o=foo
[ clap::parse::arg_matcher] ArgMatcher::needs_more_vals: max_vals...1
[ clap::parse::parser] Parser::remove_overrides
[ clap::parse::parser] Parser::remove_overrides:iter:foo
[ clap::parse::validator] Validator::validate
[ clap::parse::parser] Parser::add_env: Checking arg `--help`
[ clap::parse::parser] Parser::add_env: Skipping existing arg `--foo <FOO>`
[ clap::parse::parser] Parser::add_env: Checking arg `<INPUT>`
[ clap::parse::parser] Parser::add_defaults
[ clap::parse::parser] Parser::add_defaults:iter:foo:
[ clap::parse::parser] Parser::add_value: doesn't have conditional defaults
[ clap::parse::parser] Parser::add_value:iter:foo: doesn't have default vals
[ clap::parse::parser] Parser::add_value:iter:foo: doesn't have default missing vals
[ clap::parse::parser] Parser::add_defaults:iter:input:
[ clap::parse::parser] Parser::add_value: doesn't have conditional defaults
[ clap::parse::parser] Parser::add_value:iter:input: doesn't have default vals
[ clap::parse::parser] Parser::add_value:iter:input: doesn't have default missing vals
[ clap::parse::validator] Validator::validate_conflicts
[ clap::parse::validator] Validator::validate_exclusive
[ clap::parse::validator] Validator::validate_exclusive:iter:foo
[ clap::parse::validator] Validator::gather_conflicts
[ clap::parse::validator] Validator::gather_conflicts:iter: id=foo
[ clap::build::app] App::groups_for_arg: id=foo
[ clap::parse::validator] Validator::validate_required: required=ChildGraph([Child { id: input, children: [] }])
[ clap::parse::validator] Validator::gather_requirements
[ clap::parse::validator] Validator::gather_requirements:iter:foo
[ clap::parse::validator] Validator::validate_required:iter:aog=input
[ clap::parse::validator] Validator::validate_required:iter: This is an arg
[ clap::parse::validator] Validator::is_missing_required_ok: input
[ clap::parse::validator] Validator::validate_arg_conflicts: a="input"
[ clap::parse::validator] Validator::missing_required_error; incl=[]
[ clap::parse::validator] Validator::missing_required_error: reqs=ChildGraph([Child { id: input, children: [] }])
[ clap::output::usage] Usage::get_required_usage_from: incls=[], matcher=true, incl_last=true
[ clap::output::usage] Usage::get_required_usage_from: unrolled_reqs={input}
[ clap::output::usage] Usage::get_required_usage_from:iter:input
[ clap::output::usage] Usage::get_required_usage_from: ret_val=["<INPUT>"]
[ clap::parse::validator] Validator::missing_required_error: req_args=[
"<INPUT>",
]
[ clap::output::usage] Usage::create_usage_with_title
[ clap::output::usage] Usage::create_usage_no_title
[ clap::output::usage] Usage::create_smart_usage
[ clap::output::usage] Usage::get_required_usage_from: incls=[foo], matcher=false, incl_last=true
[ clap::output::usage] Usage::get_required_usage_from: unrolled_reqs={input}
[ clap::output::usage] Usage::get_required_usage_from:iter:foo
[ clap::output::usage] Usage::get_required_usage_from:iter:input
[ clap::output::usage] Usage::get_required_usage_from: ret_val=["--foo <FOO>", "<INPUT>"]
[ clap::build::app] App::color: Color setting...
[ clap::build::app] Auto
[ clap::output::fmt] is_a_tty: stderr=true
Please complete the following tasks
Rust Version
rustc 1.56.0 (09c42c458 2021-10-18)
Clap Version
master
Minimal reproducible code
Steps to reproduce the bug with the above code
or
Actual Behaviour
Expected Behaviour
Additional Context
There needs to be some special handling of options with optional arguments.
Optional option-arguments are bad
First of all, users really need to be discouraged (if we ever add some lint-like feature, e.g.
#[clap(enable-warnings)).POSIX says:
Solaris says:
Parsing
I know some people have a preference for
-f OptArgover-fOptArg, but if the option-argument is optional, then only the latter is correct. If there is a space, it means the optional argument is not there.From POSIX.1-2017 - Ch. 12: Utility Conventions:
Same thing with the long option, which is a GNU extension.
From GNU C Library Reference Manual - Ch. 25.1.1: Program Argument Syntax Conventions:
See this SO question about how
getopthandles this:getoptdoes not parse optional arguments to parameters.In clap terms, these are saying we should only allow
--long--long=value-s-svalueIn contrast, clap supports
--long--long=value--long value-s-s value-s=value-svaluerequires_equals(true)--long--long=value-s-s=valueDebug Output