ArgMatcher with max_values consumes one more argument than it should

[sphynx]

Rust Version

rustc-1.36.0-nightly

Affected Version of clap

2.33.0

Bug or Feature Request Summary

If I set max_values = 1 for an option I expect that the option should consume only one argument and leave the rest for the next parsers. However, due to one-off error in ArgMatcher, it now consumes two arguments (and then fails validation, because it took one more than it should).

For example, I expect that:

prog --field 1 FILE

Should be parsed correct if --field has max-values=1 and FILE is a positional arguments. However, FILE is consumed by ArgMatcher as the second value for the --file option, which then leads to validation error.

Steps to Reproduce the issue

cargo run

Sample Code or Link to Sample Code

use clap::{App, Arg};

fn main() {
    let res = App::new("prog")
        .arg(
            Arg::with_name("field")
                .takes_value(true)
                .multiple(false)
                .max_values(1)
                .long("field"),
        )
        .arg(
            Arg::with_name("positional")
                .required(true)
                .index(1),
        )
        .get_matches_from_safe(vec!["prog", "--field", "1", "file"]);

    assert!(res.is_ok());
}

Debug output

Compile clap with cargo features "debug" such as:

[dependencies]
clap = { version = "2", features = ["debug"] }

Debug Output

DEBUG:clap:Parser::propagate_settings: self=prog, g_settings=AppFlags(

(empty),

)

DEBUG:clap:Parser::get_matches_with;

DEBUG:clap:Parser::create_help_and_version;

DEBUG:clap:Parser::create_help_and_version: Building --help

DEBUG:clap:Parser::create_help_and_version: Building --version

DEBUG:clap:Parser::get_matches_with: Begin parsing '"--field"' ([45, 45, 102, 105, 101, 108, 100])

DEBUG:clap:Parser::is_new_arg:"--field":NotFound

DEBUG:clap:Parser::is_new_arg: arg_allows_tac=false

DEBUG:clap:Parser::is_new_arg: -- found

DEBUG:clap:Parser::is_new_arg: starts_new_arg=true

DEBUG:clap:Parser::possible_subcommand: arg="--field"

DEBUG:clap:Parser::get_matches_with: possible_sc=false, sc=None

DEBUG:clap:ArgMatcher::process_arg_overrides:None;

DEBUG:clap:Parser::parse_long_arg;

DEBUG:clap:Parser::parse_long_arg: Does it contain '='...No

DEBUG:clap:OptBuilder::fmt:field

DEBUG:clap:Parser::parse_long_arg: Found valid opt '--field '

DEBUG:clap:Parser::parse_opt; opt=field, val=None

DEBUG:clap:Parser::parse_opt; opt.settings=ArgFlags(EMPTY_VALS | TAKES_VAL | DELIM_NOT_SET)

DEBUG:clap:Parser::parse_opt; Checking for val...None

DEBUG:clap:ArgMatcher::inc_occurrence_of: arg=field

DEBUG:clap:ArgMatcher::inc_occurrence_of: first instance

DEBUG:clap:Parser::groups_for_arg: name=field

DEBUG:clap:Parser::groups_for_arg: No groups defined

DEBUG:clap:Parser::parse_opt: More arg vals required...

DEBUG:clap:Parser:get_matches_with: After parse_long_arg Opt("field")

DEBUG:clap:Parser::get_matches_with: Begin parsing '"1"' ([49])

DEBUG:clap:Parser::is_new_arg:"1":Opt("field")

DEBUG:clap:Parser::is_new_arg: arg_allows_tac=false

DEBUG:clap:Parser::is_new_arg: probably value

DEBUG:clap:Parser::is_new_arg: starts_new_arg=false

DEBUG:clap:Parser::add_val_to_arg; arg=field, val="1"

DEBUG:clap:Parser::add_val_to_arg; trailing_vals=false, DontDelimTrailingVals=false

DEBUG:clap:Parser::add_single_val_to_arg;

DEBUG:clap:Parser::add_single_val_to_arg: adding val..."1"

DEBUG:clap:Parser::groups_for_arg: name=field

DEBUG:clap:Parser::groups_for_arg: No groups defined

DEBUG:clap:ArgMatcher::needs_more_vals: o=field

DEBUG:clap:ArgMatcher::needs_more_vals: max_vals...1

DEBUG:clap:Parser::get_matches_with: Begin parsing '"file"' ([102, 105, 108, 101])

DEBUG:clap:Parser::is_new_arg:"file":Opt("field")

DEBUG:clap:Parser::is_new_arg: arg_allows_tac=false

DEBUG:clap:Parser::is_new_arg: probably value

DEBUG:clap:Parser::is_new_arg: starts_new_arg=false

DEBUG:clap:Parser::add_val_to_arg; arg=field, val="file"

DEBUG:clap:Parser::add_val_to_arg; trailing_vals=false, DontDelimTrailingVals=false

DEBUG:clap:Parser::add_single_val_to_arg;

DEBUG:clap:Parser::add_single_val_to_arg: adding val..."file"

DEBUG:clap:Parser::groups_for_arg: name=field

DEBUG:clap:Parser::groups_for_arg: No groups defined

DEBUG:clap:ArgMatcher::needs_more_vals: o=field

DEBUG:clap:ArgMatcher::needs_more_vals: max_vals...1

DEBUG:clap:ArgMatcher::process_arg_overrides:Some("field");

DEBUG:clap:Parser::remove_overrides:[];

DEBUG:clap:Validator::validate;

DEBUG:clap:Parser::add_defaults;

DEBUG:clap:Parser::add_defaults:iter:field: doesn't have conditional defaults

DEBUG:clap:Parser::add_defaults:iter:field: doesn't have default vals

DEBUG:clap:Parser::add_defaults:iter:positional: doesn't have conditional defaults

DEBUG:clap:Parser::add_defaults:iter:positional: doesn't have default vals

DEBUG:clap:Validator::validate_blacklist;

DEBUG:clap:Validator::validate_blacklist:iter:field;

DEBUG:clap:Parser::groups_for_arg: name=field

DEBUG:clap:Parser::groups_for_arg: No groups defined

DEBUG:clap:Validator::validate_required: required=["positional"];

DEBUG:clap:Validator::validate_required:iter:positional:

DEBUG:clap:Validator::is_missing_required_ok: a=positional

DEBUG:clap:Validator::validate_arg_conflicts: a="positional";

DEBUG:clap:Validator::validate_required_unless: a="positional";

DEBUG:clap:Validator::missing_required_error: extra=None

DEBUG:clap:Parser::color;

DEBUG:clap:Parser::color: Color setting...Auto

DEBUG:clap:is_a_tty: stderr=true

DEBUG:clap:Validator::missing_required_error: reqs=[

"positional",

]

DEBUG:clap:usage::get_required_usage_from: reqs=["positional"], extra=None

DEBUG:clap:usage::get_required_usage_from: after init desc_reqs=[]

DEBUG:clap:usage::get_required_usage_from: no more children

DEBUG:clap:usage::get_required_usage_from: final desc_reqs=["positional"]

DEBUG:clap:usage::get_required_usage_from: args_in_groups=[]

DEBUG:clap:Colorizer::error;

DEBUG:clap:Validator::missing_required_error: req_args="\n    \u{1b}[1;31m\u{1b}[0m"

DEBUG:clap:usage::create_usage_with_title;

DEBUG:clap:usage::create_usage_no_title;

DEBUG:clap:usage::smart_usage;

DEBUG:clap:usage::get_required_usage_from: reqs=["positional", "field"], extra=None

DEBUG:clap:usage::get_required_usage_from: after init desc_reqs=[]

DEBUG:clap:usage::get_required_usage_from: no more children

DEBUG:clap:usage::get_required_usage_from: final desc_reqs=["field", "positional"]

DEBUG:clap:usage::get_required_usage_from: args_in_groups=[]

DEBUG:clap:usage::get_required_usage_from:iter:field:

DEBUG:clap:OptBuilder::fmt:field

DEBUG:clap:Parser::color;

DEBUG:clap:Parser::color: Color setting...Auto

DEBUG:clap:is_a_tty: stderr=true

DEBUG:clap:Colorizer::error;

DEBUG:clap:Colorizer::good;

thread 'main' panicked at 'assertion failed: res.is_ok()', src/main.rs:19:5

note: Run with RUST_BACKTRACE=1 environment variable to display a backtrace.