1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
// Std
use std::{
    borrow::Cow,
    ffi::{OsStr, OsString},
    fmt::{Debug, Display},
    iter::{Cloned, Map},
    slice::Iter,
    str::FromStr,
};

// Third Party
use indexmap::IndexMap;

// Internal
use crate::{
    parse::MatchedArg,
    util::{termcolor::ColorChoice, Id, Key},
    {Error, INVALID_UTF8},
};

#[derive(Debug, Clone)]
pub(crate) struct SubCommand {
    pub(crate) id: Id,
    pub(crate) name: String,
    pub(crate) matches: ArgMatches,
}

/// Used to get information about the arguments that were supplied to the program at runtime by
/// the user. New instances of this struct are obtained by using the [`App::get_matches`] family of
/// methods.
///
/// # Examples
///
/// ```no_run
/// # use clap::{App, Arg};
/// let matches = App::new("MyApp")
///     .arg(Arg::new("out")
///         .long("output")
///         .required(true)
///         .takes_value(true))
///     .arg(Arg::new("debug")
///         .short('d')
///         .multiple(true))
///     .arg(Arg::new("cfg")
///         .short('c')
///         .takes_value(true))
///     .get_matches(); // builds the instance of ArgMatches
///
/// // to get information about the "cfg" argument we created, such as the value supplied we use
/// // various ArgMatches methods, such as ArgMatches::value_of
/// if let Some(c) = matches.value_of("cfg") {
///     println!("Value for -c: {}", c);
/// }
///
/// // The ArgMatches::value_of method returns an Option because the user may not have supplied
/// // that argument at runtime. But if we specified that the argument was "required" as we did
/// // with the "out" argument, we can safely unwrap because `clap` verifies that was actually
/// // used at runtime.
/// println!("Value for --output: {}", matches.value_of("out").unwrap());
///
/// // You can check the presence of an argument
/// if matches.is_present("out") {
///     // Another way to check if an argument was present, or if it occurred multiple times is to
///     // use occurrences_of() which returns 0 if an argument isn't found at runtime, or the
///     // number of times that it occurred, if it was. To allow an argument to appear more than
///     // once, you must use the .multiple(true) method, otherwise it will only return 1 or 0.
///     if matches.occurrences_of("debug") > 2 {
///         println!("Debug mode is REALLY on, don't be crazy");
///     } else {
///         println!("Debug mode kind of on");
///     }
/// }
/// ```
/// [`App::get_matches`]: ./struct.App.html#method.get_matches
#[derive(Debug, Clone)]
pub struct ArgMatches {
    pub(crate) args: IndexMap<Id, MatchedArg>,
    pub(crate) subcommand: Option<Box<SubCommand>>,
}

impl Default for ArgMatches {
    fn default() -> Self {
        ArgMatches {
            args: IndexMap::new(),
            subcommand: None,
        }
    }
}

impl ArgMatches {
    /// Gets the value of a specific [option] or [positional] argument (i.e. an argument that takes
    /// an additional value at runtime). If the option wasn't present at runtime
    /// it returns `None`.
    ///
    /// *NOTE:* If getting a value for an option or positional argument that allows multiples,
    /// prefer [`ArgMatches::values_of`] as `ArgMatches::value_of` will only return the *first*
    /// value.
    ///
    /// # Panics
    ///
    /// This method will [`panic!`] if the value contains invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("output")
    ///         .takes_value(true))
    ///     .get_matches_from(vec!["myapp", "something"]);
    ///
    /// assert_eq!(m.value_of("output"), Some("something"));
    /// ```
    /// [option]: ./struct.Arg.html#method.takes_value
    /// [positional]: ./struct.Arg.html#method.index
    /// [`ArgMatches::values_of`]: ./struct.ArgMatches.html#method.values_of
    /// [`panic!`]: https://doc.rust-lang.org/std/macro.panic!.html
    pub fn value_of<T: Key>(&self, id: T) -> Option<&str> {
        if let Some(arg) = self.args.get(&Id::from(id)) {
            if let Some(v) = arg.vals.get(0) {
                return Some(v.to_str().expect(INVALID_UTF8));
            }
        }
        None
    }

    /// Gets the lossy value of a specific argument. If the argument wasn't present at runtime
    /// it returns `None`. A lossy value is one which contains invalid UTF-8 code points, those
    /// invalid points will be replaced with `\u{FFFD}`
    ///
    /// *NOTE:* If getting a value for an option or positional argument that allows multiples,
    /// prefer [`Arg::values_of_lossy`] as `value_of_lossy()` will only return the *first* value.
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, Arg};
    /// use std::ffi::OsString;
    /// use std::os::unix::ffi::{OsStrExt,OsStringExt};
    ///
    /// let m = App::new("utf8")
    ///     .arg(Arg::from("<arg> 'some arg'"))
    ///     .get_matches_from(vec![OsString::from("myprog"),
    ///                             // "Hi {0xe9}!"
    ///                             OsString::from_vec(vec![b'H', b'i', b' ', 0xe9, b'!'])]);
    /// assert_eq!(&*m.value_of_lossy("arg").unwrap(), "Hi \u{FFFD}!");
    /// ```
    /// [`Arg::values_of_lossy`]: ./struct.ArgMatches.html#method.values_of_lossy
    pub fn value_of_lossy<T: Key>(&self, id: T) -> Option<Cow<'_, str>> {
        if let Some(arg) = self.args.get(&Id::from(id)) {
            if let Some(v) = arg.vals.get(0) {
                return Some(v.to_string_lossy());
            }
        }
        None
    }

    /// Gets the OS version of a string value of a specific argument. If the option wasn't present
    /// at runtime it returns `None`. An OS value on Unix-like systems is any series of bytes,
    /// regardless of whether or not they contain valid UTF-8 code points. Since [`String`]s in
    /// Rust are guaranteed to be valid UTF-8, a valid filename on a Unix system as an argument
    /// value may contain invalid UTF-8 code points.
    ///
    /// *NOTE:* If getting a value for an option or positional argument that allows multiples,
    /// prefer [`ArgMatches::values_of_os`] as `Arg::value_of_os` will only return the *first*
    /// value.
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, Arg};
    /// use std::ffi::OsString;
    /// use std::os::unix::ffi::{OsStrExt,OsStringExt};
    ///
    /// let m = App::new("utf8")
    ///     .arg(Arg::from("<arg> 'some arg'"))
    ///     .get_matches_from(vec![OsString::from("myprog"),
    ///                             // "Hi {0xe9}!"
    ///                             OsString::from_vec(vec![b'H', b'i', b' ', 0xe9, b'!'])]);
    /// assert_eq!(&*m.value_of_os("arg").unwrap().as_bytes(), [b'H', b'i', b' ', 0xe9, b'!']);
    /// ```
    /// [`String`]: https://doc.rust-lang.org/std/string/struct.String.html
    /// [`ArgMatches::values_of_os`]: ./struct.ArgMatches.html#method.values_of_os
    pub fn value_of_os<T: Key>(&self, id: T) -> Option<&OsStr> {
        self.args
            .get(&Id::from(id))
            .and_then(|arg| arg.vals.get(0).map(OsString::as_os_str))
    }

    /// Gets a [`Values`] struct which implements [`Iterator`] for values of a specific argument
    /// (i.e. an argument that takes multiple values at runtime). If the option wasn't present at
    /// runtime it returns `None`
    ///
    /// # Panics
    ///
    /// This method will panic if any of the values contain invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myprog")
    ///     .arg(Arg::new("output")
    ///         .multiple(true)
    ///         .short('o')
    ///         .takes_value(true))
    ///     .get_matches_from(vec![
    ///         "myprog", "-o", "val1", "val2", "val3"
    ///     ]);
    /// let vals: Vec<&str> = m.values_of("output").unwrap().collect();
    /// assert_eq!(vals, ["val1", "val2", "val3"]);
    /// ```
    /// [`Values`]: ./struct.Values.html
    /// [`Iterator`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html
    pub fn values_of<T: Key>(&self, id: T) -> Option<Values> {
        self.args.get(&Id::from(id)).map(|arg| {
            fn to_str_slice(o: &OsString) -> &str {
                o.to_str().expect(INVALID_UTF8)
            }
            let to_str_slice: fn(&OsString) -> &str = to_str_slice; // coerce to fn pointer

            Values {
                iter: arg.vals.iter().map(to_str_slice),
            }
        })
    }

    /// Gets the lossy values of a specific argument. If the option wasn't present at runtime
    /// it returns `None`. A lossy value is one where if it contains invalid UTF-8 code points,
    /// those invalid points will be replaced with `\u{FFFD}`
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, Arg};
    /// use std::ffi::OsString;
    /// use std::os::unix::ffi::OsStringExt;
    ///
    /// let m = App::new("utf8")
    ///     .arg(Arg::from("<arg>... 'some arg'"))
    ///     .get_matches_from(vec![OsString::from("myprog"),
    ///                             // "Hi"
    ///                             OsString::from_vec(vec![b'H', b'i']),
    ///                             // "{0xe9}!"
    ///                             OsString::from_vec(vec![0xe9, b'!'])]);
    /// let mut itr = m.values_of_lossy("arg").unwrap().into_iter();
    /// assert_eq!(&itr.next().unwrap()[..], "Hi");
    /// assert_eq!(&itr.next().unwrap()[..], "\u{FFFD}!");
    /// assert_eq!(itr.next(), None);
    /// ```
    pub fn values_of_lossy<T: Key>(&self, id: T) -> Option<Vec<String>> {
        self.args.get(&Id::from(id)).map(|arg| {
            arg.vals
                .iter()
                .map(|v| v.to_string_lossy().into_owned())
                .collect()
        })
    }

    /// Gets a [`OsValues`] struct which is implements [`Iterator`] for [`OsString`] values of a
    /// specific argument. If the option wasn't present at runtime it returns `None`. An OS value
    /// on Unix-like systems is any series of bytes, regardless of whether or not they contain
    /// valid UTF-8 code points. Since [`String`]s in Rust are guaranteed to be valid UTF-8, a valid
    /// filename as an argument value on Linux (for example) may contain invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    #[cfg_attr(not(unix), doc = " ```ignore")]
    #[cfg_attr(unix, doc = " ```")]
    /// # use clap::{App, Arg};
    /// use std::ffi::{OsStr,OsString};
    /// use std::os::unix::ffi::{OsStrExt,OsStringExt};
    ///
    /// let m = App::new("utf8")
    ///     .arg(Arg::from("<arg>... 'some arg'"))
    ///     .get_matches_from(vec![OsString::from("myprog"),
    ///                                 // "Hi"
    ///                                 OsString::from_vec(vec![b'H', b'i']),
    ///                                 // "{0xe9}!"
    ///                                 OsString::from_vec(vec![0xe9, b'!'])]);
    ///
    /// let mut itr = m.values_of_os("arg").unwrap().into_iter();
    /// assert_eq!(itr.next(), Some(OsStr::new("Hi")));
    /// assert_eq!(itr.next(), Some(OsStr::from_bytes(&[0xe9, b'!'])));
    /// assert_eq!(itr.next(), None);
    /// ```
    /// [`OsValues`]: ./struct.OsValues.html
    /// [`Iterator`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html
    /// [`OsString`]: https://doc.rust-lang.org/std/ffi/struct.OsString.html
    /// [`String`]: https://doc.rust-lang.org/std/string/struct.String.html
    pub fn values_of_os<'a, T: Key>(&'a self, id: T) -> Option<OsValues<'a>> {
        fn to_str_slice(o: &OsString) -> &OsStr {
            &*o
        }
        let to_str_slice: fn(&'a OsString) -> &'a OsStr = to_str_slice; // coerce to fn pointer

        self.args.get(&Id::from(id)).map(|arg| OsValues {
            iter: arg.vals.iter().map(to_str_slice),
        })
    }

    /// Gets the value of a specific argument (i.e. an argument that takes an additional
    /// value at runtime) and then converts it into the result type using [`std::str::FromStr`].
    ///
    /// There are two types of errors, parse failures and those where the argument wasn't present
    /// (such as a non-required argument). Check [`ErrorKind`] to distinguish them.
    ///
    /// *NOTE:* If getting a value for an option or positional argument that allows multiples,
    /// prefer [`ArgMatches::values_of_t`] as this method will only return the *first*
    /// value.
    ///
    /// # Panics
    ///
    /// This method will [`panic!`] if the value contains invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    /// ```
    /// # extern crate clap;
    /// # use clap::App;
    /// let matches = App::new("myapp")
    ///               .arg("[length] 'Set the length to use as a pos whole num, i.e. 20'")
    ///               .get_matches_from(&["test", "12"]);
    ///
    /// // Specify the type explicitly (or use turbofish)
    /// let len: u32 = matches.value_of_t("length").unwrap_or_else(|e| e.exit());
    /// assert_eq!(len, 12);
    ///
    /// // You can often leave the type for rustc to figure out
    /// let also_len = matches.value_of_t("length").unwrap_or_else(|e| e.exit());
    /// // Something that expects u32
    /// let _: u32 = also_len;
    /// ```
    ///
    /// [`std::str::FromStr`]: https://doc.rust-lang.org/std/str/trait.FromStr.html
    /// [`ErrorKind`]: enum.ErrorKind.html
    /// [`ArgMatches::values_of_t`]: ./struct.ArgMatches.html#method.values_of_t
    /// [`panic!`]: https://doc.rust-lang.org/std/macro.panic!.html
    pub fn value_of_t<R>(&self, name: &str) -> Result<R, Error>
    where
        R: FromStr,
        <R as FromStr>::Err: Display,
    {
        if let Some(v) = self.value_of(name) {
            v.parse::<R>().map_err(|e| {
                let message = format!(
                    "The argument '{}' isn't a valid value for '{}': {}",
                    v, name, e
                );

                Error::value_validation(name.to_string(), v.to_string(), message, ColorChoice::Auto)
            })
        } else {
            Err(Error::argument_not_found_auto(name.to_string()))
        }
    }

    /// Gets the value of a specific argument (i.e. an argument that takes an additional
    /// value at runtime) and then converts it into the result type using [`std::str::FromStr`].
    ///
    /// If either the value is not present or parsing failed, exits the program.
    ///
    /// # Panics
    ///
    /// This method will [`panic!`] if the value contains invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    /// ```
    /// # extern crate clap;
    /// # use clap::App;
    /// let matches = App::new("myapp")
    ///               .arg("[length] 'Set the length to use as a pos whole num, i.e. 20'")
    ///               .get_matches_from(&["test", "12"]);
    ///
    /// // Specify the type explicitly (or use turbofish)
    /// let len: u32 = matches.value_of_t_or_exit("length");
    /// assert_eq!(len, 12);
    ///
    /// // You can often leave the type for rustc to figure out
    /// let also_len = matches.value_of_t_or_exit("length");
    /// // Something that expects u32
    /// let _: u32 = also_len;
    /// ```
    ///
    /// [`std::str::FromStr`]: https://doc.rust-lang.org/std/str/trait.FromStr.html
    /// [`panic!`]: https://doc.rust-lang.org/std/macro.panic!.html
    pub fn value_of_t_or_exit<R>(&self, name: &str) -> R
    where
        R: FromStr,
        <R as FromStr>::Err: Display,
    {
        self.value_of_t(name).unwrap_or_else(|e| e.exit())
    }

    /// Gets the typed values of a specific argument (i.e. an argument that takes multiple
    /// values at runtime) and then converts them into the result type using [`std::str::FromStr`].
    ///
    /// If parsing (of any value) has failed, returns Err.
    ///
    /// # Panics
    ///
    /// This method will [`panic!`] if any of the values contains invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    /// ```
    /// # extern crate clap;
    /// # use clap::App;
    /// let matches = App::new("myapp")
    ///               .arg("[length]... 'A sequence of integers because integers are neat!'")
    ///               .get_matches_from(&["test", "12", "77", "40"]);
    ///
    /// // Specify the type explicitly (or use turbofish)
    /// let len: Vec<u32> = matches.values_of_t("length").unwrap_or_else(|e| e.exit());
    /// assert_eq!(len, vec![12, 77, 40]);
    ///
    /// // You can often leave the type for rustc to figure out
    /// let also_len = matches.values_of_t("length").unwrap_or_else(|e| e.exit());
    /// // Something that expects Vec<u32>
    /// let _: Vec<u32> = also_len;
    /// ```
    ///
    /// [`std::str::FromStr`]: https://doc.rust-lang.org/std/str/trait.FromStr.html
    /// [`panic!`]: https://doc.rust-lang.org/std/macro.panic!.html
    pub fn values_of_t<R>(&self, name: &str) -> Result<Vec<R>, Error>
    where
        R: FromStr,
        <R as FromStr>::Err: Display,
    {
        if let Some(vals) = self.values_of(name) {
            vals.map(|v| {
                v.parse::<R>().map_err(|e| {
                    let message = format!("The argument '{}' isn't a valid value: {}", v, e);

                    Error::value_validation(
                        name.to_string(),
                        v.to_string(),
                        message,
                        ColorChoice::Auto,
                    )
                })
            })
            .collect()
        } else {
            Err(Error::argument_not_found_auto(name.to_string()))
        }
    }

    /// Gets the typed values of a specific argument (i.e. an argument that takes multiple
    /// values at runtime) and then converts them into the result type using [`std::str::FromStr`].
    ///
    /// If parsing (of any value) has failed, exits the program.
    ///
    /// # Panics
    ///
    /// This method will [`panic!`] if any of the values contains invalid UTF-8 code points.
    ///
    /// # Examples
    ///
    /// ```
    /// # extern crate clap;
    /// # use clap::App;
    /// let matches = App::new("myapp")
    ///               .arg("[length]... 'A sequence of integers because integers are neat!'")
    ///               .get_matches_from(&["test", "12", "77", "40"]);
    ///
    /// // Specify the type explicitly (or use turbofish)
    /// let len: Vec<u32> = matches.values_of_t_or_exit("length");
    /// assert_eq!(len, vec![12, 77, 40]);
    ///
    /// // You can often leave the type for rustc to figure out
    /// let also_len = matches.values_of_t_or_exit("length");
    /// // Something that expects Vec<u32>
    /// let _: Vec<u32> = also_len;
    /// ```
    ///
    /// [`std::str::FromStr`]: https://doc.rust-lang.org/std/str/trait.FromStr.html
    /// [`panic!`]: https://doc.rust-lang.org/std/macro.panic!.html
    pub fn values_of_t_or_exit<R>(&self, name: &str) -> Vec<R>
    where
        R: FromStr,
        <R as FromStr>::Err: Display,
    {
        self.values_of_t(name).unwrap_or_else(|e| e.exit())
    }

    /// Returns `true` if an argument was present at runtime, otherwise `false`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myprog")
    ///     .arg(Arg::new("debug")
    ///         .short('d'))
    ///     .get_matches_from(vec![
    ///         "myprog", "-d"
    ///     ]);
    ///
    /// assert!(m.is_present("debug"));
    /// ```
    pub fn is_present<T: Key>(&self, id: T) -> bool {
        let id = Id::from(id);

        if let Some(ref sc) = self.subcommand {
            if sc.id == id {
                return true;
            }
        }
        self.args.contains_key(&id)
    }

    /// Returns the number of times an argument was used at runtime. If an argument isn't present
    /// it will return `0`.
    ///
    /// **NOTE:** This returns the number of times the argument was used, *not* the number of
    /// values. For example, `-o val1 val2 val3 -o val4` would return `2` (2 occurrences, but 4
    /// values).
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, ArgSettings};
    /// let m = App::new("myprog")
    ///     .arg(Arg::new("debug")
    ///         .short('d')
    ///         .setting(ArgSettings::MultipleOccurrences))
    ///     .get_matches_from(vec![
    ///         "myprog", "-d", "-d", "-d"
    ///     ]);
    ///
    /// assert_eq!(m.occurrences_of("debug"), 3);
    /// ```
    ///
    /// This next example shows that counts actual uses of the argument, not just `-`'s
    ///
    /// ```rust
    /// # use clap::{App, Arg, ArgSettings};
    /// let m = App::new("myprog")
    ///     .arg(Arg::new("debug")
    ///         .short('d')
    ///         .setting(ArgSettings::MultipleOccurrences))
    ///     .arg(Arg::new("flag")
    ///         .short('f'))
    ///     .get_matches_from(vec![
    ///         "myprog", "-ddfd"
    ///     ]);
    ///
    /// assert_eq!(m.occurrences_of("debug"), 3);
    /// assert_eq!(m.occurrences_of("flag"), 1);
    /// ```
    pub fn occurrences_of<T: Key>(&self, id: T) -> u64 {
        self.args.get(&Id::from(id)).map_or(0, |a| a.occurs)
    }

    /// Gets the starting index of the argument in respect to all other arguments. Indices are
    /// similar to argv indices, but are not exactly 1:1.
    ///
    /// For flags (i.e. those arguments which don't have an associated value), indices refer
    /// to occurrence of the switch, such as `-f`, or `--flag`. However, for options the indices
    /// refer to the *values* `-o val` would therefore not represent two distinct indices, only the
    /// index for `val` would be recorded. This is by design.
    ///
    /// Besides the flag/option descrepancy, the primary difference between an argv index and clap
    /// index, is that clap continues counting once all arguments have properly separated, whereas
    /// an argv index does not.
    ///
    /// The examples should clear this up.
    ///
    /// *NOTE:* If an argument is allowed multiple times, this method will only give the *first*
    /// index.
    ///
    /// # Examples
    ///
    /// The argv indices are listed in the comments below. See how they correspond to the clap
    /// indices. Note that if it's not listed in a clap index, this is because it's not saved in
    /// in an `ArgMatches` struct for querying.
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("flag")
    ///         .short('f'))
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true))
    ///     .get_matches_from(vec!["myapp", "-f", "-o", "val"]);
    ///             // ARGV idices: ^0       ^1    ^2    ^3
    ///             // clap idices:          ^1          ^3
    ///
    /// assert_eq!(m.index_of("flag"), Some(1));
    /// assert_eq!(m.index_of("option"), Some(3));
    /// ```
    ///
    /// Now notice, if we use one of the other styles of options:
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("flag")
    ///         .short('f'))
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true))
    ///     .get_matches_from(vec!["myapp", "-f", "-o=val"]);
    ///             // ARGV idices: ^0       ^1    ^2
    ///             // clap idices:          ^1       ^3
    ///
    /// assert_eq!(m.index_of("flag"), Some(1));
    /// assert_eq!(m.index_of("option"), Some(3));
    /// ```
    ///
    /// Things become much more complicated, or clear if we look at a more complex combination of
    /// flags. Let's also throw in the final option style for good measure.
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("flag")
    ///         .short('f'))
    ///     .arg(Arg::new("flag2")
    ///         .short('F'))
    ///     .arg(Arg::new("flag3")
    ///         .short('z'))
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true))
    ///     .get_matches_from(vec!["myapp", "-fzF", "-oval"]);
    ///             // ARGV idices: ^0      ^1       ^2
    ///             // clap idices:         ^1,2,3    ^5
    ///             //
    ///             // clap sees the above as 'myapp -f -z -F -o val'
    ///             //                         ^0    ^1 ^2 ^3 ^4 ^5
    /// assert_eq!(m.index_of("flag"), Some(1));
    /// assert_eq!(m.index_of("flag2"), Some(3));
    /// assert_eq!(m.index_of("flag3"), Some(2));
    /// assert_eq!(m.index_of("option"), Some(5));
    /// ```
    ///
    /// One final combination of flags/options to see how they combine:
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("flag")
    ///         .short('f'))
    ///     .arg(Arg::new("flag2")
    ///         .short('F'))
    ///     .arg(Arg::new("flag3")
    ///         .short('z'))
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true)
    ///         .multiple(true))
    ///     .get_matches_from(vec!["myapp", "-fzFoval"]);
    ///             // ARGV idices: ^0       ^1
    ///             // clap idices:          ^1,2,3^5
    ///             //
    ///             // clap sees the above as 'myapp -f -z -F -o val'
    ///             //                         ^0    ^1 ^2 ^3 ^4 ^5
    /// assert_eq!(m.index_of("flag"), Some(1));
    /// assert_eq!(m.index_of("flag2"), Some(3));
    /// assert_eq!(m.index_of("flag3"), Some(2));
    /// assert_eq!(m.index_of("option"), Some(5));
    /// ```
    ///
    /// The last part to mention is when values are sent in multiple groups with a [delimiter].
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true)
    ///         .multiple(true))
    ///     .get_matches_from(vec!["myapp", "-o=val1,val2,val3"]);
    ///             // ARGV idices: ^0       ^1
    ///             // clap idices:             ^2   ^3   ^4
    ///             //
    ///             // clap sees the above as 'myapp -o val1 val2 val3'
    ///             //                         ^0    ^1 ^2   ^3   ^4
    /// assert_eq!(m.index_of("option"), Some(2));
    /// ```
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    /// [delimiter]: ./struct.Arg.html#method.value_delimiter
    pub fn index_of<T: Key>(&self, name: T) -> Option<usize> {
        if let Some(arg) = self.args.get(&Id::from(name)) {
            if let Some(i) = arg.indices.get(0) {
                return Some(*i);
            }
        }
        None
    }

    /// Gets all indices of the argument in respect to all other arguments. Indices are
    /// similar to argv indices, but are not exactly 1:1.
    ///
    /// For flags (i.e. those arguments which don't have an associated value), indices refer
    /// to occurrence of the switch, such as `-f`, or `--flag`. However, for options the indices
    /// refer to the *values* `-o val` would therefore not represent two distinct indices, only the
    /// index for `val` would be recorded. This is by design.
    ///
    /// *NOTE:* For more information about how clap indices compare to argv indices, see
    /// [`ArgMatches::index_of`]
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true)
    ///         .use_delimiter(true)
    ///         .multiple(true))
    ///     .get_matches_from(vec!["myapp", "-o=val1,val2,val3"]);
    ///             // ARGV idices: ^0       ^1
    ///             // clap idices:             ^2   ^3   ^4
    ///             //
    ///             // clap sees the above as 'myapp -o val1 val2 val3'
    ///             //                         ^0    ^1 ^2   ^3   ^4
    /// assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2, 3, 4]);
    /// ```
    ///
    /// Another quick example is when flags and options are used together
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true)
    ///         .multiple(true))
    ///     .arg(Arg::new("flag")
    ///         .short('f')
    ///         .multiple_occurrences(true))
    ///     .get_matches_from(vec!["myapp", "-o", "val1", "-f", "-o", "val2", "-f"]);
    ///             // ARGV idices: ^0       ^1    ^2      ^3    ^4    ^5      ^6
    ///             // clap idices:                ^2      ^3          ^5      ^6
    ///
    /// assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2, 5]);
    /// assert_eq!(m.indices_of("flag").unwrap().collect::<Vec<_>>(), &[3, 6]);
    /// ```
    ///
    /// One final example, which is an odd case; if we *don't* use  value delimiter as we did with
    /// the first example above instead of `val1`, `val2` and `val3` all being distinc values, they
    /// would all be a single value of `val1,val2,val3`, in which case they'd only receive a single
    /// index.
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myapp")
    ///     .arg(Arg::new("option")
    ///         .short('o')
    ///         .takes_value(true)
    ///         .multiple(true))
    ///     .get_matches_from(vec!["myapp", "-o=val1,val2,val3"]);
    ///             // ARGV idices: ^0       ^1
    ///             // clap idices:             ^2
    ///             //
    ///             // clap sees the above as 'myapp -o "val1,val2,val3"'
    ///             //                         ^0    ^1  ^2
    /// assert_eq!(m.indices_of("option").unwrap().collect::<Vec<_>>(), &[2]);
    /// ```
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    /// [`ArgMatches::index_of`]: ./struct.ArgMatches.html#method.index_of
    /// [delimiter]: ./struct.Arg.html#method.value_delimiter
    pub fn indices_of<T: Key>(&self, id: T) -> Option<Indices<'_>> {
        self.args.get(&Id::from(id)).map(|arg| Indices {
            iter: arg.indices.iter().cloned(),
        })
    }

    /// Because [`Subcommand`]s are essentially "sub-[`App`]s" they have their own [`ArgMatches`]
    /// as well. This method returns the [`ArgMatches`] for a particular subcommand or `None` if
    /// the subcommand wasn't present at runtime.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg, };
    /// let app_m = App::new("myprog")
    ///     .arg(Arg::new("debug")
    ///         .short('d'))
    ///     .subcommand(App::new("test")
    ///         .arg(Arg::new("opt")
    ///             .long("option")
    ///             .takes_value(true)))
    ///     .get_matches_from(vec![
    ///         "myprog", "-d", "test", "--option", "val"
    ///     ]);
    ///
    /// // Both parent commands, and child subcommands can have arguments present at the same times
    /// assert!(app_m.is_present("debug"));
    ///
    /// // Get the subcommand's ArgMatches instance
    /// if let Some(sub_m) = app_m.subcommand_matches("test") {
    ///     // Use the struct like normal
    ///     assert_eq!(sub_m.value_of("opt"), Some("val"));
    /// }
    /// ```
    /// [`Subcommand`]: ./struct..html
    /// [`App`]: ./struct.App.html
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    pub fn subcommand_matches<T: Key>(&self, id: T) -> Option<&ArgMatches> {
        if let Some(ref s) = self.subcommand {
            if s.id == id.into() {
                return Some(&s.matches);
            }
        }
        None
    }

    /// Because [`Subcommand`]s are essentially "sub-[`App`]s" they have their own [`ArgMatches`]
    /// as well.But simply getting the sub-[`ArgMatches`] doesn't help much if we don't also know
    /// which subcommand was actually used. This method returns the name of the subcommand that was
    /// used at runtime, or `None` if one wasn't.
    ///
    /// *NOTE*: Subcommands form a hierarchy, where multiple subcommands can be used at runtime,
    /// but only a single subcommand from any group of sibling commands may used at once.
    ///
    /// An ASCII art depiction may help explain this better...Using a fictional version of `git` as
    /// the demo subject. Imagine the following are all subcommands of `git` (note, the author is
    /// aware these aren't actually all subcommands in the real `git` interface, but it makes
    /// explanation easier)
    ///
    /// ```notrust
    ///              Top Level App (git)                         TOP
    ///                              |
    ///       -----------------------------------------
    ///      /             |                \          \
    ///   clone          push              add       commit      LEVEL 1
    ///     |           /    \            /    \       |
    ///    url      origin   remote    ref    name   message     LEVEL 2
    ///             /                  /\
    ///          path            remote  local                   LEVEL 3
    /// ```
    ///
    /// Given the above fictional subcommand hierarchy, valid runtime uses would be (not an all
    /// inclusive list, and not including argument options per command for brevity and clarity):
    ///
    /// ```sh
    /// $ git clone url
    /// $ git push origin path
    /// $ git add ref local
    /// $ git commit message
    /// ```
    ///
    /// Notice only one command per "level" may be used. You could not, for example, do `$ git
    /// clone url push origin path`
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, };
    ///  let app_m = App::new("git")
    ///      .subcommand(App::new("clone"))
    ///      .subcommand(App::new("push"))
    ///      .subcommand(App::new("commit"))
    ///      .get_matches();
    ///
    /// match app_m.subcommand_name() {
    ///     Some("clone")  => {}, // clone was used
    ///     Some("push")   => {}, // push was used
    ///     Some("commit") => {}, // commit was used
    ///     _              => {}, // Either no subcommand or one not tested for...
    /// }
    /// ```
    /// [`Subcommand`]: ./struct..html
    /// [`App`]: ./struct.App.html
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    #[inline]
    pub fn subcommand_name(&self) -> Option<&str> {
        self.subcommand.as_ref().map(|sc| &*sc.name)
    }

    /// This brings together [`ArgMatches::subcommand_matches`] and [`ArgMatches::subcommand_name`]
    /// by returning a tuple with both pieces of information.
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, };
    ///  let app_m = App::new("git")
    ///      .subcommand(App::new("clone"))
    ///      .subcommand(App::new("push"))
    ///      .subcommand(App::new("commit"))
    ///      .get_matches();
    ///
    /// match app_m.subcommand() {
    ///     Some(("clone",  sub_m)) => {}, // clone was used
    ///     Some(("push",   sub_m)) => {}, // push was used
    ///     Some(("commit", sub_m)) => {}, // commit was used
    ///     _                       => {}, // Either no subcommand or one not tested for...
    /// }
    /// ```
    ///
    /// Another useful scenario is when you want to support third party, or external, subcommands.
    /// In these cases you can't know the subcommand name ahead of time, so use a variable instead
    /// with pattern matching!
    ///
    /// ```rust
    /// # use clap::{App, AppSettings};
    /// // Assume there is an external subcommand named "subcmd"
    /// let app_m = App::new("myprog")
    ///     .setting(AppSettings::AllowExternalSubcommands)
    ///     .get_matches_from(vec![
    ///         "myprog", "subcmd", "--option", "value", "-fff", "--flag"
    ///     ]);
    ///
    /// // All trailing arguments will be stored under the subcommand's sub-matches using an empty
    /// // string argument name
    /// match app_m.subcommand() {
    ///     Some((external, sub_m)) => {
    ///          let ext_args: Vec<&str> = sub_m.values_of("").unwrap().collect();
    ///          assert_eq!(external, "subcmd");
    ///          assert_eq!(ext_args, ["--option", "value", "-fff", "--flag"]);
    ///     },
    ///     _ => {},
    /// }
    /// ```
    /// [`ArgMatches::subcommand_matches`]: ./struct.ArgMatches.html#method.subcommand_matches
    /// [`ArgMatches::subcommand_name`]: ./struct.ArgMatches.html#method.subcommand_name
    #[inline]
    pub fn subcommand(&self) -> Option<(&str, &ArgMatches)> {
        self.subcommand.as_ref().map(|sc| (&*sc.name, &sc.matches))
    }
}

// The following were taken and adapted from vec_map source
// repo: https://github.com/contain-rs/vec-map
// commit: be5e1fa3c26e351761b33010ddbdaf5f05dbcc33
// license: MIT - Copyright (c) 2015 The Rust Project Developers

/// An iterator for getting multiple values out of an argument via the [`ArgMatches::values_of`]
/// method.
///
/// # Examples
///
/// ```rust
/// # use clap::{App, Arg};
/// let m = App::new("myapp")
///     .arg(Arg::new("output")
///         .short('o')
///         .multiple(true)
///         .takes_value(true))
///     .get_matches_from(vec!["myapp", "-o", "val1", "val2"]);
///
/// let mut values = m.values_of("output").unwrap();
///
/// assert_eq!(values.next(), Some("val1"));
/// assert_eq!(values.next(), Some("val2"));
/// assert_eq!(values.next(), None);
/// ```
/// [`ArgMatches::values_of`]: ./struct.ArgMatches.html#method.values_of
#[derive(Clone)]
#[allow(missing_debug_implementations)]
pub struct Values<'a> {
    iter: Map<Iter<'a, OsString>, fn(&'a OsString) -> &'a str>,
}

impl<'a> Iterator for Values<'a> {
    type Item = &'a str;

    fn next(&mut self) -> Option<&'a str> {
        self.iter.next()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.iter.size_hint()
    }
}

impl<'a> DoubleEndedIterator for Values<'a> {
    fn next_back(&mut self) -> Option<&'a str> {
        self.iter.next_back()
    }
}

impl<'a> ExactSizeIterator for Values<'a> {}

/// Creates an empty iterator.
impl<'a> Default for Values<'a> {
    fn default() -> Self {
        static EMPTY: [OsString; 0] = [];
        // This is never called because the iterator is empty:
        fn to_str_slice(_: &OsString) -> &str {
            unreachable!()
        };
        Values {
            iter: EMPTY[..].iter().map(to_str_slice),
        }
    }
}

/// An iterator for getting multiple values out of an argument via the [`ArgMatches::values_of_os`]
/// method. Usage of this iterator allows values which contain invalid UTF-8 code points unlike
/// [`Values`].
///
/// # Examples
///
#[cfg_attr(not(unix), doc = " ```ignore")]
#[cfg_attr(unix, doc = " ```")]
/// # use clap::{App, Arg};
/// use std::ffi::OsString;
/// use std::os::unix::ffi::{OsStrExt,OsStringExt};
///
/// let m = App::new("utf8")
///     .arg(Arg::from("<arg> 'some arg'"))
///     .get_matches_from(vec![OsString::from("myprog"),
///                             // "Hi {0xe9}!"
///                             OsString::from_vec(vec![b'H', b'i', b' ', 0xe9, b'!'])]);
/// assert_eq!(&*m.value_of_os("arg").unwrap().as_bytes(), [b'H', b'i', b' ', 0xe9, b'!']);
/// ```
/// [`ArgMatches::values_of_os`]: ./struct.ArgMatches.html#method.values_of_os
/// [`Values`]: ./struct.Values.html
#[derive(Clone)]
#[allow(missing_debug_implementations)]
pub struct OsValues<'a> {
    iter: Map<Iter<'a, OsString>, fn(&'a OsString) -> &'a OsStr>,
}

impl<'a> Iterator for OsValues<'a> {
    type Item = &'a OsStr;

    fn next(&mut self) -> Option<&'a OsStr> {
        self.iter.next()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.iter.size_hint()
    }
}

impl<'a> DoubleEndedIterator for OsValues<'a> {
    fn next_back(&mut self) -> Option<&'a OsStr> {
        self.iter.next_back()
    }
}

impl<'a> ExactSizeIterator for OsValues<'a> {}

/// Creates an empty iterator.
impl Default for OsValues<'_> {
    fn default() -> Self {
        static EMPTY: [OsString; 0] = [];
        // This is never called because the iterator is empty:
        fn to_str_slice(_: &OsString) -> &OsStr {
            unreachable!()
        };
        OsValues {
            iter: EMPTY[..].iter().map(to_str_slice),
        }
    }
}

/// An iterator for getting multiple indices out of an argument via the [`ArgMatches::indices_of`]
/// method.
///
/// # Examples
///
/// ```rust
/// # use clap::{App, Arg};
/// let m = App::new("myapp")
///     .arg(Arg::new("output")
///         .short('o')
///         .multiple(true)
///         .takes_value(true))
///     .get_matches_from(vec!["myapp", "-o", "val1", "val2"]);
///
/// let mut indices = m.indices_of("output").unwrap();
///
/// assert_eq!(indices.next(), Some(2));
/// assert_eq!(indices.next(), Some(3));
/// assert_eq!(indices.next(), None);
/// ```
/// [`ArgMatches::indices_of`]: ./struct.ArgMatches.html#method.indices_of
#[derive(Clone)]
#[allow(missing_debug_implementations)]
pub struct Indices<'a> {
    iter: Cloned<Iter<'a, usize>>,
}

impl<'a> Iterator for Indices<'a> {
    type Item = usize;

    fn next(&mut self) -> Option<usize> {
        self.iter.next()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.iter.size_hint()
    }
}

impl<'a> DoubleEndedIterator for Indices<'a> {
    fn next_back(&mut self) -> Option<usize> {
        self.iter.next_back()
    }
}

impl<'a> ExactSizeIterator for Indices<'a> {}

/// Creates an empty iterator.
impl<'a> Default for Indices<'a> {
    fn default() -> Self {
        static EMPTY: [usize; 0] = [];
        // This is never called because the iterator is empty:
        Indices {
            iter: EMPTY[..].iter().cloned(),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_default_values() {
        let mut values: Values = Values::default();
        assert_eq!(values.next(), None);
    }

    #[test]
    fn test_default_values_with_shorter_lifetime() {
        let matches = ArgMatches::default();
        let mut values = matches.values_of("").unwrap_or_default();
        assert_eq!(values.next(), None);
    }

    #[test]
    fn test_default_osvalues() {
        let mut values: OsValues = OsValues::default();
        assert_eq!(values.next(), None);
    }

    #[test]
    fn test_default_osvalues_with_shorter_lifetime() {
        let matches = ArgMatches::default();
        let mut values = matches.values_of_os("").unwrap_or_default();
        assert_eq!(values.next(), None);
    }

    #[test]
    fn test_default_indices() {
        let mut indices: Indices = Indices::default();
        assert_eq!(indices.next(), None);
    }

    #[test]
    fn test_default_indices_with_shorter_lifetime() {
        let matches = ArgMatches::default();
        let mut indices = matches.indices_of("").unwrap_or_default();
        assert_eq!(indices.next(), None);
    }
}