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
// Std
use std::borrow::Cow;
use std::collections::HashMap;
use std::ffi::{OsStr, OsString};
use std::iter::Map;
use std::slice::Iter;

// Internal
use INVALID_UTF8;
use args::MatchedArg;
use args::SubCommand;

/// Used to get information about the arguments that where 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::with_name("out")
///         .long("output")
///         .required(true)
///         .takes_value(true))
///     .arg(Arg::with_name("debug")
///         .short("d")
///         .multiple(true))
///     .arg(Arg::with_name("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<'a> {
    #[doc(hidden)]
    pub args: HashMap<&'a str, MatchedArg>,
    #[doc(hidden)]
    pub subcommand: Option<Box<SubCommand<'a>>>,
    #[doc(hidden)]
    pub usage: Option<String>,
}

impl<'a> Default for ArgMatches<'a> {
    fn default() -> Self {
        ArgMatches {
            args: HashMap::new(),
            subcommand: None,
            usage: None,
        }
    }
}

impl<'a> ArgMatches<'a> {
    #[doc(hidden)]
    pub fn new() -> Self { ArgMatches { ..Default::default() } }

    /// 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::with_name("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<S: AsRef<str>>(&self, name: S) -> Option<&str> {
        if let Some(arg) = self.args.get(name.as_ref()) {
            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_usage("<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<S: AsRef<str>>(&'a self, name: S) -> Option<Cow<'a, str>> {
        if let Some(arg) = self.args.get(name.as_ref()) {
            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_usage("<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<S: AsRef<str>>(&self, name: S) -> Option<&OsStr> {
        self.args
            .get(name.as_ref())
            .map_or(None, |arg| arg.vals.get(0).map(|v| v.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::with_name("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<S: AsRef<str>>(&'a self, name: S) -> Option<Values<'a>> {
        if let Some(arg) = self.args.get(name.as_ref()) {
            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
            return Some(Values { iter: arg.vals.iter().map(to_str_slice) });
        }
        None
    }

    /// 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_usage("<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<S: AsRef<str>>(&'a self, name: S) -> Option<Vec<String>> {
        if let Some(arg) = self.args.get(name.as_ref()) {
            return Some(arg.vals
                .iter()
                .map(|v| v.to_string_lossy().into_owned())
                .collect());
        }
        None
    }

    /// 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_usage("<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<S: AsRef<str>>(&'a self, name: S) -> 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
        if let Some(arg) = self.args.get(name.as_ref()) {
            return Some(OsValues { iter: arg.vals.iter().map(to_str_slice) });
        }
        None
    }

    /// Returns `true` if an argument was present at runtime, otherwise `false`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// # use clap::{App, Arg};
    /// let m = App::new("myprog")
    ///     .arg(Arg::with_name("debug")
    ///         .short("d"))
    ///     .get_matches_from(vec![
    ///         "myprog", "-d"
    ///     ]);
    ///
    /// assert!(m.is_present("debug"));
    /// ```
    pub fn is_present<S: AsRef<str>>(&self, name: S) -> bool {
        if let Some(ref sc) = self.subcommand {
            if sc.name == name.as_ref() {
                return true;
            }
        }
        self.args.contains_key(name.as_ref())
    }

    /// 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};
    /// let m = App::new("myprog")
    ///     .arg(Arg::with_name("debug")
    ///         .short("d")
    ///         .multiple(true))
    ///     .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};
    /// let m = App::new("myprog")
    ///     .arg(Arg::with_name("debug")
    ///         .short("d")
    ///         .multiple(true))
    ///     .arg(Arg::with_name("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<S: AsRef<str>>(&self, name: S) -> u64 {
        self.args.get(name.as_ref()).map_or(0, |a| a.occurs)
    }

    /// 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, SubCommand};
    /// let app_m = App::new("myprog")
    ///     .arg(Arg::with_name("debug")
    ///         .short("d"))
    ///     .subcommand(SubCommand::with_name("test")
    ///         .arg(Arg::with_name("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.SubCommand.html
    /// [`App`]: ./struct.App.html
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    pub fn subcommand_matches<S: AsRef<str>>(&self, name: S) -> Option<&ArgMatches<'a>> {
        if let Some(ref s) = self.subcommand {
            if s.name == name.as_ref() {
                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, SubCommand};
    ///  let app_m = App::new("git")
    ///      .subcommand(SubCommand::with_name("clone"))
    ///      .subcommand(SubCommand::with_name("push"))
    ///      .subcommand(SubCommand::with_name("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.SubCommand.html
    /// [`App`]: ./struct.App.html
    /// [`ArgMatches`]: ./struct.ArgMatches.html
    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, SubCommand};
    ///  let app_m = App::new("git")
    ///      .subcommand(SubCommand::with_name("clone"))
    ///      .subcommand(SubCommand::with_name("push"))
    ///      .subcommand(SubCommand::with_name("commit"))
    ///      .get_matches();
    ///
    /// match app_m.subcommand() {
    ///     ("clone",  Some(sub_m)) => {}, // clone was used
    ///     ("push",   Some(sub_m)) => {}, // push was used
    ///     ("commit", Some(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() {
    ///     (external, Some(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
    pub fn subcommand(&self) -> (&str, Option<&ArgMatches<'a>>) {
        self.subcommand.as_ref().map_or(("", None), |sc| (&sc.name[..], Some(&sc.matches)))
    }

    /// Returns a string slice of the usage statement for the [`App`] or [`SubCommand`]
    ///
    /// # Examples
    ///
    /// ```no_run
    /// # use clap::{App, Arg, SubCommand};
    /// let app_m = App::new("myprog")
    ///     .subcommand(SubCommand::with_name("test"))
    ///     .get_matches();
    ///
    /// println!("{}", app_m.usage());
    /// ```
    /// [`Subcommand`]: ./struct.SubCommand.html
    /// [`App`]: ./struct.App.html
    pub fn usage(&self) -> &str { self.usage.as_ref().map_or("", |u| &u[..]) }
}


// The following were taken and adapated 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::with_name("output")
///         .takes_value(true))
///     .get_matches_from(vec!["myapp", "something"]);
///
/// assert_eq!(m.value_of("output"), Some("something"));
/// ```
/// [`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 Default for Values<'static> {
    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) }
    }
}

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

/// 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_usage("<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() }
}

/// Creates an empty iterator.
impl Default for OsValues<'static> {
    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) }
    }
}

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