1//! This module contains traits that are usable with the `#[derive(...)]`
2//! macros in `clap_derive`.
3
4use crate::builder::PossibleValue;
5use crate::{ArgMatches, Command, Error};
6
7use std::ffi::OsString;
8
9/// Parse command-line arguments into `Self`.
10///
11/// The primary one-stop-shop trait used to create an instance of a `clap`
12/// [`Command`], conduct the parsing, and turn the resulting [`ArgMatches`] back
13/// into concrete instance of the user struct.
14///
15/// This trait is primarily a convenience on top of [`FromArgMatches`] +
16/// [`CommandFactory`] which uses those two underlying traits to build the two
17/// fundamental functions `parse` which uses the `std::env::args_os` iterator,
18/// and `parse_from` which allows the consumer to supply the iterator (along
19/// with fallible options for each).
20///
21/// See also [`Subcommand`] and [`Args`].
22///
23/// **NOTE:** Deriving requires the `derive` feature flag
24pub trait Parser: FromArgMatches + CommandFactory + Sized {
25 /// Parse from `std::env::args_os()`, exit on error
26 fn parse() -> Self {
27 let mut matches = <Self as CommandFactory>::command().get_matches();
28 let res = <Self as FromArgMatches>::from_arg_matches_mut(&mut matches)
29 .map_err(format_error::<Self>);
30 match res {
31 Ok(s) => s,
32 Err(e) => {
33 // Since this is more of a development-time error, we aren't doing as fancy of a quit
34 // as `get_matches`
35 e.exit()
36 }
37 }
38 }
39
40 /// Parse from `std::env::args_os()`, return Err on error.
41 fn try_parse() -> Result<Self, Error> {
42 let mut matches = ok!(<Self as CommandFactory>::command().try_get_matches());
43 <Self as FromArgMatches>::from_arg_matches_mut(&mut matches).map_err(format_error::<Self>)
44 }
45
46 /// Parse from iterator, exit on error
47 fn parse_from<I, T>(itr: I) -> Self
48 where
49 I: IntoIterator<Item = T>,
50 T: Into<OsString> + Clone,
51 {
52 let mut matches = <Self as CommandFactory>::command().get_matches_from(itr);
53 let res = <Self as FromArgMatches>::from_arg_matches_mut(&mut matches)
54 .map_err(format_error::<Self>);
55 match res {
56 Ok(s) => s,
57 Err(e) => {
58 // Since this is more of a development-time error, we aren't doing as fancy of a quit
59 // as `get_matches_from`
60 e.exit()
61 }
62 }
63 }
64
65 /// Parse from iterator, return Err on error.
66 fn try_parse_from<I, T>(itr: I) -> Result<Self, Error>
67 where
68 I: IntoIterator<Item = T>,
69 T: Into<OsString> + Clone,
70 {
71 let mut matches = ok!(<Self as CommandFactory>::command().try_get_matches_from(itr));
72 <Self as FromArgMatches>::from_arg_matches_mut(&mut matches).map_err(format_error::<Self>)
73 }
74
75 /// Update from iterator, exit on error
76 fn update_from<I, T>(&mut self, itr: I)
77 where
78 I: IntoIterator<Item = T>,
79 T: Into<OsString> + Clone,
80 {
81 let mut matches = <Self as CommandFactory>::command_for_update().get_matches_from(itr);
82 let res = <Self as FromArgMatches>::update_from_arg_matches_mut(self, &mut matches)
83 .map_err(format_error::<Self>);
84 if let Err(e) = res {
85 // Since this is more of a development-time error, we aren't doing as fancy of a quit
86 // as `get_matches_from`
87 e.exit()
88 }
89 }
90
91 /// Update from iterator, return Err on error.
92 fn try_update_from<I, T>(&mut self, itr: I) -> Result<(), Error>
93 where
94 I: IntoIterator<Item = T>,
95 T: Into<OsString> + Clone,
96 {
97 let mut matches =
98 ok!(<Self as CommandFactory>::command_for_update().try_get_matches_from(itr));
99 <Self as FromArgMatches>::update_from_arg_matches_mut(self, &mut matches)
100 .map_err(format_error::<Self>)
101 }
102}
103
104/// Create a [`Command`] relevant for a user-defined container.
105///
106/// Derived as part of [`Parser`].
107pub trait CommandFactory: Sized {
108 /// Build a [`Command`] that can instantiate `Self`.
109 ///
110 /// See [`FromArgMatches::from_arg_matches_mut`] for instantiating `Self`.
111 fn command() -> Command;
112 /// Build a [`Command`] that can update `self`.
113 ///
114 /// See [`FromArgMatches::update_from_arg_matches_mut`] for updating `self`.
115 fn command_for_update() -> Command;
116}
117
118/// Converts an instance of [`ArgMatches`] to a user-defined container.
119///
120/// Derived as part of [`Parser`], [`Args`], and [`Subcommand`].
121pub trait FromArgMatches: Sized {
122 /// Instantiate `Self` from [`ArgMatches`], parsing the arguments as needed.
123 ///
124 /// Motivation: If our application had two CLI options, `--name
125 /// <STRING>` and the flag `--debug`, we may create a struct as follows:
126 ///
127 /// ```rust
128 /// # #[cfg(feature = "derive")] {
129 /// struct Context {
130 /// name: String,
131 /// debug: bool
132 /// }
133 /// # }
134 /// ```
135 ///
136 /// We then need to convert the `ArgMatches` that `clap` generated into our struct.
137 /// `from_arg_matches` serves as the equivalent of:
138 ///
139 /// ```rust
140 /// # #[cfg(feature = "derive")] {
141 /// # use clap::ArgMatches;
142 /// # struct Context {
143 /// # name: String,
144 /// # debug: bool
145 /// # }
146 /// impl From<ArgMatches> for Context {
147 /// fn from(m: ArgMatches) -> Self {
148 /// Context {
149 /// name: m.get_one::<String>("name").unwrap().clone(),
150 /// debug: m.get_flag("debug"),
151 /// }
152 /// }
153 /// }
154 /// # }
155 /// ```
156 fn from_arg_matches(matches: &ArgMatches) -> Result<Self, Error>;
157
158 /// Instantiate `Self` from [`ArgMatches`], parsing the arguments as needed.
159 ///
160 /// Motivation: If our application had two CLI options, `--name
161 /// <STRING>` and the flag `--debug`, we may create a struct as follows:
162 ///
163 /// ```rust
164 /// # #[cfg(feature = "derive")] {
165 /// struct Context {
166 /// name: String,
167 /// debug: bool
168 /// }
169 /// # }
170 /// ```
171 ///
172 /// We then need to convert the `ArgMatches` that `clap` generated into our struct.
173 /// `from_arg_matches_mut` serves as the equivalent of:
174 ///
175 /// ```rust
176 /// # #[cfg(feature = "derive")] {
177 /// # use clap::ArgMatches;
178 /// # struct Context {
179 /// # name: String,
180 /// # debug: bool
181 /// # }
182 /// impl From<ArgMatches> for Context {
183 /// fn from(m: ArgMatches) -> Self {
184 /// Context {
185 /// name: m.get_one::<String>("name").unwrap().to_string(),
186 /// debug: m.get_flag("debug"),
187 /// }
188 /// }
189 /// }
190 /// # }
191 /// ```
192 fn from_arg_matches_mut(matches: &mut ArgMatches) -> Result<Self, Error> {
193 Self::from_arg_matches(matches)
194 }
195
196 /// Assign values from `ArgMatches` to `self`.
197 fn update_from_arg_matches(&mut self, matches: &ArgMatches) -> Result<(), Error>;
198
199 /// Assign values from `ArgMatches` to `self`.
200 fn update_from_arg_matches_mut(&mut self, matches: &mut ArgMatches) -> Result<(), Error> {
201 self.update_from_arg_matches(matches)
202 }
203}
204
205/// Parse a set of arguments into a user-defined container.
206///
207/// Implementing this trait lets a parent container delegate argument parsing behavior to `Self`.
208/// with:
209/// - `#[command(flatten)] args: ChildArgs`: Attribute can only be used with struct fields that impl
210/// `Args`.
211/// - `Variant(ChildArgs)`: No attribute is used with enum variants that impl `Args`.
212///
213/// **NOTE:** Deriving requires the `derive` feature flag
214pub trait Args: FromArgMatches + Sized {
215 /// Report the [`ArgGroup::id`][crate::ArgGroup::id] for this set of arguments
216 fn group_id() -> Option<crate::Id> {
217 None
218 }
219 /// Append to [`Command`] so it can instantiate `Self`.
220 ///
221 /// See also [`CommandFactory`].
222 fn augment_args(cmd: Command) -> Command;
223 /// Append to [`Command`] so it can update `self`.
224 ///
225 /// This is used to implement `#[command(flatten)]`
226 ///
227 /// See also [`CommandFactory`].
228 fn augment_args_for_update(cmd: Command) -> Command;
229}
230
231/// Parse a sub-command into a user-defined enum.
232///
233/// Implementing this trait lets a parent container delegate subcommand behavior to `Self`.
234/// with:
235/// - `#[command(subcommand)] field: SubCmd`: Attribute can be used with either struct fields or enum
236/// variants that impl `Subcommand`.
237/// - `#[command(flatten)] Variant(SubCmd)`: Attribute can only be used with enum variants that impl
238/// `Subcommand`.
239///
240/// **NOTE:** Deriving requires the `derive` feature flag
241pub trait Subcommand: FromArgMatches + Sized {
242 /// Append to [`Command`] so it can instantiate `Self`.
243 ///
244 /// See also [`CommandFactory`].
245 fn augment_subcommands(cmd: Command) -> Command;
246 /// Append to [`Command`] so it can update `self`.
247 ///
248 /// This is used to implement `#[command(flatten)]`
249 ///
250 /// See also [`CommandFactory`].
251 fn augment_subcommands_for_update(cmd: Command) -> Command;
252 /// Test whether `Self` can parse a specific subcommand
253 fn has_subcommand(name: &str) -> bool;
254}
255
256/// Parse arguments into enums.
257///
258/// When deriving [`Parser`], a field whose type implements `ValueEnum` can have the attribute
259/// `#[arg(value_enum)]` which will
260/// - Call [`EnumValueParser`][crate::builder::EnumValueParser]
261/// - Allowing using the `#[arg(default_value_t)]` attribute without implementing `Display`.
262///
263/// **NOTE:** Deriving requires the `derive` feature flag
264pub trait ValueEnum: Sized + Clone {
265 /// All possible argument values, in display order.
266 fn value_variants<'a>() -> &'a [Self];
267
268 /// Parse an argument into `Self`.
269 fn from_str(input: &str, ignore_case: bool) -> Result<Self, String> {
270 Self::value_variants()
271 .iter()
272 .find(|v| {
273 v.to_possible_value()
274 .expect("ValueEnum::value_variants contains only values with a corresponding ValueEnum::to_possible_value")
275 .matches(input, ignore_case)
276 })
277 .cloned()
278 .ok_or_else(|| format!("invalid variant: {input}"))
279 }
280
281 /// The canonical argument value.
282 ///
283 /// The value is `None` for skipped variants.
284 fn to_possible_value(&self) -> Option<PossibleValue>;
285}
286
287impl<T: Parser> Parser for Box<T> {
288 fn parse() -> Self {
289 Box::new(<T as Parser>::parse())
290 }
291
292 fn try_parse() -> Result<Self, Error> {
293 <T as Parser>::try_parse().map(Box::new)
294 }
295
296 fn parse_from<I, It>(itr: I) -> Self
297 where
298 I: IntoIterator<Item = It>,
299 It: Into<OsString> + Clone,
300 {
301 Box::new(<T as Parser>::parse_from(itr))
302 }
303
304 fn try_parse_from<I, It>(itr: I) -> Result<Self, Error>
305 where
306 I: IntoIterator<Item = It>,
307 It: Into<OsString> + Clone,
308 {
309 <T as Parser>::try_parse_from(itr).map(Box::new)
310 }
311}
312
313impl<T: CommandFactory> CommandFactory for Box<T> {
314 fn command<'help>() -> Command {
315 <T as CommandFactory>::command()
316 }
317 fn command_for_update<'help>() -> Command {
318 <T as CommandFactory>::command_for_update()
319 }
320}
321
322impl<T: FromArgMatches> FromArgMatches for Box<T> {
323 fn from_arg_matches(matches: &ArgMatches) -> Result<Self, Error> {
324 <T as FromArgMatches>::from_arg_matches(matches).map(Box::new)
325 }
326 fn from_arg_matches_mut(matches: &mut ArgMatches) -> Result<Self, Error> {
327 <T as FromArgMatches>::from_arg_matches_mut(matches).map(Box::new)
328 }
329 fn update_from_arg_matches(&mut self, matches: &ArgMatches) -> Result<(), Error> {
330 <T as FromArgMatches>::update_from_arg_matches(self, matches)
331 }
332 fn update_from_arg_matches_mut(&mut self, matches: &mut ArgMatches) -> Result<(), Error> {
333 <T as FromArgMatches>::update_from_arg_matches_mut(self, matches)
334 }
335}
336
337impl<T: Args> Args for Box<T> {
338 fn augment_args(cmd: Command) -> Command {
339 <T as Args>::augment_args(cmd)
340 }
341 fn augment_args_for_update(cmd: Command) -> Command {
342 <T as Args>::augment_args_for_update(cmd)
343 }
344}
345
346impl<T: Subcommand> Subcommand for Box<T> {
347 fn augment_subcommands(cmd: Command) -> Command {
348 <T as Subcommand>::augment_subcommands(cmd)
349 }
350 fn augment_subcommands_for_update(cmd: Command) -> Command {
351 <T as Subcommand>::augment_subcommands_for_update(cmd)
352 }
353 fn has_subcommand(name: &str) -> bool {
354 <T as Subcommand>::has_subcommand(name)
355 }
356}
357
358fn format_error<I: CommandFactory>(err: crate::Error) -> crate::Error {
359 let mut cmd = I::command();
360 err.format(&mut cmd)
361}
362