Merge pull request #5051 from joshtriplett/mut-args

Add `Command::mut_args` to modify all arguments of a `Command`

clap_builder/src/builder/command.rs

@@ -252,6 +252,52 @@ impl Command {
         self
     }
 
+    /// Allows one to mutate all [`Arg`]s after they've been added to a [`Command`].
+    ///
+    /// This does not affect the built-in `--help` or `--version` arguments.
+    ///
+    /// # Examples
+    ///
+    #[cfg_attr(feature = "string", doc = "```")]
+    #[cfg_attr(not(feature = "string"), doc = "```ignore")]
+    /// # use clap_builder as clap;
+    /// # use clap::{Command, Arg, ArgAction};
+    ///
+    /// let mut cmd = Command::new("foo")
+    ///     .arg(Arg::new("bar")
+    ///         .long("bar")
+    ///         .action(ArgAction::SetTrue))
+    ///     .arg(Arg::new("baz")
+    ///         .long("baz")
+    ///         .action(ArgAction::SetTrue))
+    ///     .mut_args(|a| {
+    ///         if let Some(l) = a.get_long().map(|l| format!("prefix-{l}")) {
+    ///             a.long(l)
+    ///         } else {
+    ///             a
+    ///         }
+    ///     });
+    ///
+    /// let res = cmd.try_get_matches_from_mut(vec!["foo", "--bar"]);
+    ///
+    /// // Since we changed `bar`'s long to "prefix-bar" this should err as there
+    /// // is no `--bar` anymore, only `--prefix-bar`.
+    ///
+    /// assert!(res.is_err());
+    ///
+    /// let res = cmd.try_get_matches_from_mut(vec!["foo", "--prefix-bar"]);
+    /// assert!(res.is_ok());
+    /// ```
+    #[must_use]
+    #[cfg_attr(debug_assertions, track_caller)]
+    pub fn mut_args<F>(mut self, f: F) -> Self
+    where
+        F: FnMut(Arg) -> Arg,
+    {
+        self.args.mut_args(f);
+        self
+    }
+
     /// Allows one to mutate a [`Command`] after it's been added as a subcommand.
     ///
     /// This can be useful for modifying auto-generated arguments of nested subcommands with

clap_builder/src/mkeymap.rs

@@ -123,6 +123,15 @@ impl MKeyMap {
         self.args.iter_mut()
     }
 
+    /// Mutate every argument.
+    pub(crate) fn mut_args<F>(&mut self, f: F)
+    where
+        F: FnMut(Arg) -> Arg,
+    {
+        let mut args = std::mem::take(&mut self.args);
+        self.args.extend(args.drain(..).map(f));
+    }
+
     /// We need a lazy build here since some we may change args after creating
     /// the map, you can checkout who uses `args_mut`.
     pub(crate) fn _build(&mut self) {