feat: add pick_or, pick_or_default, and pick_or_route shorthands

Remove the `Default` bound from `pick()` and `EntryPicker::pick()`,
allowing non-Default types to be used as arguments.

Add `IntoPicker::pick_or`, `pick_or_default`, and `pick_or_route`
convenience methods for common fallback patterns.

Fix token splitting in `arg!` macro to correctly handle angle brackets.

1 files changed, 73 insertions, 1 deletions

diff --git a/arg_picker/src/picker.rs b/arg_picker/src/picker.rs
index f31a5b6..f722fb5 100644
--- a/arg_picker/src/picker.rs
+++ b/arg_picker/src/picker.rs
@@ -369,11 +369,83 @@ pub trait IntoPicker<'a> {
     fn pick<N>(self, arg: impl Into<&'a PickerArg<'a, N>>) -> PickerPattern1<'a, N, ()>
     where
         Self: Sized,
-        N: Pickable<'a> + Default + Sized,
+        N: Pickable<'a> + Sized,
     {
         Picker::build_pattern1(self.to_picker().args, arg.into(), None::<()>)
     }
 
+    /// Starts building a picker pattern with the first argument, using a default value provider.
+    ///
+    /// This is a shorthand for calling `.pick(arg).or(func)`.
+    ///
+    /// # Type Parameters
+    ///
+    /// * `Next` — The nominal type of the first argument; must implement [`Pickable`].
+    ///
+    /// # Parameters
+    ///
+    /// * `arg` — The argument definition, typically obtained from [`crate::macros::arg`].
+    /// * `func` — A closure that provides a default value if the arg is not provided by the user.
+    fn pick_or<Next, F>(
+        self,
+        arg: impl Into<&'a PickerArg<'a, Next>>,
+        func: F,
+    ) -> PickerPattern1<'a, Next, ()>
+    where
+        Self: Sized,
+        Next: Pickable<'a> + Sized,
+        F: FnMut() -> Next + 'static,
+    {
+        self.pick(arg).or(func)
+    }
+
+    /// Starts building a picker pattern with the first argument, using a default value.
+    ///
+    /// This is a shorthand for calling `.pick(arg).or_default()`.
+    ///
+    /// # Type Parameters
+    ///
+    /// * `Next` — The nominal type of the first argument; must implement [`Pickable`] and [`Default`].
+    ///
+    /// # Parameters
+    ///
+    /// * `arg` — The argument definition, typically obtained from [`crate::macros::arg`].
+    fn pick_or_default<Next>(
+        self,
+        arg: impl Into<&'a PickerArg<'a, Next>>,
+    ) -> PickerPattern1<'a, Next, ()>
+    where
+        Self: Sized,
+        Next: Pickable<'a> + Default + Sized,
+    {
+        self.pick(arg).or_default()
+    }
+
+    /// Starts building a picker pattern with the first argument, using a route if the arg is not provided.
+    ///
+    /// This is a shorthand for calling `.pick(arg).or_route(func)`.
+    ///
+    /// # Type Parameters
+    ///
+    /// * `Next` — The nominal type of the first argument; must implement [`Pickable`].
+    ///
+    /// # Parameters
+    ///
+    /// * `arg` — The argument definition, typically obtained from [`crate::macros::arg`].
+    /// * `func` — A closure that produces a route value if the arg is not provided by the user.
+    fn pick_or_route<Next, F, Route>(
+        self,
+        arg: impl Into<&'a PickerArg<'a, Next>>,
+        func: F,
+    ) -> PickerPattern1<'a, Next, Route>
+    where
+        Self: Sized,
+        Next: Pickable<'a> + Sized,
+        F: FnMut() -> Route + 'static,
+    {
+        self.pick(arg).with_route::<Route>().or_route(func)
+    }
+
     /// Converts the value into a `Picker` with a specified route type.
     ///
     /// This method allows changing the route (phantom type parameter) of the picker.