Add Default derive and Option Pickable implementation

3 files changed, 18 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1b7bf1a..26fcabf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -57,6 +57,10 @@ fn render_greeting(prev: Greeting, res: &MyRes) {
 }
 ```
 
+5. **\[picker\]** Implement `Pickable` for `Option<T>`  
+
+Added `impl<T: Pickable<Output = T> + Default> Pickable for Option<T>`, allowing optional values to be directly parsed via `Pickable` without manually handling the `Option` wrapping logic.
+
 #### **BREAKING CHANGES** (API CHANGES):
 1. **\[core\]** Panic Unwind will not be supported when the `async` feature is enabled
 2. **\[core\]** `modify_res` signature changed: now returns `Return` instead of `()`
diff --git a/mingling/src/parser/picker.rs b/mingling/src/parser/picker.rs
index 725d4e6..b0cdb70 100644
--- a/mingling/src/parser/picker.rs
+++ b/mingling/src/parser/picker.rs
@@ -14,6 +14,7 @@ pub mod path;
 ///
 /// The `Picker` struct holds parsed arguments and provides a fluent interface
 /// to extract values associated with specific flags.
+#[derive(Default)]
 pub struct Picker {
     /// The parsed command-line arguments.
     pub args: Argument,
diff --git a/mingling/src/parser/picker/builtin.rs b/mingling/src/parser/picker/builtin.rs
index 9fbbfd1..e7a178d 100644
--- a/mingling/src/parser/picker/builtin.rs
+++ b/mingling/src/parser/picker/builtin.rs
@@ -60,6 +60,7 @@ impl Pickable for bool {
     }
 }
 
+/// Special: parses a size string (e.g. "10MB") into a `usize` representing the number of bytes.
 impl Pickable for usize {
     type Output = usize;
 
@@ -73,6 +74,7 @@ impl Pickable for usize {
     }
 }
 
+/// Special: parses a comma-separated list of size strings (e.g. "10MB,20KB") into a `Vec<usize>`.
 impl Pickable for Vec<usize> {
     type Output = Vec<usize>;
 
@@ -90,6 +92,7 @@ impl Pickable for Vec<usize> {
     }
 }
 
+/// Special: dumps the remaining arguments into an `Argument` struct.
 impl Pickable for Argument {
     type Output = Argument;
 
@@ -100,3 +103,13 @@ impl Pickable for Argument {
         Some(args.dump_remains().into())
     }
 }
+
+/// Special: parses a single value of type `T` using the `Pickable` implementation for `T`, and wraps it in an `Option`.
+impl<T: Pickable<Output = T> + Default> Pickable for Option<T> {
+    type Output = Option<T>;
+
+    fn pick(args: &mut Argument, flag: mingling_core::Flag) -> Option<Self::Output> {
+        let r = T::pick(args, flag);
+        Some(r)
+    }
+}