From 4c43b4fea2cdd270f26e71cc783d1c02a106b31f Mon Sep 17 00:00:00 2001
From: Erick Tryzelaar <erick.tryzelaar@gmail.com>
Date: Thu, 2 Oct 2014 19:24:38 -0700
Subject: [PATCH] Variation to support option and a json-ish value

---
 serde2/src/bin.rs |  81 +++++++++++++++++++++++++++++++----
 serde2/src/de2.rs | 107 +++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 172 insertions(+), 16 deletions(-)

diff --git a/serde2/src/bin.rs b/serde2/src/bin.rs
index b5d95d1f..55662d4e 100644
--- a/serde2/src/bin.rs
+++ b/serde2/src/bin.rs
@@ -3,8 +3,9 @@ extern crate serde2;
 use serde2::de2;
 use serde2::de2::{Deserialize, Deserializer};
 
+#[deriving(Show)]
 enum Token {
-    //Null,
+    Null,
     Int(int),
     //String(String),
     SeqStart(uint),
@@ -58,11 +59,9 @@ impl<Iter: Iterator<Token>> Deserializer<Error> for MyDeserializer<Iter> {
         V: de2::Visitor<MyDeserializer<Iter>, R, Error>,
     >(&mut self, visitor: &mut V) -> Result<R, Error> {
         match self.next() {
-            /*
             Some(Null) => {
                 visitor.visit_null(self)
             }
-            */
             Some(Int(v)) => {
                 visitor.visit_int(self, v)
             }
@@ -88,6 +87,21 @@ impl<Iter: Iterator<Token>> Deserializer<Error> for MyDeserializer<Iter> {
         }
     }
 
+    fn visit_option<
+        T: Deserialize<MyDeserializer<Iter>, Error>,
+    >(&mut self) -> Result<Option<T>, Error> {
+        match self.peek() {
+            Some(&Null) => {
+                self.next();
+                Ok(None)
+            }
+            _ => {
+                let v = try!(Deserialize::deserialize(self));
+                Ok(Some(v))
+            }
+        }
+    }
+
     fn syntax_error(&mut self) -> Error {
         SyntaxError
     }
@@ -173,7 +187,7 @@ mod json {
 
     #[deriving(Show)]
     pub enum Value {
-        //Null,
+        Null,
         //Bool(bool),
         Int(int),
         //String(String),
@@ -192,11 +206,9 @@ mod json {
                 D: de2::Deserializer<E>,
                 E,
             > de2::Visitor<D, Value, E> for Visitor {
-                /*
                 fn visit_null(&mut self, _d: &mut D) -> Result<Value, E> {
                     Ok(Null)
                 }
-                */
 
                 fn visit_int(&mut self, _d: &mut D, v: int) -> Result<Value, E> {
                     Ok(Int(v))
@@ -208,6 +220,17 @@ mod json {
                 }
                 */
 
+                /*
+                fn visit_option<
+                    Visitor: de2::OptionVisitor<D, E>,
+                >(&mut self, d: &mut D, mut visitor: Visitor) -> Result<Value, E> {
+                    match visitor.next(d) {
+                        Some(v) => v,
+                        None => Ok(Null),
+                    }
+                }
+                */
+
                 fn visit_seq<
                     Visitor: de2::SeqVisitor<D, E>,
                 >(&mut self, d: &mut D, mut visitor: Visitor) -> Result<Value, E> {
@@ -266,7 +289,7 @@ fn main() {
         SeqStart(2),
         Int(1),
         Int(2),
-        End
+        End,
     );
     let mut state = MyDeserializer::new(tokens.into_iter());
 
@@ -279,7 +302,7 @@ fn main() {
         SeqStart(2),
         Int(1),
         Int(2),
-        End
+        End,
     );
     let mut state = MyDeserializer::new(tokens.into_iter());
 
@@ -292,7 +315,47 @@ fn main() {
         SeqStart(2),
         Int(1),
         Int(2),
-        End
+        End,
+    );
+    let mut state = MyDeserializer::new(tokens.into_iter());
+
+    let v: Result<json::Value, Error> = Deserialize::deserialize(&mut state);
+    println!("{}", v);
+
+    ////
+
+    let tokens = vec!(
+        Int(1),
+    );
+    let mut state = MyDeserializer::new(tokens.into_iter());
+
+    let v: Result<Option<int>, Error> = Deserialize::deserialize(&mut state);
+    println!("{}", v);
+
+    ////
+
+    let tokens = vec!(
+        Null,
+    );
+    let mut state = MyDeserializer::new(tokens.into_iter());
+
+    let v: Result<Option<int>, Error> = Deserialize::deserialize(&mut state);
+    println!("{}", v);
+
+    ////
+
+    let tokens = vec!(
+        Int(1),
+    );
+    let mut state = MyDeserializer::new(tokens.into_iter());
+
+    let v: Result<json::Value, Error> = Deserialize::deserialize(&mut state);
+    println!("{}", v);
+
+    ////
+
+    let tokens = vec!(
+        Null,
     );
     let mut state = MyDeserializer::new(tokens.into_iter());
 
diff --git a/serde2/src/de2.rs b/serde2/src/de2.rs
index 6a535ec5..b8c155e5 100644
--- a/serde2/src/de2.rs
+++ b/serde2/src/de2.rs
@@ -10,26 +10,56 @@ pub trait Deserialize<D, E> {
 pub trait Deserializer<E> {
     fn visit<
         R,
-        V: Visitor<Self, R, E>
+        V: Visitor<Self, R, E>,
     >(&mut self, visitor: &mut V) -> Result<R, E>;
 
+    fn visit_option<
+        T: Deserialize<Self, E>,
+    >(&mut self) -> Result<Option<T>, E>;
+
     fn syntax_error(&mut self) -> E;
 
     fn end_of_stream_error(&mut self) -> E;
 }
 
 pub trait Visitor<D: Deserializer<E>, R, E> {
+    fn visit_null(&mut self, d: &mut D) -> Result<R, E> {
+        Err(d.syntax_error())
+    }
+
     fn visit_int(&mut self, d: &mut D, _v: int) -> Result<R, E> {
         Err(d.syntax_error())
     }
 
+    /*
+    fn visit_option<
+        V: OptionVisitor<D, E>
+    >(&mut self, d: &mut D, _visitor: V) -> Result<R, E> {
+        Err(d.syntax_error())
+    }
+    */
+
     fn visit_seq<
         V: SeqVisitor<D, E>
-    >(&mut self, d: &mut D, _v: V) -> Result<R, E> {
+    >(&mut self, d: &mut D, _visitor: V) -> Result<R, E> {
         Err(d.syntax_error())
     }
 }
 
+/*
+pub trait OptionVisitor<D, R, T: Deserialize<D, E>, E> {
+    /*
+    fn next<
+        T: Deserialize<D, E>,
+    >(&mut self, d: &mut D) -> Option<Result<T, E>>;
+    */
+
+    fn visit<
+        T: Deserialize<D, E>,
+    >(&mut self, d: &mut D) -> Result<Option<T>, E>;
+}
+*/
+
 pub trait SeqVisitor<D, E> {
     fn next<
         T: Deserialize<D, E>,
@@ -43,6 +73,27 @@ pub trait SeqVisitor<D, E> {
     }
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
+impl<
+    D: Deserializer<E>,
+    E,
+> Deserialize<D, E> for () {
+    fn deserialize(d: &mut D) -> Result<(), E> {
+        struct Visitor;
+
+        impl<D: Deserializer<E>, E> self::Visitor<D, (), E> for Visitor {
+            fn visit_null(&mut self, _d: &mut D) -> Result<(), E> {
+                Ok(())
+            }
+        }
+
+        d.visit(&mut Visitor)
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 impl<
     D: Deserializer<E>,
     E,
@@ -60,6 +111,51 @@ impl<
     }
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
+impl<
+    T: Deserialize<D, E>,
+    D: Deserializer<E>,
+    E,
+> Deserialize<D, E> for Option<T> {
+    fn deserialize(d: &mut D) -> Result<Option<T>, E> {
+        /*
+        struct Visitor;
+
+        impl<
+            R: Deserialize<D, E>,
+            D: Deserializer<E>,
+            E,
+        > self::OptionVisitor<D, E> for Visitor {
+            /*
+            fn visit_option<
+                V: OptionVisitor<D, E>,
+            >(&mut self, d: &mut D, mut visitor: V) -> Result<Option<R>, E> {
+                match visitor.next(d) {
+                    Some(value) => {
+                        Ok(Some(try!(value)))
+                    }
+                    None => {
+                        Ok(None)
+                    }
+                }
+            }
+            */
+
+            fn visit<
+                T: Deserialize<D, E>,
+            >(&mut self, d: &mut D, value: Option<T>) -> Result<Option<T>, E> {
+                Ok(value)
+            }
+        }
+        */
+
+        d.visit_option()
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 impl<
     T: Deserialize<D, E>,
     D: Deserializer<E>,
@@ -81,11 +177,8 @@ impl<
 
                 loop {
                     match visitor.next(d) {
-                        Some(Ok(value)) => {
-                            values.push(value);
-                        }
-                        Some(Err(err)) => {
-                            return Err(err);
+                        Some(value) => {
+                            values.push(try!(value));
                         }
                         None => {
                             break;