Merge #64

64: Implement `Deserializer` for `Value` r=kvark a=torkleyy

Just had this idea, so I thought I could implement it.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ron"
-version = "0.1.4"
+version = "0.1.5"
 license = "MIT/Apache-2.0"
 keywords = ["parser", "serde", "serialization"]
 authors = [

src/value.rs

@@ -4,6 +4,10 @@ use std::cmp::{Eq, Ordering};
 use std::collections::BTreeMap;
 use std::hash::{Hash, Hasher};
 
+use serde::de::{DeserializeSeed, Deserializer, MapAccess, SeqAccess, Visitor};
+
+use de::{Error as RonError, Result};
+
 /// A wrapper for `f64` which guarantees that the inner value
 /// is finite and thus implements `Eq`, `Hash` and `Ord`.
 #[derive(Copy, Clone, Debug, PartialOrd, PartialEq)]
@@ -51,3 +55,151 @@ pub enum Value {
     Seq(Vec<Value>),
     Unit,
 }
+
+/// Deserializer implementation for RON `Value`.
+/// This does not support enums (because `Value` doesn't store them).
+impl<'de> Deserializer<'de> for Value {
+    type Error = RonError;
+
+    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value>
+    where
+        V: Visitor<'de>,
+    {
+        match self {
+            Value::Bool(b) => visitor.visit_bool(b),
+            Value::Char(c) => visitor.visit_char(c),
+            Value::Map(m) => visitor.visit_map(Map {
+                keys: m.keys().cloned().rev().collect(),
+                values: m.values().cloned().rev().collect(),
+            }),
+            Value::Number(n) => visitor.visit_f64(n.get()),
+            Value::Option(Some(o)) => visitor.visit_some(*o),
+            Value::Option(None) => visitor.visit_none(),
+            Value::String(s) => visitor.visit_string(s),
+            Value::Seq(mut seq) => {
+                seq.reverse();
+
+                visitor.visit_seq(Seq { seq })
+            }
+            Value::Unit => visitor.visit_unit(),
+        }
+    }
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map struct enum identifier ignored_any
+    }
+}
+
+struct Map {
+    keys: Vec<Value>,
+    values: Vec<Value>,
+}
+
+impl<'de> MapAccess<'de> for Map {
+    type Error = RonError;
+
+    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>>
+    where
+        K: DeserializeSeed<'de>,
+    {
+        // The `Vec` is reversed, so we can pop to get the originally first element
+        self.keys
+            .pop()
+            .map_or(Ok(None), |v| seed.deserialize(v).map(Some))
+    }
+
+    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value>
+    where
+        V: DeserializeSeed<'de>,
+    {
+        // The `Vec` is reversed, so we can pop to get the originally first element
+        self.values
+            .pop()
+            .map(|v| seed.deserialize(v))
+            .expect("Contract violation")
+    }
+}
+
+struct Seq {
+    seq: Vec<Value>,
+}
+
+impl<'de> SeqAccess<'de> for Seq {
+    type Error = RonError;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>>
+    where
+        T: DeserializeSeed<'de>,
+    {
+        // The `Vec` is reversed, so we can pop to get the originally first element
+        self.seq
+            .pop()
+            .map_or(Ok(None), |v| seed.deserialize(v).map(Some))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::fmt::Debug;
+    use serde::Deserialize;
+    use super::*;
+
+    fn assert_same<'de, T>(s: &'de str)
+    where
+        T: Debug + Deserialize<'de> + PartialEq,
+    {
+        use de::from_str;
+
+        let direct: T = from_str(s).unwrap();
+        let value: Value = from_str(s).unwrap();
+        let value = T::deserialize(value).unwrap();
+
+        assert_eq!(direct, value, "Deserialization for {:?} is not the same", s);
+    }
+
+    #[test]
+    fn boolean() {
+        assert_same::<bool>("true");
+        assert_same::<bool>("false");
+    }
+
+    #[test]
+    fn float() {
+        assert_same::<f64>("0.123");
+        assert_same::<f64>("-4.19");
+    }
+
+    #[test]
+    fn char() {
+        assert_same::<char>("'4'");
+        assert_same::<char>("'c'");
+    }
+
+    #[test]
+    fn map() {
+        assert_same::<BTreeMap<char, String>>(
+            "{
+'a': \"Hello\",
+'b': \"Bye\",
+        }",
+        );
+    }
+
+    #[test]
+    fn option() {
+        assert_same::<Option<char>>("Some('a')");
+        assert_same::<Option<char>>("None");
+    }
+
+    #[test]
+    fn seq() {
+        assert_same::<Vec<f64>>("[1.0, 2.0, 3.0, 4.0]");
+    }
+
+    #[test]
+    fn unit() {
+        assert_same::<()>("()");
+    }
+}