Add Deserializer::visit_enum to help json enum deserialization

serde2/src/de.rs

@@ -36,6 +36,17 @@ pub trait Deserializer {
     {
         self.visit(visitor)
     }
+
+    /// The `visit_enum` method allows a `Deserialize` type to inform the
+    /// `Deserializer` that it's expecting an enum value. This allows
+    /// deserializers that provide a custom enumeration serialization to
+    /// properly deserialize the type.
+    #[inline]
+    fn visit_enum<V>(&mut self, visitor: V) -> Result<V::Value, Self::Error>
+        where V: Visitor,
+    {
+        self.visit(visitor)
+    }
 }
 
 pub trait Visitor {
@@ -211,6 +222,8 @@ pub trait Visitor {
     }
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
 pub trait SeqVisitor {
     type Error: Error;
 
@@ -225,6 +238,29 @@ pub trait SeqVisitor {
     }
 }
 
+impl<'a, V> SeqVisitor for &'a mut V where V: SeqVisitor {
+    type Error = V::Error;
+
+    #[inline]
+    fn visit<T>(&mut self) -> Result<Option<T>, V::Error>
+        where T: Deserialize
+    {
+        (**self).visit()
+    }
+
+    #[inline]
+    fn end(&mut self) -> Result<(), V::Error> {
+        (**self).end()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (**self).size_hint()
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 pub trait MapVisitor {
     type Error: Error;
 
@@ -256,6 +292,44 @@ pub trait MapVisitor {
     }
 }
 
+impl<'a, V_> MapVisitor for &'a mut V_ where V_: MapVisitor {
+    type Error = V_::Error;
+
+    #[inline]
+    fn visit<K, V>(&mut self) -> Result<Option<(K, V)>, V_::Error>
+        where K: Deserialize,
+              V: Deserialize,
+    {
+        (**self).visit()
+    }
+
+    #[inline]
+    fn visit_key<K>(&mut self) -> Result<Option<K>, V_::Error>
+        where K: Deserialize
+    {
+        (**self).visit_key()
+    }
+
+    #[inline]
+    fn visit_value<V>(&mut self) -> Result<V, V_::Error>
+        where V: Deserialize
+    {
+        (**self).visit_value()
+    }
+
+    #[inline]
+    fn end(&mut self) -> Result<(), V_::Error> {
+        (**self).end()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (**self).size_hint()
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
 pub trait EnumVisitor {
     type Error: Error;
 
@@ -276,6 +350,8 @@ pub trait EnumVisitor {
     }
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
 pub trait EnumSeqVisitor {
     type Value;
 
@@ -283,6 +359,8 @@ pub trait EnumSeqVisitor {
         where V: SeqVisitor;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+
 pub trait EnumMapVisitor {
     type Value;
 
@@ -374,12 +452,12 @@ impl<
 > self::Visitor for PrimitiveVisitor<T> {
     type Value = T;
 
-    impl_deserialize_num_method!(isize, visit_isize, from_int);
+    impl_deserialize_num_method!(isize, visit_isize, from_isize);
     impl_deserialize_num_method!(i8, visit_i8, from_i8);
     impl_deserialize_num_method!(i16, visit_i16, from_i16);
     impl_deserialize_num_method!(i32, visit_i32, from_i32);
     impl_deserialize_num_method!(i64, visit_i64, from_i64);
-    impl_deserialize_num_method!(usize, visit_usize, from_uint);
+    impl_deserialize_num_method!(usize, visit_usize, from_usize);
     impl_deserialize_num_method!(u8, visit_u8, from_u8);
     impl_deserialize_num_method!(u16, visit_u16, from_u16);
     impl_deserialize_num_method!(u32, visit_u32, from_u32);

serde2/src/json/de.rs

@@ -104,17 +104,11 @@ impl<Iter: Iterator<Item=u8>> Deserializer<Iter> {
             }
             b'[' => {
                 self.bump();
-                visitor.visit_seq(SeqVisitor {
-                    de: self,
-                    first: true,
-                })
+                visitor.visit_seq(SeqVisitor::new(self))
             }
             b'{' => {
                 self.bump();
-                visitor.visit_map(MapVisitor {
-                    de: self,
-                    first: true,
-                })
+                visitor.visit_map(MapVisitor::new(self))
             }
             _ => {
                 Err(self.error(ErrorCode::ExpectedSomeValue))
@@ -367,6 +361,19 @@ impl<Iter: Iterator<Item=u8>> Deserializer<Iter> {
             }
         }
     }
+
+    fn parse_object_colon(&mut self) -> Result<(), Error> {
+        self.parse_whitespace();
+
+        if self.ch_is(b':') {
+            self.bump();
+            Ok(())
+        } else if self.eof() {
+            Err(self.error(ErrorCode::EOFWhileParsingObject))
+        } else {
+            Err(self.error(ErrorCode::ExpectedColon))
+        }
+    }
 }
 
 impl<Iter: Iterator<Item=u8>> de::Deserializer for Deserializer<Iter> {
@@ -396,6 +403,38 @@ impl<Iter: Iterator<Item=u8>> de::Deserializer for Deserializer<Iter> {
             visitor.visit_some(self)
         }
     }
+
+    #[inline]
+    fn visit_enum<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
+        where V: de::Visitor,
+    {
+        self.parse_whitespace();
+
+        if self.ch_is(b'{') {
+            self.bump();
+            self.parse_whitespace();
+
+            try!(self.parse_string());
+            try!(self.parse_object_colon());
+
+            let variant = str::from_utf8(&self.buf).unwrap().to_string();
+
+            let value = try!(visitor.visit_variant(&variant, EnumVisitor {
+                de: self,
+            }));
+
+            self.parse_whitespace();
+
+            if self.ch_is(b'}') {
+                self.bump();
+                Ok(value)
+            } else {
+                return Err(self.error(ErrorCode::ExpectedSomeValue));
+            }
+        } else {
+            Err(self.error(ErrorCode::ExpectedSomeValue))
+        }
+    }
 }
 
 struct SeqVisitor<'a, Iter: 'a> {
@@ -403,7 +442,18 @@ struct SeqVisitor<'a, Iter: 'a> {
     first: bool,
 }
 
-impl<'a, Iter: Iterator<Item=u8>> de::SeqVisitor for SeqVisitor<'a, Iter> {
+impl<'a, Iter> SeqVisitor<'a, Iter> {
+    fn new(de: &'a mut Deserializer<Iter>) -> Self {
+        SeqVisitor {
+            de: de,
+            first: true,
+        }
+    }
+}
+
+impl<'a, Iter> de::SeqVisitor for SeqVisitor<'a, Iter>
+    where Iter: Iterator<Item=u8>
+{
     type Error = Error;
 
     fn visit<T>(&mut self) -> Result<Option<T>, Error>
@@ -433,6 +483,8 @@ impl<'a, Iter: Iterator<Item=u8>> de::SeqVisitor for SeqVisitor<'a, Iter> {
     }
 
     fn end(&mut self) -> Result<(), Error> {
+        self.de.parse_whitespace();
+
         if self.de.ch_is(b']') {
             self.de.bump();
             Ok(())
@@ -449,7 +501,18 @@ struct MapVisitor<'a, Iter: 'a> {
     first: bool,
 }
 
-impl<'a, Iter: Iterator<Item=u8>> de::MapVisitor for MapVisitor<'a, Iter> {
+impl<'a, Iter> MapVisitor<'a, Iter> {
+    fn new(de: &'a mut Deserializer<Iter>) -> Self {
+        MapVisitor {
+            de: de,
+            first: true,
+        }
+    }
+}
+
+impl<'a, Iter> de::MapVisitor for MapVisitor<'a, Iter>
+    where Iter: Iterator<Item=u8>
+{
     type Error = Error;
 
     fn visit_key<K>(&mut self) -> Result<Option<K>, Error>
@@ -489,22 +552,14 @@ impl<'a, Iter: Iterator<Item=u8>> de::MapVisitor for MapVisitor<'a, Iter> {
     fn visit_value<V>(&mut self) -> Result<V, Error>
         where V: de::Deserialize,
     {
-        self.de.parse_whitespace();
-
-        if self.de.ch_is(b':') {
-            self.de.bump();
-        } else if self.de.eof() {
-            return Err(self.de.error(ErrorCode::EOFWhileParsingObject));
-        } else {
-            return Err(self.de.error(ErrorCode::ExpectedColon));
-        }
-
-        self.de.parse_whitespace();
+        try!(self.de.parse_object_colon());
 
         Ok(try!(de::Deserialize::deserialize(self.de)))
     }
 
     fn end(&mut self) -> Result<(), Error> {
+        self.de.parse_whitespace();
+
         if self.de.ch_is(b']') {
             self.de.bump();
             Ok(())
@@ -516,6 +571,44 @@ impl<'a, Iter: Iterator<Item=u8>> de::MapVisitor for MapVisitor<'a, Iter> {
     }
 }
 
+struct EnumVisitor<'a, Iter: 'a> {
+    de: &'a mut Deserializer<Iter>,
+}
+
+impl<'a, Iter: Iterator<Item=u8>> de::EnumVisitor for EnumVisitor<'a, Iter> {
+    type Error = Error;
+
+    fn visit_unit(&mut self) -> Result<(), Error> {
+        de::Deserialize::deserialize(self.de)
+    }
+
+    fn visit_seq<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
+        where V: de::EnumSeqVisitor,
+    {
+        self.de.parse_whitespace();
+
+        if self.de.ch_is(b'[') {
+            self.de.bump();
+            visitor.visit(SeqVisitor::new(self.de))
+        } else {
+            Err(self.de.error(ErrorCode::ExpectedSomeValue))
+        }
+    }
+
+    fn visit_map<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
+        where V: de::EnumMapVisitor,
+    {
+        self.de.parse_whitespace();
+
+        if self.de.ch_is(b'{') {
+            self.de.bump();
+            visitor.visit(MapVisitor::new(self.de))
+        } else {
+            Err(self.de.error(ErrorCode::ExpectedSomeValue))
+        }
+    }
+}
+
 /// Decodes a json value from an `Iterator<u8>`.
 pub fn from_iter<I, T>(iter: I) -> Result<T, Error>
     where I: Iterator<Item=u8>,

serde2/src/json/value.rs

@@ -46,11 +46,6 @@ impl de::Deserialize for Value {
         impl de::Visitor for ValueVisitor {
             type Value = Value;
 
-            #[inline]
-            fn visit_unit<E>(&mut self) -> Result<Value, E> {
-                Ok(Value::Null)
-            }
-
             #[inline]
             fn visit_bool<E>(&mut self, value: bool) -> Result<Value, E> {
                 Ok(Value::Bool(value))
@@ -90,6 +85,11 @@ impl de::Deserialize for Value {
                 de::Deserialize::deserialize(deserializer)
             }
 
+            #[inline]
+            fn visit_unit<E>(&mut self) -> Result<Value, E> {
+                Ok(Value::Null)
+            }
+
             #[inline]
             fn visit_seq<V>(&mut self, visitor: V) -> Result<Value, V::Error>
                 where V: de::SeqVisitor,
@@ -157,7 +157,7 @@ impl Serializer {
     pub fn unwrap(mut self) -> Value {
         match self.state.pop().unwrap() {
             State::Value(value) => value,
-            _ => panic!(),
+            state => panic!("expected value, found {:?}", state),
         }
     }
 }
@@ -258,12 +258,12 @@ impl ser::Visitor for Serializer {
 
         while let Some(()) = try!(visitor.visit(self)) { }
 
-        match self.state.pop().unwrap() {
-            State::Array(values) => {
-                self.state.push(State::Value(Value::Array(values)));
-            }
-            _ => panic!(),
-        }
+        let values = match self.state.pop().unwrap() {
+            State::Array(values) => values,
+            state => panic!("Expected array, found {:?}", state),
+        };
+
+        self.state.push(State::Value(Value::Array(values)));
 
         Ok(())
     }
@@ -276,7 +276,7 @@ impl ser::Visitor for Serializer {
 
         let value = match self.state.pop().unwrap() {
             State::Value(value) => value,
-            _ => panic!(),
+            state => panic!("expected value, found {:?}", state),
         };
 
         let mut object = BTreeMap::new();
@@ -296,12 +296,12 @@ impl ser::Visitor for Serializer {
 
         let value = match self.state.pop().unwrap() {
             State::Value(value) => value,
-            _ => panic!(),
+            state => panic!("expected value, found {:?}", state),
         };
 
         match *self.state.last_mut().unwrap() {
             State::Array(ref mut values) => { values.push(value); }
-            _ => panic!(),
+            ref state => panic!("expected array, found {:?}", state),
         }
 
         Ok(())
@@ -317,12 +317,12 @@ impl ser::Visitor for Serializer {
 
         while let Some(()) = try!(visitor.visit(self)) { }
 
-        match self.state.pop().unwrap() {
-            State::Object(values) => {
-                self.state.push(State::Value(Value::Object(values)));
-            }
-            _ => panic!(),
-        }
+        let values = match self.state.pop().unwrap() {
+            State::Object(values) => values,
+            state => panic!("expected object, found {:?}", state),
+        };
+
+        self.state.push(State::Value(Value::Object(values)));
 
         Ok(())
     }
@@ -335,7 +335,7 @@ impl ser::Visitor for Serializer {
 
         let value = match self.state.pop().unwrap() {
             State::Value(value) => value,
-            _ => panic!(),
+            state => panic!("expected value, found {:?}", state),
         };
 
         let mut object = BTreeMap::new();
@@ -436,6 +436,46 @@ impl de::Deserializer for Deserializer {
             None => Err(de::Error::end_of_stream_error()),
         }
     }
+
+    #[inline]
+    fn visit_enum<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
+        where V: de::Visitor,
+    {
+        let value = match self.value.take() {
+            Some(Value::Object(value)) => value,
+            Some(_) => { return Err(de::Error::syntax_error()); }
+            None => { return Err(de::Error::end_of_stream_error()); }
+        };
+
+        let mut iter = value.into_iter();
+
+        let value = match iter.next() {
+            Some((variant, Value::Array(fields))) => {
+                let len = fields.len();
+                try!(visitor.visit_variant(&variant, SeqDeserializer {
+                    de: self,
+                    iter: fields.into_iter(),
+                    len: len,
+                }))
+            }
+            Some((variant, Value::Object(fields))) => {
+                let len = fields.len();
+                try!(visitor.visit_variant(&variant, MapDeserializer {
+                    de: self,
+                    iter: fields.into_iter(),
+                    value: None,
+                    len: len,
+                }))
+            }
+            Some(_) => { return Err(de::Error::syntax_error()); }
+            None => { return Err(de::Error::syntax_error()); }
+        };
+
+        match iter.next() {
+            Some(_) => Err(de::Error::syntax_error()),
+            None => Ok(value)
+        }
+    }
 }
 
 struct SeqDeserializer<'a> {
@@ -473,6 +513,24 @@ impl<'a> de::SeqVisitor for SeqDeserializer<'a> {
     }
 }
 
+impl<'a> de::EnumVisitor for SeqDeserializer<'a> {
+    type Error = Error;
+
+    fn visit_unit(&mut self) -> Result<(), Error> {
+        if self.len == 0 {
+            Ok(())
+        } else {
+            Err(de::Error::syntax_error())
+        }
+    }
+
+    fn visit_seq<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
+        where V: de::EnumSeqVisitor,
+    {
+        visitor.visit(self)
+    }
+}
+
 struct MapDeserializer<'a> {
     de: &'a mut Deserializer,
     iter: btree_map::IntoIter<String, Value>,
@@ -518,6 +576,16 @@ impl<'a> de::MapVisitor for MapDeserializer<'a> {
     }
 }
 
+impl<'a> de::EnumVisitor for MapDeserializer<'a> {
+    type Error = Error;
+
+    fn visit_map<V>(&mut self, mut visitor: V) -> Result<V::Value, Error>
+        where V: de::EnumMapVisitor,
+    {
+        visitor.visit(self)
+    }
+}
+
 /// Shortcut function to encode a `T` into a JSON `Value`
 pub fn to_value<T>(value: &T) -> Value
     where T: ser::Serialize