Disallow serde serialize/deserialize unsigned integer types (#72)

* [#70] Disallow serde serialize/deserialize unsigned integer types

* add compat mod for backward compatibility

* Added breaking changes in README

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bson"
-version = "0.7.1"
+version = "0.8.0"
 authors = [
     "Y. T. Chung <zonyitoo@gmail.com>",
     "Kevin Yeh <kevinyeah@utexas.edu>"

README.md

@@ -16,8 +16,9 @@ This crate works with Cargo and can be found on
 
 ```toml
 [dependencies]
-bson = "0.7"
+bson = "0.8"
 ```
+
 ## Usage
 Link the library in _main.rs_:
 
@@ -34,7 +35,7 @@ pub struct Person {
     #[serde(rename = "_id")]  // Use MongoDB's special primary key field name when serializing 
     pub id: String,
     pub name: String,
-    pub age: u32
+    pub age: i32
 }
 ```
 
@@ -68,3 +69,29 @@ let person_document = mongoCollection.find_one(Some(doc! { "_id" => "12345" }),
 // Deserialize the document into a Person instance
 let person = bson::from_bson(bson::Bson::Document(person_document))?
 ```
+
+## Breaking Changes
+
+In the BSON specification, _unsigned integer types_ are unsupported; for example, `u32`. In the older version of this crate (< `v0.8.0`), if you uses `serde` to serialize _unsigned integer types_ into BSON, it will store them with `Bson::FloatingPoint` type. From `v0.8.0`, we removed this behavior and simply returned an error when you want to serialize _unsigned integer types_ to BSON. [#72](https://github.com/zonyitoo/bson-rs/pull/72)
+
+For backward compatibility, we've provided a mod `bson::compat::u2f` to explicitly serialize _unsigned integer types_ into BSON's floating point value as follows:
+
+```rust
+#[test]
+fn test_compat_u2f() {
+    #[derive(Serialize, Deserialize, Eq, PartialEq, Debug)]
+    struct Foo {
+        #[serde(with = "bson::compat::u2f")]
+        x: u32
+    }
+
+    let foo = Foo { x: 20 };
+    let b = bson::to_bson(&foo).unwrap();
+    assert_eq!(b, Bson::Document(doc! { "x" => (Bson::FloatingPoint(20.0)) }));
+
+    let de_foo = bson::from_bson::<Foo>(b).unwrap();
+    assert_eq!(de_foo, foo);
+}
+```
+
+In this example, we added an attribute `#[serde(with = "bson::compat::u2f")]` on field `x`, which will tell `serde` to use the `bson::compat::u2f::serialize` and `bson::compat::u2f::deserialize` methods to process this field.

src/bson.rs

@@ -85,7 +85,7 @@ impl Debug for Bson {
             &Bson::FloatingPoint(p) => write!(f, "FloatingPoint({:?})", p),
             &Bson::String(ref s) => write!(f, "String({:?})", s),
             &Bson::Array(ref vec) => write!(f, "Array({:?})", vec),
-            &Bson::Document(ref doc) => write!(f, "Document({})", doc),
+            &Bson::Document(ref doc) => write!(f, "Document({:?})", doc),
             &Bson::Boolean(b) => write!(f, "Boolean({:?})", b),
             &Bson::Null => write!(f, "Null"),
             &Bson::RegExp(ref pat, ref opt) => write!(f, "RegExp(/{:?}/{:?})", pat, opt),

src/compat/mod.rs

@@ -0,0 +1,3 @@
+//! Backward compatibility
+
+pub mod u2f;

src/compat/u2f.rs

@@ -0,0 +1,79 @@
+//! Convert unsigned types to/from `Bson::FloatingPoint`
+
+use serde::{Serializer, Deserializer, Deserialize};
+
+/// Converts primitive unsigned types to `f64`
+pub trait ToF64 {
+    /// Converts to `f64` value
+    fn to_f64(&self) -> f64;
+}
+
+impl ToF64 for u8 {
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+}
+
+impl ToF64 for u16 {
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+}
+
+impl ToF64 for u32 {
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+}
+
+impl ToF64 for u64 {
+    fn to_f64(&self) -> f64 {
+        *self as f64
+    }
+}
+
+/// Serialize unsigned types to `Bson::FloatingPoint`
+pub fn serialize<T, S>(v: &T, s: S) -> Result<S::Ok, S::Error>
+    where T: ToF64,
+          S: Serializer
+{
+    s.serialize_f64(v.to_f64())
+}
+
+/// Converts from `f64` value
+pub trait FromF64 {
+    /// Converts from `f64` value
+    fn from_f64(v: f64) -> Self;
+}
+
+impl FromF64 for u8 {
+    fn from_f64(v: f64) -> u8 {
+        v as u8
+    }
+}
+
+impl FromF64 for u16 {
+    fn from_f64(v: f64) -> u16 {
+        v as u16
+    }
+}
+
+impl FromF64 for u32 {
+    fn from_f64(v: f64) -> u32 {
+        v as u32
+    }
+}
+
+impl FromF64 for u64 {
+    fn from_f64(v: f64) -> u64 {
+        v as u64
+    }
+}
+
+/// Deserialize unsigned types to `Bson::FloatingPoint`
+pub fn deserialize<'de, T, D>(d: D) -> Result<T, D::Error>
+    where D: Deserializer<'de>,
+          T: FromF64
+{
+    f64::deserialize(d).map(T::from_f64)
+}

src/decoder/serde.rs

@@ -3,7 +3,7 @@ use std::fmt;
 
 use serde::de::{self, Deserialize, Deserializer, Visitor, MapAccess, SeqAccess, VariantAccess,
                 DeserializeSeed, EnumAccess};
-use serde::de::Unexpected;
+use serde::de::{Error, Unexpected};
 
 use bson::{Bson, UtcDateTime};
 use oid::ObjectId;
@@ -62,35 +62,66 @@ impl<'de> Visitor<'de> for BsonVisitor {
     }
 
     #[inline]
-    fn visit_bool<E>(self, value: bool) -> Result<Bson, E> {
+    fn visit_bool<E>(self, value: bool) -> Result<Bson, E>
+        where E: Error
+    {
         Ok(Bson::Boolean(value))
     }
 
     #[inline]
-    fn visit_i8<E>(self, value: i8) -> Result<Bson, E> {
+    fn visit_i8<E>(self, value: i8) -> Result<Bson, E>
+        where E: Error
+    {
         Ok(Bson::I32(value as i32))
     }
 
+    #[inline]
+    fn visit_u8<E>(self, value: u8) -> Result<Bson, E>
+        where E: Error
+    {
+        Err(Error::invalid_type(Unexpected::Unsigned(value as u64), &"a signed integer"))
+    }
 
     #[inline]
-    fn visit_i16<E>(self, value: i16) -> Result<Bson, E> {
+    fn visit_i16<E>(self, value: i16) -> Result<Bson, E>
+        where E: Error
+    {
         Ok(Bson::I32(value as i32))
     }
 
+    #[inline]
+    fn visit_u16<E>(self, value: u16) -> Result<Bson, E>
+        where E: Error
+    {
+        Err(Error::invalid_type(Unexpected::Unsigned(value as u64), &"a signed integer"))
+    }
 
     #[inline]
-    fn visit_i32<E>(self, value: i32) -> Result<Bson, E> {
+    fn visit_i32<E>(self, value: i32) -> Result<Bson, E>
+        where E: Error
+    {
         Ok(Bson::I32(value))
     }
 
     #[inline]
-    fn visit_i64<E>(self, value: i64) -> Result<Bson, E> {
+    fn visit_u32<E>(self, value: u32) -> Result<Bson, E>
+        where E: Error
+    {
+        Err(Error::invalid_type(Unexpected::Unsigned(value as u64), &"a signed integer"))
+    }
+
+    #[inline]
+    fn visit_i64<E>(self, value: i64) -> Result<Bson, E>
+        where E: Error
+    {
         Ok(Bson::I64(value))
     }
 
     #[inline]
-    fn visit_u64<E>(self, value: u64) -> Result<Bson, E> {
-        Ok(Bson::I64(value as i64))
+    fn visit_u64<E>(self, value: u64) -> Result<Bson, E>
+        where E: Error
+    {
+        Err(Error::invalid_type(Unexpected::Unsigned(value), &"a signed integer"))
     }
 
     #[inline]

src/encoder/error.rs

@@ -9,6 +9,7 @@ pub enum EncoderError {
     IoError(io::Error),
     InvalidMapKeyType(Bson),
     Unknown(String),
+    UnsupportedUnsignedType,
 }
 
 impl From<io::Error> for EncoderError {
@@ -25,6 +26,7 @@ impl fmt::Display for EncoderError {
                 write!(fmt, "Invalid map key type: {:?}", bson)
             }
             &EncoderError::Unknown(ref inner) => inner.fmt(fmt),
+            &EncoderError::UnsupportedUnsignedType => write!(fmt, "BSON does not support unsigned type"),
         }
     }
 }
@@ -35,6 +37,7 @@ impl error::Error for EncoderError {
             &EncoderError::IoError(ref inner) => inner.description(),
             &EncoderError::InvalidMapKeyType(_) => "Invalid map key type",
             &EncoderError::Unknown(ref inner) => inner,
+            &EncoderError::UnsupportedUnsignedType => "BSON does not support unsigned type",
         }
     }
     fn cause(&self) -> Option<&error::Error> {

src/encoder/serde.rs

@@ -87,38 +87,38 @@ impl Serializer for Encoder {
     }
 
     #[inline]
-    fn serialize_i16(self, value: i16) -> EncoderResult<Bson> {
-        self.serialize_i32(value as i32)
+    fn serialize_u8(self, _value: u8) -> EncoderResult<Bson> {
+        Err(EncoderError::UnsupportedUnsignedType)
     }
 
     #[inline]
-    fn serialize_i32(self, value: i32) -> EncoderResult<Bson> {
-        Ok(Bson::I32(value))
+    fn serialize_i16(self, value: i16) -> EncoderResult<Bson> {
+        self.serialize_i32(value as i32)
     }
 
     #[inline]
-    fn serialize_i64(self, value: i64) -> EncoderResult<Bson> {
-        Ok(Bson::I64(value))
+    fn serialize_u16(self, _value: u16) -> EncoderResult<Bson> {
+        Err(EncoderError::UnsupportedUnsignedType)
     }
 
     #[inline]
-    fn serialize_u8(self, value: u8) -> EncoderResult<Bson> {
-        self.serialize_u64(value as u64)
+    fn serialize_i32(self, value: i32) -> EncoderResult<Bson> {
+        Ok(Bson::I32(value))
     }
 
     #[inline]
-    fn serialize_u16(self, value: u16) -> EncoderResult<Bson> {
-        self.serialize_u64(value as u64)
+    fn serialize_u32(self, _value: u32) -> EncoderResult<Bson> {
+        Err(EncoderError::UnsupportedUnsignedType)
     }
 
     #[inline]
-    fn serialize_u32(self, value: u32) -> EncoderResult<Bson> {
-        self.serialize_u64(value as u64)
+    fn serialize_i64(self, value: i64) -> EncoderResult<Bson> {
+        Ok(Bson::I64(value))
     }
 
     #[inline]
-    fn serialize_u64(self, value: u64) -> EncoderResult<Bson> {
-        Ok(Bson::FloatingPoint(value as f64))
+    fn serialize_u64(self, _value: u64) -> EncoderResult<Bson> {
+        Err(EncoderError::UnsupportedUnsignedType)
     }
 
     #[inline]

src/lib.rs

@@ -68,3 +68,4 @@ mod bson;
 mod encoder;
 mod decoder;
 pub mod ordered;
+pub mod compat;

tests/serde.rs

@@ -80,3 +80,20 @@ fn test_ser_datetime() {
     let xfoo: Foo = bson::from_bson(x).unwrap();
     assert_eq!(xfoo, foo);
 }
+
+
+#[test]
+fn test_compat_u2f() {
+    #[derive(Serialize, Deserialize, Eq, PartialEq, Debug)]
+    struct Foo {
+        #[serde(with = "bson::compat::u2f")]
+        x: u32
+    }
+
+    let foo = Foo { x: 20 };
+    let b = bson::to_bson(&foo).unwrap();
+    assert_eq!(b, Bson::Document(doc! { "x" => (Bson::FloatingPoint(20.0)) }));
+
+    let de_foo = bson::from_bson::<Foo>(b).unwrap();
+    assert_eq!(de_foo, foo);
+}