RUST-503 Support serializing directly to Document (#210)

Author: isabelatkinson

src/de/mod.rs

@@ -355,3 +355,11 @@ where
     let de = Deserializer::new(bson);
     Deserialize::deserialize(de)
 }
+
+/// Decode a BSON `Document` into a `T` Deserializable.
+pub fn from_document<T>(doc: Document) -> Result<T>
+where
+    T: DeserializeOwned,
+{
+    from_bson(Bson::Document(doc))
+}

src/lib.rs

@@ -196,9 +196,9 @@ pub use self::{
         Regex,
         Timestamp,
     },
-    de::{from_bson, Deserializer},
+    de::{from_bson, from_document, Deserializer},
     decimal128::Decimal128,
-    ser::{to_bson, Serializer},
+    ser::{to_bson, to_document, Serializer},
 };
 
 #[macro_use]

src/ser/mod.rs

@@ -36,7 +36,7 @@ use chrono::Timelike;
 #[cfg(feature = "decimal128")]
 use crate::decimal128::Decimal128;
 use crate::{
-    bson::{Binary, Bson, DbPointer, JavaScriptCodeWithScope, Regex},
+    bson::{Binary, Bson, DbPointer, Document, JavaScriptCodeWithScope, Regex},
     spec::BinarySubtype,
 };
 use ::serde::Serialize;
@@ -189,3 +189,19 @@ where
     let ser = Serializer::new();
     value.serialize(ser)
 }
+
+/// Encode a `T` Serializable into a BSON `Document`.
+pub fn to_document<T: ?Sized>(value: &T) -> Result<Document>
+where
+    T: Serialize,
+{
+    match to_bson(value)? {
+        Bson::Document(doc) => Ok(doc),
+        bson => Err(Error::SerializationError {
+            message: format!(
+                "Could not be serialized to Document, got {:?} instead",
+                bson.element_type()
+            ),
+        }),
+    }
+}

src/tests/modules/ser.rs

@@ -1,8 +1,10 @@
+use std::{collections::BTreeMap, u16, u32, u64, u8};
+
+use assert_matches::assert_matches;
+
 #[cfg(feature = "decimal128")]
 use crate::decimal128::Decimal128;
 use crate::{from_bson, oid::ObjectId, ser, tests::LOCK, to_bson, Bson};
-use assert_matches::assert_matches;
-use std::{collections::BTreeMap, u16, u32, u64, u8};
 
 #[test]
 #[allow(clippy::float_cmp)]

src/tests/modules/serializer_deserializer.rs

@@ -3,13 +3,18 @@ use std::{
     io::{Cursor, Write},
 };
 
+use serde::{Deserialize, Serialize};
+
 #[cfg(feature = "decimal128")]
 use crate::decimal128::Decimal128;
 use crate::{
+    de::from_document,
     doc,
     oid::ObjectId,
+    ser::Error,
     spec::BinarySubtype,
     tests::LOCK,
+    to_document,
     Binary,
     Bson,
     Document,
@@ -470,3 +475,53 @@ fn test_serialize_deserialize_db_pointer() {
     let deserialized = Document::from_reader(&mut Cursor::new(buf)).unwrap();
     assert_eq!(deserialized, doc);
 }
+
+#[test]
+fn test_serialize_deserialize_document() {
+    let _guard = LOCK.run_concurrently();
+
+    #[derive(Debug, Deserialize, Serialize, PartialEq)]
+    struct Point {
+        x: i32,
+        y: i32,
+    }
+    let src = Point { x: 1, y: 2 };
+
+    let doc = to_document(&src).unwrap();
+    assert_eq!(doc, doc! { "x": 1, "y": 2 });
+
+    let point: Point = from_document(doc).unwrap();
+    assert_eq!(src, point);
+
+    #[derive(Debug, Deserialize, Serialize, PartialEq)]
+    struct Line {
+        p1: Point,
+        p2: Point,
+    }
+    let src = Line {
+        p1: Point { x: 0, y: 0 },
+        p2: Point { x: 1, y: 1 },
+    };
+
+    let doc = to_document(&src).unwrap();
+    assert_eq!(
+        doc,
+        doc! { "p1": { "x": 0, "y": 0 }, "p2": { "x": 1, "y": 1 } }
+    );
+
+    let line: Line = from_document(doc).unwrap();
+    assert_eq!(src, line);
+
+    let x = 1;
+    let err = to_document(&x).unwrap_err();
+    match err {
+        Error::SerializationError { message } => {
+            assert!(message.contains("Could not be serialized to Document"));
+        }
+        e => panic!("expected SerializationError, got {}", e),
+    }
+
+    let bad_point = doc! { "x": "one", "y": "two" };
+    let bad_point: Result<Point, crate::de::Error> = from_document(bad_point);
+    assert!(bad_point.is_err());
+}