RUST-648 Reintroduce Document decoding w/ lossy UTF-8 conversion (#232)

Author: patrickfreed

src/document.rs

@@ -524,8 +524,7 @@ impl Document {
         Ok(())
     }
 
-    /// Attempts to deserialize a `Document` from a byte stream.
-    pub fn from_reader<R: Read + ?Sized>(reader: &mut R) -> crate::de::Result<Document> {
+    fn decode<R: Read + ?Sized>(reader: &mut R, utf_lossy: bool) -> crate::de::Result<Document> {
         let mut doc = Document::new();
 
         let length = read_i32(reader)?;
@@ -550,7 +549,7 @@ impl Document {
                         break;
                     }
 
-                    let (key, val) = deserialize_bson_kvp(cursor, tag, false)?;
+                    let (key, val) = deserialize_bson_kvp(cursor, tag, utf_lossy)?;
                     doc.insert(key, val);
                 }
                 Ok(())
@@ -559,6 +558,21 @@ impl Document {
 
         Ok(doc)
     }
+
+    /// Attempts to deserialize a `Document` from a byte stream.
+    pub fn from_reader<R: Read + ?Sized>(reader: &mut R) -> crate::de::Result<Document> {
+        Self::decode(reader, false)
+    }
+
+    /// Attempt to deserialize a `Document` that may contain invalid UTF-8 strings from a byte
+    /// stream.
+    ///
+    /// This is mainly useful when reading raw BSON returned from a MongoDB server, which
+    /// in rare cases can contain invalidly truncated strings (https://jira.mongodb.org/browse/SERVER-24007).
+    /// For most use cases, `Document::from_reader` can be used instead.
+    pub fn from_reader_utf8_lossy<R: Read + ?Sized>(reader: &mut R) -> crate::de::Result<Document> {
+        Self::decode(reader, true)
+    }
 }
 
 pub struct Entry<'a> {

src/tests/modules/serializer_deserializer.rs

@@ -64,6 +64,21 @@ fn test_serialize_deserialize_utf8_string() {
     assert_eq!(deserialized, doc);
 }
 
+#[test]
+fn test_encode_decode_utf8_string_invalid() {
+    let bytes = b"\x80\xae".to_vec();
+    let src = unsafe { String::from_utf8_unchecked(bytes) };
+
+    let doc = doc! { "key": src };
+
+    let mut buf = Vec::new();
+    doc.to_writer(&mut buf).unwrap();
+
+    let expected = doc! { "key": "��" };
+    let decoded = Document::from_reader_utf8_lossy(&mut Cursor::new(buf)).unwrap();
+    assert_eq!(decoded, expected);
+}
+
 #[test]
 fn test_serialize_deserialize_array() {
     let _guard = LOCK.run_concurrently();