fixing the find or delete serde inconsistency (#948)

Cargo.toml

@@ -195,6 +195,7 @@ time = "0.3.9"
 tokio = { version = ">= 0.0.0", features = ["fs"] }
 tracing-subscriber = "0.3.16"
 regex = "1.6.0"
+serde-hex = "0.1.0"
 
 [package.metadata.docs.rs]
 rustdoc-args = ["--cfg", "docsrs"]
@@ -210,4 +211,4 @@ features = [
     "aws-auth",
     "tracing-unstable",
     "in-use-encryption-unstable"
-]
+]

src/operation/find_and_modify.rs

@@ -4,11 +4,12 @@ mod test;
 
 use std::fmt::Debug;
 
+use bson::{from_slice, RawBson};
 use serde::{de::DeserializeOwned, Deserialize};
 
 use self::options::FindAndModifyOptions;
 use crate::{
-    bson::{doc, from_document, Bson, Document},
+    bson::{doc, Document},
     bson_util,
     cmap::{Command, RawCommandResponse, StreamDescription},
     coll::{
@@ -133,11 +134,15 @@ where
         response: RawCommandResponse,
         _description: &StreamDescription,
     ) -> Result<Self::O> {
+        #[derive(Debug, Deserialize)]
+        pub(crate) struct Response {
+            value: RawBson,
+        }
         let response: Response = response.body()?;
 
         match response.value {
-            Bson::Document(doc) => Ok(Some(from_document(doc)?)),
-            Bson::Null => Ok(None),
+            RawBson::Document(doc) => Ok(Some(from_slice(doc.as_bytes())?)),
+            RawBson::Null => Ok(None),
             other => Err(ErrorKind::InvalidResponse {
                 message: format!(
                     "expected document for value field of findAndModify response, but instead got \
@@ -157,8 +162,3 @@ where
         Retryability::Write
     }
 }
-
-#[derive(Debug, Deserialize)]
-pub(crate) struct Response {
-    value: Bson,
-}

src/test/client.rs

@@ -1,7 +1,7 @@
 use std::{borrow::Cow, collections::HashMap, sync::Arc, time::Duration};
 
 use bson::Document;
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use tokio::sync::{RwLockReadGuard, RwLockWriteGuard};
 
 use crate::{
@@ -976,6 +976,39 @@ async fn manual_shutdown_immediate_with_resources() {
     assert!(events.get_command_started_events(&["delete"]).is_empty());
 }
 
+#[cfg_attr(feature = "tokio-runtime", tokio::test)]
+#[cfg_attr(feature = "async-std-runtime", async_std::test)]
+async fn find_one_and_delete_serde_consistency() {
+    let client = Client::test_builder().build().await;
+
+    let coll = client
+        .database("find_one_and_delete_serde_consistency")
+        .collection("test");
+
+    #[derive(Debug, Serialize, Deserialize)]
+    struct Foo {
+        #[serde(with = "serde_hex::SerHexSeq::<serde_hex::StrictPfx>")]
+        problematic: Vec<u8>,
+    }
+
+    let doc = Foo {
+        problematic: vec![0, 1, 2, 3, 4, 5, 6, 7],
+    };
+
+    coll.insert_one(&doc, None).await.unwrap();
+    let rec: Foo = coll.find_one(doc! {}, None).await.unwrap().unwrap();
+    assert_eq!(doc.problematic, rec.problematic);
+    let rec: Foo = coll
+        .find_one_and_delete(doc! {}, None)
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(doc.problematic, rec.problematic);
+
+    let nothing = coll.find_one_and_delete(doc! {}, None).await.unwrap();
+    assert!(nothing.is_none());
+}
+
 // Verifies that `Client::warm_connection_pool` succeeds.
 #[cfg_attr(feature = "tokio-runtime", tokio::test)]
 #[cfg_attr(feature = "async-std-runtime", async_std::test)]