updated transactions to expect callback functions to return a ScopedBoxFuture in place of BoxFuture -- this change allows transactions to be called with closures which capture variables rather than move them

Author: treysidechain

Cargo.lock

@@ -24,6 +24,7 @@ mysql_common = {version = "0.29.0", optional = true}
 bb8 = {version = "0.8", optional = true}
 deadpool = {version = "0.9", optional = true}
 mobc = {version = "0.7", optional = true}
+scoped-futures = { rev = "362cd58", git = "https://github.com/sidechainme/scoped-futures", features = [] }
 
 [dev-dependencies]
 tokio = {version = "1.12.0", features = ["rt", "macros", "rt-multi-thread"]}

Cargo.toml

@@ -70,8 +70,8 @@ use diesel::backend::Backend;
 use diesel::query_builder::{AsQuery, QueryFragment, QueryId};
 use diesel::row::Row;
 use diesel::{ConnectionResult, QueryResult};
-use futures::future::BoxFuture;
 use futures::{Future, Stream};
+use scoped_futures::ScopedBoxFuture;
 
 #[cfg(feature = "mysql")]
 mod mysql;
@@ -221,11 +221,11 @@ where
     /// #     Ok(())
     /// # }
     /// ```
-    async fn transaction<R, E, F>(&mut self, callback: F) -> Result<R, E>
+    async fn transaction<'a, R, E, F>(&mut self, callback: F) -> Result<R, E>
     where
-        F: FnOnce(&mut Self) -> BoxFuture<Result<R, E>> + Send,
-        E: From<diesel::result::Error> + Send,
-        R: Send,
+        F: for<'r> FnOnce(&'r mut Self) -> ScopedBoxFuture<'a, 'r, Result<R, E>> + Send + 'a,
+        E: From<diesel::result::Error> + Send + 'a,
+        R: Send + 'a,
     {
         Self::TransactionManager::transaction(self, callback).await
     }

src/lib.rs

@@ -1,6 +1,6 @@
 use diesel::result::Error;
 use diesel::QueryResult;
-use futures::future::BoxFuture;
+use scoped_futures::ScopedFuture;
 use std::borrow::Cow;
 use std::num::NonZeroU32;
 
@@ -50,9 +50,9 @@ pub trait TransactionManager<Conn: AsyncConnection>: Send {
     ///
     /// Each implementation of this function needs to fulfill the documented
     /// behaviour of [`AsyncConnection::transaction`]
-    async fn transaction<F, R, E>(conn: &mut Conn, callback: F) -> Result<R, E>
+    async fn transaction<'a, F, R, E>(conn: &mut Conn, callback: F) -> Result<R, E>
     where
-        F: FnOnce(&mut Conn) -> BoxFuture<Result<R, E>> + Send,
+        F: for<'r> FnOnce(&'r mut Conn) -> ScopedBoxFuture<'a, 'r, Result<R, E>> + Send + 'a,
         E: From<Error> + Send,
         R: Send,
     {