From 11f02f3fe3f2bbb7fec04f72b1b20b503f3d2c0e Mon Sep 17 00:00:00 2001
From: Utkarsh Gupta <utkarshgupta137@gmail.com>
Date: Thu, 9 Nov 2023 18:31:49 +0000
Subject: [PATCH] Return impl AsyncBufRead from into_async_read

---
 CHANGELOG.next.toml                             |  6 ++++++
 .../aws-smithy-types/external-types.toml        |  2 +-
 .../aws-smithy-types/src/byte_stream.rs         | 17 ++++++++---------
 3 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/CHANGELOG.next.toml b/CHANGELOG.next.toml
index d5c139994a..638b7c6319 100644
--- a/CHANGELOG.next.toml
+++ b/CHANGELOG.next.toml
@@ -17,6 +17,12 @@ references = ["smithy-rs#3126", "aws-sdk-rust#930"]
 meta = { "breaking" = false, "tada" = false, "bug" = true }
 author = "rcoh"
 
+[[aws-sdk-rust]]
+message = "Change `ByteStream::into_async_read` to return `AsyncBufRead`"
+references = ["smithy-rs#3164"]
+meta = { "breaking" = false, "tada" = false, "bug" = true }
+author = "utkarshgupta137"
+
 [[smithy-rs]]
 message = "The HTTP `Request`, `Response`, `Headers`, and `HeaderValue` types have been moved from `aws_smithy_runtime_api::client::http::*` into `aws_smithy_runtime_api::http`"
 references = ["smithy-rs#3138"]
diff --git a/rust-runtime/aws-smithy-types/external-types.toml b/rust-runtime/aws-smithy-types/external-types.toml
index 4609bce1d1..54b8256817 100644
--- a/rust-runtime/aws-smithy-types/external-types.toml
+++ b/rust-runtime/aws-smithy-types/external-types.toml
@@ -7,7 +7,7 @@ allowed_external_types = [
     "hyper::body::body::Body",
 
     # TODO(https://github.com/awslabs/smithy-rs/issues/2412): Support cargo-features for cargo-check-external-types
-    "tokio::io::async_read::AsyncRead",
+    "tokio::io::async_read::AsyncBufRead",
 
     # TODO(https://github.com/awslabs/smithy-rs/issues/2412): Support cargo-features for cargo-check-external-types
     "tokio::fs::file::File",
diff --git a/rust-runtime/aws-smithy-types/src/byte_stream.rs b/rust-runtime/aws-smithy-types/src/byte_stream.rs
index ac4329b3ed..8a36a9ba1e 100644
--- a/rust-runtime/aws-smithy-types/src/byte_stream.rs
+++ b/rust-runtime/aws-smithy-types/src/byte_stream.rs
@@ -204,17 +204,16 @@ pin_project! {
     ///
     ///     _Note: The `rt-tokio` feature must be active to use `.into_async_read()`._
     ///
-    ///     It's possible to convert a `ByteStream` into a struct that implements [`tokio::io::AsyncRead`](tokio::io::AsyncRead).
-    ///     Then, you can use pre-existing tools like [`tokio::io::BufReader`](tokio::io::BufReader):
+    ///     It's possible to convert a `ByteStream` into a struct that implements [`tokio::io::AsyncBufRead`](tokio::io::AsyncBufRead).
     ///     ```no_run
     ///     use aws_smithy_types::byte_stream::ByteStream;
     ///     use aws_smithy_types::body::SdkBody;
-    ///     use tokio::io::{AsyncBufReadExt, BufReader};
+    ///     use tokio::io::AsyncBufReadExt;
     ///     #[cfg(feature = "rt-tokio")]
     ///     async fn example() -> std::io::Result<()> {
     ///        let stream = ByteStream::new(SdkBody::from("hello!\nThis is some data"));
-    ///        // Wrap the stream in a BufReader
-    ///        let buf_reader = BufReader::new(stream.into_async_read());
+    ///        // Convert the stream to a BufReader
+    ///        let buf_reader = stream.into_async_read();
     ///        let mut lines = buf_reader.lines();
     ///        assert_eq!(lines.next_line().await?, Some("hello!".to_owned()));
     ///        assert_eq!(lines.next_line().await?, Some("This is some data".to_owned()));
@@ -423,23 +422,23 @@ impl ByteStream {
     }
 
     #[cfg(feature = "rt-tokio")]
-    /// Convert this `ByteStream` into a struct that implements [`AsyncRead`](tokio::io::AsyncRead).
+    /// Convert this `ByteStream` into a struct that implements [`AsyncBufRead`](tokio::io::AsyncBufRead).
     ///
     /// # Example
     ///
     /// ```rust
-    /// use tokio::io::{BufReader, AsyncBufReadExt};
+    /// use tokio::io::AsyncBufReadExt;
     /// use aws_smithy_types::byte_stream::ByteStream;
     ///
     /// # async fn dox(my_bytestream: ByteStream) -> std::io::Result<()> {
-    /// let mut lines =  BufReader::new(my_bytestream.into_async_read()).lines();
+    /// let mut lines =  my_bytestream.into_async_read().lines();
     /// while let Some(line) = lines.next_line().await? {
     ///   // Do something line by line
     /// }
     /// # Ok(())
     /// # }
     /// ```
-    pub fn into_async_read(self) -> impl tokio::io::AsyncRead {
+    pub fn into_async_read(self) -> impl tokio::io::AsyncBufRead {
         // The `Stream` trait is currently unstable so we can only use it in private.
         // Here, we create a local struct just to enable the trait for `ByteStream` and pass it
         // to `StreamReader`.