Improve message usage in proc-macro

Reuse storage for the buffer send to child process of proc-macro.

2 files changed, 13 insertions, 6 deletions

diff --git a/crates/proc_macro_api/src/msg.rs b/crates/proc_macro_api/src/msg.rs
index 21e56cc83..f525df152 100644
--- a/crates/proc_macro_api/src/msg.rs
+++ b/crates/proc_macro_api/src/msg.rs
@@ -55,8 +55,8 @@ pub enum ErrorCode {
 }
 
 pub trait Message: Serialize + DeserializeOwned {
-    fn read(inp: &mut impl BufRead) -> io::Result<Option<Self>> {
-        Ok(match read_json(inp)? {
+    fn read(inp: &mut impl BufRead, buf: &mut String) -> io::Result<Option<Self>> {
+        Ok(match read_json(inp, buf)? {
             None => None,
             Some(text) => {
                 let mut deserializer = serde_json::Deserializer::from_str(&text);
@@ -76,9 +76,13 @@ pub trait Message: Serialize + DeserializeOwned {
 impl Message for Request {}
 impl Message for Response {}
 
-fn read_json(inp: &mut impl BufRead) -> io::Result<Option<String>> {
+fn read_json<'a>(
+    inp: &mut impl BufRead,
+    mut buf: &'a mut String,
+) -> io::Result<Option<&'a String>> {
     loop {
-        let mut buf = String::new();
+        buf.clear();
+
         inp.read_line(&mut buf)?;
         buf.pop(); // Remove trailing '\n'
 
diff --git a/crates/proc_macro_api/src/process.rs b/crates/proc_macro_api/src/process.rs
index 30bb1b687..99d05aef3 100644
--- a/crates/proc_macro_api/src/process.rs
+++ b/crates/proc_macro_api/src/process.rs
@@ -90,8 +90,10 @@ impl ProcMacroProcessSrv {
 fn client_loop(task_rx: Receiver<Task>, mut process: Process) {
     let (mut stdin, mut stdout) = process.stdio().expect("couldn't access child stdio");
 
+    let mut buf = String::new();
+
     for Task { req, result_tx } in task_rx {
-        match send_request(&mut stdin, &mut stdout, req) {
+        match send_request(&mut stdin, &mut stdout, req, &mut buf) {
             Ok(res) => result_tx.send(res).unwrap(),
             Err(err) => {
                 log::error!(
@@ -152,7 +154,8 @@ fn send_request(
     mut writer: &mut impl Write,
     mut reader: &mut impl BufRead,
     req: Request,
+    buf: &mut String,
 ) -> io::Result<Option<Response>> {
     req.write(&mut writer)?;
-    Response::read(&mut reader)
+    Response::read(&mut reader, buf)
 }