4 files changed, 38 insertions, 15 deletions

diff --git a/crates/proc_macro_api/src/msg.rs b/crates/proc_macro_api/src/msg.rs
index 970f165ed..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);
@@ -76,14 +76,29 @@ pub trait Message: Serialize + DeserializeOwned {
 impl Message for Request {}
 impl Message for Response {}
 
-fn read_json(inp: &mut impl BufRead) -> io::Result<Option<String>> {
-    let mut buf = String::new();
-    inp.read_line(&mut buf)?;
-    buf.pop(); // Remove trailing '\n'
-    Ok(match buf.len() {
-        0 => None,
-        _ => Some(buf),
-    })
+fn read_json<'a>(
+    inp: &mut impl BufRead,
+    mut buf: &'a mut String,
+) -> io::Result<Option<&'a String>> {
+    loop {
+        buf.clear();
+
+        inp.read_line(&mut buf)?;
+        buf.pop(); // Remove trailing '\n'
+
+        if buf.is_empty() {
+            return Ok(None);
+        }
+
+        // Some ill behaved macro try to use stdout for debugging
+        // We ignore it here
+        if !buf.starts_with("{") {
+            log::error!("proc-macro tried to print : {}", buf);
+            continue;
+        }
+
+        return Ok(Some(buf));
+    }
 }
 
 fn write_json(out: &mut impl Write, msg: &str) -> io::Result<()> {
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)
 }
diff --git a/crates/proc_macro_srv/src/cli.rs b/crates/proc_macro_srv/src/cli.rs
index d428b9567..bc48f1c43 100644
--- a/crates/proc_macro_srv/src/cli.rs
+++ b/crates/proc_macro_srv/src/cli.rs
@@ -6,8 +6,9 @@ use std::io;
 
 pub fn run() -> io::Result<()> {
     let mut srv = ProcMacroSrv::default();
+    let mut buf = String::new();
 
-    while let Some(req) = read_request()? {
+    while let Some(req) = read_request(&mut buf)? {
         let res = match req {
             msg::Request::ListMacro(task) => srv.list_macros(&task).map(msg::Response::ListMacro),
             msg::Request::ExpansionMacro(task) => {
@@ -30,8 +31,8 @@ pub fn run() -> io::Result<()> {
     Ok(())
 }
 
-fn read_request() -> io::Result<Option<msg::Request>> {
-    msg::Request::read(&mut io::stdin().lock())
+fn read_request(buf: &mut String) -> io::Result<Option<msg::Request>> {
+    msg::Request::read(&mut io::stdin().lock(), buf)
 }
 
 fn write_response(msg: msg::Response) -> io::Result<()> {
diff --git a/crates/rust-analyzer/tests/rust-analyzer/main.rs b/crates/rust-analyzer/tests/rust-analyzer/main.rs
index 19516de7b..4442cbff6 100644
--- a/crates/rust-analyzer/tests/rust-analyzer/main.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/main.rs
@@ -712,6 +712,10 @@ pub fn foo(_input: TokenStream) -> TokenStream {
     // We hard code the output here for preventing to use any deps
     let mut res = TokenStream::new();
 
+    // ill behaved proc-macro will use the stdout
+    // we should ignore it
+    println!("I am bad guy");
+
     // impl Bar for Foo { fn bar() {} }
     let mut tokens = vec![t!("impl"), t!("Bar"), t!("for"), t!("Foo")];
     let mut fn_stream = TokenStream::new();