1 files changed, 89 insertions, 0 deletions

diff --git a/crates/proc_macro_api/src/msg.rs b/crates/proc_macro_api/src/msg.rs
new file mode 100644
index 000000000..f84ebdbc5
--- /dev/null
+++ b/crates/proc_macro_api/src/msg.rs
@@ -0,0 +1,89 @@
+//! Defines messages for cross-process message passing based on `ndjson` wire protocol
+
+use std::{
+    convert::TryFrom,
+    io::{self, BufRead, Write},
+};
+
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
+
+use crate::{
+    rpc::{ListMacrosResult, ListMacrosTask},
+    ExpansionResult, ExpansionTask,
+};
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub enum Request {
+    ListMacro(ListMacrosTask),
+    ExpansionMacro(ExpansionTask),
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub enum Response {
+    Error(ResponseError),
+    ListMacro(ListMacrosResult),
+    ExpansionMacro(ExpansionResult),
+}
+
+macro_rules! impl_try_from_response {
+    ($ty:ty, $tag:ident) => {
+        impl TryFrom<Response> for $ty {
+            type Error = &'static str;
+            fn try_from(value: Response) -> Result<Self, Self::Error> {
+                match value {
+                    Response::$tag(res) => Ok(res),
+                    _ => Err(concat!("Failed to convert response to ", stringify!($tag))),
+                }
+            }
+        }
+    };
+}
+
+impl_try_from_response!(ListMacrosResult, ListMacro);
+impl_try_from_response!(ExpansionResult, ExpansionMacro);
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct ResponseError {
+    pub code: ErrorCode,
+    pub message: String,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub enum ErrorCode {
+    ServerErrorEnd,
+    ExpansionError,
+}
+
+pub trait Message: Serialize + DeserializeOwned {
+    fn read(inp: &mut impl BufRead) -> io::Result<Option<Self>> {
+        Ok(match read_json(inp)? {
+            None => None,
+            Some(text) => Some(serde_json::from_str(&text)?),
+        })
+    }
+    fn write(self, out: &mut impl Write) -> io::Result<()> {
+        let text = serde_json::to_string(&self)?;
+        write_json(out, &text)
+    }
+}
+
+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 traling '\n'
+    Ok(match buf.len() {
+        0 => None,
+        _ => Some(buf),
+    })
+}
+
+fn write_json(out: &mut impl Write, msg: &str) -> io::Result<()> {
+    log::debug!("> {}", msg);
+    out.write_all(msg.as_bytes())?;
+    out.write_all(b"\n")?;
+    out.flush()?;
+    Ok(())
+}