Implement ra_proc_macro client logic

4 files changed, 745 insertions, 18 deletions

diff --git a/crates/ra_proc_macro/src/lib.rs b/crates/ra_proc_macro/src/lib.rs
index 5e21dd487..a0a478dc8 100644
--- a/crates/ra_proc_macro/src/lib.rs
+++ b/crates/ra_proc_macro/src/lib.rs
@@ -5,55 +5,102 @@
 //! is used to provide basic infrastructure  for communication between two
 //! processes: Client (RA itself), Server (the external program)
 
+mod rpc;
+mod process;
+pub mod msg;
+
+use process::ProcMacroProcessSrv;
 use ra_tt::{SmolStr, Subtree};
+use rpc::ProcMacroKind;
 use std::{
     path::{Path, PathBuf},
     sync::Arc,
 };
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+pub use rpc::{ExpansionResult, ExpansionTask};
+
+#[derive(Debug, Clone)]
 pub struct ProcMacroProcessExpander {
     process: Arc<ProcMacroProcessSrv>,
+    dylib_path: PathBuf,
     name: SmolStr,
 }
 
+impl Eq for ProcMacroProcessExpander {}
+impl PartialEq for ProcMacroProcessExpander {
+    fn eq(&self, other: &Self) -> bool {
+        self.name == other.name
+            && self.dylib_path == other.dylib_path
+            && Arc::ptr_eq(&self.process, &other.process)
+    }
+}
+
 impl ra_tt::TokenExpander for ProcMacroProcessExpander {
     fn expand(
         &self,
-        _subtree: &Subtree,
+        subtree: &Subtree,
         _attr: Option<&Subtree>,
     ) -> Result<Subtree, ra_tt::ExpansionError> {
-        // FIXME: do nothing for now
-        Ok(Subtree::default())
+        self.process.custom_derive(&self.dylib_path, subtree, &self.name)
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct ProcMacroProcessSrv {
-    path: PathBuf,
-}
-
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum ProcMacroClient {
+#[derive(Debug, Clone)]
+enum ProcMacroClientKind {
     Process { process: Arc<ProcMacroProcessSrv> },
     Dummy,
 }
 
+#[derive(Debug, Clone)]
+pub struct ProcMacroClient {
+    kind: ProcMacroClientKind,
+}
+
 impl ProcMacroClient {
-    pub fn extern_process(process_path: &Path) -> ProcMacroClient {
-        let process = ProcMacroProcessSrv { path: process_path.into() };
-        ProcMacroClient::Process { process: Arc::new(process) }
+    pub fn extern_process(process_path: &Path) -> Result<ProcMacroClient, std::io::Error> {
+        let process = ProcMacroProcessSrv::run(process_path)?;
+        Ok(ProcMacroClient { kind: ProcMacroClientKind::Process { process: Arc::new(process) } })
     }
 
     pub fn dummy() -> ProcMacroClient {
-        ProcMacroClient::Dummy
+        ProcMacroClient { kind: ProcMacroClientKind::Dummy }
     }
 
     pub fn by_dylib_path(
         &self,
-        _dylib_path: &Path,
+        dylib_path: &Path,
     ) -> Vec<(SmolStr, Arc<dyn ra_tt::TokenExpander>)> {
-        // FIXME: return empty for now
-        vec![]
+        match &self.kind {
+            ProcMacroClientKind::Dummy => vec![],
+            ProcMacroClientKind::Process { process } => {
+                let macros = match process.find_proc_macros(dylib_path) {
+                    Err(err) => {
+                        eprintln!("Fail to find proc macro. Error: {:#?}", err);
+                        return vec![];
+                    }
+                    Ok(macros) => macros,
+                };
+
+                macros
+                    .into_iter()
+                    .filter_map(|(name, kind)| {
+                        // FIXME: Support custom derive only for now.
+                        match kind {
+                            ProcMacroKind::CustomDerive => {
+                                let name = SmolStr::new(&name);
+                                let expander: Arc<dyn ra_tt::TokenExpander> =
+                                    Arc::new(ProcMacroProcessExpander {
+                                        process: process.clone(),
+                                        name: name.clone(),
+                                        dylib_path: dylib_path.into(),
+                                    });
+                                Some((name, expander))
+                            }
+                            _ => None,
+                        }
+                    })
+                    .collect()
+            }
+        }
     }
 }
diff --git a/crates/ra_proc_macro/src/msg.rs b/crates/ra_proc_macro/src/msg.rs
new file mode 100644
index 000000000..2fb065d32
--- /dev/null
+++ b/crates/ra_proc_macro/src/msg.rs
@@ -0,0 +1,218 @@
+//! A simplified version of lsp base protocol for rpc
+
+use std::{
+    fmt,
+    io::{self, BufRead, Write},
+};
+
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
+
+#[derive(Serialize, Deserialize, Debug, Clone)]
+#[serde(untagged)]
+pub enum Message {
+    Request(Request),
+    Response(Response),
+}
+
+impl From<Request> for Message {
+    fn from(request: Request) -> Message {
+        Message::Request(request)
+    }
+}
+
+impl From<Response> for Message {
+    fn from(response: Response) -> Message {
+        Message::Response(response)
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[serde(transparent)]
+pub struct RequestId(IdRepr);
+
+#[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[serde(untagged)]
+enum IdRepr {
+    U64(u64),
+    String(String),
+}
+
+impl From<u64> for RequestId {
+    fn from(id: u64) -> RequestId {
+        RequestId(IdRepr::U64(id))
+    }
+}
+
+impl From<String> for RequestId {
+    fn from(id: String) -> RequestId {
+        RequestId(IdRepr::String(id))
+    }
+}
+
+impl fmt::Display for RequestId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match &self.0 {
+            IdRepr::U64(it) => fmt::Display::fmt(it, f),
+            IdRepr::String(it) => fmt::Display::fmt(it, f),
+        }
+    }
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct Request {
+    pub id: RequestId,
+    pub method: String,
+    pub params: serde_json::Value,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct Response {
+    // JSON RPC allows this to be null if it was impossible
+    // to decode the request's id. Ignore this special case
+    // and just die horribly.
+    pub id: RequestId,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub result: Option<serde_json::Value>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub error: Option<ResponseError>,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct ResponseError {
+    pub code: i32,
+    pub message: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub data: Option<serde_json::Value>,
+}
+
+#[derive(Clone, Copy, Debug)]
+#[allow(unused)]
+pub enum ErrorCode {
+    // Defined by JSON RPC
+    ParseError = -32700,
+    InvalidRequest = -32600,
+    MethodNotFound = -32601,
+    InvalidParams = -32602,
+    InternalError = -32603,
+    ServerErrorStart = -32099,
+    ServerErrorEnd = -32000,
+    ServerNotInitialized = -32002,
+    UnknownErrorCode = -32001,
+
+    // Defined by protocol
+    ExpansionError = -32900,
+}
+
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct Notification {
+    pub method: String,
+    pub params: serde_json::Value,
+}
+
+impl Message {
+    pub fn read(r: &mut impl BufRead) -> io::Result<Option<Message>> {
+        let text = match read_msg_text(r)? {
+            None => return Ok(None),
+            Some(text) => text,
+        };
+        let msg = serde_json::from_str(&text)?;
+        Ok(Some(msg))
+    }
+    pub fn write(self, w: &mut impl Write) -> io::Result<()> {
+        #[derive(Serialize)]
+        struct JsonRpc {
+            jsonrpc: &'static str,
+            #[serde(flatten)]
+            msg: Message,
+        }
+        let text = serde_json::to_string(&JsonRpc { jsonrpc: "2.0", msg: self })?;
+        write_msg_text(w, &text)
+    }
+}
+
+impl Response {
+    pub fn new_ok<R: Serialize>(id: RequestId, result: R) -> Response {
+        Response { id, result: Some(serde_json::to_value(result).unwrap()), error: None }
+    }
+    pub fn new_err(id: RequestId, code: i32, message: String) -> Response {
+        let error = ResponseError { code, message, data: None };
+        Response { id, result: None, error: Some(error) }
+    }
+}
+
+impl Request {
+    pub fn new<P: Serialize>(id: RequestId, method: String, params: P) -> Request {
+        Request { id, method, params: serde_json::to_value(params).unwrap() }
+    }
+    pub fn extract<P: DeserializeOwned>(self, method: &str) -> Result<(RequestId, P), Request> {
+        if self.method == method {
+            let params = serde_json::from_value(self.params).unwrap_or_else(|err| {
+                panic!("Invalid request\nMethod: {}\n error: {}", method, err)
+            });
+            Ok((self.id, params))
+        } else {
+            Err(self)
+        }
+    }
+}
+
+impl Notification {
+    pub fn new(method: String, params: impl Serialize) -> Notification {
+        Notification { method, params: serde_json::to_value(params).unwrap() }
+    }
+    pub fn extract<P: DeserializeOwned>(self, method: &str) -> Result<P, Notification> {
+        if self.method == method {
+            let params = serde_json::from_value(self.params).unwrap();
+            Ok(params)
+        } else {
+            Err(self)
+        }
+    }
+}
+
+fn read_msg_text(inp: &mut impl BufRead) -> io::Result<Option<String>> {
+    fn invalid_data(error: impl Into<Box<dyn std::error::Error + Send + Sync>>) -> io::Error {
+        io::Error::new(io::ErrorKind::InvalidData, error)
+    }
+    macro_rules! invalid_data {
+        ($($tt:tt)*) => (invalid_data(format!($($tt)*)))
+    }
+
+    let mut size = None;
+    let mut buf = String::new();
+    loop {
+        buf.clear();
+        if inp.read_line(&mut buf)? == 0 {
+            return Ok(None);
+        }
+        if !buf.ends_with("\r\n") {
+            return Err(invalid_data!("malformed header: {:?}", buf));
+        }
+        let buf = &buf[..buf.len() - 2];
+        if buf.is_empty() {
+            break;
+        }
+        let mut parts = buf.splitn(2, ": ");
+        let header_name = parts.next().unwrap();
+        let header_value =
+            parts.next().ok_or_else(|| invalid_data!("malformed header: {:?}", buf))?;
+        if header_name == "Content-Length" {
+            size = Some(header_value.parse::<usize>().map_err(invalid_data)?);
+        }
+    }
+    let size: usize = size.ok_or_else(|| invalid_data!("no Content-Length"))?;
+    let mut buf = buf.into_bytes();
+    buf.resize(size, 0);
+    inp.read_exact(&mut buf)?;
+    let buf = String::from_utf8(buf).map_err(invalid_data)?;
+    log::debug!("< {}", buf);
+    Ok(Some(buf))
+}
+
+fn write_msg_text(out: &mut impl Write, msg: &str) -> io::Result<()> {
+    log::debug!("> {}", msg);
+    write!(out, "Content-Length: {}\r\n\r\n", msg.len())?;
+    out.write_all(msg.as_bytes())?;
+    out.flush()?;
+    Ok(())
+}
diff --git a/crates/ra_proc_macro/src/process.rs b/crates/ra_proc_macro/src/process.rs
new file mode 100644
index 000000000..a9095af11
--- /dev/null
+++ b/crates/ra_proc_macro/src/process.rs
@@ -0,0 +1,202 @@
+use crossbeam_channel::{bounded, Receiver, Sender};
+use ra_tt::Subtree;
+
+use crate::msg::{ErrorCode, Message, Request, Response, ResponseError};
+use crate::rpc::{ExpansionResult, ExpansionTask, ListMacrosResult, ListMacrosTask, ProcMacroKind};
+
+use io::{BufRead, BufReader};
+use std::{
+    io::{self, Write},
+    path::{Path, PathBuf},
+    process::{Child, Command, Stdio},
+    thread::spawn,
+};
+
+#[derive(Debug, Default)]
+pub(crate) struct ProcMacroProcessSrv {
+    inner: Option<Handle>,
+}
+
+struct Task {
+    req: Message,
+    result_tx: Sender<Message>,
+}
+
+#[derive(Debug)]
+struct Handle {
+    sender: Sender<Task>,
+}
+
+struct Process {
+    path: PathBuf,
+    child: Child,
+}
+
+impl Process {
+    fn run(process_path: &Path) -> Result<Process, io::Error> {
+        let child = Command::new(process_path.clone())
+            .stdin(Stdio::piped())
+            .stdout(Stdio::piped())
+            .spawn()?;
+
+        Ok(Process { path: process_path.into(), child })
+    }
+
+    fn restart(&mut self) -> Result<(), io::Error> {
+        let _ = self.child.kill();
+        self.child =
+            Command::new(self.path.clone()).stdin(Stdio::piped()).stdout(Stdio::piped()).spawn()?;
+        Ok(())
+    }
+
+    fn stdio(&mut self) -> Option<(impl Write, impl BufRead)> {
+        let stdin = self.child.stdin.take()?;
+        let stdout = self.child.stdout.take()?;
+        let read = BufReader::new(stdout);
+
+        Some((stdin, read))
+    }
+}
+
+impl ProcMacroProcessSrv {
+    pub fn run(process_path: &Path) -> Result<ProcMacroProcessSrv, io::Error> {
+        let process = Process::run(process_path)?;
+
+        let (task_tx, task_rx) = bounded(0);
+
+        let _ = spawn(move || {
+            client_loop(task_rx, process);
+        });
+        Ok(ProcMacroProcessSrv { inner: Some(Handle { sender: task_tx }) })
+    }
+
+    pub fn find_proc_macros(
+        &self,
+        dylib_path: &Path,
+    ) -> Result<Vec<(String, ProcMacroKind)>, ra_tt::ExpansionError> {
+        let task = ListMacrosTask { lib: dylib_path.to_path_buf() };
+
+        let result: ListMacrosResult = self.send_task("list_macros", task)?;
+        Ok(result.macros)
+    }
+
+    pub fn custom_derive(
+        &self,
+        dylib_path: &Path,
+        subtree: &Subtree,
+        derive_name: &str,
+    ) -> Result<Subtree, ra_tt::ExpansionError> {
+        let task = ExpansionTask {
+            macro_body: subtree.clone(),
+            macro_name: derive_name.to_string(),
+            attributes: None,
+            lib: dylib_path.to_path_buf(),
+        };
+
+        let result: ExpansionResult = self.send_task("custom_derive", task)?;
+        Ok(result.expansion)
+    }
+
+    pub fn send_task<'a, T, R>(&self, method: &str, task: T) -> Result<R, ra_tt::ExpansionError>
+    where
+        T: serde::Serialize,
+        R: serde::de::DeserializeOwned + Default,
+    {
+        let handle = match &self.inner {
+            None => return Err(ra_tt::ExpansionError::Unknown("No handle is found.".to_string())),
+            Some(it) => it,
+        };
+
+        let msg = serde_json::to_value(task).unwrap();
+
+        // FIXME: use a proper request id
+        let id = 0;
+        let req = Request { id: id.into(), method: method.into(), params: msg };
+
+        let (result_tx, result_rx) = bounded(0);
+
+        handle.sender.send(Task { req: req.into(), result_tx }).unwrap();
+        let response = result_rx.recv().unwrap();
+
+        match response {
+            Message::Request(_) => {
+                return Err(ra_tt::ExpansionError::Unknown(
+                    "Return request from ra_proc_srv".into(),
+                ))
+            }
+            Message::Response(res) => {
+                if let Some(err) = res.error {
+                    return Err(ra_tt::ExpansionError::ExpansionError(err.message));
+                }
+                match res.result {
+                    None => Ok(R::default()),
+                    Some(res) => {
+                        let result: R = serde_json::from_value(res)
+                            .map_err(|err| ra_tt::ExpansionError::JsonError(err.to_string()))?;
+                        Ok(result)
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn client_loop(task_rx: Receiver<Task>, mut process: Process) {
+    let (mut stdin, mut stdout) = match process.stdio() {
+        None => return,
+        Some(it) => it,
+    };
+
+    loop {
+        let task = match task_rx.recv() {
+            Ok(task) => task,
+            Err(_) => break,
+        };
+
+        let res = match send_message(&mut stdin, &mut stdout, task.req) {
+            Ok(res) => res,
+            Err(_err) => {
+                let res = Response {
+                    id: 0.into(),
+                    result: None,
+                    error: Some(ResponseError {
+                        code: ErrorCode::ServerErrorEnd as i32,
+                        message: "Server closed".into(),
+                        data: None,
+                    }),
+                };
+                if task.result_tx.send(res.into()).is_err() {
+                    break;
+                }
+                // Restart the process
+                if process.restart().is_err() {
+                    break;
+                }
+                let stdio = match process.stdio() {
+                    None => break,
+                    Some(it) => it,
+                };
+                stdin = stdio.0;
+                stdout = stdio.1;
+                continue;
+            }
+        };
+
+        if let Some(res) = res {
+            if task.result_tx.send(res).is_err() {
+                break;
+            }
+        }
+    }
+
+    let _ = process.child.kill();
+}
+
+fn send_message(
+    mut writer: &mut impl Write,
+    mut reader: &mut impl BufRead,
+    msg: Message,
+) -> Result<Option<Message>, io::Error> {
+    msg.write(&mut writer)?;
+    Ok(Message::read(&mut reader)?)
+}
diff --git a/crates/ra_proc_macro/src/rpc.rs b/crates/ra_proc_macro/src/rpc.rs
new file mode 100644
index 000000000..e7eaf7c15
--- /dev/null
+++ b/crates/ra_proc_macro/src/rpc.rs
@@ -0,0 +1,260 @@
+//! Data struture serialization related stuffs for RPC
+
+use ra_tt::{
+    Delimiter, DelimiterKind, Ident, Leaf, Literal, Punct, SmolStr, Spacing, Subtree, TokenId,
+    TokenTree,
+};
+use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
+
+#[derive(Clone, Eq, PartialEq, Debug, Serialize, Deserialize)]
+pub struct ListMacrosTask {
+    pub lib: PathBuf,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Serialize, Deserialize)]
+pub enum ProcMacroKind {
+    CustomDerive,
+    FuncLike,
+    Attr,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Default, Serialize, Deserialize)]
+pub struct ListMacrosResult {
+    pub macros: Vec<(String, ProcMacroKind)>,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Serialize, Deserialize)]
+pub struct ExpansionTask {
+    /// Argument of macro call.
+    ///
+    /// In custom derive that would be a struct or enum; in attribute-like macro - underlying
+    /// item; in function-like macro - the macro body.
+    #[serde(with = "SubtreeDef")]
+    pub macro_body: Subtree,
+
+    /// Names of macros to expand.
+    ///
+    /// In custom derive those are names of derived traits (`Serialize`, `Getters`, etc.). In
+    /// attribute-like and functiona-like macros - single name of macro itself (`show_streams`).
+    pub macro_name: String,
+
+    /// Possible attributes for the attribute-like macros.
+    #[serde(with = "opt_subtree_def")]
+    pub attributes: Option<Subtree>,
+
+    pub lib: PathBuf,
+}
+
+#[derive(Clone, Eq, PartialEq, Debug, Default, Serialize, Deserialize)]
+pub struct ExpansionResult {
+    #[serde(with = "SubtreeDef")]
+    pub expansion: Subtree,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "DelimiterKind")]
+enum DelimiterKindDef {
+    Parenthesis,
+    Brace,
+    Bracket,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "TokenId")]
+struct TokenIdDef(u32);
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Delimiter")]
+struct DelimiterDef {
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+    #[serde(with = "DelimiterKindDef")]
+    pub kind: DelimiterKind,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Subtree")]
+struct SubtreeDef {
+    #[serde(default, with = "opt_delimiter_def")]
+    pub delimiter: Option<Delimiter>,
+    #[serde(with = "vec_token_tree")]
+    pub token_trees: Vec<TokenTree>,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "TokenTree")]
+enum TokenTreeDef {
+    #[serde(with = "LeafDef")]
+    Leaf(Leaf),
+    #[serde(with = "SubtreeDef")]
+    Subtree(Subtree),
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Leaf")]
+enum LeafDef {
+    #[serde(with = "LiteralDef")]
+    Literal(Literal),
+    #[serde(with = "PunctDef")]
+    Punct(Punct),
+    #[serde(with = "IdentDef")]
+    Ident(Ident),
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Literal")]
+struct LiteralDef {
+    pub text: SmolStr,
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Punct")]
+struct PunctDef {
+    pub char: char,
+    #[serde(with = "SpacingDef")]
+    pub spacing: Spacing,
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Spacing")]
+enum SpacingDef {
+    Alone,
+    Joint,
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(remote = "Ident")]
+struct IdentDef {
+    pub text: SmolStr,
+    #[serde(with = "TokenIdDef")]
+    pub id: TokenId,
+}
+
+mod opt_delimiter_def {
+    use super::{Delimiter, DelimiterDef};
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S>(value: &Option<Delimiter>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        #[derive(Serialize)]
+        struct Helper<'a>(#[serde(with = "DelimiterDef")] &'a Delimiter);
+        value.as_ref().map(Helper).serialize(serializer)
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Option<Delimiter>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct Helper(#[serde(with = "DelimiterDef")] Delimiter);
+        let helper = Option::deserialize(deserializer)?;
+        Ok(helper.map(|Helper(external)| external))
+    }
+}
+
+mod opt_subtree_def {
+    use super::{Subtree, SubtreeDef};
+    use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S>(value: &Option<Subtree>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        #[derive(Serialize)]
+        struct Helper<'a>(#[serde(with = "SubtreeDef")] &'a Subtree);
+        value.as_ref().map(Helper).serialize(serializer)
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Option<Subtree>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct Helper(#[serde(with = "SubtreeDef")] Subtree);
+        let helper = Option::deserialize(deserializer)?;
+        Ok(helper.map(|Helper(external)| external))
+    }
+}
+
+mod vec_token_tree {
+    use super::{TokenTree, TokenTreeDef};
+    use serde::{ser::SerializeSeq, Deserialize, Deserializer, Serialize, Serializer};
+
+    pub fn serialize<S>(value: &Vec<TokenTree>, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        #[derive(Serialize)]
+        struct Helper<'a>(#[serde(with = "TokenTreeDef")] &'a TokenTree);
+
+        let items: Vec<_> = value.iter().map(Helper).collect();
+        let mut seq = serializer.serialize_seq(Some(items.len()))?;
+        for element in items {
+            seq.serialize_element(&element)?;
+        }
+        seq.end()
+    }
+
+    pub fn deserialize<'de, D>(deserializer: D) -> Result<Vec<TokenTree>, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        #[derive(Deserialize)]
+        struct Helper(#[serde(with = "TokenTreeDef")] TokenTree);
+
+        let helper = Vec::deserialize(deserializer)?;
+        Ok(helper.into_iter().map(|Helper(external)| external).collect())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn fixture_token_tree() -> Subtree {
+        let mut subtree = Subtree::default();
+        subtree
+            .token_trees
+            .push(TokenTree::Leaf(Ident { text: "struct".into(), id: TokenId(0) }.into()));
+        subtree
+            .token_trees
+            .push(TokenTree::Leaf(Ident { text: "Foo".into(), id: TokenId(1) }.into()));
+        subtree.token_trees.push(TokenTree::Subtree(
+            Subtree {
+                delimiter: Some(Delimiter { id: TokenId(2), kind: DelimiterKind::Brace }),
+                token_trees: vec![],
+            }
+            .into(),
+        ));
+        subtree
+    }
+
+    #[test]
+    fn test_proc_macro_rpc_works() {
+        let tt = fixture_token_tree();
+        let task = ExpansionTask {
+            macro_body: tt.clone(),
+            macro_name: Default::default(),
+            attributes: None,
+            lib: Default::default(),
+        };
+
+        let json = serde_json::to_string(&task).unwrap();
+        let back: ExpansionTask = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(task.macro_body, back.macro_body);
+
+        let result = ExpansionResult { expansion: tt.clone() };
+        let json = serde_json::to_string(&task).unwrap();
+        let back: ExpansionResult = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(result, back);
+    }
+}