7 files changed, 781 insertions, 0 deletions

diff --git a/crates/server/Cargo.toml b/crates/server/Cargo.toml
new file mode 100644
index 000000000..e6d1b18c3
--- /dev/null
+++ b/crates/server/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "m"
+version = "0.1.0"
+authors = ["Aleksey Kladov <[email protected]>"]
+
+[dependencies]
+failure = "0.1.2"
+languageserver-types = "0.48.0"
+serde_json = "1.0.24"
+serde = "1.0.71"
+serde_derive = "1.0.71"
+drop_bomb = "0.1.0"
+crossbeam-channel = "0.2.4"
+threadpool = "1.7.1"
+flexi_logger = "0.9.0"
+log = "0.4.3"
+libeditor = { path = "../libeditor" }
+libanalysis = { path = "../libanalysis" }
diff --git a/crates/server/src/caps.rs b/crates/server/src/caps.rs
new file mode 100644
index 000000000..3d89c64a9
--- /dev/null
+++ b/crates/server/src/caps.rs
@@ -0,0 +1,36 @@
+use languageserver_types::{
+    ServerCapabilities,
+    TextDocumentSyncCapability,
+    TextDocumentSyncOptions,
+    TextDocumentSyncKind,
+};
+
+pub const SERVER_CAPABILITIES: ServerCapabilities = ServerCapabilities {
+    text_document_sync: Some(TextDocumentSyncCapability::Options(
+        TextDocumentSyncOptions {
+            open_close: Some(true),
+            change: Some(TextDocumentSyncKind::Full),
+            will_save: None,
+            will_save_wait_until: None,
+            save: None,
+        }
+    )),
+    hover_provider: None,
+    completion_provider: None,
+    signature_help_provider: None,
+    definition_provider: None,
+    type_definition_provider: None,
+    implementation_provider: None,
+    references_provider: None,
+    document_highlight_provider: None,
+    document_symbol_provider: None,
+    workspace_symbol_provider: None,
+    code_action_provider: None,
+    code_lens_provider: None,
+    document_formatting_provider: None,
+    document_range_formatting_provider: None,
+    document_on_type_formatting_provider: None,
+    rename_provider: None,
+    color_provider: None,
+    execute_command_provider: None,
+};
diff --git a/crates/server/src/dispatch.rs b/crates/server/src/dispatch.rs
new file mode 100644
index 000000000..2da0996e3
--- /dev/null
+++ b/crates/server/src/dispatch.rs
@@ -0,0 +1,174 @@
+use std::marker::PhantomData;
+
+use serde::{
+    ser::Serialize,
+    de::DeserializeOwned,
+};
+use serde_json;
+use drop_bomb::DropBomb;
+
+use ::{
+    Result,
+    req::{Request, Notification},
+    io::{Io, RawMsg, RawResponse, RawRequest, RawNotification},
+};
+
+pub struct Responder<R: Request> {
+    id: u64,
+    bomb: DropBomb,
+    ph: PhantomData<R>,
+}
+
+impl<R: Request> Responder<R>
+    where
+        R::Params: DeserializeOwned,
+        R::Result: Serialize,
+{
+    pub fn response(self, io: &mut Io, resp: Result<R::Result>) -> Result<()> {
+        match resp {
+            Ok(res) => self.result(io, res)?,
+            Err(e) => {
+                self.error(io)?;
+                return Err(e);
+            }
+        }
+        Ok(())
+    }
+
+    pub fn result(mut self, io: &mut Io, result: R::Result) -> Result<()> {
+        self.bomb.defuse();
+        io.send(RawMsg::Response(RawResponse {
+            id: Some(self.id),
+            result: serde_json::to_value(result)?,
+            error: serde_json::Value::Null,
+        }));
+        Ok(())
+    }
+
+    pub fn error(mut self, io: &mut Io) -> Result<()> {
+        self.bomb.defuse();
+        error(io, self.id, ErrorCode::InternalError, "internal error")
+    }
+}
+
+
+fn parse_request_as<R>(raw: RawRequest) -> Result<::std::result::Result<(R::Params, Responder<R>), RawRequest>>
+    where
+        R: Request,
+        R::Params: DeserializeOwned,
+        R::Result: Serialize,
+{
+    if raw.method != R::METHOD {
+        return Ok(Err(raw));
+    }
+
+    let params: R::Params = serde_json::from_value(raw.params)?;
+    let responder = Responder {
+        id: raw.id,
+        bomb: DropBomb::new("dropped request"),
+        ph: PhantomData,
+    };
+    Ok(Ok((params, responder)))
+}
+
+pub fn handle_request<R, F>(req: &mut Option<RawRequest>, f: F) -> Result<()>
+    where
+        R: Request,
+        R::Params: DeserializeOwned,
+        R::Result: Serialize,
+        F: FnOnce(R::Params, Responder<R>) -> Result<()>
+{
+    match req.take() {
+        None => Ok(()),
+        Some(r) => match parse_request_as::<R>(r)? {
+            Ok((params, responder)) => f(params, responder),
+            Err(r) => {
+                *req = Some(r);
+                Ok(())
+            },
+        }
+    }
+}
+
+pub fn expect_request<R>(io: &mut Io, raw: RawRequest) -> Result<Option<(R::Params, Responder<R>)>>
+    where
+        R: Request,
+        R::Params: DeserializeOwned,
+        R::Result: Serialize,
+{
+    let ret = match parse_request_as::<R>(raw)? {
+        Ok(x) => Some(x),
+        Err(raw) => {
+            unknown_method(io, raw)?;
+            None
+        }
+    };
+    Ok(ret)
+}
+
+fn parse_notification_as<N>(raw: RawNotification) -> Result<::std::result::Result<N::Params, RawNotification>>
+    where
+        N: Notification,
+        N::Params: DeserializeOwned,
+{
+    if raw.method != N::METHOD {
+        return Ok(Err(raw));
+    }
+    let params: N::Params = serde_json::from_value(raw.params)?;
+    Ok(Ok(params))
+}
+
+pub fn handle_notification<N, F>(not: &mut Option<RawNotification>, f: F) -> Result<()>
+    where
+        N: Notification,
+        N::Params: DeserializeOwned,
+        F: FnOnce(N::Params) -> Result<()>
+{
+    match not.take() {
+        None => Ok(()),
+        Some(n) => match parse_notification_as::<N>(n)? {
+            Ok(params) => f(params),
+            Err(n) => {
+                *not = Some(n);
+                Ok(())
+            },
+        }
+    }
+}
+
+
+pub fn unknown_method(io: &mut Io, raw: RawRequest) -> Result<()> {
+    error(io, raw.id, ErrorCode::MethodNotFound, "unknown method")
+}
+
+fn error(io: &mut Io, id: u64, code: ErrorCode, message: &'static str) -> Result<()> {
+    #[derive(Serialize)]
+    struct Error {
+        code: i32,
+        message: &'static str,
+    }
+    io.send(RawMsg::Response(RawResponse {
+        id: Some(id),
+        result: serde_json::Value::Null,
+        error: serde_json::to_value(Error {
+            code: code as i32,
+            message,
+        })?,
+    }));
+    Ok(())
+}
+
+
+#[allow(unused)]
+enum ErrorCode {
+    ParseError = -32700,
+    InvalidRequest = -32600,
+    MethodNotFound = -32601,
+    InvalidParams = -32602,
+    InternalError = -32603,
+    ServerErrorStart = -32099,
+    ServerErrorEnd = -32000,
+    ServerNotInitialized = -32002,
+    UnknownErrorCode = -32001,
+    RequestCancelled = -32800,
+}
diff --git a/crates/server/src/handlers.rs b/crates/server/src/handlers.rs
new file mode 100644
index 000000000..5ee87a4dd
--- /dev/null
+++ b/crates/server/src/handlers.rs
@@ -0,0 +1,61 @@
+use languageserver_types::{Range, Position};
+use libanalysis::World;
+use libeditor::{self, LineIndex, LineCol, TextRange, TextUnit};
+use {req, Result, FilePath};
+
+pub fn handle_syntax_tree(
+    world: World,
+    params: req::SyntaxTreeParams,
+) -> Result<String> {
+    let path = params.text_document.file_path()?;
+    let file = world.file_syntax(&path)?;
+    Ok(libeditor::syntax_tree(&file))
+}
+
+pub fn handle_extend_selection(
+    world: World,
+    params: req::ExtendSelectionParams,
+) -> Result<req::ExtendSelectionResult> {
+    let path = params.text_document.file_path()?;
+    let file = world.file_syntax(&path)?;
+    let line_index = world.file_line_index(&path)?;
+    let selections = params.selections.into_iter()
+        .map(|r| {
+            let r = to_text_range(&line_index, r);
+            let r = libeditor::extend_selection(&file, r).unwrap_or(r);
+            to_vs_range(&line_index, r)
+        })
+        .collect();
+    Ok(req::ExtendSelectionResult { selections })
+}
+
+
+fn to_text_range(line_index: &LineIndex, range: Range) -> TextRange {
+    TextRange::from_to(
+        to_text_unit(line_index, range.start),
+        to_text_unit(line_index, range.end),
+    )
+}
+
+fn to_text_unit(line_index: &LineIndex, position: Position) -> TextUnit {
+    // TODO: UTF-16
+    let line_col = LineCol {
+        line: position.line as u32,
+        col: (position.character as u32).into(),
+    };
+    line_index.offset(line_col)
+}
+
+
+fn to_vs_range(line_index: &LineIndex, range: TextRange) -> Range {
+    Range::new(
+        to_vs_position(line_index, range.start()),
+        to_vs_position(line_index, range.end()),
+    )
+}
+
+fn to_vs_position(line_index: &LineIndex, offset: TextUnit) -> Position {
+    let line_col = line_index.line_col(offset);
+    // TODO: UTF-16
+    Position::new(line_col.line as u64, u32::from(line_col.col) as u64)
+}
diff --git a/crates/server/src/io.rs b/crates/server/src/io.rs
new file mode 100644
index 000000000..5eafc6942
--- /dev/null
+++ b/crates/server/src/io.rs
@@ -0,0 +1,202 @@
+use std::{
+    thread,
+    io::{
+        stdout, stdin,
+        BufRead, Write,
+    },
+};
+use serde_json::{Value, from_str, to_string};
+use crossbeam_channel::{Receiver, Sender, bounded};
+
+use Result;
+
+
+#[derive(Debug, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum RawMsg {
+    Request(RawRequest),
+    Notification(RawNotification),
+    Response(RawResponse),
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct RawRequest {
+    pub id: u64,
+    pub method: String,
+    pub params: Value,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct RawNotification {
+    pub method: String,
+    pub params: Value,
+}
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct RawResponse {
+    pub id: Option<u64>,
+    pub result: Value,
+    pub error: Value,
+}
+
+struct MsgReceiver {
+    chan: Receiver<RawMsg>,
+    thread: Option<thread::JoinHandle<Result<()>>>,
+}
+
+impl MsgReceiver {
+    fn recv(&mut self) -> Result<RawMsg> {
+        match self.chan.recv() {
+            Some(msg) => Ok(msg),
+            None => {
+                self.cleanup()?;
+                unreachable!()
+            }
+        }
+    }
+
+    fn cleanup(&mut self) -> Result<()> {
+        self.thread
+            .take()
+            .ok_or_else(|| format_err!("MsgReceiver thread panicked"))?
+            .join()
+            .map_err(|_| format_err!("MsgReceiver thread panicked"))??;
+        bail!("client disconnected")
+    }
+
+    fn stop(self) -> Result<()> {
+        // Can't really self.thread.join() here, b/c it might be
+        // blocking on read
+        Ok(())
+    }
+}
+
+struct MsgSender {
+    chan: Sender<RawMsg>,
+    thread: thread::JoinHandle<Result<()>>,
+}
+
+impl MsgSender {
+    fn send(&mut self, msg: RawMsg) {
+        self.chan.send(msg)
+    }
+
+    fn stop(self) -> Result<()> {
+        drop(self.chan);
+        self.thread.join()
+            .map_err(|_| format_err!("MsgSender thread panicked"))??;
+        Ok(())
+    }
+}
+
+pub struct Io {
+    receiver: MsgReceiver,
+    sender: MsgSender,
+}
+
+impl Io {
+    pub fn from_stdio() -> Io {
+        let sender = {
+            let (tx, rx) = bounded(16);
+            MsgSender {
+                chan: tx,
+                thread: thread::spawn(move || {
+                    let stdout = stdout();
+                    let mut stdout = stdout.lock();
+                    for msg in rx {
+                        #[derive(Serialize)]
+                        struct JsonRpc {
+                            jsonrpc: &'static str,
+                            #[serde(flatten)]
+                            msg: RawMsg,
+                        }
+                        let text = to_string(&JsonRpc {
+                            jsonrpc: "2.0",
+                            msg,
+                        })?;
+                        write_msg_text(&mut stdout, &text)?;
+                    }
+                    Ok(())
+                }),
+            }
+        };
+        let receiver = {
+            let (tx, rx) = bounded(16);
+            MsgReceiver {
+                chan: rx,
+                thread: Some(thread::spawn(move || {
+                    let stdin = stdin();
+                    let mut stdin = stdin.lock();
+                    while let Some(text) = read_msg_text(&mut stdin)? {
+                        let msg: RawMsg = from_str(&text)?;
+                        tx.send(msg);
+                    }
+                    Ok(())
+                })),
+            }
+        };
+        Io { receiver, sender }
+    }
+
+    pub fn send(&mut self, msg: RawMsg) {
+        self.sender.send(msg)
+    }
+
+    pub fn recv(&mut self) -> Result<RawMsg> {
+        self.receiver.recv()
+    }
+
+    pub fn receiver(&mut self) -> &mut Receiver<RawMsg> {
+        &mut self.receiver.chan
+    }
+
+    pub fn cleanup_receiver(&mut self) -> Result<()> {
+        self.receiver.cleanup()
+    }
+
+    pub fn stop(self) -> Result<()> {
+        self.receiver.stop()?;
+        self.sender.stop()?;
+        Ok(())
+    }
+}
+
+
+fn read_msg_text(inp: &mut impl BufRead) -> Result<Option<String>> {
+    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") {
+            bail!("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(|| format_err!("malformed header: {:?}", buf))?;
+        if header_name == "Content-Length" {
+            size = Some(header_value.parse::<usize>()?);
+        }
+    }
+    let size = size.ok_or_else(|| format_err!("no Content-Length"))?;
+    let mut buf = buf.into_bytes();
+    buf.resize(size, 0);
+    inp.read_exact(&mut buf)?;
+    let buf = String::from_utf8(buf)?;
+    debug!("< {}", buf);
+    Ok(Some(buf))
+}
+
+fn write_msg_text(out: &mut impl Write, msg: &str) -> Result<()> {
+    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/server/src/main.rs b/crates/server/src/main.rs
new file mode 100644
index 000000000..116abce1c
--- /dev/null
+++ b/crates/server/src/main.rs
@@ -0,0 +1,249 @@
+#[macro_use]
+extern crate failure;
+#[macro_use]
+extern crate serde_derive;
+extern crate serde;
+extern crate serde_json;
+extern crate languageserver_types;
+extern crate drop_bomb;
+#[macro_use]
+extern crate crossbeam_channel;
+extern crate threadpool;
+#[macro_use]
+extern crate log;
+extern crate flexi_logger;
+extern crate libeditor;
+extern crate libanalysis;
+
+mod io;
+mod caps;
+mod req;
+mod dispatch;
+mod handlers;
+
+use std::path::PathBuf;
+
+use threadpool::ThreadPool;
+use crossbeam_channel::{bounded, Sender, Receiver};
+use flexi_logger::Logger;
+use libanalysis::WorldState;
+use languageserver_types::{TextDocumentItem, VersionedTextDocumentIdentifier, TextDocumentIdentifier};
+
+use ::{
+    io::{Io, RawMsg},
+    handlers::{handle_syntax_tree, handle_extend_selection},
+};
+
+pub type Result<T> = ::std::result::Result<T, ::failure::Error>;
+
+fn main() -> Result<()> {
+    Logger::with_env_or_str("m=trace, libanalysis=trace")
+        .log_to_file()
+        .directory("log")
+        .start()?;
+    info!("starting server");
+    match ::std::panic::catch_unwind(|| main_inner()) {
+        Ok(res) => {
+            info!("shutting down: {:?}", res);
+            res
+        }
+        Err(_) => {
+            error!("server panicked");
+            bail!("server panicked")
+        }
+    }
+}
+
+fn main_inner() -> Result<()> {
+    let mut io = Io::from_stdio();
+    let res = initialize(&mut io);
+    info!("shutting down IO...");
+    let io_res = io.stop();
+    info!("... IO is down");
+    match (res, io_res) {
+        (Ok(()), Ok(())) => Ok(()),
+        (res, Ok(())) => res,
+        (Ok(()), io_res) => io_res,
+        (res, Err(io_err)) => {
+            error!("shutdown error: {:?}", io_err);
+            res
+        }
+    }
+}
+
+fn initialize(io: &mut Io) -> Result<()> {
+    loop {
+        match io.recv()? {
+            RawMsg::Request(req) => {
+                if let Some((_params, resp)) = dispatch::expect_request::<req::Initialize>(io, req)? {
+                    resp.result(io, req::InitializeResult {
+                        capabilities: caps::SERVER_CAPABILITIES
+                    })?;
+                    match io.recv()? {
+                        RawMsg::Notification(n) => {
+                            if n.method != "initialized" {
+                                bail!("expected initialized notification");
+                            }
+                        }
+                        _ => {
+                            bail!("expected initialized notification");
+                        }
+                    }
+                    return initialized(io);
+                }
+            }
+            RawMsg::Notification(n) => {
+                bail!("expected initialize request, got {:?}", n)
+            }
+            RawMsg::Response(res) => {
+                bail!("expected initialize request, got {:?}", res)
+            }
+        }
+    }
+}
+
+type Thunk = Box<for<'a> FnBox<&'a mut Io, Result<()>>>;
+
+fn initialized(io: &mut Io) -> Result<()> {
+    let mut world = WorldState::new();
+    let mut pool = ThreadPool::new(4);
+    let (sender, receiver) = bounded::<Thunk>(16);
+    let res = main_loop(io, &mut world, &mut pool, sender, receiver.clone());
+    info!("waiting for background jobs to finish...");
+    receiver.for_each(drop);
+    pool.join();
+    info!("...background jobs have finished");
+    res
+}
+
+fn main_loop(
+    io: &mut Io,
+    world: &mut WorldState,
+    pool: &mut ThreadPool,
+    sender: Sender<Thunk>,
+    receiver: Receiver<Thunk>,
+) -> Result<()> {
+    info!("server initialized, serving requests");
+    loop {
+        enum Event {
+            Msg(RawMsg),
+            Thunk(Thunk),
+            ReceiverDead,
+        }
+
+        let event = select! {
+            recv(io.receiver(), msg) => match msg {
+                Some(msg) => Event::Msg(msg),
+                None => Event::ReceiverDead,
+            },
+            recv(receiver, thunk) => Event::Thunk(thunk.unwrap()),
+        };
+
+        let msg = match event {
+            Event::ReceiverDead => {
+                io.cleanup_receiver()?;
+                unreachable!();
+            }
+            Event::Thunk(thunk) => {
+                thunk.call_box(io)?;
+                continue;
+            }
+            Event::Msg(msg) => msg,
+        };
+
+        match msg {
+            RawMsg::Request(req) => {
+                let mut req = Some(req);
+                dispatch::handle_request::<req::SyntaxTree, _>(&mut req, |params, resp| {
+                    let world = world.snapshot();
+                    let sender = sender.clone();
+                    pool.execute(move || {
+                        let res = handle_syntax_tree(world, params);
+                        sender.send(Box::new(|io: &mut Io| resp.response(io, res)))
+                    });
+                    Ok(())
+                })?;
+                dispatch::handle_request::<req::ExtendSelection, _>(&mut req, |params, resp| {
+                    let world = world.snapshot();
+                    let sender = sender.clone();
+                    pool.execute(move || {
+                        let res = handle_extend_selection(world, params);
+                        sender.send(Box::new(|io: &mut Io| resp.response(io, res)))
+                    });
+                    Ok(())
+                })?;
+                dispatch::handle_request::<req::Shutdown, _>(&mut req, |(), resp| {
+                    resp.result(io, ())?;
+                    Ok(())
+                })?;
+                if let Some(req) = req {
+                    error!("unknown method: {:?}", req);
+                    dispatch::unknown_method(io, req)?;
+                }
+            }
+            RawMsg::Notification(not) => {
+                let mut not = Some(not);
+                dispatch::handle_notification::<req::DidOpenTextDocument, _>(&mut not, |params| {
+                    let path = params.text_document.file_path()?;
+                    world.change_overlay(path, Some(params.text_document.text));
+                    Ok(())
+                })?;
+                dispatch::handle_notification::<req::DidChangeTextDocument, _>(&mut not, |mut params| {
+                    let path = params.text_document.file_path()?;
+                    let text = params.content_changes.pop()
+                        .ok_or_else(|| format_err!("empty changes"))?
+                        .text;
+                    world.change_overlay(path, Some(text));
+                    Ok(())
+                })?;
+                dispatch::handle_notification::<req::DidCloseTextDocument, _>(&mut not, |params| {
+                    let path = params.text_document.file_path()?;
+                    world.change_overlay(path, None);
+                    Ok(())
+                })?;
+
+                if let Some(not) = not {
+                    error!("unhandled notification: {:?}", not)
+                }
+            }
+            msg => {
+                eprintln!("msg = {:?}", msg);
+            }
+        }
+    }
+}
+
+trait FnBox<A, R>: Send {
+    fn call_box(self: Box<Self>, a: A) -> R;
+}
+
+impl<A, R, F: FnOnce(A) -> R + Send> FnBox<A, R> for F {
+    fn call_box(self: Box<F>, a: A) -> R {
+        (*self)(a)
+    }
+}
+
+trait FilePath {
+    fn file_path(&self) -> Result<PathBuf>;
+}
+
+impl FilePath for TextDocumentItem {
+    fn file_path(&self) -> Result<PathBuf> {
+        self.uri.to_file_path()
+            .map_err(|()| format_err!("invalid uri: {}", self.uri))
+    }
+}
+
+impl FilePath for VersionedTextDocumentIdentifier {
+    fn file_path(&self) -> Result<PathBuf> {
+        self.uri.to_file_path()
+            .map_err(|()| format_err!("invalid uri: {}", self.uri))
+    }
+}
+
+impl FilePath for TextDocumentIdentifier {
+    fn file_path(&self) -> Result<PathBuf> {
+        self.uri.to_file_path()
+            .map_err(|()| format_err!("invalid uri: {}", self.uri))
+    }
+}
diff --git a/crates/server/src/req.rs b/crates/server/src/req.rs
new file mode 100644
index 000000000..4e588159b
--- /dev/null
+++ b/crates/server/src/req.rs
@@ -0,0 +1,41 @@
+use languageserver_types::{TextDocumentIdentifier, Range};
+
+pub use languageserver_types::{
+    request::*, notification::*,
+    InitializeResult,
+};
+
+pub enum SyntaxTree {}
+
+impl Request for SyntaxTree {
+    type Params = SyntaxTreeParams;
+    type Result = String;
+    const METHOD: &'static str = "m/syntaxTree";
+}
+
+#[derive(Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct SyntaxTreeParams {
+    pub text_document: TextDocumentIdentifier
+}
+
+pub enum ExtendSelection {}
+
+impl Request for ExtendSelection {
+    type Params = ExtendSelectionParams;
+    type Result = ExtendSelectionResult;
+    const METHOD: &'static str = "m/extendSelection";
+}
+
+#[derive(Deserialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct ExtendSelectionParams {
+    pub text_document: TextDocumentIdentifier,
+    pub selections: Vec<Range>,
+}
+
+#[derive(Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct ExtendSelectionResult {
+    pub selections: Vec<Range>,
+}