Add support for LSP DidChangeWatchedFiles (#7665)

* Add initial support for LSP DidChangeWatchedFiles

* Move file event Handler to helix-lsp

* Simplify file event handling

* Refactor file event handling

* Block on future within LSP file event handler

* Fully qualify uses of the file_event::Handler type

* Rename ops field to options

* Revert newline removal from helix-view/Cargo.toml

* Ensure file event Handler is cleaned up when lsp client is shutdown

8 files changed, 325 insertions, 29 deletions

diff --git a/Cargo.lock b/Cargo.lock
index a26bdfca..85848f9b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -51,9 +51,9 @@ dependencies = [
 
 [[package]]
 name = "aho-corasick"
-version = "1.0.1"
+version = "1.0.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "67fc08ce920c31afb70f013dcce1bfc3a3195de6a228474e45e1f145b36f8d04"
+checksum = "43f6cb1bf222025340178f382c426f13757b2960e89779dfcb319c32542a5a41"
 dependencies = [
  "memchr",
 ]
@@ -126,13 +126,12 @@ checksum = "630be753d4e58660abd17930c71b647fe46c27ea6b63cc59e1e3851406972e42"
 
 [[package]]
 name = "bstr"
-version = "1.4.0"
+version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c3d4260bcc2e8fc9df1eac4919a720effeb63a3f0952f5bf4944adfa18897f09"
+checksum = "6798148dccfbff0fae41c7574d2fa8f1ef3492fba0face179de5d8d447d67b05"
 dependencies = [
  "memchr",
- "once_cell",
- "regex-automata 0.1.10",
+ "regex-automata",
  "serde",
 ]
 
@@ -1149,11 +1148,11 @@ dependencies = [
 
 [[package]]
 name = "globset"
-version = "0.4.10"
+version = "0.4.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "029d74589adefde59de1a0c4f4732695c32805624aec7b68d91503d4dba79afc"
+checksum = "1391ab1f92ffcc08911957149833e682aa3fe252b9f45f966d2ef972274c97df"
 dependencies = [
- "aho-corasick 0.7.20",
+ "aho-corasick 1.0.2",
  "bstr",
  "fnv",
  "log",
@@ -1292,6 +1291,7 @@ dependencies = [
  "anyhow",
  "futures-executor",
  "futures-util",
+ "globset",
  "helix-core",
  "helix-loader",
  "helix-parsec",
@@ -1878,25 +1878,19 @@ version = "1.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b2eae68fc220f7cf2532e4494aded17545fce192d59cd996e0fe7887f4ceb575"
 dependencies = [
- "aho-corasick 1.0.1",
+ "aho-corasick 1.0.2",
  "memchr",
- "regex-automata 0.3.2",
+ "regex-automata",
  "regex-syntax 0.7.3",
 ]
 
 [[package]]
 name = "regex-automata"
-version = "0.1.10"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c230d73fb8d8c1b9c0b3135c5142a8acee3a0558fb8db5cf1cb65f8d7862132"
-
-[[package]]
-name = "regex-automata"
 version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "83d3daa6976cffb758ec878f108ba0e062a45b2d6ca3a2cca965338855476caf"
 dependencies = [
- "aho-corasick 1.0.1",
+ "aho-corasick 1.0.2",
  "memchr",
  "regex-syntax 0.7.3",
 ]
diff --git a/helix-lsp/Cargo.toml b/helix-lsp/Cargo.toml
index b4abeb8a..33c63e0a 100644
--- a/helix-lsp/Cargo.toml
+++ b/helix-lsp/Cargo.toml
@@ -19,6 +19,7 @@ helix-parsec = { version = "0.6", path = "../helix-parsec" }
 anyhow = "1.0"
 futures-executor = "0.3"
 futures-util = { version = "0.3", features = ["std", "async-await"], default-features = false }
+globset = "0.4.11"
 log = "0.4"
 lsp-types = { version = "0.94" }
 serde = { version = "1.0", features = ["derive"] }
diff --git a/helix-lsp/src/client.rs b/helix-lsp/src/client.rs
index 92ab03db..ed9a2f83 100644
--- a/helix-lsp/src/client.rs
+++ b/helix-lsp/src/client.rs
@@ -544,6 +544,10 @@ impl Client {
                         normalizes_line_endings: Some(false),
                         change_annotation_support: None,
                     }),
+                    did_change_watched_files: Some(lsp::DidChangeWatchedFilesClientCapabilities {
+                        dynamic_registration: Some(true),
+                        relative_pattern_support: Some(false),
+                    }),
                     ..Default::default()
                 }),
                 text_document: Some(lsp::TextDocumentClientCapabilities {
@@ -1453,4 +1457,13 @@ impl Client {
 
         Some(self.call::<lsp::request::ExecuteCommand>(params))
     }
+
+    pub fn did_change_watched_files(
+        &self,
+        changes: Vec<lsp::FileEvent>,
+    ) -> impl Future<Output = std::result::Result<(), Error>> {
+        self.notify::<lsp::notification::DidChangeWatchedFiles>(lsp::DidChangeWatchedFilesParams {
+            changes,
+        })
+    }
 }
diff --git a/helix-lsp/src/file_event.rs b/helix-lsp/src/file_event.rs
new file mode 100644
index 00000000..26a27c98
--- /dev/null
+++ b/helix-lsp/src/file_event.rs
@@ -0,0 +1,193 @@
+use std::{collections::HashMap, path::PathBuf, sync::Weak};
+
+use globset::{GlobBuilder, GlobSetBuilder};
+use tokio::sync::mpsc;
+
+use crate::{lsp, Client};
+
+enum Event {
+    FileChanged {
+        path: PathBuf,
+    },
+    Register {
+        client_id: usize,
+        client: Weak<Client>,
+        registration_id: String,
+        options: lsp::DidChangeWatchedFilesRegistrationOptions,
+    },
+    Unregister {
+        client_id: usize,
+        registration_id: String,
+    },
+    RemoveClient {
+        client_id: usize,
+    },
+}
+
+#[derive(Default)]
+struct ClientState {
+    client: Weak<Client>,
+    registered: HashMap<String, globset::GlobSet>,
+}
+
+/// The Handler uses a dedicated tokio task to respond to file change events by
+/// forwarding changes to LSPs that have registered for notifications with a
+/// matching glob.
+///
+/// When an LSP registers for the DidChangeWatchedFiles notification, the
+/// Handler is notified by sending the registration details in addition to a
+/// weak reference to the LSP client. This is done so that the Handler can have
+/// access to the client without preventing the client from being dropped if it
+/// is closed and the Handler isn't properly notified.
+#[derive(Clone, Debug)]
+pub struct Handler {
+    tx: mpsc::UnboundedSender<Event>,
+}
+
+impl Default for Handler {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl Handler {
+    pub fn new() -> Self {
+        let (tx, rx) = mpsc::unbounded_channel();
+        tokio::spawn(Self::run(rx));
+        Self { tx }
+    }
+
+    pub fn register(
+        &self,
+        client_id: usize,
+        client: Weak<Client>,
+        registration_id: String,
+        options: lsp::DidChangeWatchedFilesRegistrationOptions,
+    ) {
+        let _ = self.tx.send(Event::Register {
+            client_id,
+            client,
+            registration_id,
+            options,
+        });
+    }
+
+    pub fn unregister(&self, client_id: usize, registration_id: String) {
+        let _ = self.tx.send(Event::Unregister {
+            client_id,
+            registration_id,
+        });
+    }
+
+    pub fn file_changed(&self, path: PathBuf) {
+        let _ = self.tx.send(Event::FileChanged { path });
+    }
+
+    pub fn remove_client(&self, client_id: usize) {
+        let _ = self.tx.send(Event::RemoveClient { client_id });
+    }
+
+    async fn run(mut rx: mpsc::UnboundedReceiver<Event>) {
+        let mut state: HashMap<usize, ClientState> = HashMap::new();
+        while let Some(event) = rx.recv().await {
+            match event {
+                Event::FileChanged { path } => {
+                    log::debug!("Received file event for {:?}", &path);
+
+                    state.retain(|id, client_state| {
+                        if !client_state
+                            .registered
+                            .values()
+                            .any(|glob| glob.is_match(&path))
+                        {
+                            return true;
+                        }
+                        let Some(client) = client_state.client.upgrade() else {
+                            log::warn!("LSP client was dropped: {id}");
+                            return false;
+                        };
+                        let Ok(uri) = lsp::Url::from_file_path(&path) else {
+                            return true;
+                        };
+                        log::debug!(
+                            "Sending didChangeWatchedFiles notification to client '{}'",
+                            client.name()
+                        );
+                        if let Err(err) = crate::block_on(client
+                            .did_change_watched_files(vec![lsp::FileEvent {
+                                uri,
+                                // We currently always send the CHANGED state
+                                // since we don't actually have more context at
+                                // the moment.
+                                typ: lsp::FileChangeType::CHANGED,
+                            }]))
+                        {
+                            log::warn!("Failed to send didChangeWatchedFiles notification to client: {err}");
+                        }
+                        true
+                    });
+                }
+                Event::Register {
+                    client_id,
+                    client,
+                    registration_id,
+                    options: ops,
+                } => {
+                    log::debug!(
+                        "Registering didChangeWatchedFiles for client '{}' with id '{}'",
+                        client_id,
+                        registration_id
+                    );
+
+                    let mut entry = state.entry(client_id).or_insert_with(ClientState::default);
+                    entry.client = client;
+
+                    let mut builder = GlobSetBuilder::new();
+                    for watcher in ops.watchers {
+                        if let lsp::GlobPattern::String(pattern) = watcher.glob_pattern {
+                            if let Ok(glob) = GlobBuilder::new(&pattern).build() {
+                                builder.add(glob);
+                            }
+                        }
+                    }
+                    match builder.build() {
+                        Ok(globset) => {
+                            entry.registered.insert(registration_id, globset);
+                        }
+                        Err(err) => {
+                            // Remove any old state for that registration id and
+                            // remove the entire client if it's now empty.
+                            entry.registered.remove(&registration_id);
+                            if entry.registered.is_empty() {
+                                state.remove(&client_id);
+                            }
+                            log::warn!(
+                                "Unable to build globset for LSP didChangeWatchedFiles {err}"
+                            )
+                        }
+                    }
+                }
+                Event::Unregister {
+                    client_id,
+                    registration_id,
+                } => {
+                    log::debug!(
+                        "Unregistering didChangeWatchedFiles with id '{}' for client '{}'",
+                        registration_id,
+                        client_id
+                    );
+                    if let Some(client_state) = state.get_mut(&client_id) {
+                        client_state.registered.remove(&registration_id);
+                        if client_state.registered.is_empty() {
+                            state.remove(&client_id);
+                        }
+                    }
+                }
+                Event::RemoveClient { client_id } => {
+                    log::debug!("Removing LSP client: {client_id}");
+                    state.remove(&client_id);
+                }
+            }
+        }
+    }
+}
diff --git a/helix-lsp/src/lib.rs b/helix-lsp/src/lib.rs
index 95c61086..90f0c3fd 100644
--- a/helix-lsp/src/lib.rs
+++ b/helix-lsp/src/lib.rs
@@ -1,4 +1,5 @@
 mod client;
+pub mod file_event;
 pub mod jsonrpc;
 pub mod snippet;
 mod transport;
@@ -547,6 +548,7 @@ pub enum MethodCall {
     WorkspaceFolders,
     WorkspaceConfiguration(lsp::ConfigurationParams),
     RegisterCapability(lsp::RegistrationParams),
+    UnregisterCapability(lsp::UnregistrationParams),
 }
 
 impl MethodCall {
@@ -570,6 +572,10 @@ impl MethodCall {
                 let params: lsp::RegistrationParams = params.parse()?;
                 Self::RegisterCapability(params)
             }
+            lsp::request::UnregisterCapability::METHOD => {
+                let params: lsp::UnregistrationParams = params.parse()?;
+                Self::UnregisterCapability(params)
+            }
             _ => {
                 return Err(Error::Unhandled);
             }
@@ -629,6 +635,7 @@ pub struct Registry {
     syn_loader: Arc<helix_core::syntax::Loader>,
     counter: usize,
     pub incoming: SelectAll<UnboundedReceiverStream<(usize, Call)>>,
+    pub file_event_handler: file_event::Handler,
 }
 
 impl Registry {
@@ -638,6 +645,7 @@ impl Registry {
             syn_loader,
             counter: 0,
             incoming: SelectAll::new(),
+            file_event_handler: file_event::Handler::new(),
         }
     }
 
@@ -650,6 +658,7 @@ impl Registry {
     }
 
     pub fn remove_by_id(&mut self, id: usize) {
+        self.file_event_handler.remove_client(id);
         self.inner.retain(|_, language_servers| {
             language_servers.retain(|ls| id != ls.id());
             !language_servers.is_empty()
@@ -715,6 +724,7 @@ impl Registry {
                         .unwrap();
 
                     for old_client in old_clients {
+                        self.file_event_handler.remove_client(old_client.id());
                         tokio::spawn(async move {
                             let _ = old_client.force_shutdown().await;
                         });
@@ -731,6 +741,7 @@ impl Registry {
     pub fn stop(&mut self, name: &str) {
         if let Some(clients) = self.inner.remove(name) {
             for client in clients {
+                self.file_event_handler.remove_client(client.id());
                 tokio::spawn(async move {
                     let _ = client.force_shutdown().await;
                 });
diff --git a/helix-term/src/application.rs b/helix-term/src/application.rs
index b8950ae0..dc461198 100644
--- a/helix-term/src/application.rs
+++ b/helix-term/src/application.rs
@@ -5,7 +5,11 @@ use helix_core::{
     path::get_relative_path,
     pos_at_coords, syntax, Selection,
 };
-use helix_lsp::{lsp, util::lsp_pos_to_pos, LspProgressMap};
+use helix_lsp::{
+    lsp::{self, notification::Notification},
+    util::lsp_pos_to_pos,
+    LspProgressMap,
+};
 use helix_view::{
     align_view,
     document::DocumentSavedEventResult,
@@ -1080,17 +1084,65 @@ impl Application {
                             .collect();
                         Ok(json!(result))
                     }
-                    Ok(MethodCall::RegisterCapability(_params)) => {
-                        log::warn!("Ignoring a client/registerCapability request because dynamic capability registration is not enabled. Please report this upstream to the language server");
-                        // Language Servers based on the `vscode-languageserver-node` library often send
-                        // client/registerCapability even though we do not enable dynamic registration
-                        // for any capabilities. We should send a MethodNotFound JSONRPC error in this
-                        // case but that rejects the registration promise in the server which causes an
-                        // exit. So we work around this by ignoring the request and sending back an OK
-                        // response.
+                    Ok(MethodCall::RegisterCapability(params)) => {
+                        if let Some(client) = self
+                            .editor
+                            .language_servers
+                            .iter_clients()
+                            .find(|client| client.id() == server_id)
+                        {
+                            for reg in params.registrations {
+                                match reg.method.as_str() {
+                                    lsp::notification::DidChangeWatchedFiles::METHOD => {
+                                        let Some(options) = reg.register_options else {
+                                            continue;
+                                        };
+                                        let ops: lsp::DidChangeWatchedFilesRegistrationOptions =
+                                            match serde_json::from_value(options) {
+                                                Ok(ops) => ops,
+                                                Err(err) => {
+                                                    log::warn!("Failed to deserialize DidChangeWatchedFilesRegistrationOptions: {err}");
+                                                    continue;
+                                                }
+                                            };
+                                        self.editor.language_servers.file_event_handler.register(
+                                            client.id(),
+                                            Arc::downgrade(client),
+                                            reg.id,
+                                            ops,
+                                        )
+                                    }
+                                    _ => {
+                                        // Language Servers based on the `vscode-languageserver-node` library often send
+                                        // client/registerCapability even though we do not enable dynamic registration
+                                        // for most capabilities. We should send a MethodNotFound JSONRPC error in this
+                                        // case but that rejects the registration promise in the server which causes an
+                                        // exit. So we work around this by ignoring the request and sending back an OK
+                                        // response.
+                                        log::warn!("Ignoring a client/registerCapability request because dynamic capability registration is not enabled. Please report this upstream to the language server");
+                                    }
+                                }
+                            }
+                        }
 
                         Ok(serde_json::Value::Null)
                     }
+                    Ok(MethodCall::UnregisterCapability(params)) => {
+                        for unreg in params.unregisterations {
+                            match unreg.method.as_str() {
+                                lsp::notification::DidChangeWatchedFiles::METHOD => {
+                                    self.editor
+                                        .language_servers
+                                        .file_event_handler
+                                        .unregister(server_id, unreg.id);
+                                }
+                                _ => {
+                                    log::warn!("Received unregistration request for unsupported method: {}", unreg.method);
+                                }
+                            }
+                        }
+                        Ok(serde_json::Value::Null)
+                    }
                 };
 
                 tokio::spawn(language_server!().reply(id, reply));
diff --git a/helix-term/src/commands/typed.rs b/helix-term/src/commands/typed.rs
index dfc71dfd..063658c6 100644
--- a/helix-term/src/commands/typed.rs
+++ b/helix-term/src/commands/typed.rs
@@ -1283,7 +1283,14 @@ fn reload(
     doc.reload(view, &cx.editor.diff_providers, redraw_handle)
         .map(|_| {
             view.ensure_cursor_in_view(doc, scrolloff);
-        })
+        })?;
+    if let Some(path) = doc.path() {
+        cx.editor
+            .language_servers
+            .file_event_handler
+            .file_changed(path.clone());
+    }
+    Ok(())
 }
 
 fn reload_all(
@@ -1324,6 +1331,12 @@ fn reload_all(
 
         let redraw_handle = cx.editor.redraw_handle.clone();
         doc.reload(view, &cx.editor.diff_providers, redraw_handle)?;
+        if let Some(path) = doc.path() {
+            cx.editor
+                .language_servers
+                .file_event_handler
+                .file_changed(path.clone());
+        }
 
         for view_id in view_ids {
             let view = view_mut!(cx.editor, view_id);
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index affe87dd..20469ae9 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -1535,7 +1535,18 @@ impl Editor {
 
         let path = path.map(|path| path.into());
         let doc = doc_mut!(self, &doc_id);
-        let future = doc.save(path, force)?;
+        let doc_save_future = doc.save(path, force)?;
+
+        // When a file is written to, notify the file event handler.
+        // Note: This can be removed once proper file watching is implemented.
+        let handler = self.language_servers.file_event_handler.clone();
+        let future = async move {
+            let res = doc_save_future.await;
+            if let Ok(event) = &res {
+                handler.file_changed(event.path.clone());
+            }
+            res
+        };
 
         use futures_util::stream;
 
@@ -1671,6 +1682,14 @@ impl Editor {
         &self,
         timeout: Option<u64>,
     ) -> Result<(), tokio::time::error::Elapsed> {
+        // Remove all language servers from the file event handler.
+        // Note: this is non-blocking.
+        for client in self.language_servers.iter_clients() {
+            self.language_servers
+                .file_event_handler
+                .remove_client(client.id());
+        }
+
         tokio::time::timeout(
             Duration::from_millis(timeout.unwrap_or(3000)),
             future::join_all(