implement proper lsp-workspace support

fix typo

Co-authored-by: LeoniePhiline <22329650+LeoniePhiline@users.noreply.github.com>

book/src/languages.md

@@ -64,7 +64,7 @@ These configuration keys are available:
 | `grammar`             | The tree-sitter grammar to use (defaults to the value of `name`) |
 | `formatter`           | The formatter for the language, it will take precedence over the lsp when defined. The formatter must be able to take the original file as input from stdin and write the formatted file to stdout |
 | `text-width`          |  Maximum line length. Used for the `:reflow` command and soft-wrapping if `soft-wrap.wrap_at_text_width` is set, defaults to `editor.text-width`   |
-| `workspace-lsp-roots`     | Directories relative to the workspace root that are treated as LSP roots. Should only be set in `.helix/config.toml`. Overwrites the setting of the same name in `config.toml` if set. | `` |
+| `workspace-lsp-roots`     | Directories relative to the workspace root that are treated as LSP roots. Should only be set in `.helix/config.toml`. Overwrites the setting of the same name in `config.toml` if set. |
 
 ### File-type detection and the `file-types` key
 

helix-loader/src/config.rs

@@ -9,35 +9,38 @@ pub fn default_lang_config() -> toml::Value {
 
 /// User configured languages.toml file, merged with the default config.
 pub fn user_lang_config() -> Result<toml::Value, toml::de::Error> {
-    let config = [crate::config_dir(), crate::find_workspace().join(".helix")]
-        .into_iter()
-        .map(|path| path.join("languages.toml"))
-        .filter_map(|file| {
-            std::fs::read_to_string(file)
-                .map(|config| toml::from_str(&config))
-                .ok()
-        })
-        .collect::<Result<Vec<_>, _>>()?
-        .into_iter()
-        .fold(default_lang_config(), |a, b| {
-            // combines for example
-            // b:
-            //   [[language]]
-            //   name = "toml"
-            //   language-server = { command = "taplo", args = ["lsp", "stdio"] }
-            //
-            // a:
-            //   [[language]]
-            //   language-server = { command = "/usr/bin/taplo" }
-            //
-            // into:
-            //   [[language]]
-            //   name = "toml"
-            //   language-server = { command = "/usr/bin/taplo" }
-            //
-            // thus it overrides the third depth-level of b with values of a if they exist, but otherwise merges their values
-            crate::merge_toml_values(a, b, 3)
-        });
+    let config = [
+        crate::config_dir(),
+        crate::find_workspace().0.join(".helix"),
+    ]
+    .into_iter()
+    .map(|path| path.join("languages.toml"))
+    .filter_map(|file| {
+        std::fs::read_to_string(file)
+            .map(|config| toml::from_str(&config))
+            .ok()
+    })
+    .collect::<Result<Vec<_>, _>>()?
+    .into_iter()
+    .fold(default_lang_config(), |a, b| {
+        // combines for example
+        // b:
+        //   [[language]]
+        //   name = "toml"
+        //   language-server = { command = "taplo", args = ["lsp", "stdio"] }
+        //
+        // a:
+        //   [[language]]
+        //   language-server = { command = "/usr/bin/taplo" }
+        //
+        // into:
+        //   [[language]]
+        //   name = "toml"
+        //   language-server = { command = "/usr/bin/taplo" }
+        //
+        // thus it overrides the third depth-level of b with values of a if they exist, but otherwise merges their values
+        crate::merge_toml_values(a, b, 3)
+    });
 
     Ok(config)
 }

helix-loader/src/lib.rs

@@ -129,7 +129,7 @@ pub fn config_file() -> PathBuf {
 }
 
 pub fn workspace_config_file() -> PathBuf {
-    find_workspace().join(".helix").join("config.toml")
+    find_workspace().0.join(".helix").join("config.toml")
 }
 
 pub fn lang_config_file() -> PathBuf {
@@ -283,14 +283,19 @@ mod merge_toml_tests {
 }
 
 /// Finds the current workspace folder.
-/// Used as a ceiling dir for root resolve, for the filepicker and other related
-pub fn find_workspace() -> PathBuf {
+/// Used as a ceiling dir for LSP root resolution, the filepicker and potentially as a future filewatching root
+///
+/// This function starts searching the FS upward from the CWD
+/// and returns the first directory that contains either `.git` or `.helix`.
+/// If no workspace was found returns (CWD, true).
+/// Otherwise (workspace, false) is returned
+pub fn find_workspace() -> (PathBuf, bool) {
     let current_dir = std::env::current_dir().expect("unable to determine current directory");
     for ancestor in current_dir.ancestors() {
         if ancestor.join(".git").exists() || ancestor.join(".helix").exists() {
-            return ancestor.to_owned();
+            return (ancestor.to_owned(), false);
         }
     }
 
-    current_dir
+    (current_dir, true)
 }

helix-lsp/Cargo.toml

@@ -27,3 +27,4 @@ thiserror = "1.0"
 tokio = { version = "1.26", features = ["rt", "rt-multi-thread", "io-util", "io-std", "time", "process", "macros", "fs", "parking_lot", "sync"] }
 tokio-stream = "0.1.12"
 which = "4.4"
+parking_lot = "0.12.1"

helix-lsp/src/client.rs

@@ -1,13 +1,17 @@
 use crate::{
-    find_root, jsonrpc,
+    find_lsp_workspace, jsonrpc,
     transport::{Payload, Transport},
     Call, Error, OffsetEncoding, Result,
 };
 
-use helix_core::{ChangeSet, Rope};
+use helix_core::{find_workspace, ChangeSet, Rope};
 use helix_loader::{self, VERSION_AND_GIT_HASH};
-use lsp::PositionEncodingKind;
+use lsp::{
+    notification::DidChangeWorkspaceFolders, DidChangeWorkspaceFoldersParams, OneOf,
+    PositionEncodingKind, WorkspaceFolder, WorkspaceFoldersChangeEvent,
+};
 use lsp_types as lsp;
+use parking_lot::Mutex;
 use serde::Deserialize;
 use serde_json::Value;
 use std::future::Future;
@@ -26,6 +30,17 @@ use tokio::{
     },
 };
 
+fn workspace_for_uri(uri: lsp::Url) -> WorkspaceFolder {
+    lsp::WorkspaceFolder {
+        name: uri
+            .path_segments()
+            .and_then(|segments| segments.last())
+            .map(|basename| basename.to_string())
+            .unwrap_or_default(),
+        uri,
+    }
+}
+
 #[derive(Debug)]
 pub struct Client {
     id: usize,
@@ -36,11 +51,120 @@ pub struct Client {
     config: Option<Value>,
     root_path: std::path::PathBuf,
     root_uri: Option<lsp::Url>,
-    workspace_folders: Vec<lsp::WorkspaceFolder>,
+    workspace_folders: Mutex<Vec<lsp::WorkspaceFolder>>,
+    initalize_notify: Arc<Notify>,
+    /// workspace folders added while the server is still initalizing
     req_timeout: u64,
 }
 
 impl Client {
+    pub fn try_add_doc(
+        self: &Arc<Self>,
+        root_markers: &[String],
+        manual_roots: &[PathBuf],
+        doc_path: Option<&std::path::PathBuf>,
+        may_support_workspace: bool,
+    ) -> bool {
+        let (workspace, workspace_is_cwd) = find_workspace();
+        let root = find_lsp_workspace(
+            doc_path
+                .and_then(|x| x.parent().and_then(|x| x.to_str()))
+                .unwrap_or("."),
+            root_markers,
+            manual_roots,
+            &workspace,
+            workspace_is_cwd,
+        );
+        let root_uri = root
+            .as_ref()
+            .and_then(|root| lsp::Url::from_file_path(root).ok());
+
+        if self.root_path == root.unwrap_or(workspace)
+            || root_uri.as_ref().map_or(false, |root_uri| {
+                self.workspace_folders
+                    .lock()
+                    .iter()
+                    .any(|workspace| &workspace.uri == root_uri)
+            })
+        {
+            // workspace URI is already registered so we can use this client
+            return true;
+        }
+
+        // this server definitly doesn't support multiple workspace, no need to check capabilities
+        if !may_support_workspace {
+            return false;
+        }
+
+        let Some(capabilities) = self.capabilities.get() else {
+            let client = Arc::clone(self);
+            // initalization hasn't finished yet, deal with this new root later
+            // TODO: In the edgecase that a **new root** is added
+            // for an LSP that **doesn't support workspace_folders** before initaliation is finished
+            // the new roots are ignored.
+            // That particular edgecase would require retroactively spawning new LSP
+            // clients and therefore also require us to retroactively update the corresponding
+            // documents LSP client handle. It's doable but a pretty weird edgecase so let's
+            // wait and see if anyone ever runs into it.
+            tokio::spawn(async move {
+                client.initalize_notify.notified().await;
+                if let Some(workspace_folders_caps) = client
+                    .capabilities()
+                    .workspace
+                    .as_ref()
+                    .and_then(|cap| cap.workspace_folders.as_ref())
+                    .filter(|cap| cap.supported.unwrap_or(false))
+                {
+                    client.add_workspace_folder(
+                        root_uri,
+                        &workspace_folders_caps.change_notifications,
+                    );
+                }
+            });
+            return true;
+        };
+
+        if let Some(workspace_folders_caps) = capabilities
+            .workspace
+            .as_ref()
+            .and_then(|cap| cap.workspace_folders.as_ref())
+            .filter(|cap| cap.supported.unwrap_or(false))
+        {
+            self.add_workspace_folder(root_uri, &workspace_folders_caps.change_notifications);
+            true
+        } else {
+            // the server doesn't support multi workspaces, we need a new client
+            false
+        }
+    }
+
+    fn add_workspace_folder(
+        &self,
+        root_uri: Option<lsp::Url>,
+        change_notifications: &Option<OneOf<bool, String>>,
+    ) {
+        // root_uri is None just means that there isn't really any LSP workspace
+        // associated with this file. For servers that support multiple workspaces
+        // there is just one server so we can always just use that shared instance.
+        // No need to add a new workspace root here as there is no logical root for this file
+        // let the server deal with this
+        let Some(root_uri) = root_uri else {
+            return;
+        };
+
+        // server supports workspace folders, let's add the new root to the list
+        self.workspace_folders
+            .lock()
+            .push(workspace_for_uri(root_uri.clone()));
+        if &Some(OneOf::Left(false)) == change_notifications {
+            // server specifically opted out of DidWorkspaceChange notifications
+            // let's assume the server will request the workspace folders itself
+            // and that we can therefore reuse the client (but are done now)
+            return;
+        }
+        tokio::spawn(self.did_change_workspace(vec![workspace_for_uri(root_uri)], Vec::new()));
+    }
+
     #[allow(clippy::type_complexity)]
     #[allow(clippy::too_many_arguments)]
     pub fn start(
@@ -76,30 +200,25 @@ impl Client {
 
         let (server_rx, server_tx, initialize_notify) =
             Transport::start(reader, writer, stderr, id);
-
-        let root_path = find_root(
+        let (workspace, workspace_is_cwd) = find_workspace();
+        let root = find_lsp_workspace(
             doc_path
                 .and_then(|x| x.parent().and_then(|x| x.to_str()))
                 .unwrap_or("."),
             root_markers,
             manual_roots,
+            &workspace,
+            workspace_is_cwd,
         );
 
-        let root_uri = lsp::Url::from_file_path(root_path.clone()).ok();
+        // `root_uri` and `workspace_folder` can be empty in case there is no workspace
+        // `root_url` can not, use `workspace` as a fallback
+        let root_path = root.clone().unwrap_or_else(|| workspace.clone());
+        let root_uri = root.and_then(|root| lsp::Url::from_file_path(root).ok());
 
-        // TODO: support multiple workspace folders
         let workspace_folders = root_uri
             .clone()
-            .map(|root| {
-                vec![lsp::WorkspaceFolder {
-                    name: root
-                        .path_segments()
-                        .and_then(|segments| segments.last())
-                        .map(|basename| basename.to_string())
-                        .unwrap_or_default(),
-                    uri: root,
-                }]
-            })
+            .map(|root| vec![workspace_for_uri(root)])
             .unwrap_or_default();
 
         let client = Self {
@@ -110,10 +229,10 @@ impl Client {
             capabilities: OnceCell::new(),
             config,
             req_timeout,
-
             root_path,
             root_uri,
-            workspace_folders,
+            workspace_folders: Mutex::new(workspace_folders),
+            initalize_notify: initialize_notify.clone(),
         };
 
         Ok((client, server_rx, initialize_notify))
@@ -169,8 +288,10 @@ impl Client {
         self.config.as_ref()
     }
 
-    pub fn workspace_folders(&self) -> &[lsp::WorkspaceFolder] {
-        &self.workspace_folders
+    pub async fn workspace_folders(
+        &self,
+    ) -> parking_lot::MutexGuard<'_, Vec<lsp::WorkspaceFolder>> {
+        self.workspace_folders.lock()
     }
 
     /// Execute a RPC request on the language server.
@@ -298,7 +419,7 @@ impl Client {
         #[allow(deprecated)]
         let params = lsp::InitializeParams {
             process_id: Some(std::process::id()),
-            workspace_folders: Some(self.workspace_folders.clone()),
+            workspace_folders: Some(self.workspace_folders.lock().clone()),
             // root_path is obsolete, but some clients like pyright still use it so we specify both.
             // clients will prefer _uri if possible
             root_path: self.root_path.to_str().map(|path| path.to_owned()),
@@ -469,6 +590,16 @@ impl Client {
         )
     }
 
+    pub fn did_change_workspace(
+        &self,
+        added: Vec<WorkspaceFolder>,
+        removed: Vec<WorkspaceFolder>,
+    ) -> impl Future<Output = Result<()>> {
+        self.notify::<DidChangeWorkspaceFolders>(DidChangeWorkspaceFoldersParams {
+            event: WorkspaceFoldersChangeEvent { added, removed },
+        })
+    }
+
     // -------------------------------------------------------------------------------------------
     // Text document
     // -------------------------------------------------------------------------------------------