feature: Add a UnindexedProject notification and a corresponding setting.

crates/hir-ty/src/diagnostics/match_check/pat_analysis.rs

@@ -359,7 +359,7 @@ impl<'p> TypeCx for MatchCheckCtx<'p> {
         &'a self,
         ctor: &'a rustc_pattern_analysis::constructor::Constructor<Self>,
         ty: &'a Self::Ty,
-    ) -> impl Iterator<Item = Self::Ty> + ExactSizeIterator + Captures<'a> {
+    ) -> impl ExactSizeIterator<Item = Self::Ty> + Captures<'a> {
         let single = |ty| smallvec![ty];
         let tys: SmallVec<[_; 2]> = match ctor {
             Struct | Variant(_) | UnionField => match ty.kind(Interner) {

crates/rust-analyzer/src/config.rs

@@ -478,6 +478,9 @@ config_data! {
         /// Whether to show `can't find Cargo.toml` error message.
         notifications_cargoTomlNotFound: bool      = "true",
 
+        /// Whether to send an UnindexedProject notification to the client.
+        notifications_unindexedProject: bool      = "false",
+
         /// How many worker threads in the main loop. The default `null` means to pick automatically.
         numThreads: Option<usize> = "null",
 
@@ -745,6 +748,7 @@ pub enum FilesWatcher {
 #[derive(Debug, Clone)]
 pub struct NotificationsConfig {
     pub cargo_toml_not_found: bool,
+    pub unindexed_project: bool,
 }
 
 #[derive(Debug, Clone)]
@@ -1220,7 +1224,10 @@ impl Config {
     }
 
     pub fn notifications(&self) -> NotificationsConfig {
-        NotificationsConfig { cargo_toml_not_found: self.data.notifications_cargoTomlNotFound }
+        NotificationsConfig {
+            cargo_toml_not_found: self.data.notifications_cargoTomlNotFound,
+            unindexed_project: self.data.notifications_unindexedProject,
+        }
     }
 
     pub fn cargo_autoreload(&self) -> bool {

crates/rust-analyzer/src/global_state.rs

@@ -33,7 +33,7 @@ use crate::{
     mem_docs::MemDocs,
     op_queue::OpQueue,
     reload,
-    task_pool::TaskPool,
+    task_pool::{TaskPool, TaskQueue},
 };
 
 // Enforces drop order
@@ -126,6 +126,17 @@ pub(crate) struct GlobalState {
         OpQueue<(), (Arc<Vec<ProjectWorkspace>>, Vec<anyhow::Result<WorkspaceBuildScripts>>)>,
     pub(crate) fetch_proc_macros_queue: OpQueue<Vec<ProcMacroPaths>, bool>,
     pub(crate) prime_caches_queue: OpQueue,
+
+    /// A deferred task queue.
+    ///
+    /// This queue is used for doing database-dependent work inside of sync
+    /// handlers, as accessing the database may block latency-sensitive
+    /// interactions and should be moved away from the main thread.
+    ///
+    /// For certain features, such as [`lsp_ext::UnindexedProjectParams`],
+    /// this queue should run only *after* [`GlobalState::process_changes`] has
+    /// been called.
+    pub(crate) deferred_task_queue: TaskQueue,
 }
 
 /// An immutable snapshot of the world's state at a point in time.
@@ -165,6 +176,11 @@ impl GlobalState {
             Handle { handle, receiver }
         };
 
+        let task_queue = {
+            let (sender, receiver) = unbounded();
+            TaskQueue { sender, receiver }
+        };
+
         let mut analysis_host = AnalysisHost::new(config.lru_parse_query_capacity());
         if let Some(capacities) = config.lru_query_capacities() {
             analysis_host.update_lru_capacities(capacities);
@@ -208,6 +224,8 @@ impl GlobalState {
             fetch_proc_macros_queue: OpQueue::default(),
 
             prime_caches_queue: OpQueue::default(),
+
+            deferred_task_queue: task_queue,
         };
         // Apply any required database inputs from the config.
         this.update_configuration(config);

crates/rust-analyzer/src/handlers/notification.rs

@@ -70,7 +70,15 @@ pub(crate) fn handle_did_open_text_document(
         if already_exists {
             tracing::error!("duplicate DidOpenTextDocument: {}", path);
         }
+
         state.vfs.write().0.set_file_contents(path, Some(params.text_document.text.into_bytes()));
+        if state.config.notifications().unindexed_project {
+            tracing::debug!("queuing task");
+            let _ = state
+                .deferred_task_queue
+                .sender
+                .send(crate::main_loop::QueuedTask::CheckIfIndexed(params.text_document.uri));
+        }
     }
     Ok(())
 }

crates/rust-analyzer/src/lsp/ext.rs

@@ -703,3 +703,16 @@ pub struct CompletionImport {
 pub struct ClientCommandOptions {
     pub commands: Vec<String>,
 }
+
+pub enum UnindexedProject {}
+
+impl Notification for UnindexedProject {
+    type Params = UnindexedProjectParams;
+    const METHOD: &'static str = "rust-analyzer/unindexedProject";
+}
+
+#[derive(Deserialize, Serialize, Debug)]
+#[serde(rename_all = "camelCase")]
+pub struct UnindexedProjectParams {
+    pub text_documents: Vec<TextDocumentIdentifier>,
+}

crates/rust-analyzer/src/main_loop.rs

@@ -1,5 +1,6 @@
 //! The main loop of `rust-analyzer` responsible for dispatching LSP
 //! requests/replies and notifications back to the client.
+use crate::lsp::ext;
 use std::{
     fmt,
     time::{Duration, Instant},
@@ -56,6 +57,7 @@ pub fn main_loop(config: Config, connection: Connection) -> anyhow::Result<()> {
 enum Event {
     Lsp(lsp_server::Message),
     Task(Task),
+    QueuedTask(QueuedTask),
     Vfs(vfs::loader::Message),
     Flycheck(flycheck::Message),
 }
@@ -67,13 +69,20 @@ impl fmt::Display for Event {
             Event::Task(_) => write!(f, "Event::Task"),
             Event::Vfs(_) => write!(f, "Event::Vfs"),
             Event::Flycheck(_) => write!(f, "Event::Flycheck"),
+            Event::QueuedTask(_) => write!(f, "Event::QueuedTask"),
         }
     }
 }
 
+#[derive(Debug)]
+pub(crate) enum QueuedTask {
+    CheckIfIndexed(lsp_types::Url),
+}
+
 #[derive(Debug)]
 pub(crate) enum Task {
     Response(lsp_server::Response),
+    ClientNotification(ext::UnindexedProjectParams),
     Retry(lsp_server::Request),
     Diagnostics(Vec<(FileId, Vec<lsp_types::Diagnostic>)>),
     PrimeCaches(PrimeCachesProgress),
@@ -115,6 +124,7 @@ impl fmt::Debug for Event {
         match self {
             Event::Lsp(it) => fmt::Debug::fmt(it, f),
             Event::Task(it) => fmt::Debug::fmt(it, f),
+            Event::QueuedTask(it) => fmt::Debug::fmt(it, f),
             Event::Vfs(it) => fmt::Debug::fmt(it, f),
             Event::Flycheck(it) => fmt::Debug::fmt(it, f),
         }
@@ -193,6 +203,9 @@ impl GlobalState {
             recv(self.task_pool.receiver) -> task =>
                 Some(Event::Task(task.unwrap())),
 
+            recv(self.deferred_task_queue.receiver) -> task =>
+                Some(Event::QueuedTask(task.unwrap())),
+
             recv(self.fmt_pool.receiver) -> task =>
                 Some(Event::Task(task.unwrap())),
 
@@ -211,7 +224,7 @@ impl GlobalState {
             .entered();
 
         let event_dbg_msg = format!("{event:?}");
-        tracing::debug!("{:?} handle_event({})", loop_start, event_dbg_msg);
+        tracing::debug!(?loop_start, ?event, "handle_event");
         if tracing::enabled!(tracing::Level::INFO) {
             let task_queue_len = self.task_pool.handle.len();
             if task_queue_len > 0 {
@@ -226,6 +239,16 @@ impl GlobalState {
                 lsp_server::Message::Notification(not) => self.on_notification(not)?,
                 lsp_server::Message::Response(resp) => self.complete_request(resp),
             },
+            Event::QueuedTask(task) => {
+                let _p =
+                    tracing::span!(tracing::Level::INFO, "GlobalState::handle_event/queued_task")
+                        .entered();
+                self.handle_queued_task(task);
+                // Coalesce multiple task events into one loop turn
+                while let Ok(task) = self.deferred_task_queue.receiver.try_recv() {
+                    self.handle_queued_task(task);
+                }
+            }
             Event::Task(task) => {
                 let _p = tracing::span!(tracing::Level::INFO, "GlobalState::handle_event/task")
                     .entered();
@@ -498,6 +521,9 @@ impl GlobalState {
     fn handle_task(&mut self, prime_caches_progress: &mut Vec<PrimeCachesProgress>, task: Task) {
         match task {
             Task::Response(response) => self.respond(response),
+            Task::ClientNotification(params) => {
+                self.send_notification::<lsp_ext::UnindexedProject>(params)
+            }
             // Only retry requests that haven't been cancelled. Otherwise we do unnecessary work.
             Task::Retry(req) if !self.is_completed(&req) => self.on_request(req),
             Task::Retry(_) => (),
@@ -638,6 +664,31 @@ impl GlobalState {
         }
     }
 
+    fn handle_queued_task(&mut self, task: QueuedTask) {
+        match task {
+            QueuedTask::CheckIfIndexed(uri) => {
+                let snap = self.snapshot();
+
+                self.task_pool.handle.spawn_with_sender(ThreadIntent::Worker, move |sender| {
+                    let _p = tracing::span!(tracing::Level::INFO, "GlobalState::check_if_indexed")
+                        .entered();
+                    tracing::debug!(?uri, "handling uri");
+                    let id = from_proto::file_id(&snap, &uri).expect("unable to get FileId");
+                    if let Ok(crates) = &snap.analysis.crates_for(id) {
+                        if crates.is_empty() {
+                            let params = ext::UnindexedProjectParams {
+                                text_documents: vec![lsp_types::TextDocumentIdentifier { uri }],
+                            };
+                            sender.send(Task::ClientNotification(params)).unwrap();
+                        } else {
+                            tracing::debug!(?uri, "is indexed");
+                        }
+                    }
+                });
+            }
+        }
+    }
+
     fn handle_flycheck_msg(&mut self, message: flycheck::Message) {
         match message {
             flycheck::Message::AddDiagnostic { id, workspace_root, diagnostic } => {

crates/rust-analyzer/src/task_pool.rs

@@ -4,6 +4,8 @@
 use crossbeam_channel::Sender;
 use stdx::thread::{Pool, ThreadIntent};
 
+use crate::main_loop::QueuedTask;
+
 pub(crate) struct TaskPool<T> {
     sender: Sender<T>,
     pool: Pool,
@@ -40,3 +42,12 @@ impl<T> TaskPool<T> {
         self.pool.len()
     }
 }
+
+/// `TaskQueue`, like its name suggests, queues tasks.
+///
+/// This should only be used used if a task must run after [`GlobalState::process_changes`]
+/// has been called.
+pub(crate) struct TaskQueue {
+    pub(crate) sender: crossbeam_channel::Sender<QueuedTask>,
+    pub(crate) receiver: crossbeam_channel::Receiver<QueuedTask>,
+}

crates/rust-analyzer/tests/slow-tests/main.rs

@@ -30,7 +30,7 @@ use lsp_types::{
     PartialResultParams, Position, Range, RenameFilesParams, TextDocumentItem,
     TextDocumentPositionParams, WorkDoneProgressParams,
 };
-use rust_analyzer::lsp::ext::{OnEnter, Runnables, RunnablesParams};
+use rust_analyzer::lsp::ext::{OnEnter, Runnables, RunnablesParams, UnindexedProject};
 use serde_json::json;
 use stdx::format_to_acc;
 use test_utils::skip_slow_tests;
@@ -587,6 +587,66 @@ fn main() {{}}
     );
 }
 
+#[test]
+fn test_opening_a_file_outside_of_indexed_workspace() {
+    if skip_slow_tests() {
+        return;
+    }
+
+    let tmp_dir = TestDir::new();
+    let path = tmp_dir.path();
+
+    let project = json!({
+        "roots": [path],
+        "crates": [ {
+            "root_module": path.join("src/crate_one/lib.rs"),
+            "deps": [],
+            "edition": "2015",
+            "cfg": [ "cfg_atom_1", "feature=\"cfg_1\""],
+        } ]
+    });
+
+    let code = format!(
+        r#"
+//- /rust-project.json
+{project}
+
+//- /src/crate_one/lib.rs
+mod bar;
+
+fn main() {{}}
+"#,
+    );
+
+    let server = Project::with_fixture(&code)
+        .tmp_dir(tmp_dir)
+        .with_config(serde_json::json!({
+            "notifications": {
+                "unindexedProject": true
+            },
+        }))
+        .server()
+        .wait_until_workspace_is_loaded();
+
+    let uri = server.doc_id("src/crate_two/lib.rs").uri;
+    server.notification::<DidOpenTextDocument>(DidOpenTextDocumentParams {
+        text_document: TextDocumentItem {
+            uri: uri.clone(),
+            language_id: "rust".to_string(),
+            version: 0,
+            text: "/// Docs\nfn foo() {}".to_string(),
+        },
+    });
+    let expected = json!({
+        "textDocuments": [
+            {
+                "uri": uri
+            }
+        ]
+    });
+    server.expect_notification::<UnindexedProject>(expected);
+}
+
 #[test]
 fn diagnostics_dont_block_typing() {
     if skip_slow_tests() {

crates/rust-analyzer/tests/slow-tests/support.rs

@@ -9,7 +9,7 @@ use std::{
 use crossbeam_channel::{after, select, Receiver};
 use lsp_server::{Connection, Message, Notification, Request};
 use lsp_types::{notification::Exit, request::Shutdown, TextDocumentIdentifier, Url};
-use rust_analyzer::{config::Config, lsp, main_loop, tracing};
+use rust_analyzer::{config::Config, lsp, main_loop};
 use serde::Serialize;
 use serde_json::{json, to_string_pretty, Value};
 use test_utils::FixtureWithProjectMeta;
@@ -91,7 +91,7 @@ impl Project<'_> {
 
         static INIT: Once = Once::new();
         INIT.call_once(|| {
-            let _ = tracing::Config {
+            let _ = rust_analyzer::tracing::Config {
                 writer: TestWriter::default(),
                 // Deliberately enable all `error` logs if the user has not set RA_LOG, as there is usually
                 // useful information in there for debugging.
@@ -214,6 +214,40 @@ impl Server {
         self.send_notification(r)
     }
 
+    pub(crate) fn expect_notification<N>(&self, expected: Value)
+    where
+        N: lsp_types::notification::Notification,
+        N::Params: Serialize,
+    {
+        while let Some(Message::Notification(actual)) =
+            recv_timeout(&self.client.receiver).unwrap_or_else(|_| panic!("timed out"))
+        {
+            if actual.method == N::METHOD {
+                let actual = actual
+                    .clone()
+                    .extract::<Value>(N::METHOD)
+                    .expect("was not able to extract notification");
+
+                tracing::debug!(?actual, "got notification");
+                if let Some((expected_part, actual_part)) = find_mismatch(&expected, &actual) {
+                    panic!(
+                            "JSON mismatch\nExpected:\n{}\nWas:\n{}\nExpected part:\n{}\nActual part:\n{}\n",
+                            to_string_pretty(&expected).unwrap(),
+                            to_string_pretty(&actual).unwrap(),
+                            to_string_pretty(expected_part).unwrap(),
+                            to_string_pretty(actual_part).unwrap(),
+                        );
+                } else {
+                    tracing::debug!("sucessfully matched notification");
+                    return;
+                }
+            } else {
+                continue;
+            }
+        }
+        panic!("never got expected notification");
+    }
+
     #[track_caller]
     pub(crate) fn request<R>(&self, params: R::Params, expected_resp: Value)
     where

docs/dev/lsp-extensions.md

@@ -1,5 +1,5 @@
 <!---
-lsp/ext.rs hash: c0bf3acd7a9e72b2
+lsp/ext.rs hash: 8be79cc3b7f10ad7
 
 If you need to change the above hash to make the test pass, please check if you
 need to adjust this doc as well and ping this issue:
@@ -445,6 +445,25 @@ Reloads project information (that is, re-executes `cargo metadata`).
 
 Rebuilds build scripts and proc-macros, and runs the build scripts to reseed the build data.
 
+## Unindexed Project
+
+**Experimental Client Capability:** `{ "unindexedProject": boolean }`
+
+**Method:** `rust-analyzer/unindexedProject`
+
+**Notification:**
+
+```typescript
+interface UnindexedProjectParams {
+    /// A list of documents that rust-analyzer has determined are not indexed.
+    textDocuments: lc.TextDocumentIdentifier[]
+}
+```
+
+This notification is sent from the server to the client. The client is expected
+to determine the appropriate owners of `textDocuments` and update `linkedProjects`
+if an owner can be determined successfully.
+
 ## Server Status
 
 **Experimental Client Capability:** `{ "serverStatusNotification": boolean }`

docs/user/generated_config.adoc

@@ -745,6 +745,11 @@ Sets the LRU capacity of the specified queries.
 --
 Whether to show `can't find Cargo.toml` error message.
 --
+[[rust-analyzer.notifications.unindexedProject]]rust-analyzer.notifications.unindexedProject (default: `false`)::
++
+--
+Whether to send an UnindexedProject notification to the client.
+--
 [[rust-analyzer.numThreads]]rust-analyzer.numThreads (default: `null`)::
 +
 --

editors/code/package.json

@@ -1468,6 +1468,11 @@
                     "default": true,
                     "type": "boolean"
                 },
+                "rust-analyzer.notifications.unindexedProject": {
+                    "markdownDescription": "Whether to send an UnindexedProject notification to the client.",
+                    "default": false,
+                    "type": "boolean"
+                },
                 "rust-analyzer.numThreads": {
                     "markdownDescription": "How many worker threads in the main loop. The default `null` means to pick automatically.",
                     "default": null,

editors/code/src/ctx.ts

@@ -234,6 +234,23 @@ export class Ctx implements RustAnalyzerExtensionApi {
                     this.outputChannel!.show();
                 }),
             );
+            this.pushClientCleanup(
+                this._client.onNotification(ra.unindexedProject, async (params) => {
+                    if (this.config.discoverProjectRunner) {
+                        const command = `${this.config.discoverProjectRunner}.discoverWorkspaceCommand`;
+                        log.info(`running command: ${command}`);
+                        const uris = params.textDocuments.map((doc) =>
+                            vscode.Uri.parse(doc.uri, true),
+                        );
+                        const projects: JsonProject[] = await vscode.commands.executeCommand(
+                            command,
+                            uris,
+                        );
+                        this.setWorkspaces(projects);
+                        await this.notifyRustAnalyzer();
+                    }
+                }),
+            );
         }
         return this._client;
     }

editors/code/src/lsp_ext.ts

@@ -220,3 +220,9 @@ export type RecursiveMemoryLayoutNode = {
 export type RecursiveMemoryLayout = {
     nodes: RecursiveMemoryLayoutNode[];
 };
+
+export const unindexedProject = new lc.NotificationType<UnindexedProjectParams>(
+    "rust-analyzer/unindexedProject",
+);
+
+export type UnindexedProjectParams = { textDocuments: lc.TextDocumentIdentifier[] };