fix(diagnostics): run upon change, with a hack for throttling

README.md

@@ -37,13 +37,8 @@ Language Server Protocol implementation for nushell
 - [x] [textDocument/didChange](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_didChange),
       [textDocument/didClose](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_didClose),
       and [textDocument/didOpen](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_didOpen)
+- [x] [textDocument/publishDiagnostics](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_publishDiagnostics) -> `nu --ide-check`
 - [ ] [textDocument/inlayHint](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_inlayHint) -> `nu --ide-check`
-- [ ] [textDocument/publishDiagnostics](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_publishDiagnostics) -> `nu --ide-check`
-
-  - [x] triggered once per [textDocument/didOpen](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_synchronization)
-  - [ ] triggered every [textDocument/didChange](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_didChange)
-  - [ ] debounced/throttled to avoid performance issues
-
 - [ ] [textDocument/diagnostic](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_pullDiagnostics) -> `nu --ide-check`
 - [ ] [textDocument/formatting](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_formatting) -> [`nufmt`](https://github.com/nushell/nufmt)
 - [ ] [workspace/configuration](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#workspace_configuration)

src/backend/language_server.rs

@@ -14,12 +14,17 @@ use tower_lsp::LanguageServer;
 #[tower_lsp::async_trait]
 impl LanguageServer for Backend {
     async fn did_change(&self, params: DidChangeTextDocumentParams) {
+        let uri = params.text_document.uri.clone();
         if let Err(e) = self.try_did_change(params) {
             self.client
                 .log_message(MessageType::ERROR, format!("{e:?}"))
                 .await;
         }
-        // TODO: trigger debounced `nu --ide-check`
+        if let Err(e) = self.throttled_validate_document(&uri).await {
+            self.client
+                .log_message(MessageType::ERROR, format!("{e:?}"))
+                .await;
+        };
     }
 
     async fn did_change_workspace_folders(&self, params: DidChangeWorkspaceFoldersParams) {
@@ -49,7 +54,6 @@ impl LanguageServer for Backend {
                 .log_message(MessageType::ERROR, format!("{e:?}"))
                 .await;
         }
-        // TODO: trigger debounced `nu --ide-check` instead
         if let Err(e) = self.validate_document(&uri).await {
             self.client
                 .log_message(MessageType::ERROR, format!("{e:?}"))

src/backend/mod.rs

@@ -1,4 +1,5 @@
 use std::sync::OnceLock;
+use std::time::{Duration, Instant};
 use std::{ffi::OsStr, sync::RwLock};
 
 pub(crate) mod language_server;
@@ -21,6 +22,7 @@ pub(crate) struct Backend {
     client: Client,
     documents: RwLock<TextDocuments>,
     ide_settings: RwLock<IdeSettings>,
+    last_validated: RwLock<Instant>,
 }
 
 impl Backend {
@@ -53,9 +55,31 @@ impl Backend {
             client,
             documents: RwLock::new(TextDocuments::new()),
             ide_settings: RwLock::new(IdeSettings::default()),
+            last_validated: RwLock::new(Instant::now()),
         }
     }
 
+    async fn throttled_validate_document(&self, uri: &Url) -> Result<()> {
+        // TODO: this is a quick imperfect hack, but eventually we probably want a thorough solution using threads/channels?
+        // TODO: ensure that we validate at least once after the most recent throttling (i.e. debounce instead of throttle)
+        let then = {
+            *self.last_validated.read().map_err(|e| {
+                map_err_to_internal_error(&e, format!("cannot read throttling marker: {e:?}"))
+            })?
+        };
+        if then.elapsed() < Duration::from_millis(500) {
+            return Ok(());
+        }
+
+        self.validate_document(uri).await?;
+
+        let mut then = self.last_validated.write().map_err(|e| {
+            map_err_to_internal_error(&e, format!("cannot write throttling marker: {e:?}"))
+        })?;
+        *then = Instant::now();
+        Ok(())
+    }
+
     fn try_did_change(&self, params: DidChangeTextDocumentParams) -> Result<()> {
         let mut documents = self.documents.write().map_err(|e| {
             map_err_to_internal_error(&e, format!("cannot write to document cache: {e:?}"))