lsp: Add support for clangd's inactiveRegions extension (#26146)

Closes #13089 

Here we use `experimental` to advertise our support for
`inactiveRegions`. Note that clangd does not currently have a stable
release that reads the `experimental` object (PR
https://github.com/llvm/llvm-project/pull/116531), this can be tested
with one of clangd's recent "unstable snapshots" in their
[releases](https://github.com/clangd/clangd/releases).

Release Notes:

- Added support for clangd's `inactiveRegions` extension.

![Screen Recording 2025-03-05 at 22 39
58](https://github.com/user-attachments/assets/ceade8bd-4d8e-43c3-9520-ad44efa50d2f)

---------

Co-authored-by: Peter Tripp <peter@zed.dev>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/project/src/lsp_store/rust_analyzer_ext.rs

@@ -0,0 +1,83 @@
+use ::serde::{Deserialize, Serialize};
+use gpui::{PromptLevel, WeakEntity};
+use lsp::LanguageServer;
+
+use crate::{LanguageServerPromptRequest, LspStore, LspStoreEvent};
+
+pub const RUST_ANALYZER_NAME: &str = "rust-analyzer";
+
+/// Experimental: Informs the end user about the state of the server
+///
+/// [Rust Analyzer Specification](https://github.com/rust-lang/rust-analyzer/blob/master/docs/dev/lsp-extensions.md#server-status)
+#[derive(Debug)]
+enum ServerStatus {}
+
+/// Other(String) variant to handle unknown values due to this still being experimental
+#[derive(Debug, PartialEq, Deserialize, Serialize, Clone)]
+#[serde(rename_all = "camelCase")]
+enum ServerHealthStatus {
+    Ok,
+    Warning,
+    Error,
+    Other(String),
+}
+
+#[derive(Debug, PartialEq, Deserialize, Serialize, Clone)]
+#[serde(rename_all = "camelCase")]
+struct ServerStatusParams {
+    pub health: ServerHealthStatus,
+    pub message: Option<String>,
+}
+
+impl lsp::notification::Notification for ServerStatus {
+    type Params = ServerStatusParams;
+    const METHOD: &'static str = "experimental/serverStatus";
+}
+
+pub fn register_notifications(lsp_store: WeakEntity<LspStore>, language_server: &LanguageServer) {
+    let name = language_server.name();
+    let server_id = language_server.server_id();
+
+    let this = lsp_store;
+
+    language_server
+        .on_notification::<ServerStatus, _>({
+            let name = name.to_string();
+            move |params, mut cx| {
+                let this = this.clone();
+                let name = name.to_string();
+                if let Some(ref message) = params.message {
+                    let message = message.trim();
+                    if !message.is_empty() {
+                        let formatted_message = format!(
+                            "Language server {name} (id {server_id}) status update: {message}"
+                        );
+                        match params.health {
+                            ServerHealthStatus::Ok => log::info!("{}", formatted_message),
+                            ServerHealthStatus::Warning => log::warn!("{}", formatted_message),
+                            ServerHealthStatus::Error => {
+                                log::error!("{}", formatted_message);
+                                let (tx, _rx) = smol::channel::bounded(1);
+                                let request = LanguageServerPromptRequest {
+                                    level: PromptLevel::Critical,
+                                    message: params.message.unwrap_or_default(),
+                                    actions: Vec::new(),
+                                    response_channel: tx,
+                                    lsp_name: name.clone(),
+                                };
+                                let _ = this
+                                    .update(&mut cx, |_, cx| {
+                                        cx.emit(LspStoreEvent::LanguageServerPrompt(request));
+                                    })
+                                    .ok();
+                            }
+                            ServerHealthStatus::Other(status) => {
+                                log::info!("Unknown server health: {status}\n{formatted_message}")
+                            }
+                        }
+                    }
+                }
+            }
+        })
+        .detach();
+}