Support dynamic formatting capabilities [un]registration (#14478)

Closes https://github.com/zed-industries/zed/issues/12661

Release Notes:

- Added dynamic [un]registration for LSP formatting capabilities
([#12661](https://github.com/zed-industries/zed/issues/12661))

crates/lsp/src/lsp.rs

@@ -7,7 +7,7 @@ use anyhow::{anyhow, Context, Result};
 use collections::HashMap;
 use futures::{channel::oneshot, io::BufWriter, select, AsyncRead, AsyncWrite, Future, FutureExt};
 use gpui::{AppContext, AsyncAppContext, BackgroundExecutor, Task};
-use parking_lot::Mutex;
+use parking_lot::{Mutex, RwLock};
 use postage::{barrier, prelude::Stream};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use serde_json::{json, value::RawValue, Value};
@@ -24,6 +24,7 @@ use std::{
     ffi::OsString,
     fmt,
     io::Write,
+    ops::DerefMut,
     path::PathBuf,
     pin::Pin,
     sync::{
@@ -69,7 +70,7 @@ pub struct LanguageServer {
     next_id: AtomicI32,
     outbound_tx: channel::Sender<String>,
     name: Arc<str>,
-    capabilities: ServerCapabilities,
+    capabilities: RwLock<ServerCapabilities>,
     code_action_kinds: Option<Vec<CodeActionKind>>,
     notification_handlers: Arc<Mutex<HashMap<&'static str, NotificationHandler>>>,
     response_handlers: Arc<Mutex<Option<HashMap<RequestId, ResponseHandler>>>>,
@@ -640,10 +641,13 @@ impl LanguageServer {
                         ..Default::default()
                     }),
                     formatting: Some(DynamicRegistrationClientCapabilities {
-                        dynamic_registration: None,
+                        dynamic_registration: Some(true),
+                    }),
+                    range_formatting: Some(DynamicRegistrationClientCapabilities {
+                        dynamic_registration: Some(true),
                     }),
                     on_type_formatting: Some(DynamicRegistrationClientCapabilities {
-                        dynamic_registration: None,
+                        dynamic_registration: Some(true),
                     }),
                     signature_help: Some(SignatureHelpClientCapabilities {
                         signature_information: Some(SignatureInformationSettings {
@@ -693,7 +697,7 @@ impl LanguageServer {
             if let Some(info) = response.server_info {
                 self.name = info.name.into();
             }
-            self.capabilities = response.capabilities;
+            self.capabilities = RwLock::new(response.capabilities);
 
             self.notify::<notification::Initialized>(InitializedParams {})?;
             Ok(Arc::new(self))
@@ -908,8 +912,12 @@ impl LanguageServer {
     }
 
     /// Get the reported capabilities of the running language server.
-    pub fn capabilities(&self) -> &ServerCapabilities {
-        &self.capabilities
+    pub fn capabilities(&self) -> ServerCapabilities {
+        self.capabilities.read().clone()
+    }
+
+    pub fn update_capabilities(&self, update: impl FnOnce(&mut ServerCapabilities)) {
+        update(self.capabilities.write().deref_mut());
     }
 
     /// Get the id of the running language server.