chore(lsp/tests): diagnostic synchronization (reland) (#19270)

Merge on approval as it fixes the flaky test.

1 files changed, 15 insertions, 3 deletions

diff --git a/cli/lsp/mod.rs b/cli/lsp/mod.rs
index 0d5552519..d13c90089 100644
--- a/cli/lsp/mod.rs
+++ b/cli/lsp/mod.rs
@@ -8,6 +8,8 @@ use crate::lsp::language_server::LanguageServer;
 pub use repl::ReplCompletionItem;
 pub use repl::ReplLanguageServer;
 
+use self::diagnostics::should_send_diagnostic_batch_index_notifications;
+
 mod analysis;
 mod cache;
 mod capabilities;
@@ -36,7 +38,7 @@ pub async fn start() -> Result<(), AnyError> {
   let stdin = tokio::io::stdin();
   let stdout = tokio::io::stdout();
 
-  let (service, socket) = LspService::build(|client| {
+  let builder = LspService::build(|client| {
     language_server::LanguageServer::new(client::Client::from_tower(client))
   })
   .custom_method(lsp_custom::CACHE_REQUEST, LanguageServer::cache_request)
@@ -58,8 +60,18 @@ pub async fn start() -> Result<(), AnyError> {
     lsp_custom::VIRTUAL_TEXT_DOCUMENT,
     LanguageServer::virtual_text_document,
   )
-  .custom_method(lsp_custom::INLAY_HINT, LanguageServer::inlay_hint)
-  .finish();
+  .custom_method(lsp_custom::INLAY_HINT, LanguageServer::inlay_hint);
+
+  let builder = if should_send_diagnostic_batch_index_notifications() {
+    builder.custom_method(
+      lsp_custom::LATEST_DIAGNOSTIC_BATCH_INDEX,
+      LanguageServer::latest_diagnostic_batch_index_request,
+    )
+  } else {
+    builder
+  };
+
+  let (service, socket) = builder.finish();
 
   Server::new(stdin, stdout, socket).serve(service).await;