Only allow one proc-macro process

crates/rust-analyzer/src/reload.rs

@@ -269,6 +269,7 @@ impl GlobalState {
         let project_folders =
             ProjectFolders::new(&workspaces, &files_config.exclude, workspace_build_data.as_ref());
 
+        if self.proc_macro_client.is_none() {
             self.proc_macro_client = match self.config.proc_macro_srv() {
                 None => None,
                 Some((path, args)) => match ProcMacroClient::extern_process(path.clone(), args) {
@@ -283,6 +284,7 @@ impl GlobalState {
                     }
                 },
             };
+        }
 
         let watch = match files_config.watcher {
             FilesWatcher::Client => vec![],