fix: Every workspace should have a proc-macro server

crates/proc-macro-api/src/lib.rs

@@ -87,6 +87,7 @@ pub struct ProcMacroClient {
     /// That means that concurrent salsa requests may block each other when expanding proc macros,
     /// which is unfortunate, but simple and good enough for the time being.
     pool: Arc<ProcMacroServerPool>,
+    /// The path to the proc-macro server binary.
     path: AbsPathBuf,
 }
 

crates/rust-analyzer/src/global_state.rs

@@ -105,8 +105,13 @@ pub(crate) struct GlobalState {
     pub(crate) shutdown_requested: bool,
     pub(crate) last_reported_status: lsp_ext::ServerStatusParams,
 
-    // proc macros
+    /// Clients of the proc-macro server.
+    ///
+    /// One client per workspace, in the same order as `self.workspaces`. We don't store
+    /// the client in `self.workspaces` so that we can reload workspaces without
+    /// restarting the proc-macro server.
     pub(crate) proc_macro_clients: Arc<[Option<anyhow::Result<ProcMacroClient>>]>,
+
     pub(crate) build_deps_changed: bool,
 
     // Flycheck

crates/rust-analyzer/src/reload.rs

@@ -659,7 +659,7 @@ impl GlobalState {
             Config::user_config_dir_path().as_deref(),
         );
 
-        if (self.proc_macro_clients.is_empty() || !same_workspaces)
+        if (self.proc_macro_clients.len() < self.workspaces.len() || !same_workspaces)
             && self.config.expand_proc_macros()
         {
             info!("Spawning proc-macro servers");