From 1b08f203ea446391e3836ac213e3a715762acd23 Mon Sep 17 00:00:00 2001
From: Justin Spahr-Summers <justin@anthropic.com>
Date: Thu, 14 Nov 2024 14:02:51 +0000
Subject: [PATCH] Catch errors that occur when a handler is invoked, but before
 it returns a Promise

---
 src/shared/protocol.ts | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/src/shared/protocol.ts b/src/shared/protocol.ts
index 752d2cc0..ab8421bf 100644
--- a/src/shared/protocol.ts
+++ b/src/shared/protocol.ts
@@ -190,11 +190,14 @@ export abstract class Protocol<
       return;
     }
 
-    handler(notification).catch((error) =>
-      this._onerror(
-        new Error(`Uncaught error in notification handler: ${error}`),
-      ),
-    );
+    // Starting with Promise.resolve() puts any synchronous errors into the monad as well.
+    Promise.resolve()
+      .then(() => handler(notification))
+      .catch((error) =>
+        this._onerror(
+          new Error(`Uncaught error in notification handler: ${error}`),
+        ),
+      );
   }
 
   private _onrequest(request: JSONRPCRequest): void {
@@ -222,7 +225,9 @@ export abstract class Protocol<
     const abortController = new AbortController();
     this._requestHandlerAbortControllers.set(request.id, abortController);
 
-    handler(request, { signal: abortController.signal })
+    // Starting with Promise.resolve() puts any synchronous errors into the monad as well.
+    Promise.resolve()
+      .then(() => handler(request, { signal: abortController.signal }))
       .then(
         (result) => {
           if (abortController.signal.aborted) {