Restore cancellation token behavior (#11693)

Ensure that cancelling an RPC call does not result in an automatic rejection
on the calling side. Instead the token is passed to the receiving side and
handled there. This restores the cancellation strategy that was used with the
old json-rpc architecture (prior to 1.28).

Contributed on behalf of STMicroelectronics.

packages/core/src/common/message-rpc/rpc-protocol.ts

@@ -132,23 +132,23 @@ export class RpcProtocol {
         // The last element of the request args might be a cancellation token. As these tokens are not serializable we have to remove it from the
         // args array and the `CANCELLATION_TOKEN_KEY` string instead.
         const cancellationToken: CancellationToken | undefined = args.length && CancellationToken.is(args[args.length - 1]) ? args.pop() : undefined;
-        if (cancellationToken && cancellationToken.isCancellationRequested) {
-            return Promise.reject(this.cancelError());
-        }
 
         if (cancellationToken) {
             args.push(RpcProtocol.CANCELLATION_TOKEN_KEY);
-            cancellationToken.onCancellationRequested(() => {
-                this.sendCancel(id);
-                this.pendingRequests.get(id)?.reject(this.cancelError());
-            }
-            );
         }
+
         this.pendingRequests.set(id, reply);
 
         const output = this.channel.getWriteBuffer();
         this.encoder.request(output, id, method, args);
         output.commit();
+
+        if (cancellationToken?.isCancellationRequested) {
+            this.sendCancel(id);
+        } else {
+            cancellationToken?.onCancellationRequested(() => this.sendCancel(id));
+        }
+
         return reply.promise;
     }
 
@@ -164,12 +164,6 @@ export class RpcProtocol {
         output.commit();
     }
 
-    cancelError(): Error {
-        const error = new Error('"Request has already been canceled by the sender"');
-        error.name = 'Cancel';
-        return error;
-    }
-
     protected handleCancel(id: number): void {
         const cancellationTokenSource = this.cancellationTokenSources.get(id);
         if (cancellationTokenSource) {