fix: select db in cluster mode causes unhandled errors (#1311)

Closes #1310

Author: luin

lib/redis/event_handler.ts

@@ -54,7 +54,11 @@ export function connectHandler(self) {
     }
 
     if (self.condition.select) {
-      self.select(self.condition.select);
+      self.select(self.condition.select).catch((err) => {
+        // If the node is in cluster mode, select is disallowed.
+        // In this case, reconnect won't help.
+        self.silentEmit("error", err);
+      });
     }
 
     if (!self.options.enableReadyCheck) {

test/functional/connection.ts

@@ -531,4 +531,22 @@ describe("disconnection", function () {
       done();
     });
   });
+
+  it("emits an error if select is not allowed", function (done) {
+    const errMessage = "select is not allowed";
+    const node = new MockServer(30001, function (argv) {
+      if (argv[0] === "select") {
+        return new Error(errMessage);
+      }
+    });
+    const redis = new Redis({ port: 30001, db: 2 });
+    redis.on("error", (err) => {
+      if (err.message === errMessage) {
+        redis.disconnect();
+        node.disconnect(() => {
+          done();
+        });
+      }
+    });
+  });
 });