Return an error when db.connect() is called multiple times (#2576)

lib/src/api/err/mod.rs

@@ -33,6 +33,10 @@ pub enum Error {
 	#[error("Connection uninitialised")]
 	ConnectionUninitialised,
 
+	/// Tried to call `connect` on an instance already connected
+	#[error("Already connected")]
+	AlreadyConnected,
+
 	/// `Query::bind` not called with an object nor a key/value tuple
 	#[error("Invalid bindings: {0}")]
 	InvalidBindings(Value),

lib/src/api/mod.rs

@@ -103,15 +103,18 @@ where
 
 	fn into_future(self) -> Self::IntoFuture {
 		Box::pin(async move {
+			// Avoid establising another connection if already connected
+			if self.router.get().is_some() {
+				return Err(Error::AlreadyConnected.into());
+			}
 			let arc = Client::connect(self.address?, self.capacity).await?.router;
 			let cell = Arc::into_inner(arc).expect("new connection to have no references");
 			let router = cell.into_inner().expect("router to be set");
-			if self.router.set(router).is_ok() {
+			self.router.set(router).map_err(|_| Error::AlreadyConnected)?;
 			let client = Surreal {
 				router: self.router,
 			};
 			client.check_server_version().await?;
-			}
 			Ok(())
 		})
 	}