Clean up SeedService.poll_ready with a 'ref mut'

Co-Authored-By: Henry de Valence <hdevalence@hdevalence.ca>

zebrad/src/commands/seed.rs

@@ -17,8 +17,6 @@ use crate::{config::ZebradConfig, prelude::*};
 /// Whether our `SeedService` is poll_ready or not.
 #[derive(Debug)]
 enum SeederState {
-    // This is kinda gross but ¯\_(ツ)_/¯
-    TempState,
     /// Waiting for the address book to be shared with us via the oneshot channel.
     AwaitingAddressBook(oneshot::Receiver<Arc<Mutex<AddressBook>>>),
     /// Address book received, ready to service requests.
@@ -39,37 +37,27 @@ impl Service<Request> for SeedService {
     fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         debug!("SeedService.state: {:?}", self.state);
 
-        let mut poll_result = Poll::Pending;
-
-        // We want to be able to consume the state, but it's behind a mutable
-        // reference, so we can't move it out of self without swapping in a
-        // placeholder, even if we immediately overwrite the placeholder.
-        let tmp_state = std::mem::replace(&mut self.state, SeederState::TempState);
-
-        self.state = match tmp_state {
-            SeederState::AwaitingAddressBook(mut rx) => match rx.try_recv() {
+        match self.state {
+            SeederState::Ready(_) => return Poll::Ready(Ok(())),
+            SeederState::AwaitingAddressBook(ref mut rx) => match rx.try_recv() {
+                Err(e) => {
+                    error!("SeedService oneshot sender dropped: {:?}", e);
+                    return Poll::Ready(Err(e.into()));
+                }
+                Ok(None) => {
+                    debug!("SeedService got a message with `None` in it. 🤔");
+                    return Poll::Pending;
+                }
                 Ok(Some(address_book)) => {
                     info!(
                         "SeedService received address_book via oneshot {:?}",
                         address_book
                     );
-                    poll_result = Poll::Ready(Ok(()));
-                    SeederState::Ready(address_book)
+                    self.state = SeederState::Ready(address_book);
+                    return Poll::Ready(Ok(()));
                 }
-                // Sets self.state to a new instance of what it
-                // already was; we can't just return `tmp_state`
-                // because we've plucked it apart via `rx` and moved
-                // parts around already in this block.
-                _ => SeederState::AwaitingAddressBook(rx),
             },
-            SeederState::Ready(_) => {
-                poll_result = Poll::Ready(Ok(()));
-                tmp_state
-            }
-            SeederState::TempState => tmp_state,
-        };
-
-        return poll_result;
+        }
     }
 
     fn call(&mut self, req: Request) -> Self::Future {