src/lib.rs

@@ -100,8 +100,12 @@ fn with_control<T>(
 /// idle session is replaced and logged in again. Nothing inside a transfer or
 /// mutation retries, because its missing reply may hide a completed change.
 fn ready() -> Result<(), ErrorCode> {
-  if with_control(|control| control.expect("NOOP")).is_ok() {
-    return Ok(());
+  if !CONTROL.with_borrow(Option::is_none) {
+    match with_control(|control| control.expect("NOOP")) {
+      Ok(_) => return Ok(()),
+      Err(ErrorCode::Unavailable) => {}
+      Err(error) => return Err(error),
+    }
   }
   let session = SESSION
     .with_borrow(Clone::clone)

src/session_tests.rs

@@ -58,3 +58,20 @@ async fn recovery_before_a_mutation_never_replays_a_lost_mutation_reply()
   assert_eq!(summary.mkdir_commands, 1);
   Ok(())
 }
+
+#[tokio::test]
+async fn cancelled_preflight_never_reconnects_or_executes_the_mutation()
+-> TestResult {
+  let fixture = test_host::install(test_host::Scenario::CancelledPreflight);
+  guest(Ftp::open("ftp".into(), config()))?;
+  assert!(matches!(
+    Ftp::mkdir(Locator::Path("/cancelled".into())),
+    Err(ErrorCode::Cancelled)
+  ));
+  Ftp::close();
+  let summary = fixture.summary();
+  assert_eq!(summary.control_connections, 1);
+  assert_eq!(summary.listings, 0);
+  assert_eq!(summary.mkdir_commands, 0);
+  Ok(())
+}

src/test_host.rs

@@ -13,6 +13,7 @@ const LISTING: &[u8] = b"type=file;size=3;  report.md \r\n";
 
 #[derive(Clone, Copy)]
 pub enum Scenario {
+  CancelledPreflight,
   ExpiredListing,
   LostMutationReply,
 }
@@ -142,6 +143,9 @@ impl Tcp {
           state.listings += 1;
           "150 Listing\r\n226 Complete\r\n"
         }
+        "NOOP" if matches!(state.scenario, Scenario::CancelledPreflight) => {
+          return Err(HostError::Cancelled);
+        }
         "NOOP"
           if index == 0
             && (matches!(state.scenario, Scenario::LostMutationReply)
@@ -157,6 +161,13 @@ impl Tcp {
           state.mkdir_commands += 1;
           return Ok(bytes.len() as u32);
         }
+        "MKD /cancelled"
+          if index == 1
+            && matches!(state.scenario, Scenario::CancelledPreflight) =>
+        {
+          state.mkdir_commands += 1;
+          return Err(HostError::Unavailable);
+        }
         _ => return Err(HostError::InvalidInput),
       }
     };