chore: remove println from tests (#5015)

This patch removes println statements from tests. Some of these were
used to test that types implement `fmt::Debug`. These println statements
have been replaced with an equivalent test that does not output to
STDOUT. The rest of the println statements are most likely left over
from debugging sessions.

tokio/src/runtime/tests/task_combinations.rs

@@ -1,3 +1,4 @@
+use std::fmt;
 use std::future::Future;
 use std::panic;
 use std::pin::Pin;
@@ -149,6 +150,8 @@ fn test_combinations() {
     }
 }
 
+fn is_debug<T: fmt::Debug>(_: &T) {}
+
 #[allow(clippy::too_many_arguments)]
 fn test_combination(
     rt: CombiRuntime,
@@ -184,7 +187,15 @@ fn test_combination(
         return;
     }
 
-    println!("Runtime {:?}, LocalSet {:?}, Task {:?}, Output {:?}, JoinInterest {:?}, JoinHandle {:?}, AbortHandle {:?}, Abort {:?} ({:?})", rt, ls, task, output, ji, jh, ah, abort, abort_src);
+    is_debug(&rt);
+    is_debug(&ls);
+    is_debug(&task);
+    is_debug(&output);
+    is_debug(&ji);
+    is_debug(&jh);
+    is_debug(&ah);
+    is_debug(&abort);
+    is_debug(&abort_src);
 
     // A runtime optionally with a LocalSet
     struct Rt {

tokio/tests/rt_handle_block_on.rs

@@ -505,39 +505,30 @@ where
     F: Fn(),
 {
     {
-        println!("current thread runtime");
-
         let rt = new_current_thread();
         let _enter = rt.enter();
         f();
 
-        println!("current thread runtime after shutdown");
         rt.shutdown_timeout(Duration::from_secs(1000));
         f();
     }
 
     #[cfg(not(tokio_wasi))]
     {
-        println!("multi thread (1 thread) runtime");
-
         let rt = new_multi_thread(1);
         let _enter = rt.enter();
         f();
 
-        println!("multi thread runtime after shutdown");
         rt.shutdown_timeout(Duration::from_secs(1000));
         f();
     }
 
     #[cfg(not(tokio_wasi))]
     {
-        println!("multi thread (4 threads) runtime");
-
         let rt = new_multi_thread(4);
         let _enter = rt.enter();
         f();
 
-        println!("multi thread runtime after shutdown");
         rt.shutdown_timeout(Duration::from_secs(1000));
         f();
     }

tokio/tests/rt_threaded.rs

@@ -480,9 +480,7 @@ fn wake_during_shutdown() {
         fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
             let me = Pin::into_inner(self);
             let mut lock = me.shared.lock().unwrap();
-            println!("poll {}", me.put_waker);
             if me.put_waker {
-                println!("putting");
                 lock.waker = Some(cx.waker().clone());
             }
             Poll::Pending
@@ -491,13 +489,11 @@ fn wake_during_shutdown() {
 
     impl Drop for MyFuture {
         fn drop(&mut self) {
-            println!("drop {} start", self.put_waker);
             let mut lock = self.shared.lock().unwrap();
             if !self.put_waker {
                 lock.waker.take().unwrap().wake();
             }
             drop(lock);
-            println!("drop {} stop", self.put_waker);
         }
     }
 

tokio/tests/sync_mpsc.rs

@@ -15,6 +15,7 @@ use tokio::sync::mpsc::{self, channel};
 use tokio::sync::oneshot;
 use tokio_test::*;
 
+use std::fmt;
 use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering::{Acquire, Release};
 use std::sync::Arc;
@@ -220,9 +221,9 @@ async fn no_t_bounds_buffer() {
     let (tx, mut rx) = mpsc::channel(100);
 
     // sender should be Debug even though T isn't Debug
-    println!("{:?}", tx);
+    is_debug(&tx);
     // same with Receiver
-    println!("{:?}", rx);
+    is_debug(&rx);
     // and sender should be Clone even though T isn't Clone
     assert!(tx.clone().try_send(NoImpls).is_ok());
 
@@ -236,9 +237,9 @@ async fn no_t_bounds_unbounded() {
     let (tx, mut rx) = mpsc::unbounded_channel();
 
     // sender should be Debug even though T isn't Debug
-    println!("{:?}", tx);
+    is_debug(&tx);
     // same with Receiver
-    println!("{:?}", rx);
+    is_debug(&rx);
     // and sender should be Clone even though T isn't Clone
     assert!(tx.clone().send(NoImpls).is_ok());
 
@@ -940,3 +941,5 @@ async fn test_tx_capacity() {
     assert_eq!(tx.capacity(), 8);
     assert_eq!(tx.max_capacity(), 10);
 }
+
+fn is_debug<T: fmt::Debug>(_: &T) {}

tokio/tests/task_abort.rs

@@ -26,10 +26,7 @@ fn test_abort_without_panic_3157() {
         .unwrap();
 
     rt.block_on(async move {
-        let handle = tokio::spawn(async move {
+        let handle = tokio::spawn(async move { tokio::time::sleep(Duration::new(100, 0)).await });
-            println!("task started");
-            tokio::time::sleep(Duration::new(100, 0)).await
-        });
 
         // wait for task to sleep.
         tokio::time::sleep(Duration::from_millis(10)).await;
@@ -159,7 +156,6 @@ fn test_abort_wakes_task_3964() {
         let handle = tokio::spawn(async move {
             // Make sure the Arc is moved into the task
             let _notify_dropped = notify_dropped;
-            println!("task started");
             tokio::time::sleep(Duration::new(100, 0)).await
         });
 
@@ -187,7 +183,6 @@ fn test_abort_task_that_panics_on_drop_contained() {
         let handle = tokio::spawn(async move {
             // Make sure the Arc is moved into the task
             let _panic_dropped = PanicOnDrop;
-            println!("task started");
             tokio::time::sleep(Duration::new(100, 0)).await
         });
 
@@ -211,7 +206,6 @@ fn test_abort_task_that_panics_on_drop_returned() {
         let handle = tokio::spawn(async move {
             // Make sure the Arc is moved into the task
             let _panic_dropped = PanicOnDrop;
-            println!("task started");
             tokio::time::sleep(Duration::new(100, 0)).await
         });
 

tokio/tests/task_local_set.rs

@@ -284,14 +284,12 @@ fn join_local_future_elsewhere() {
     local.block_on(&rt, async move {
         let (tx, rx) = oneshot::channel();
         let join = task::spawn_local(async move {
-            println!("hello world running...");
             assert!(
                 ON_RT_THREAD.with(|cell| cell.get()),
                 "local task must run on local thread, no matter where it is awaited"
             );
             rx.await.unwrap();
 
-            println!("hello world task done");
             "hello world"
         });
         let join2 = task::spawn(async move {
@@ -301,11 +299,8 @@ fn join_local_future_elsewhere() {
             );
 
             tx.send(()).expect("task shouldn't have ended yet");
-            println!("waking up hello world...");
 
             join.await.expect("task should complete successfully");
-
-            println!("hello world task joined");
         });
         join2.await.unwrap()
     });
@@ -395,9 +390,7 @@ fn with_timeout(timeout: Duration, f: impl FnOnce() + Send + 'static) {
         ),
         // Did the test thread panic? We'll find out for sure when we `join`
         // with it.
-        Err(RecvTimeoutError::Disconnected) => {
+        Err(RecvTimeoutError::Disconnected) => {}
-            println!("done_rx dropped, did the test thread panic?");
-        }
         // Test completed successfully!
         Ok(()) => {}
     }
@@ -510,7 +503,6 @@ async fn local_tasks_are_polled_after_tick_inner() {
                 time::sleep(Duration::from_millis(20)).await;
                 let rx1 = RX1.load(SeqCst);
                 let rx2 = RX2.load(SeqCst);
-                println!("EXPECT = {}; RX1 = {}; RX2 = {}", EXPECTED, rx1, rx2);
                 assert_eq!(EXPECTED, rx1);
                 assert_eq!(EXPECTED, rx2);
             });

tokio/tests/time_sleep.rs

@@ -189,10 +189,7 @@ async fn greater_than_max() {
 
 #[tokio::test]
 async fn short_sleeps() {
-    for i in 0..10000 {
+    for _ in 0..10000 {
-        if (i % 10) == 0 {
-            eprintln!("=== {}", i);
-        }
         tokio::time::sleep(std::time::Duration::from_millis(0)).await;
     }
 }

tokio/tests/uds_datagram.rs

@@ -29,9 +29,7 @@ async fn echo() -> io::Result<()> {
     let server_socket = UnixDatagram::bind(server_path.clone())?;
 
     tokio::spawn(async move {
-        if let Err(e) = echo_server(server_socket).await {
+        let _ = echo_server(server_socket).await;
-            eprintln!("Error in echo server: {}", e);
-        }
     });
 
     {
@@ -55,9 +53,7 @@ async fn echo_from() -> io::Result<()> {
     let server_socket = UnixDatagram::bind(server_path.clone())?;
 
     tokio::spawn(async move {
-        if let Err(e) = echo_server(server_socket).await {
+        let _ = echo_server(server_socket).await;
-            eprintln!("Error in echo server: {}", e);
-        }
     });
 
     {