Auto merge of #78227 - SergioBenitez:test-stdout-threading, r=m-ou-se

Capture output from threads spawned in tests

This is revival of #75172.

Original text:
> Fixes #42474.
>
> r? `@​dtolnay` since you expressed interest in this, but feel free to redirect if you aren't the right person anymore.

---

Closes #75172.

7 files changed, 127 insertions, 2 deletions

diff --git a/src/test/ui/panic-while-printing.rs b/src/test/ui/panic-while-printing.rs
index 7e9fa16b084..21fc12759f8 100644
--- a/src/test/ui/panic-while-printing.rs
+++ b/src/test/ui/panic-while-printing.rs
@@ -5,7 +5,7 @@
 
 use std::fmt;
 use std::fmt::{Display, Formatter};
-use std::io::set_panic;
+use std::io::{self, set_panic, LocalOutput, Write};
 
 pub struct A;
 
@@ -15,8 +15,23 @@ impl Display for A {
     }
 }
 
+struct Sink;
+impl Write for Sink {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        Ok(buf.len())
+    }
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+impl LocalOutput for Sink {
+    fn clone_box(&self) -> Box<dyn LocalOutput> {
+        Box::new(Sink)
+    }
+}
+
 fn main() {
-    set_panic(Some(Box::new(Vec::new())));
+    set_panic(Some(Box::new(Sink)));
     assert!(std::panic::catch_unwind(|| {
         eprintln!("{}", A);
     })
diff --git a/src/test/ui/test-thread-capture.rs b/src/test/ui/test-thread-capture.rs
new file mode 100644
index 00000000000..6bec48cd816
--- /dev/null
+++ b/src/test/ui/test-thread-capture.rs
@@ -0,0 +1,31 @@
+// compile-flags: --test
+// run-fail
+// run-flags: --test-threads=1
+// check-run-results
+// exec-env:RUST_BACKTRACE=0
+// ignore-emscripten no threads support
+
+#[test]
+fn thready_pass() {
+    println!("fee");
+    std::thread::spawn(|| {
+        println!("fie");
+        println!("foe");
+    })
+    .join()
+    .unwrap();
+    println!("fum");
+}
+
+#[test]
+fn thready_fail() {
+    println!("fee");
+    std::thread::spawn(|| {
+        println!("fie");
+        println!("foe");
+    })
+    .join()
+    .unwrap();
+    println!("fum");
+    panic!();
+}
diff --git a/src/test/ui/test-thread-capture.run.stdout b/src/test/ui/test-thread-capture.run.stdout
new file mode 100644
index 00000000000..1102aadab02
--- /dev/null
+++ b/src/test/ui/test-thread-capture.run.stdout
@@ -0,0 +1,21 @@
+
+running 2 tests
+test thready_fail ... FAILED
+test thready_pass ... ok
+
+failures:
+
+---- thready_fail stdout ----
+fee
+fie
+foe
+fum
+thread 'main' panicked at 'explicit panic', $DIR/test-thread-capture.rs:30:5
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+
+
+failures:
+    thready_fail
+
+test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
+
diff --git a/src/test/ui/test-thread-nocapture.rs b/src/test/ui/test-thread-nocapture.rs
new file mode 100644
index 00000000000..82df6e77cb1
--- /dev/null
+++ b/src/test/ui/test-thread-nocapture.rs
@@ -0,0 +1,31 @@
+// compile-flags: --test
+// run-fail
+// run-flags: --test-threads=1 --nocapture
+// check-run-results
+// exec-env:RUST_BACKTRACE=0
+// ignore-emscripten no threads support
+
+#[test]
+fn thready_pass() {
+    println!("fee");
+    std::thread::spawn(|| {
+        println!("fie");
+        println!("foe");
+    })
+    .join()
+    .unwrap();
+    println!("fum");
+}
+
+#[test]
+fn thready_fail() {
+    println!("fee");
+    std::thread::spawn(|| {
+        println!("fie");
+        println!("foe");
+    })
+    .join()
+    .unwrap();
+    println!("fum");
+    panic!();
+}
diff --git a/src/test/ui/test-thread-nocapture.run.stderr b/src/test/ui/test-thread-nocapture.run.stderr
new file mode 100644
index 00000000000..98bd96d0abe
--- /dev/null
+++ b/src/test/ui/test-thread-nocapture.run.stderr
@@ -0,0 +1,2 @@
+thread 'main' panicked at 'explicit panic', $DIR/test-thread-nocapture.rs:30:5
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
diff --git a/src/test/ui/test-thread-nocapture.run.stdout b/src/test/ui/test-thread-nocapture.run.stdout
new file mode 100644
index 00000000000..77b42ed88d6
--- /dev/null
+++ b/src/test/ui/test-thread-nocapture.run.stdout
@@ -0,0 +1,20 @@
+
+running 2 tests
+test thready_fail ... fee
+fie
+foe
+fum
+FAILED
+test thready_pass ... fee
+fie
+foe
+fum
+ok
+
+failures:
+
+failures:
+    thready_fail
+
+test result: FAILED. 1 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
+
diff --git a/src/test/ui/threads-sendsync/task-stderr.rs b/src/test/ui/threads-sendsync/task-stderr.rs
index d474084bf20..bc4bedac196 100644
--- a/src/test/ui/threads-sendsync/task-stderr.rs
+++ b/src/test/ui/threads-sendsync/task-stderr.rs
@@ -16,6 +16,11 @@ impl Write for Sink {
     }
     fn flush(&mut self) -> io::Result<()> { Ok(()) }
 }
+impl io::LocalOutput for Sink {
+    fn clone_box(&self) -> Box<dyn io::LocalOutput> {
+        Box::new(Sink(self.0.clone()))
+    }
+}
 
 fn main() {
     let data = Arc::new(Mutex::new(Vec::new()));