Update libtest for single-threaded emscripten support

src/libtest/lib.rs

@@ -1182,26 +1182,63 @@ fn flush(&mut self) -> io::Result<()> {
             }
         }
 
-        thread::spawn(move || {
-            let data = Arc::new(Mutex::new(Vec::new()));
-            let data2 = data.clone();
-            let cfg = thread::Builder::new().name(match desc.name {
-                DynTestName(ref name) => name.clone(),
-                StaticTestName(name) => name.to_owned(),
+        // If the platform is single-threaded we're just going to run
+        // the test synchronously, regardless of the concurrency
+        // level.
+        let supports_threads = !cfg!(target_os = "emscripten");
+
+        // Buffer for capturing standard I/O
+        let data = Arc::new(Mutex::new(Vec::new()));
+        let data2 = data.clone();
+
+        if supports_threads {
+            thread::spawn(move || {
+                let cfg = thread::Builder::new().name(match desc.name {
+                    DynTestName(ref name) => name.clone(),
+                    StaticTestName(name) => name.to_owned(),
+                });
+
+                let result_guard = cfg.spawn(move || {
+                    if !nocapture {
+                        io::set_print(box Sink(data2.clone()));
+                        io::set_panic(box Sink(data2));
+                    }
+                    testfn()
+                })
+                    .unwrap();
+                let test_result = calc_result(&desc, result_guard.join());
+                let stdout = data.lock().unwrap().to_vec();
+                monitor_ch.send((desc.clone(), test_result, stdout)).unwrap();
             });
+        } else {
+            let oldio = if !nocapture {
+                Some((
+                    io::set_print(box Sink(data2.clone())),
+                    io::set_panic(box Sink(data2))
+                ))
+            } else {
+                None
+            };
+
+            use std::panic::{catch_unwind, AssertUnwindSafe};
 
-            let result_guard = cfg.spawn(move || {
-                                      if !nocapture {
-                                          io::set_print(box Sink(data2.clone()));
-                                          io::set_panic(box Sink(data2));
-                                      }
-                                      testfn()
-                                  })
-                                  .unwrap();
-            let test_result = calc_result(&desc, result_guard.join());
+            let result = catch_unwind(AssertUnwindSafe(|| {
+                testfn()
+            }));
+
+            if let Some((printio, panicio)) = oldio {
+                if let Some(printio) = printio {
+                    io::set_print(printio);
+                }
+                if let Some(panicio) = panicio {
+                    io::set_panic(panicio);
+                }
+            };
+
+            let test_result = calc_result(&desc, result);
             let stdout = data.lock().unwrap().to_vec();
             monitor_ch.send((desc.clone(), test_result, stdout)).unwrap();
-        });
+        }
     }
 
     match testfn {