fix: Avoid deadlock when nesting configure_scope (#256)

Author: Swatinem

sentry-core/src/hub.rs

@@ -396,11 +396,8 @@ impl Hub {
         F: FnOnce(&mut Scope) -> R,
     {
         with_client_impl! {{
-            let (new_scope, rv) = self.with_current_scope(|scope| {
-                let mut new_scope = (**scope).clone();
-                let rv = f(&mut new_scope);
-                (new_scope, rv)
-            });
+            let mut new_scope = self.with_current_scope(|scope| scope.clone());
+            let rv = f(&mut new_scope);
             self.with_current_scope_mut(|ptr| *ptr = new_scope);
             rv
         }}
@@ -440,7 +437,7 @@ impl Hub {
     }
 
     #[cfg(feature = "client")]
-    pub(crate) fn with_current_scope<F: FnOnce(&Arc<Scope>) -> R, R>(&self, f: F) -> R {
+    pub(crate) fn with_current_scope<F: FnOnce(&Scope) -> R, R>(&self, f: F) -> R {
         self.inner.with(|stack| f(&stack.top().scope))
     }
 

sentry/tests/test_basic.rs

@@ -120,3 +120,22 @@ fn test_factory() {
 
     assert_eq!(events.load(Ordering::SeqCst), 1);
 }
+
+#[test]
+fn test_reentrant_configure_scope() {
+    let events = sentry::test::with_captured_events(|| {
+        sentry::configure_scope(|scope1| {
+            scope1.set_tag("which_scope", "scope1");
+
+            sentry::configure_scope(|scope2| {
+                scope2.set_tag("which_scope", "scope2");
+            });
+        });
+
+        sentry::capture_message("look ma, no deadlock!", sentry::Level::Info);
+    });
+
+    assert_eq!(events.len(), 1);
+    // well, the "outer" `configure_scope` wins
+    assert_eq!(events[0].tags["which_scope"], "scope1");
+}