Fix leaking test contexts

I was unable to run the collab tests locally because I would run out of
file descriptors.

From some digging it turned out that tokio allocates a new file
descriptor to do work on the CurrentThread using KQUEUE.

We create a new tokio Runtime with each database connection, and these
database connections were being retained by the Client, which is
retained by the Context.

Cleaning up our leaked contexts fixes the problem (though does make me
wonder if a different approach might be preferrable).

crates/collab/src/tests/test_server.rs

@@ -746,9 +746,9 @@ impl TestClient {
         let window = cx.update(|cx| cx.active_window().unwrap().downcast::<Workspace>().unwrap());
 
         let view = window.root_view(cx).unwrap();
-        let cx = Box::new(VisualTestContext::from_window(*window.deref(), cx));
+        let cx = VisualTestContext::from_window(*window.deref(), cx).as_mut();
         // it might be nice to try and cleanup these at the end of each test.
-        (view, Box::leak(cx))
+        (view, cx)
     }
 }
 

crates/gpui/src/app/test_context.rs

@@ -7,7 +7,7 @@ use crate::{
 };
 use anyhow::{anyhow, bail};
 use futures::{Stream, StreamExt};
-use std::{future::Future, ops::Deref, rc::Rc, sync::Arc, time::Duration};
+use std::{cell::RefCell, future::Future, ops::Deref, rc::Rc, sync::Arc, time::Duration};
 
 /// A TestAppContext is provided to tests created with `#[gpui::test]`, it provides
 /// an implementation of `Context` with additional methods that are useful in tests.
@@ -24,6 +24,7 @@ pub struct TestAppContext {
     test_platform: Rc<TestPlatform>,
     text_system: Arc<TextSystem>,
     fn_name: Option<&'static str>,
+    on_quit: Rc<RefCell<Vec<Box<dyn FnOnce() + 'static>>>>,
 }
 
 impl Context for TestAppContext {
@@ -101,6 +102,7 @@ impl TestAppContext {
             test_platform: platform,
             text_system,
             fn_name,
+            on_quit: Rc::new(RefCell::new(Vec::default())),
         }
     }
 
@@ -119,11 +121,18 @@ impl TestAppContext {
         Self::new(self.dispatcher.clone(), self.fn_name)
     }
 
-    /// Simulates quitting the app.
+    /// Called by the test helper to end the test.
+    /// public so the macro can call it.
     pub fn quit(&self) {
+        self.on_quit.borrow_mut().drain(..).for_each(|f| f());
         self.app.borrow_mut().shutdown();
     }
 
+    /// Register cleanup to run when the test ends.
+    pub fn on_quit(&mut self, f: impl FnOnce() + 'static) {
+        self.on_quit.borrow_mut().push(Box::new(f));
+    }
+
     /// Schedules all windows to be redrawn on the next effect cycle.
     pub fn refresh(&mut self) -> Result<()> {
         let mut app = self.app.borrow_mut();
@@ -169,10 +178,9 @@ impl TestAppContext {
         let mut cx = self.app.borrow_mut();
         let window = cx.open_window(WindowOptions::default(), |cx| cx.new_view(|_| ()));
         drop(cx);
-        let cx = Box::new(VisualTestContext::from_window(*window.deref(), self));
+        let cx = VisualTestContext::from_window(*window.deref(), self).as_mut();
         cx.run_until_parked();
-        // it might be nice to try and cleanup these at the end of each test.
-        Box::leak(cx)
+        cx
     }
 
     /// Adds a new window, and returns its root view and a `VisualTestContext` which can be used
@@ -187,10 +195,11 @@ impl TestAppContext {
         let window = cx.open_window(WindowOptions::default(), |cx| cx.new_view(build_window));
         drop(cx);
         let view = window.root_view(self).unwrap();
-        let cx = Box::new(VisualTestContext::from_window(*window.deref(), self));
+        let cx = VisualTestContext::from_window(*window.deref(), self).as_mut();
         cx.run_until_parked();
+
         // it might be nice to try and cleanup these at the end of each test.
-        (view, Box::leak(cx))
+        (view, cx)
     }
 
     /// returns the TextSystem
@@ -695,6 +704,22 @@ impl<'a> VisualTestContext {
             false
         }
     }
+
+    // This returns a mutable reference to the test context (which is usually
+    // what you want when testing).
+    // A side-effect of calling this method is that the context will be retained until the
+    // end of the test (which is usually not a problem).
+    pub fn as_mut(self) -> &'static mut Self {
+        let ptr = Box::into_raw(Box::new(self));
+        // safety: on_quit will be called after the test has finished.
+        // the executor will ensure that all tasks related to the test have stopped.
+        // so there is no way for cx to be accessed after on_quit is called.
+        let cx = Box::leak(unsafe { Box::from_raw(ptr) });
+        cx.on_quit(move || unsafe {
+            drop(Box::from_raw(ptr));
+        });
+        cx
+    }
 }
 
 impl Context for VisualTestContext {