bun test: a matcher blocked on a promise that never settles fails with the test timeout

src/jsc/event_loop.rs

@@ -1019,20 +1019,31 @@ impl EventLoop {
     /// terminated mid-wait). Nothing is thrown for it; a caller inside a `JsResult`
     /// function crosses explicitly with [`jsc::Stopped::throw`].
     pub fn wait_for_promise(&mut self, promise: jsc::AnyPromise) -> Result<(), jsc::Stopped> {
+        self.wait_for_promise_or_give_up(promise, || false)
+            .map(|_settled| ())
+    }
+
+    /// [`Self::wait_for_promise`] that also returns `Ok(false)` once `give_up`,
+    /// asked before each tick, says so; `Ok(true)` means the promise settled.
+    pub fn wait_for_promise_or_give_up(
+        &mut self,
+        promise: jsc::AnyPromise,
+        mut give_up: impl FnMut() -> bool,
+    ) -> Result<bool, jsc::Stopped> {
         let jsc_vm = self.vm_ref().jsc_vm();
-        if promise.status() != PromiseStatus::Pending {
-            return Ok(());
-        }
         while promise.status() == PromiseStatus::Pending {
             if jsc_vm.execution_forbidden() || !self.vm_ref().script_allowed() {
                 return Err(jsc::Stopped);
             }
+            if give_up() {
+                return Ok(false);
+            }
             self.tick();
             if promise.status() == PromiseStatus::Pending {
                 self.auto_tick();
             }
         }
-        Ok(())
+        Ok(true)
     }
 
     pub fn wakeup(&self) {

src/runtime/test_runner/Execution.rs

@@ -100,6 +100,9 @@ pub struct Execution {
     /// `t.skip()`/`t.todo()` mark lands there before the DoneCallback is
     /// stamped).
     pub(crate) on_stack_entry_data: core::cell::Cell<Option<super::bun_test::EntryData>>,
+    /// `bun_test::WaitingEntry`s on the stack holding `on_stack_entry`'s callback blocked,
+    /// so that while non-zero, JS reaching a matcher is a continuation, not that callback.
+    pub(crate) blocking_matcher_waits: core::cell::Cell<u32>,
 }
 
 pub struct ConcurrentGroup {
@@ -282,6 +285,7 @@ impl Execution {
             group_index: 0,
             on_stack_entry: core::cell::Cell::new(None),
             on_stack_entry_data: core::cell::Cell::new(None),
+            blocking_matcher_waits: core::cell::Cell::new(0),
         }
     }
 

src/runtime/test_runner/bun_test.rs

@@ -1537,6 +1537,100 @@ impl RefData {
     }
 }
 
+/// What ends a matcher's wait for a promise (`.resolves`, `toThrow()` on an async function, an async
+/// `expect.extend` matcher) short of it settling; polled between the wait's ticks, since a promise
+/// that never settles has to fail the entry with its timeout. Attributed the way `expect()` itself is.
+pub(crate) struct WaitingEntry {
+    buntest: BunTestPtr,
+    ends_when: EndsWhen,
+}
+
+/// The first two hold a callback on the stack, which `BunTest::run` (re-entrancy guarded) cannot give
+/// up, so they watch deadlines themselves; the others only notice what the running runner did meanwhile.
+enum EndsWhen {
+    /// The on-stack callback's own code; once the matcher throws, the runner evaluates its overrun as usual.
+    EntryTimedOut(NonNull<ExecutionEntry>),
+    /// The on-stack callback is itself blocked in a matcher, so this is some continuation of the group,
+    /// which one unknown: done once every entry still executing in it has timed out.
+    GroupTimedOut,
+    /// A continuation of this entry: done once [`RefDataValue::entry`] no longer finds it (at once after `Done`).
+    RunnerGaveEntryUp(RefDataValue),
+    /// A continuation of some entry of this concurrent group.
+    GroupOver(usize),
+}
+
+impl WaitingEntry {
+    /// `None` outside a test file's execution phase (plain scripts, preloads, describe callbacks): no timeouts there.
+    pub(crate) fn current() -> Option<Self> {
+        let buntest = clone_active_strong()?;
+        let execution = &buntest.execution;
+        let ends_when = match execution.on_stack_entry.get() {
+            Some(entry) if execution.blocking_matcher_waits.get() == 0 => EndsWhen::EntryTimedOut(entry),
+            Some(_) => EndsWhen::GroupTimedOut,
+            None => match buntest.get_current_state_data() {
+                RefDataValue::Execution { group_index, entry_data: None } => EndsWhen::GroupOver(group_index),
+                RefDataValue::Collection { .. } => return None,
+                data @ (RefDataValue::Execution { entry_data: Some(_), .. }
+                | RefDataValue::Done
+                | RefDataValue::Start) => EndsWhen::RunnerGaveEntryUp(data),
+            },
+        };
+        let waiting = WaitingEntry { buntest, ends_when };
+        if waiting.blocks_callback() {
+            let counter = &waiting.buntest.execution.blocking_matcher_waits;
+            counter.set(counter.get() + 1);
+        }
+        Some(waiting)
+    }
+
+    /// Whether this wait holds `Execution::on_stack_entry`'s callback blocked underneath it.
+    fn blocks_callback(&self) -> bool {
+        matches!(self.ends_when, EndsWhen::EntryTimedOut(_) | EndsWhen::GroupTimedOut)
+    }
+
+    pub(crate) fn timed_out(&self) -> bool {
+        match &self.ends_when {
+            EndsWhen::EntryTimedOut(entry) => {
+                // SAFETY: entries live as long as the BunTest, which `self.buntest` keeps alive.
+                unsafe { entry.as_ref() }.has_timed_out(&Timespec::now_force_real_time())
+            }
+            EndsWhen::GroupTimedOut => {
+                let buntest = self.buntest.get();
+                let now = Timespec::now_force_real_time();
+                let group_timed_out = buntest.execution.active_group_ref().is_none_or(|group| {
+                    group
+                        .sequences(&buntest.execution)
+                        .iter()
+                        .filter(|sequence| sequence.executing)
+                        .all(|sequence| {
+                            sequence
+                                .active_entry
+                                // SAFETY: as above.
+                                .is_some_and(|entry| unsafe { entry.as_ref() }.has_timed_out(&now))
+                        })
+                });
+                if group_timed_out {
+                    // What the timer's `handle_timeout` queues (it may not have fired yet), ahead of the
+                    // failure the matcher's error is about to produce, so the entry reports as timed out.
+                    buntest.add_result(RefDataValue::Start);
+                }
+                group_timed_out
+            }
+            EndsWhen::RunnerGaveEntryUp(data) => data.entry(self.buntest.get()).is_none(),
+            EndsWhen::GroupOver(group_index) => *group_index != self.buntest.execution.group_index,
+        }
+    }
+}
+
+impl Drop for WaitingEntry {
+    fn drop(&mut self) {
+        if self.blocks_callback() {
+            let counter = &self.buntest.execution.blocking_matcher_waits;
+            counter.set(counter.get() - 1);
+        }
+    }
+}
+
 pub struct RunTestsTask {
     pub(crate) weak: BunTestPtrWeak,
     // `GlobalRef` (not a borrow): the JSGlobalObject is stored across the task
@@ -1951,12 +2045,17 @@ impl ExecutionEntry {
         entry
     }
 
+    /// Never true for an entry running without a timeout.
+    pub(crate) fn has_timed_out(&self, now: &Timespec) -> bool {
+        !self.timespec.eql(&Timespec::EPOCH) && self.timespec.order(now) == core::cmp::Ordering::Less
+    }
+
     pub(crate) fn evaluate_timeout(
         &self,
         sequence: &mut Execution::ExecutionSequence,
         now: &Timespec,
     ) -> bool {
-        if !self.timespec.eql(&Timespec::EPOCH) && self.timespec.order(now) == core::cmp::Ordering::Less {
+        if self.has_timed_out(now) {
             // timed out
             // SAFETY: pointer-identity comparison only — no deref, no provenance laundering.
             let is_test_entry = sequence

src/runtime/test_runner/expect.rs

@@ -437,7 +437,7 @@ impl Expect {
         )
     }
 
-    /// Shared failure path for the three `.resolves`/`.rejects` mismatch cases
+    /// Shared failure path for the `.resolves`/`.rejects` failure cases
     /// in `process_promise`. The body template's only markup is `<red>…<r>`
     /// around `received`, so it's applied here; `expected`/`label`/`received`
     /// are emitted verbatim.
@@ -471,6 +471,20 @@ impl Expect {
         }
     }
 
+    /// `VirtualMachine::wait_for_promise` that returns `false` instead once the entry the matcher runs
+    /// in is over ([`bun_test::WaitingEntry`]), so a promise that never settles fails the test instead
+    /// of hanging `bun test`. Throws only for a VM stop.
+    fn wait_for_promise(global_this: &JSGlobalObject, promise: bun_jsc::AnyPromise) -> JsResult<bool> {
+        let waiting_entry = bun_test::WaitingEntry::current();
+        global_this
+            .bun_vm()
+            .event_loop_mut()
+            .wait_for_promise_or_give_up(promise, || {
+                waiting_entry.as_ref().is_some_and(bun_test::WaitingEntry::timed_out)
+            })
+            .map_err(|stopped| stopped.throw(global_this))
+    }
+
     /// Processes the async flags (resolves/rejects), waiting for the async value if needed.
     /// If no flags, returns the original value
     /// If either flag is set, waits for the result, and returns either it as a JSValue, or null if the expectation failed (in which case if silent is false, also throws a js exception)
@@ -489,12 +503,22 @@ impl Expect {
                     let vm = global_this.vm();
                     promise.set_handled(vm);
 
-                    // SAFETY: bun_vm() returns the live thread-local VirtualMachine.
-            global_this
-                .bun_vm()
-                .as_mut()
-                .wait_for_promise(promise)
-                .map_err(|stopped| stopped.throw(global_this))?;
+                    if !Self::wait_for_promise(global_this, promise)? {
+                        if !silent {
+                            let mut formatter = ConsoleObject::Formatter::new(global_this).with_quote_strings(true);
+                            return Err(Self::throw_promise_matcher_error(
+                                global_this, custom_label, matcher_name, matcher_params, flags,
+                                if resolution == Promise::Resolves {
+                                    "Expected promise that resolves"
+                                } else {
+                                    "Expected promise that rejects"
+                                },
+                                "Received promise that was still pending when the test timed out: ",
+                                value.to_fmt(&mut formatter),
+                            ));
+                        }
+                        return Err(JsError::Thrown);
+                    }
 
                     let new_value = promise.result(vm);
                     match promise.status() {
@@ -897,9 +921,13 @@ impl Expect {
         }
 
         if let Some(promise) = return_value.as_any_promise() {
-            let waited = vm.wait_for_promise(promise);
+            let settled = Self::wait_for_promise(global_this, promise);
             scope.apply(vm);
-            waited.map_err(|stopped| stopped.throw(global_this))?;
+            if !settled? {
+                return Err(global_this.throw(format_args!(
+                    "Received function returned a promise that was still pending when the test timed out"
+                )));
+            }
             match promise.unwrap(global_this.vm(), js_promise::UnwrapMode::MarkHandled) {
                 js_promise::Unwrapped::Fulfilled(_) => {
                     return Ok((None, return_value_from_function));
@@ -1491,12 +1519,12 @@ impl Expect {
             let vm = global_this.vm();
             promise.set_handled(vm);
 
-            // SAFETY: bun_vm() returns the live thread-local VirtualMachine.
-            global_this
-                .bun_vm()
-                .as_mut()
-                .wait_for_promise(promise)
-                .map_err(|stopped| stopped.throw(global_this))?;
+            if !Self::wait_for_promise(global_this, promise)? {
+                return Err(global_this.throw(format_args!(
+                    "Matcher `{}` returned a promise that was still pending when the test timed out",
+                    matcher_name,
+                )));
+            }
 
             result = promise.result(vm);
             result.ensure_still_alive();