1 files changed, 45 insertions, 0 deletions
diff --git a/third_party/python/aiohttp/aiohttp/locks.py b/third_party/python/aiohttp/aiohttp/locks.py
new file mode 100644
index 0000000000..ce5b9c6f73
--- /dev/null
+++ b/third_party/python/aiohttp/aiohttp/locks.py
@@ -0,0 +1,45 @@
+import asyncio
+import collections
+from typing import Any, Optional
+
+try:
+    from typing import Deque
+except ImportError:
+    from typing_extensions import Deque
+
+
+class EventResultOrError:
+    """
+    This class wrappers the Event asyncio lock allowing either awake the
+    locked Tasks without any error or raising an exception.
+
+    thanks to @vorpalsmith for the simple design.
+    """
+
+    def __init__(self, loop: asyncio.AbstractEventLoop) -> None:
+        self._loop = loop
+        self._exc = None  # type: Optional[BaseException]
+        self._event = asyncio.Event()
+        self._waiters = collections.deque()  # type: Deque[asyncio.Future[Any]]
+
+    def set(self, exc: Optional[BaseException] = None) -> None:
+        self._exc = exc
+        self._event.set()
+
+    async def wait(self) -> Any:
+        waiter = self._loop.create_task(self._event.wait())
+        self._waiters.append(waiter)
+        try:
+            val = await waiter
+        finally:
+            self._waiters.remove(waiter)
+
+        if self._exc is not None:
+            raise self._exc
+
+        return val
+
+    def cancel(self) -> None:
+        """ Cancel all waiters """
+        for waiter in self._waiters:
+            waiter.cancel()