Copy async_lru for Python 3.7 compatibility

tests/external/test_open.py

@@ -0,0 +1,39 @@
+import pytest
+from great_ai.external.async_lru import alru_cache
+
+pytestmark = pytest.mark.asyncio
+
+
+async def test_alru_cache_open(check_lru, loop):
+    @alru_cache()
+    async def coro(val):
+        return val
+
+    await coro(1)
+
+    check_lru(coro, hits=0, misses=1, cache=1, tasks=0)
+
+    with pytest.raises(RuntimeError):
+        coro.open()
+
+    close = coro.close()
+
+    assert coro.closed
+
+    with pytest.raises(RuntimeError):
+        await coro()
+
+    with pytest.raises(RuntimeError):
+        coro.open()
+
+    await close
+
+    check_lru(coro, hits=0, misses=0, cache=0, tasks=0)
+
+    coro.open()
+
+    ret = await coro(1)
+
+    assert ret == 1
+
+    check_lru(coro, hits=0, misses=1, cache=1, tasks=0)