Fix @metric_scope for generator and async generator functions (#113)

Co-authored-by: Alin RADU <alinra@amazon.com>

aws_embedded_metrics/metric_scope/__init__.py

@@ -18,35 +18,70 @@
 
 
 def metric_scope(fn):  # type: ignore
+    if inspect.isasyncgenfunction(fn):
+        @wraps(fn)
+        async def async_gen_wrapper(*args, **kwargs):  # type: ignore
+            logger = create_metrics_logger()
+            if "metrics" in inspect.signature(fn).parameters:
+                kwargs["metrics"] = logger
+
+            try:
+                fn_gen = fn(*args, **kwargs)
+                while True:
+                    result = await fn_gen.__anext__()
+                    await logger.flush()
+                    yield result
+            except Exception as ex:
+                await logger.flush()
+                if not isinstance(ex, StopIteration):
+                    raise
+
+        return async_gen_wrapper
+
+    elif inspect.isgeneratorfunction(fn):
+        @wraps(fn)
+        def gen_wrapper(*args, **kwargs):  # type: ignore
+            logger = create_metrics_logger()
+            if "metrics" in inspect.signature(fn).parameters:
+                kwargs["metrics"] = logger
+
+            try:
+                fn_gen = fn(*args, **kwargs)
+                while True:
+                    result = next(fn_gen)
+                    asyncio.run(logger.flush())
+                    yield result
+            except Exception as ex:
+                asyncio.run(logger.flush())
+                if not isinstance(ex, StopIteration):
+                    raise
 
-    if asyncio.iscoroutinefunction(fn):
+        return gen_wrapper
 
+    elif asyncio.iscoroutinefunction(fn):
         @wraps(fn)
-        async def wrapper(*args, **kwargs):  # type: ignore
+        async def async_wrapper(*args, **kwargs):  # type: ignore
             logger = create_metrics_logger()
             if "metrics" in inspect.signature(fn).parameters:
                 kwargs["metrics"] = logger
+
             try:
                 return await fn(*args, **kwargs)
-            except Exception as e:
-                raise e
             finally:
                 await logger.flush()
 
-        return wrapper
-    else:
+        return async_wrapper
 
+    else:
         @wraps(fn)
         def wrapper(*args, **kwargs):  # type: ignore
             logger = create_metrics_logger()
             if "metrics" in inspect.signature(fn).parameters:
                 kwargs["metrics"] = logger
+
             try:
                 return fn(*args, **kwargs)
-            except Exception as e:
-                raise e
             finally:
-                loop = asyncio.get_event_loop()
-                loop.run_until_complete(logger.flush())
+                asyncio.run(logger.flush())
 
         return wrapper

tests/metric_scope/test_metric_scope.py

@@ -168,6 +168,43 @@ def my_handler(metrics):
     actual_timestamp_second = int(round(logger.context.meta["Timestamp"] / 1000))
     assert expected_timestamp_second == actual_timestamp_second
 
+
+def test_sync_scope_iterates_generator(mock_logger):
+    expected_results = [1, 2]
+
+    @metric_scope
+    def my_handler():
+        yield from expected_results
+        raise Exception("test exception")
+
+    actual_results = []
+    with pytest.raises(Exception, match="test exception"):
+        for result in my_handler():
+            actual_results.append(result)
+
+    assert actual_results == expected_results
+    assert InvocationTracker.invocations == 3
+
+
+@pytest.mark.asyncio
+async def test_async_scope_iterates_async_generator(mock_logger):
+    expected_results = [1, 2]
+
+    @metric_scope
+    async def my_handler():
+        for item in expected_results:
+            yield item
+            await asyncio.sleep(1)
+        raise Exception("test exception")
+
+    actual_results = []
+    with pytest.raises(Exception, match="test exception"):
+        async for result in my_handler():
+            actual_results.append(result)
+
+    assert actual_results == expected_results
+    assert InvocationTracker.invocations == 3
+
 # Test helpers