Merge pull request NOAA-OWP#130 from aaraney/re-fix-runtime-error-in-…

…restclient

Fix NOAA-OWP#99: "RuntimeError: This event loop is already running" in colab and notebook. Re-PR of NOAA-OWP#100

python/_restclient/setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = hydrotools._restclient
-version = 3.0.3
+version = 3.0.4
 author = Austin Raney
 author_email = [email protected]
 description = General REST api client with built in request caching and retries.

python/_restclient/src/hydrotools/_restclient/_restclient.py

@@ -288,6 +288,11 @@ def headers(self) -> dict:
 
     def close(self) -> None:
         """ Release aiohttp.ClientSession """
+         # Session never instantiated, thus cannot be closed
+        session = getattr(self, "_session", None)
+        if session is None:
+            return
+
         if not self._session.closed:
             if not self._loop.is_closed():
                 self._add_to_loop(self._session.close())

python/_restclient/src/hydrotools/_restclient/async_helpers.py

@@ -19,7 +19,24 @@ def __init__(
 
     def _add_to_loop(self, coro: Coroutine):
         """ Add coro to event loop via run_until_complete """
-        return self._loop.run_until_complete(coro)
+        try:
+            return self._loop.run_until_complete(coro)
+
+        except RuntimeError as e:
+            try:
+                # `RuntimeError: This event loop is already running` thrown by jupyter notebook
+                # See hydrotools #99 for context and notebook #3397 for detail
+                import nest_asyncio
+
+                nest_asyncio.apply()
+
+                return self._loop.run_until_complete(coro)
+            except ModuleNotFoundError:
+                error_message = (
+                    "nest_asycnio package not found. Install using `pip install nest_asycnio`.\n"
+                    "See https://github.com/NOAA-OWP/hydrotools/issues/99 for more detail."
+                )
+                raise ModuleNotFoundError(error_message) from e
 
     def _wrap_func_in_coro(self, func: Callable, *args, **kwargs):
         """ Create partial func; wrap and call partial in coro; return coro """

python/_restclient/tests/test_restclient.py

@@ -150,3 +150,37 @@ def test_build_url(loop):
 
         assert client.build_url(base_url) == base_url
         assert client.build_url(base_url, query_params) == f"{base_url}?key=value"
+
+
+class ModuleFoundError(Exception):
+    ...
+
+
+def test_restclient_nest_asyncio_ModuleNotFoundError(loop):
+    """Test for #99. Ensure ModuleNotFoundError raised if `nest_asyncio` not installed"""
+    import asyncio
+    import warnings
+
+    # verify `nest_asyncio` is not installed
+    try:
+        import nest_asyncio
+
+        error_message = "nest_asyncio installed. Cannot complete test."
+        raise ModuleFoundError(error_message)
+    except ModuleNotFoundError:
+        # this should occur, so continue
+        pass
+
+    async def test():
+        await asyncio.sleep(0.01)
+
+        with warnings.catch_warnings():
+            # ignore coroutine not awaited warning for output sake.
+            # This is not the purpose of this test
+            warnings.simplefilter("ignore", category=RuntimeWarning)
+            with pytest.raises(ModuleNotFoundError):
+                # implicitly verify that `nest_asyncio` is not installed
+                # this test will need to change if `nest_asyncio` becomes a requirement
+                RestClient(enable_cache=False)
+
+    loop.run_until_complete(test())