feat(async): integrate nest-asyncio for running async tools in event loops

- Added nest-asyncio as a dependency to allow calling async tools from within a running event loop.
- Updated the Tool class to apply nest-asyncio when the event loop is already running.
- Enhanced syncify utility to raise an ImportError if nest-asyncio is not installed when needed.
- Added a new test case to verify async tool calls from a running event loop.

This change improves compatibility with environments like Jupyter notebooks where event loops are already active.

Signed-off-by: TomuHirata <tomu.hirata@gmail.com>

Author: TomeHirata

dspy/adapters/types/tool.py

@@ -168,6 +168,17 @@ def _run_async_in_sync(self, coroutine):
         except RuntimeError:
             return asyncio.run(coroutine)
 
+        if loop and loop.is_running():
+            try:
+                import nest_asyncio
+
+                nest_asyncio.apply()
+            except ImportError:
+                raise ImportError(
+                    "nest_asyncio is required to call async tools from within a running event loop. "
+                    "Install it with: pip install nest-asyncio"
+                )
+
         return loop.run_until_complete(coroutine)
 
     @with_callbacks

dspy/utils/syncify.py

@@ -14,10 +14,15 @@ def run_async(coro):
         loop = None
 
     if loop and loop.is_running():
-        # If we're in a running event loop (e.g., Jupyter), use asyncio.create_task and run until done
-        import nest_asyncio
-
-        nest_asyncio.apply()
+        try:
+            import nest_asyncio
+
+            nest_asyncio.apply()
+        except ImportError:
+            raise ImportError(
+                "nest_asyncio is required to call async functions from within a running event loop. "
+                "Install it with: pip install nest-asyncio"
+            )
         return asyncio.get_event_loop().run_until_complete(coro)
     else:
         return asyncio.run(coro)

pyproject.toml

@@ -57,6 +57,7 @@ dev = [
     "build>=1.0.3",
     "litellm>=1.64.0; sys_platform == 'win32' or python_version == '3.14'",
     "litellm[proxy]>=1.64.0; sys_platform != 'win32' and python_version < '3.14'",  # Remove 3.14 condition once uvloop supports
+    "nest-asyncio>=1.6.0",
 ]
 test_extras = [
     "mcp; python_version >= '3.10'",

tests/adapters/test_tool.py

@@ -393,6 +393,16 @@ def test_async_tool_call_in_sync_mode():
         assert result == "hello 1"
 
 
+@pytest.mark.asyncio
+@pytest.mark.filterwarnings("ignore::DeprecationWarning:pytest_asyncio")
+async def test_async_tool_call_from_running_event_loop():
+    tool = Tool(async_dummy_function)
+
+    with dspy.context(allow_tool_async_sync_conversion=True):
+        result = tool(x=42, y="test")
+        assert result == "test 42"
+
+
 TOOL_CALL_TEST_CASES = [
     ([], {"tool_calls": []}),
     (
@@ -542,8 +552,6 @@ def test_tool_convert_input_schema_to_tool_args_lang_chain():
     }
 
 
-
-
 def test_tool_call_execute():
     def get_weather(city: str) -> str:
         return f"The weather in {city} is sunny"