fix: Log and no-op instead of raising when start() is called on a closed client

Every other LaunchDarkly server SDK (sync Python, Go, .NET, Node, Ruby)
degrades lifecycle misuse to a logged no-op rather than throwing. Match
that: start() on a closed AsyncLDClient logs a warning and returns.

Author: jsonbailey

ldclient/async_client.py

@@ -108,13 +108,15 @@ def __init__(self, config: AsyncConfig):
     async def start(self, start_wait: float = 5.0) -> None:
         """Start the client: create the HTTP session, data system, and event processor.
 
-        Safe to call multiple times — subsequent calls are no-ops.
+        Safe to call multiple times — subsequent calls are no-ops. Calling start()
+        after close() logs a warning and does nothing; the client stays closed.
 
         :param start_wait: seconds to wait for the data source to initialize
         """
         async with self._lifecycle_lock:
             if self._closed:
-                raise RuntimeError("Cannot start a closed AsyncLDClient")
+                log.warning("start() called on a closed AsyncLDClient; ignoring")
+                return
             if self._started:
                 return
 

ldclient/testing/test_async_client.py

@@ -353,13 +353,14 @@ async def after_evaluation(self, series_context, data, detail):
 
 
 @pytest.mark.asyncio
-async def test_start_after_close_raises():
-    """Calling start() after close() raises RuntimeError."""
+async def test_start_after_close_is_noop():
+    """Calling start() after close() logs a warning and does nothing; the client stays closed."""
     client = AsyncLDClient(_offline_config())
     await client.start()
     await client.close()
-    with pytest.raises(RuntimeError):
-        await client.start()
+    # Does not raise; the client remains closed.
+    await client.start()
+    assert client._closed is True
 
 
 @pytest.mark.asyncio