feat: deprecate async_enabled replication argument removed server-side

The `asyncEnabled` field was removed from the Weaviate server schema in
v1.38. The client still accepted `async_enabled` and forwarded it, so the
server silently dropped it and the user's intent was lost without any
indication (issue #2047).

Following the existing precedent for `max_workers` /
`alive_nodes_checking_frequency` (Dep029), the `async_enabled` argument in
`Configure.replication` / `Reconfigure.replication` now emits a
`DeprecationWarning` (Dep030) when passed, while remaining functional
against older servers. Docstrings are updated to document the removal.

Closes #2047

Author: LijuanTang94

test/collection/test_config.py

@@ -3041,6 +3041,29 @@ def test_replication_config_update_merge_with_missing_async_config() -> None:
     assert result["factor"] == 3
 
 
+@pytest.mark.parametrize(
+    "config_factory",
+    [Configure.replication, Reconfigure.replication],
+)
+def test_replication_async_enabled_emits_deprecation_warning(config_factory: object) -> None:
+    """`async_enabled` was removed from the server schema in v1.38 and must warn when passed."""
+    with pytest.warns(DeprecationWarning, match="Dep030"):
+        config_factory(async_enabled=True)  # type: ignore[operator]
+
+
+@pytest.mark.parametrize(
+    "config_factory",
+    [Configure.replication, Reconfigure.replication],
+)
+def test_replication_without_async_enabled_does_not_warn(config_factory: object) -> None:
+    """Omitting `async_enabled` must not emit the deprecation warning."""
+    import warnings
+
+    with warnings.catch_warnings():
+        warnings.simplefilter("error", DeprecationWarning)
+        config_factory(factor=3)  # type: ignore[operator]
+
+
 def test_nested_property_with_id_name_is_allowed() -> None:
     """A nested property named 'id' must not raise — only top-level 'id' is reserved."""
     prop = Property(

weaviate/collections/classes/config.py

@@ -2791,14 +2791,20 @@ def replication(
     ) -> _ReplicationConfigCreate:
         """Create a `ReplicationConfigCreate` object to be used when defining the replication configuration of Weaviate.
 
-        NOTE: `async_enabled` is only available with WeaviateDB `>=v1.26.0`
+        Note:
+            `async_enabled` was removed from the Weaviate server schema in v1.38. Passing it
+            has no effect against any server `>=v1.38` (the server silently drops it and runs
+            async replication by default for any class with a replication factor > 1) and emits
+            a ``DeprecationWarning``. The argument will be removed in a future release.
 
         Args:
             factor: The replication factor.
             async_enabled: Enabled async replication.
             deletion_strategy: How conflicts between different nodes about deleted objects are resolved.
-            async_config: The configuration for async replication. This is only relevant if `async_enabled` is `True`.
+            async_config: The configuration for async replication.
         """
+        if async_enabled is not None:
+            _Warnings.async_enabled_field_removed_server_side()
         return _ReplicationConfigCreate(
             factor=factor,
             asyncEnabled=async_enabled,
@@ -3071,12 +3077,20 @@ def replication(
 
         Use this method when defining the `replication_config` argument in `collection.update()`.
 
+        Note:
+            `async_enabled` was removed from the Weaviate server schema in v1.38. Passing it
+            has no effect against any server `>=v1.38` (the server silently drops it and runs
+            async replication by default for any class with a replication factor > 1) and emits
+            a ``DeprecationWarning``. The argument will be removed in a future release.
+
         Args:
             factor: The replication factor.
             async_enabled: Enable async replication.
             deletion_strategy: How conflicts between different nodes about deleted objects are resolved.
-            async_config: The async replication configuration. This is only applicable if `async_enabled` is set to `True`.
+            async_config: The async replication configuration.
         """
+        if async_enabled is not None:
+            _Warnings.async_enabled_field_removed_server_side()
         return _ReplicationConfigUpdate(
             factor=factor,
             asyncEnabled=async_enabled,

weaviate/warnings.py

@@ -261,6 +261,17 @@ def async_replication_field_removed_server_side(argument: str) -> None:
             stacklevel=1,
         )
 
+    @staticmethod
+    def async_enabled_field_removed_server_side() -> None:
+        warnings.warn(
+            message="""Dep030: The `async_enabled` argument in `Configure.replication` / `Reconfigure.replication` is deprecated.
+            The `asyncEnabled` field was removed from the Weaviate server schema in v1.38 and is silently ignored by newer servers,
+            where async replication runs by default for any class with a replication factor > 1.
+            The argument has no effect against any server >= 1.38 and will be removed in a future release.""",
+            category=DeprecationWarning,
+            stacklevel=1,
+        )
+
     @staticmethod
     def datetime_insertion_with_no_specified_timezone(date: datetime) -> None:
         warnings.warn(