Add an error if "use_batch_trials" is passed to AxClient (#2355)

Summary:
Pull Request resolved: #2355

This is a follow up to #2301

The user was trying to use batch trials, but we don't currently expose this via AxClient we want to add an error to let users know this isn't really having any affect.

Reviewed By: saitcakmak

Differential Revision: D56048665

fbshipit-source-id: 7dff08492e5cf52ab71579d9dcaac24beded4ff9

Author: mgarrard

ax/service/ax_client.py

@@ -1707,6 +1707,14 @@ def _set_generation_strategy(
         if any.
         """
         choose_generation_strategy_kwargs = choose_generation_strategy_kwargs or {}
+        if (
+            "use_batch_trials" in choose_generation_strategy_kwargs
+            and type(self) is AxClient
+        ):
+            raise UnsupportedError(
+                "AxClient API does not support batch trials yet."
+                " We plan to add this support in coming versions."
+            )
         random_seed = choose_generation_strategy_kwargs.pop(
             "random_seed", self._random_seed
         )

ax/telemetry/tests/test_ax_client.py

@@ -11,6 +11,7 @@
 import numpy as np
 
 from ax.core.types import TParamValue
+from ax.exceptions.core import UnsupportedError
 from ax.service.ax_client import AxClient, ObjectiveProperties
 from ax.telemetry.ax_client import AxClientCompletedRecord, AxClientCreatedRecord
 from ax.telemetry.experiment import ExperimentCompletedRecord, ExperimentCreatedRecord
@@ -130,6 +131,25 @@ def test_ax_client_completed_record_from_ax_client(self) -> None:
         )
         self._compare_axclient_completed_records(record, expected)
 
+    def test_batch_trial_warning(self) -> None:
+        ax_client = AxClient()
+        error_msg = (
+            "AxClient API does not support batch trials yet."
+            " We plan to add this support in coming versions."
+        )
+        with self.assertRaisesRegex(UnsupportedError, error_msg):
+            ax_client.create_experiment(
+                name="test_experiment",
+                parameters=[
+                    {"name": "x", "type": "range", "bounds": [-5.0, 10.0]},
+                ],
+                objectives={"branin": ObjectiveProperties(minimize=True)},
+                is_test=True,
+                choose_generation_strategy_kwargs={
+                    "use_batch_trials": True,
+                },
+            )
+
     def _compare_axclient_completed_records(
         self, record: AxClientCompletedRecord, expected: AxClientCompletedRecord
     ) -> None: