Don't silently set a generation strategy on load (#2937)

Summary: Pull Request resolved: #2937

Reviewed By: Cesar-Cardoso

Differential Revision: D64786290

ax/service/ax_client.py

@@ -50,6 +50,7 @@
     OptimizationShouldStop,
     UnsupportedError,
     UnsupportedPlotError,
+    UserInputError,
 )
 from ax.exceptions.generation_strategy import MaxParallelismReachedException
 from ax.global_stopping.strategies.base import BaseGlobalStoppingStrategy
@@ -1118,6 +1119,11 @@ def load_experiment_from_database(
         )
         logger.info(f"Loaded {experiment}.")
         if generation_strategy is None:
+            if choose_generation_strategy_kwargs is None:
+                raise UserInputError(
+                    f"No generation strategy was found for {experiment}. Please "
+                    "pass `choose_generation_strategy_kwargs` to load it with one."
+                )
             self._set_generation_strategy(
                 choose_generation_strategy_kwargs=choose_generation_strategy_kwargs
             )

ax/service/tests/test_ax_client.py

@@ -69,13 +69,17 @@
 from ax.storage.sqa_store.db import init_test_engine_and_session_factory
 from ax.storage.sqa_store.decoder import Decoder
 from ax.storage.sqa_store.encoder import Encoder
+from ax.storage.sqa_store.save import save_experiment
 from ax.storage.sqa_store.sqa_config import SQAConfig
 from ax.storage.sqa_store.structs import DBSettings
 from ax.utils.common.random import with_rng_seed
 from ax.utils.common.testutils import TestCase
 from ax.utils.common.typeutils import checked_cast, not_none
 from ax.utils.measurement.synthetic_functions import Branin
-from ax.utils.testing.core_stubs import DummyEarlyStoppingStrategy
+from ax.utils.testing.core_stubs import (
+    DummyEarlyStoppingStrategy,
+    get_branin_experiment,
+)
 from ax.utils.testing.mock import fast_botorch_optimize
 from ax.utils.testing.modeling_stubs import get_observation1, get_observation1trans
 from botorch.test_functions.multi_objective import BraninCurrin
@@ -625,6 +629,26 @@ def test_save_and_load_generation_strategy(self) -> None:
         second_client.load_experiment_from_database("unique_test_experiment")
         self.assertEqual(second_client.generation_strategy, generation_strategy)
 
+    def test_save_and_load_no_generation_strategy(self) -> None:
+        init_test_engine_and_session_factory(force_init=True)
+        config = SQAConfig()
+        encoder = Encoder(config=config)
+        decoder = Decoder(config=config)
+        db_settings = DBSettings(encoder=encoder, decoder=decoder)
+        experiment = get_branin_experiment(named=True)
+        save_experiment(experiment=experiment, config=config)
+        client = AxClient(db_settings=db_settings)
+        with self.assertRaisesRegex(
+            UserInputError, "choose_generation_strategy_kwargs"
+        ):
+            client.load_experiment_from_database(experiment.name)
+
+        client = AxClient(db_settings=db_settings)
+        client.load_experiment_from_database(
+            experiment_name=experiment.name, choose_generation_strategy_kwargs={}
+        )
+        self.assertIsNotNone(client.generation_strategy)
+
     @patch(
         f"{AxClient.__module__}.AxClient._save_experiment_to_db_if_possible",
         side_effect=Exception("patched db exception"),