[FSTORE-433] Add support for event_time as single item list for compatibility purpose (#860)

* Add support for event_time as single item list for compatibility purpose

* Add deprecation warning

Author: vatj

python/hsfs/feature_group.py

@@ -647,8 +647,27 @@ def event_time(self):
         return self._event_time
 
     @event_time.setter
-    def event_time(self, feature_name):
-        self._event_time = feature_name
+    def event_time(self, feature_name: Optional[str]):
+        if feature_name is None:
+            self._event_time = None
+            return
+        elif isinstance(feature_name, str):
+            self._event_time = feature_name
+            return
+        elif isinstance(feature_name, list) and len(feature_name) == 1:
+            if isinstance(feature_name[0], str):
+                warnings.warn(
+                    "Providing event_time as a single-element list is deprecated"
+                    + " and will be dropped in future versions. Provide the feature_name string instead.",
+                    DeprecationWarning,
+                    stacklevel=2,
+                )
+                self._event_time = feature_name[0]
+                return
+
+        raise ValueError(
+            "event_time must be a string corresponding to an existing feature name of the Feature Group."
+        )
 
     @property
     def location(self):
@@ -742,7 +761,7 @@ def __init__(
 
         self._avro_schema = None
         self._online_topic_name = online_topic_name
-        self._event_time = event_time
+        self.event_time = event_time
         self._stream = stream
         self._deltastreamer_jobconf = None
 

python/tests/test_feature_group.py

@@ -16,13 +16,18 @@
 
 
 from hsfs import (
+    feature_store,
     feature_group,
     user,
     statistics_config,
     feature,
     storage_connector,
     expectation_suite,
+    util,
 )
+from hsfs.client.exceptions import FeatureStoreException
+import pytest
+import warnings
 
 
 class TestFeatureGroup:
@@ -220,6 +225,35 @@ def test_from_response_json_stream_basic_info(self, backend_fixtures):
         assert fg.stream is True
         assert fg.expectation_suite is None
 
+    def test_constructor_with_list_event_time_for_compatibility(
+        self, mocker, backend_fixtures, dataframe_fixture_basic
+    ):
+        # Arrange
+        mocker.patch("hsfs.client.get_instance")
+        mocker.patch("hsfs.engine.get_type")
+        json = backend_fixtures["feature_store"]["get"]["response"]
+
+        # Act
+        fs = feature_store.FeatureStore.from_response_json(json)
+        with warnings.catch_warnings(record=True) as warning_record:
+            new_fg = fs.create_feature_group(
+                name="fg_name",
+                version=1,
+                description="fg_description",
+                event_time=["event_date"],
+            )
+        with pytest.raises(FeatureStoreException):
+            util.verify_attribute_key_names(new_fg, False)
+
+        # Assert
+        assert new_fg.event_time == "event_date"
+        assert len(warning_record) == 1
+        assert issubclass(warning_record[0].category, DeprecationWarning)
+        assert str(warning_record[0].message) == (
+            "Providing event_time as a single-element list is deprecated"
+            + " and will be dropped in future versions. Provide the feature_name string instead."
+        )
+
 
 class TestExternalFeatureGroup:
     def test_from_response_json(self, backend_fixtures):