Revert "Remove remaining Airflow 2.5 backcompat code from GCS Task Ha…

…ndler (#36443)" (#36453)

This reverts commit 75faf11.

airflow/providers/google/cloud/log/gcs_task_handler.py

@@ -26,6 +26,7 @@
 
 # not sure why but mypy complains on missing `storage` but it is clearly there and is importable
 from google.cloud import storage  # type: ignore[attr-defined]
+from packaging.version import Version
 
 from airflow.configuration import conf
 from airflow.exceptions import AirflowNotFoundException
@@ -47,6 +48,18 @@
 logger = logging.getLogger(__name__)
 
 
+def get_default_delete_local_copy():
+    """Load delete_local_logs conf if Airflow version > 2.6 and return False if not.
+
+    TODO: delete this function when min airflow version >= 2.6.
+    """
+    from airflow.version import version
+
+    if Version(version) < Version("2.6"):
+        return False
+    return conf.getboolean("logging", "delete_local_logs")
+
+
 class GCSTaskHandler(FileTaskHandler, LoggingMixin):
     """
     GCSTaskHandler is a python log handler that handles and reads task instance logs.
@@ -95,8 +108,8 @@ def __init__(
         self.gcp_keyfile_dict = gcp_keyfile_dict
         self.scopes = gcp_scopes
         self.project_id = project_id
-        self.delete_local_copy = kwargs.get(
-            "delete_local_copy", conf.getboolean("logging", "delete_local_logs")
+        self.delete_local_copy = (
+            kwargs["delete_local_copy"] if "delete_local_copy" in kwargs else get_default_delete_local_copy()
         )
 
     @cached_property
@@ -205,6 +218,30 @@ def _read_remote_logs(self, ti, try_number, metadata=None) -> tuple[list[str], l
             messages.append(f"Unable to read remote log {e}")
         return messages, logs
 
+    def _read(self, ti, try_number, metadata=None):
+        """
+        Read logs of given task instance and try_number from GCS.
+
+        If failed, read the log from task instance host machine.
+
+        todo: when min airflow version >= 2.6, remove this method
+
+        :param ti: task instance object
+        :param try_number: task instance try_number to read logs from
+        :param metadata: log metadata,
+                         can be used for steaming log reading and auto-tailing.
+        """
+        if hasattr(super(), "_read_remote_logs"):
+            # from Airflow 2.6, we don't implement the `_read` method.
+            # if parent has _read_remote_logs, we're >= 2.6
+            return super()._read(ti, try_number, metadata)
+
+        messages, logs = self._read_remote_logs(ti, try_number, metadata)
+        if not logs:
+            return super()._read(ti, try_number, metadata)
+
+        return "".join([f"*** {x}\n" for x in messages]) + "\n".join(logs), {"end_of_log": True}
+
     def gcs_write(self, log, remote_log_location) -> bool:
         """
         Write the log to the remote location and return `True`; fail silently and return `False` on error.

tests/providers/google/cloud/log/test_gcs_task_handler.py

@@ -248,8 +248,8 @@ def test_write_to_remote_on_close_failed_read_old_logs(self, mock_blob, mock_cli
         )
 
     @pytest.mark.parametrize(
-        "delete_local_copy, expected_existence_of_local_copy",
-        [(True, False), (False, True)],
+        "delete_local_copy, expected_existence_of_local_copy, airflow_version",
+        [(True, False, "2.6.0"), (False, True, "2.6.0"), (True, True, "2.5.0"), (False, True, "2.5.0")],
     )
     @mock.patch(
         "airflow.providers.google.cloud.log.gcs_task_handler.get_credentials_and_project_id",
@@ -265,9 +265,12 @@ def test_close_with_delete_local_copy_conf(
         local_log_location,
         delete_local_copy,
         expected_existence_of_local_copy,
+        airflow_version,
     ):
         mock_blob.from_string.return_value.download_as_bytes.return_value = b"CONTENT"
-        with conf_vars({("logging", "delete_local_logs"): str(delete_local_copy)}):
+        with conf_vars({("logging", "delete_local_logs"): str(delete_local_copy)}), mock.patch(
+            "airflow.version.version", airflow_version
+        ):
             handler = GCSTaskHandler(
                 base_log_folder=local_log_location,
                 gcs_log_folder="gs://bucket/remote/log/location",