Issue deprecation warning for plugins registering ti_deps

This is removed in Airflow3 via #45713

airflow/plugins_manager.py

@@ -27,6 +27,7 @@
 import os
 import sys
 import types
+import warnings
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, Iterable
 
@@ -431,6 +432,17 @@ def initialize_ti_deps_plugins():
     registered_ti_dep_classes = {}
 
     for plugin in plugins:
+        if not plugin.ti_deps:
+            continue
+
+        from airflow.exceptions import RemovedInAirflow3Warning
+
+        warnings.warn(
+            "Using custom `ti_deps` on operators has been removed in Airflow 3.0",
+            RemovedInAirflow3Warning,
+            stacklevel=1,
+        )
+
         registered_ti_dep_classes.update(
             {qualname(ti_dep.__class__): ti_dep.__class__ for ti_dep in plugin.ti_deps}
         )

tests/plugins/test_plugins_manager.py

@@ -28,6 +28,7 @@
 
 import pytest
 
+from airflow.exceptions import RemovedInAirflow3Warning
 from airflow.hooks.base import BaseHook
 from airflow.listeners.listener import get_listener_manager
 from airflow.plugins_manager import AirflowPlugin
@@ -270,6 +271,17 @@ class AirflowAdminMenuLinksPlugin(AirflowPlugin):
             ),
         ]
 
+    def test_deprecate_ti_deps(self):
+        class DeprecatedTIDeps(AirflowPlugin):
+            name = "ti_deps"
+
+            ti_deps = [mock.MagicMock()]
+
+        with mock_plugin_manager(plugins=[DeprecatedTIDeps()]), pytest.warns(RemovedInAirflow3Warning):
+            from airflow import plugins_manager
+
+            plugins_manager.initialize_ti_deps_plugins()
+
     def test_should_not_warning_about_fab_plugins(self, caplog):
         class AirflowAdminViewsPlugin(AirflowPlugin):
             name = "test_admin_views_plugin"

tests/serialization/test_dag_serialization.py

@@ -1612,7 +1612,7 @@ class DummyTask(BaseOperator):
         ) as dag:
             DummyTask(task_id="task1")
 
-        with pytest.raises(SerializationError):
+        with pytest.raises(SerializationError), pytest.warns(RemovedInAirflow3Warning):
             SerializedBaseOperator.serialize_operator(dag.task_dict["task1"])
 
     def test_error_on_unregistered_ti_dep_deserialization(self):
@@ -1644,7 +1644,8 @@ class DummyTask(BaseOperator):
         with DAG(dag_id="test_serialize_custom_ti_deps", schedule=None, start_date=execution_date) as dag:
             DummyTask(task_id="task1")
 
-        serialize_op = SerializedBaseOperator.serialize_operator(dag.task_dict["task1"])
+        with pytest.warns(RemovedInAirflow3Warning):
+            serialize_op = SerializedBaseOperator.serialize_operator(dag.task_dict["task1"])
 
         assert serialize_op["deps"] == [
             "airflow.ti_deps.deps.mapped_task_upstream_dep.MappedTaskUpstreamDep",