[AIRFLOW-7034] Remove feature: Assigning Dag to task using Bitshift Op (

#7685)

* [AIRFLOW-7034] Remove feature: Assigning Dag to task using Bitshift Operator

* fixup! [AIRFLOW-7034] Remove feature: Assigning Dag to task using Bitshift Operator

* fixup! fixup! [AIRFLOW-7034] Remove feature: Assigning Dag to task using Bitshift Operator

* fixup! fixup! fixup! [AIRFLOW-7034] Remove feature: Assigning Dag to task using Bitshift Operator

UPDATING.md

@@ -61,6 +61,24 @@ https://developers.google.com/style/inclusive-documentation
 
 -->
 
+### Assigning task to a DAG using bitwise shift (bit-shift) operators are no longer supported
+
+Previously, you could assign a task to a DAG as follows:
+
+```python
+dag = DAG('my_dag')
+dummy = DummyOperator(task_id='dummy')
+
+dag >> dummy
+```
+
+This is no longer supported. Instead, we recommend using the DAG as context manager:
+
+```python
+with DAG('my_dag):
+    dummy = DummyOperator(task_id='dummy')
+```
+
 ### Deprecating ignore_first_depends_on_past on backfill command and default it to True
 
 When doing backfill with `depends_on_past` dags, users will need to pass `ignore_first_depends_on_past`.

airflow/models/baseoperator.py

@@ -471,46 +471,28 @@ def __hash__(self):
     def __rshift__(self, other):
         """
         Implements Self >> Other == self.set_downstream(other)
-
-        If "Other" is a DAG, the DAG is assigned to the Operator.
         """
-        from airflow.models.dag import DAG
-        if isinstance(other, DAG):
-            # if this dag is already assigned, do nothing
-            # otherwise, do normal dag assignment
-            if not (self.has_dag() and self.dag is other):
-                self.dag = other
-        else:
-            self.set_downstream(other)
+        self.set_downstream(other)
         return other
 
     def __lshift__(self, other):
         """
         Implements Self << Other == self.set_upstream(other)
-
-        If "Other" is a DAG, the DAG is assigned to the Operator.
         """
-        from airflow.models.dag import DAG
-        if isinstance(other, DAG):
-            # if this dag is already assigned, do nothing
-            # otherwise, do normal dag assignment
-            if not (self.has_dag() and self.dag is other):
-                self.dag = other
-        else:
-            self.set_upstream(other)
+        self.set_upstream(other)
         return other
 
     def __rrshift__(self, other):
         """
-        Called for [DAG] >> [Operator] because DAGs don't have
+        Called for Operator >> [Operator] because list don't have
         __rshift__ operators.
         """
         self.__lshift__(other)
         return self
 
     def __rlshift__(self, other):
         """
-        Called for [DAG] << [Operator] because DAGs don't have
+        Called for Operator << [Operator] because list don't have
         __lshift__ operators.
         """
         self.__rshift__(other)

airflow/providers/google/cloud/operators/pubsub.py

@@ -41,8 +41,7 @@ class PubSubCreateTopicOperator(BaseOperator):
 
         with DAG('successful DAG') as dag:
             (
-                dag
-                >> PubSubTopicCreateOperator(project='my-project',
+                PubSubTopicCreateOperator(project='my-project',
                                              topic='my_new_topic')
                 >> PubSubTopicCreateOperator(project='my-project',
                                              topic='my_new_topic')
@@ -52,8 +51,7 @@ class PubSubCreateTopicOperator(BaseOperator):
 
         with DAG('failing DAG') as dag:
             (
-                dag
-                >> PubSubTopicCreateOperator(project='my-project',
+                PubSubTopicCreateOperator(project='my-project',
                                              topic='my_new_topic')
                 >> PubSubTopicCreateOperator(project='my-project',
                                              topic='my_new_topic',
@@ -182,8 +180,7 @@ class PubSubCreateSubscriptionOperator(BaseOperator):
 
         with DAG('successful DAG') as dag:
             (
-                dag
-                >> PubSubSubscriptionCreateOperator(
+                PubSubSubscriptionCreateOperator(
                     topic_project='my-project', topic='my-topic',
                     subscription='my-subscription')
                 >> PubSubSubscriptionCreateOperator(
@@ -196,8 +193,7 @@ class PubSubCreateSubscriptionOperator(BaseOperator):
 
         with DAG('failing DAG') as dag:
             (
-                dag
-                >> PubSubSubscriptionCreateOperator(
+                PubSubSubscriptionCreateOperator(
                     topic_project='my-project', topic='my-topic',
                     subscription='my-subscription')
                 >> PubSubSubscriptionCreateOperator(
@@ -210,7 +206,7 @@ class PubSubCreateSubscriptionOperator(BaseOperator):
 
         with DAG('DAG') as dag:
             (
-                dag >> PubSubSubscriptionCreateOperator(
+                PubSubSubscriptionCreateOperator(
                     topic_project='my-project', topic='my-topic')
             )
 
@@ -370,17 +366,15 @@ class PubSubDeleteTopicOperator(BaseOperator):
 
         with DAG('successful DAG') as dag:
             (
-                dag
-                >> PubSubTopicDeleteOperator(project='my-project',
+                PubSubTopicDeleteOperator(project='my-project',
                                              topic='non_existing_topic')
             )
 
     The operator can be configured to fail if the topic does not exist. ::
 
         with DAG('failing DAG') as dag:
             (
-                dag
-                >> PubSubTopicCreateOperator(project='my-project',
+                PubSubTopicCreateOperator(project='my-project',
                                              topic='non_existing_topic',
                                              fail_if_not_exists=True)
             )
@@ -482,8 +476,7 @@ class PubSubDeleteSubscriptionOperator(BaseOperator):
 
         with DAG('successful DAG') as dag:
             (
-                dag
-                >> PubSubSubscriptionDeleteOperator(project='my-project',
+                PubSubSubscriptionDeleteOperator(project='my-project',
                                                     subscription='non-existing')
             )
 
@@ -493,8 +486,7 @@ class PubSubDeleteSubscriptionOperator(BaseOperator):
 
         with DAG('failing DAG') as dag:
             (
-                dag
-                >> PubSubSubscriptionDeleteOperator(
+                PubSubSubscriptionDeleteOperator(
                      project='my-project', subscription='non-existing',
                      fail_if_not_exists=True)
             )

docs/concepts.rst

@@ -353,19 +353,6 @@ is equivalent to:
     op2.set_downstream(op3)
     op3.set_upstream(op4)
 
-For convenience, the bitshift operators can also be used with DAGs. For example:
-
-.. code:: python
-
-    dag >> op1 >> op2
-
-is equivalent to:
-
-.. code:: python
-
-    op1.dag = dag
-    op1.set_downstream(op2)
-
 We can put this all together to build a simple pipeline:
 
 .. code:: python

tests/models/test_taskinstance.py

@@ -219,36 +219,17 @@ def test_infer_dag(self):
 
     def test_bitshift_compose_operators(self):
         dag = DAG('dag', start_date=DEFAULT_DATE)
-        op1 = DummyOperator(task_id='test_op_1', owner='test')
-        op2 = DummyOperator(task_id='test_op_2', owner='test')
-        op3 = DummyOperator(task_id='test_op_3', owner='test')
-        op4 = DummyOperator(task_id='test_op_4', owner='test')
-        op5 = DummyOperator(task_id='test_op_5', owner='test')
-
-        # can't compose operators without dags
-        with self.assertRaises(AirflowException):
-            op1 >> op2
+        with dag:
+            op1 = DummyOperator(task_id='test_op_1', owner='test')
+            op2 = DummyOperator(task_id='test_op_2', owner='test')
+            op3 = DummyOperator(task_id='test_op_3', owner='test')
 
-        dag >> op1 >> op2 << op3
-
-        # make sure dag assignment carries through
-        # using __rrshift__
-        self.assertIs(op1.dag, dag)
-        self.assertIs(op2.dag, dag)
-        self.assertIs(op3.dag, dag)
+            op1 >> op2 << op3
 
         # op2 should be downstream of both
         self.assertIn(op2, op1.downstream_list)
         self.assertIn(op2, op3.downstream_list)
 
-        # test dag assignment with __rlshift__
-        dag << op4
-        self.assertIs(op4.dag, dag)
-
-        # dag assignment with __rrshift__
-        dag >> op5
-        self.assertIs(op5.dag, dag)
-
     @patch.object(DAG, 'concurrency_reached')
     def test_requeue_over_dag_concurrency(self, mock_concurrency_reached):
         mock_concurrency_reached.return_value = True