Add a @task.stub to allow tasks in other languages to be defined in dags

providers/standard/provider.yaml

@@ -141,3 +141,5 @@ task-decorators:
     name: sensor
   - class-name: airflow.providers.standard.decorators.short_circuit.short_circuit_task
     name: short_circuit
+  - class-name: airflow.providers.standard.decorators.stub.stub
+    name: stub

providers/standard/src/airflow/providers/standard/decorators/stub.py

@@ -0,0 +1,102 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+from __future__ import annotations
+
+import ast
+from collections.abc import Callable
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from airflow.sdk.bases.decorator import DecoratedOperator, TaskDecorator, task_decorator_factory
+else:
+    try:
+        from airflow.sdk.bases.decorator import DecoratedOperator, TaskDecorator, task_decorator_factory
+    except ModuleNotFoundError:
+        from airflow.decorators.base import (
+            DecoratedOperator,
+            TaskDecorator,
+            task_decorator_factory,
+        )
+
+if TYPE_CHECKING:
+    from airflow.sdk.definitions.context import Context
+
+
+class _StubOperator(DecoratedOperator):
+    custom_operator_name: str = "@task.stub"
+
+    def __init__(
+        self,
+        *,
+        python_callable: Callable,
+        task_id: str,
+        **kwargs,
+    ) -> None:
+        super().__init__(
+            python_callable=python_callable,
+            task_id=task_id,
+            **kwargs,
+        )
+        # Validate python callable
+        module = ast.parse(self.get_python_source())
+
+        if len(module.body) != 1:
+            raise RuntimeError("Expected a single statement")
+        fn = module.body[0]
+        if not isinstance(fn, ast.FunctionDef):
+            raise RuntimeError("Expected a single sync function")
+        for stmt in fn.body:
+            if isinstance(stmt, ast.Pass):
+                continue
+            if isinstance(stmt, ast.Expr):
+                if isinstance(stmt.value, ast.Constant) and isinstance(stmt.value.value, (str, type(...))):
+                    continue
+
+            raise ValueError(
+                f"Functions passed to @task.stub must be an empty function (`pass`, or `...` only) (got {stmt})"
+            )
+
+        ...
+
+    def execute(self, context: Context) -> Any:
+        raise RuntimeError(
+            "@task.stub should not be executed directly -- we expected this to go to a remote worker. "
+            "Check your pool and worker configs"
+        )
+
+
+def stub(
+    python_callable: Callable | None = None,
+    queue: str | None = None,
+    executor: str | None = None,
+    **kwargs,
+) -> TaskDecorator:
+    """
+    Define a stub task in the DAG.
+
+    Stub tasks exist in the Dag graph only, but the execution must happen in an external
+    environment via the Task Execution Interface.
+
+    """
+    return task_decorator_factory(
+        decorated_operator_class=_StubOperator,
+        python_callable=python_callable,
+        queue=queue,
+        executor=executor,
+        **kwargs,
+    )

providers/standard/src/airflow/providers/standard/get_provider_info.py

@@ -144,5 +144,6 @@ def get_provider_info():
                 "class-name": "airflow.providers.standard.decorators.short_circuit.short_circuit_task",
                 "name": "short_circuit",
             },
+            {"class-name": "airflow.providers.standard.decorators.stub.stub", "name": "stub"},
         ],
     }

providers/standard/tests/unit/standard/decorators/test_stub.py

@@ -0,0 +1,57 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+from __future__ import annotations
+
+import contextlib
+
+import pytest
+
+from airflow.providers.standard.decorators.stub import stub
+
+
+def fn_ellipsis(): ...
+
+
+def fn_pass(): ...
+
+
+def fn_doc():
+    """Some string"""
+
+
+def fn_doc_pass():
+    """Some string"""
+    pass
+
+
+def fn_code():
+    return None
+
+
+@pytest.mark.parametrize(
+    ("fn", "error"),
+    [
+        pytest.param(fn_ellipsis, contextlib.nullcontext(), id="ellipsis"),
+        pytest.param(fn_pass, contextlib.nullcontext(), id="pass"),
+        pytest.param(fn_doc, contextlib.nullcontext(), id="doc"),
+        pytest.param(fn_doc_pass, contextlib.nullcontext(), id="doc-and-pass"),
+        pytest.param(fn_code, pytest.raises(ValueError, match="must be an empty function"), id="not-empty"),
+    ],
+)
+def test_stub_signature(fn, error):
+    with error:
+        stub(fn)()