Copilot commented on code in PR #59691:
URL: https://github.com/apache/airflow/pull/59691#discussion_r3066488039
##########
airflow-core/src/airflow/models/taskinstance.py:
##########
@@ -2260,6 +2268,54 @@ def _visit_relevant_relatives_for_mapped(mapped_tasks:
Iterable[tuple[str, int]]
return visited
+def resolve_placeholder_map_index(
+ *,
+ task: Operator,
+ relative: Operator,
+ map_index: int,
+ run_id: str,
+ session: Session,
+) -> int | None:
Review Comment:
`resolve_placeholder_map_index` is a new top-level helper in
`airflow.models.taskinstance`, but it is only used internally from
`_get_relevant_map_indexes`. In this module, similar internal helpers are
prefixed with `_` (e.g. `_get_relevant_map_indexes`,
`_find_common_ancestor_mapped_group`). To avoid unintentionally expanding the
public import surface of `airflow.models.taskinstance`, consider renaming this
to `_resolve_placeholder_map_index` (and updating the call site).
##########
airflow-core/tests/unit/models/test_taskinstance.py:
##########
@@ -3102,6 +3102,95 @@ def g(v):
assert result == expected
+def test_downstream_placeholder_handles_upstream_post_expansion(dag_maker,
session):
+ """
+ Test dynamic task mapping behavior when an upstream placeholder task
+ (map_index = -1) has been replaced by the first expanded task
+ (map_index = 0).
+
+ This verifies that trigger rule evaluation correctly resolves relevant
+ upstream map indexes both when referencing the original placeholder
+ and when referencing the first expanded task instance.
+ """
+
+ with dag_maker(session=session) as dag:
+
+ @task
+ def get_mapping_source():
+ return ["one", "two", "three"]
+
+ @task
+ def mapped_task(x):
+ output = f"{x}"
+ return output
+
+ @task_group(prefix_group_id=False)
+ def the_task_group(x):
+ start = MockOperator(task_id="start")
+ upstream = mapped_task(x)
+
+ # Plain downstream inside task group (no mapping source).
Review Comment:
The comment "Plain downstream inside task group (no mapping source)." is a
bit misleading: when the task group is dynamically mapped, this downstream task
still participates in the group's mapping context (even if it doesn't directly
consume the mapped argument). Consider rewording to clarify it’s not *directly*
mapped by an expand input, but is still mapped via the mapped task group.
```suggestion
# Downstream task inside the task group that does not directly
# consume the expand input, but is still mapped via the mapped
# task group context.
```
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