Ajay9704 commented on issue #62457:
URL: https://github.com/apache/airflow/issues/62457#issuecomment-3958114803
Analysis of the start_date Inconsistency
I wanted to provide a clear summary of the inconsistency around start_date
in the template context.
What Changed in Commit 518287ce7f
The commit “Runtime context shouldn't have start_date as a key (#46961)”
removed start_date from the runtime template context produced by
get_template_context(). However, the following places were not updated and
still reference it:
task-sdk/src/airflow/sdk/definitions/context.py
(This still defines start_date: DateTime in the Context TypedDict)
airflow-core/docs/templates-ref.rst
(This still documents {{ start_date }} as an available template field)
Because these areas did not get updated, they no longer match runtime
behavior.
Current State (Misaligned)
The current behavior looks like this:
Runtime context (get_template_context())
Does not include start_date
This is correct, as the commit intentionally removed it.
TypedDict (Context, located in
task-sdk/src/airflow/sdk/definitions/context.py)
Still lists start_date
This is incorrect, because the runtime no longer provides it.
Documentation (airflow-core/docs/templates-ref.rst)
Still documents {{ start_date }}
This is incorrect, because using it now raises an error.
User Impact
Right now, if a user follows the documentation and writes:
{{ start_date }}
they receive:
KeyError: 'start_date'
The only currently valid ways to access it are:
ti.start_date
task_instance.start_date
So documentation, type hints, and runtime behavior do not match.
Two Possible Fix Approaches
I see two logical directions to resolve this inconsistency. Both are
technically valid; the maintainers' intention will decide which is appropriate.
Option A: Remove start_date from TypedDict and Documentation
(Aligns with the intent of commit 518287ce7f)
This requires:
Removing the start_date entry from the Context TypedDict
File: task-sdk/src/airflow/sdk/definitions/context.py
Removing the reference to {{ start_date }} from the documentation
File: airflow-core/docs/templates-ref.rst
This would make type hints and documentation match the current runtime
behavior.
Option B: Add start_date Back to the Runtime Context
(If the project prefers keeping the old template behavior)
This would require updating the template context assembly in:
task-sdk/src/airflow/sdk/execution_time/task_runner.py
Specifically, restoring start_date inside the cached template context.
This would make runtime, documentation, and TypedDict consistent again, but
it would partially undo commit 518287ce7f.
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