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https://issues.apache.org/jira/browse/AIRFLOW-3871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16938019#comment-16938019
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ASF subversion and git services commented on AIRFLOW-3871:
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Commit fe3926c10e89a6ba79e55763f8cd4a58b0ae6872 in airflow's branch
refs/heads/v1-10-stable from Géraud
[ https://gitbox.apache.org/repos/asf?p=airflow.git;h=fe3926c ]
[AIRFLOW-3871] Operators template fields can now render fields inside objects
(#4743)
(cherry picked from commit d567f9ab8d5fdd6d18509fd8d623b26795eca25c)
> Allow Jinja templating recursively on object attributes
> -------------------------------------------------------
>
> Key: AIRFLOW-3871
> URL: https://issues.apache.org/jira/browse/AIRFLOW-3871
> Project: Apache Airflow
> Issue Type: Wish
> Components: operators
> Affects Versions: 1.10.0
> Reporter: Galak
> Assignee: Galak
> Priority: Minor
> Fix For: 1.10.6
>
>
> Some {{Operator}} fields can be templated (using Jinja). Template rendering
> only works for string values (either direct values or values stored in
> collections).
> But a templated string inside a custom class instance won't be rendered
> Here is my scenario:
> I have a python method {{transform_data_file}} which is designed to call a
> command object. This command object constructor
> ({{MyAwesomeDataFileTransformer}}) has parameters that could be templated.
> These templated parameters are not rendered so far (see
> {{BaseOperator.render_template_from_field}} method).
> {code}
> simple_task = PythonOperator(
> task_id='simple_task',
> provide_context=True,
> python_callable=transform_data_file,
> templates_dict={
> 'transformer': MyAwesomeDataFileTransformer(
> "/data/{{ dag.dag_id }}/{{ ts }}/input_file",
> "/data/{{ dag.dag_id }}/{{ ts }}/output_file",
> )
> },
> dag=dag
> )
> {code}
> I have 3 alternatives in mind to allow rendering inner attributes:
> # Either define an Abstract Base Class declaring an abstract method
> {{render_template}}; then my command object would have to extend this
> Abstract Base Class, and then implement {{render_template}} method.
> # Or use duck typing in {{BaseOperator.render_template_from_field}} to call
> {{render_template}} method when it exists on templated custom objects; then
> my command object would just have to implement {{render_template}} method.
> # Or traverse object attributes when rendering templates and call
> {{BaseOperator.render_template}} recursively; then my command object would
> not need any change
> My preferred solution is the 3rd one, but I would like to hear about your
> opinion on this before. Maybe is there a 4th and better solution?
> I would be glad to submit a PR if this functionality is accepted.
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