[GitHub] [airflow] vemikhaylov commented on pull request #29608: Enable passing --xcom-args to tasks test CLI command

["vemikhaylov (via GitHub)" <gi...@apache.org>]

vemikhaylov commented on PR #29608:
URL: https://github.com/apache/airflow/pull/29608#issuecomment-1437501187

   @uranusjr thank you for your feedback!
   
   > Using JSON for this feels cumbersome to me.
   
   I think it does for me as well.. At the same time, it's probably worth mentioning that `--env-vars` and `--task-params` also already use JSON for the command, so it might be not a bad idea to have `--xcom-args` consistent with them.
   
   Thinking out loud which alternative options of passing things through we may also have.
   
   **1. Simplified format in CLI**
   
   (task_id, xcom_key, value) triplets joined with a delimiter (a comma below).
   
   ```
   --xcom-args get_python_echo_message,return_value,"test xcom arg" manually_push_bash_command,command,"echo \'test bash\'"
   ```
   
   Probably all the escaping and ad-hoc handling will make things even worse.
   
   **2. Values passed through a file**
   
   ```
   --xcom-args task_args.json
   ```
   
   Sorry for ".json" - Yeah, like again, the contents of the file should have some structure. We may go with yaml :)
   
   What generally doesn't look convenient here with whatever structure of the file - requiring to create a file even for simple scenarios (if passing through the file is the only option). 
   
   --
   > Also we need to find a way to support custom backends that may not store values as JSON.
   
   Let me clarify to make sure that I understand it correctly. You mean that generally the `BaseXCom` model allow us to store any binary (`LargeBinary`) `value`'s and not all of them may be passed as JSON and through CLI itself? Probably for that the approach #2 above can be used like: 
   
   ```
   --xcom-args task_args.pickle
   ```
   
   Though from the usability perspective I wouldn't stick to this option as the only available one. What do you think?
   
   


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