[GitHub] [airflow] tony-brookes commented on issue #16764: TaskGroup dependencies handled inconsistently

[GitBox <gi...@apache.org>]

tony-brookes commented on issue #16764:
URL: https://github.com/apache/airflow/issues/16764#issuecomment-1195543647

   This one really caught me out the other day as I couldn't see from the dependency lines being drawn in the graph view why my tasks were starting with their dependencies un-met.
   
   It would seem that for task groups to be totally convenient it shouldn't matter when I add the dependency information, the outcome should be the same (as others have posted.). Because that's exactly what would happen when you link two tasks.  It doesn't matter when you link them or in what order you create them.
   
   This looks like it might get a fix some time quite soon but if that is not the case perhaps some form of warning logged if tasks are added to groups AFTER dependencies have been added would at least alert people that the behaviour they expect is unlikely to be what they get. :)
   
   Do like task groups though.  Make things really simple and also lets me compose the same set of tasks multiple times in the same DAG by adding a different task group around the outside of them and letting the prefix keep them uniquely identifiable, which can be really really handy when you are programatically generating a DAG from meta data about the files you have been given to process. :)


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