turbaszek commented on pull request #8805:
URL: https://github.com/apache/airflow/pull/8805#issuecomment-636327497
@ashb I forgot what was the problem with metaclass:
```python
with DAG(dag_id='xcomargs_test', default_args={"start_date":
datetime.today()}):
op1 = DummyOperator(task_id="op1")
op2 = CustomOp(task_id="op2")
op2.field = op1.output # value is set after init
assert op1 in op2.upstream_list
```
this needs to be solved also:
https://github.com/apache/airflow/pull/8805#discussion_r423205936
But this hints another possible solution without metaclass:
```python
class BaseOperator():
def __setattr__(self, key, value):
super().__setattr__(key, value)
# Resolve upstreams set by assigning an XComArg after initializing
# an operator, example:
# op = BashOperator()
# op.bash_command = "sleep 1"
from airflow.models.xcom_arg import XComArg
if key in self.template_fields:
self.set_xcomargs_dependencies()
```
This one is nice and simple, however I am not sure if this will degradate
performance in any way .
@evgenyshulman @casassg @ashb @mik-laj thoughts?
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