Task SDK: Fix executor_config aliasing across tasks sharing default_args

[bujjibabukatta]

Summary

executor_config set in a shared default_args dict was being shared by reference across tasks and DAGs, not copied. So if one task mutated its executor_config at runtime (a normal thing to do with the Kubernetes executor), it could silently change the config for other tasks using the same default_args.

Closes #72544.

Root Cause

Every place executor_config gets passed around does a shallow copy of the outer dict, but nobody ever copied the executor_config dict itself:

• BaseOperator.__init__ just did executor_config or {} — no copy.
• TaskInstance then copied it straight from the task object again, so even after a fix in one place, it still ends up as the same shared dict at runtime.

Callback fields like on_failure_callback already avoid this by rebuilding a fresh list each time. executor_config never got the same treatment.

Fix

In BaseOperator.__init__, executor_config is now wrapped in copy.copy() before being assigned, so it no longer just falls back to executor_config or {} directly. The same change was made in TaskInstance, where task.executor_config is now copied instead of assigned as-is. Together, these ensure every task and task instance gets its own independent executor_config dict instead of sharing one.

This is a shallow copy, consistent with how callback fields are already handled. If executor_config ever holds nested mutable objects (like a V1Pod), those inner parts would still be shared by reference — open to switching to a deep copy if reviewers think that's needed.

Was generative AI tooling used ?

• Yes - Claude

Generated-by: Claude following the guidelines