[Bug]: Workflow._get_representative_launch does not return the most recent completed launch

[thoschr]

Code snippet

import datetime
from fireworks.core.firework import Firework, Launch, Workflow

UTC = datetime.timezone.utc
launch_dir = "." 

completed_1 = Launch(
    state="COMPLETED",
    launch_dir=launch_dir,
    state_history=[{"state": "COMPLETED", "created_on": datetime.datetime(2020, 1, 1, tzinfo=UTC)}],
)
completed_2 = Launch(
    state="COMPLETED",
    launch_dir=launch_dir,
    state_history=[{"state": "COMPLETED", "created_on": datetime.datetime(2021, 1, 1, tzinfo=UTC)}],
)
running = Launch(state="RUNNING", launch_dir=launch_dir)

fw = Firework("fireworks.core.firework.FiretaskBase", launches=[running, completed_1, completed_2])

result = Workflow._get_representative_launch(fw)
print("returned launch time_end:", result.time_end)
print("expected (most recent):  ", completed_2.time_end)
assert result is completed_2, f"BUG: expected completed_2 (most recent) but got the one with time_end={result.time_end}"
print("OK - no bug")

What happened?

I want to use Workflow._get_representative_launch to get the most recent completed launch among several completed launches. A bug in the code leads to that the first completed launch is returned instead.

Version

v2.1.4 at commit 7168655

Which OS?

• MacOS
• Windows
• Linux

Log output

returned launch time_end: 2020-01-01 00:00:00+00:00
expected (most recent):   2021-01-01 00:00:00+00:00
Traceback (most recent call last):
  File "/home/thoschr/testing/fireworks/bug/test.py", line 24, in <module>
    assert result is completed_2, f"BUG: expected completed_2 (most recent) but got the one with time_end={result.time_end}"
           ^^^^^^^^^^^^^^^^^^^^^
AssertionError: BUG: expected completed_2 (most recent) but got the one with time_end=2020-01-01 00:00:00+00:00