Don't return the root of a CoT twice when it's also a link

[Eijebong]

Creating the CoT here, with no_check_task being default (False)

scriptworker/src/scriptworker/cot/verify.py

Lines 2089 to 2091 in 6b0b66b

	cot = ChainOfTrust(context, opts.task_type, task_id=opts.task_id)
	check_task = opts.no_check_task is False
	await verify_chain_of_trust(cot, check_task=check_task)

Then because check_task is true, it calls build_link with itself, adding a LinkOfTrust with the same task ID.

scriptworker/src/scriptworker/cot/verify.py

Lines 2044 to 2045 in 6b0b66b

	if check_task:
	await build_link(chain, chain.name, chain.task_id)

Then we call verify_task_types on that chain, which calls get_all_links_in_chain and actually verifies links. That's where the log is coming from.

scriptworker/src/scriptworker/cot/verify.py

Lines 1806 to 1813 in 6b0b66b

	for obj in chain.get_all_links_in_chain():
	task_type = obj.task_type
	log.info("Verifying {} {} as a {} task...".format(obj.name, obj.task_id, task_type))
	task_count.setdefault(task_type, 0)
	task_count[task_type] += 1
	# Run tests synchronously for now. We can parallelize if efficiency
	# is more important than a single simple logfile.
	await valid_task_types[task_type](chain, obj)

The problem is that get_all_links_in_chain returns [self] + self.links if the CoT object isn't a decision task

scriptworker/src/scriptworker/cot/verify.py

Line 212 in 6b0b66b

def get_all_links_in_chain(self):

So it ends up returning the root task twice, one because of [self] and once because check_task added the root as a LoT to the CoT.

---

get_all_links_in_chain was added in
0356bbb but at the time, check_task didn't exist so it was correct. The bug was introduced by 8b6ab79 which started adding the root of a CoT as a link, making get_all_links_in_chain return "dupes" for it.

This most likely never got caught because it only happens when check_task is True which isn't the case for scriptworkers, only verify_cot and only when checking a non decision task.

This fixes the issue by not relying on the task type to know whether or not it should return itself in the chain but by looking down the graph to see if it's already included or not.

[bhearsum]

Thanks for the sleuthing and the fix!