Fix ECS ServicesStable waiter when deployments key is absent

[veeceey]

Fixes #3314

The ServicesStable waiter crashes with a JMESPathTypeError when the
DescribeServices response doesn't include a deployments field for a
service. This can happen when a service is deployed using CodeDeploy's
Blue/Green deployment strategy.

The root cause is the JMESPath expression length(deployments) receiving
null when the key is absent. I've changed it to length(deployments || [])
so it falls back to an empty array. A service without deployments will have
length 0 (not 1), so it's correctly treated as not yet stable and the waiter
retries instead of blowing up.

Testing

Added functional tests in tests/functional/test_ecs.py covering:

• Service response with missing deployments key (previously crashed, now retries)
• Service response with deployments present and stable (succeeds as before)

All existing waiter config lint tests continue to pass (tests/functional/test_waiter_config.py — 148 tests).

[veeceey]

Friendly ping - any chance someone could take a look at this when they get a chance? Happy to make any changes if needed.

[veeceey]

hi there, just following up — let me know if I should make any changes on this

[SamRemis]

Hi @veeceey,

Thank you for your PR. We explain a bit more in our contribution guide, but all of the files in the data folder aren't able to be edited directly in botocore. These files are owned by the service team and submitted to all SDKs, not just botocore.

@adev-code , could you take a look at this and contact the service team so we can get this confirmed and fixed upstream?

[RyanFitzSimmonsAK]

I've raised this issue to the service team for them to address upstream.

Ticket # for internal use : P397024257

[veeceey]

Thanks @SamRemis and @RyanFitzSimmonsAK — appreciate you flagging this to the service team. Makes total sense that the data files are generated upstream. I'll keep an eye on the ticket and happy to help if there's anything else needed on this end.