Fix: EventBus: Exists prefix not considered for rule matching

[maxhoheiser]

Motivation

As reported in #8512 and #7305 the current behavior does not fully match the aws cli behavior regarding the EventBridge pattern {"exists": True}.

This rule:

{
	"source": ["core.update-account-command"],
	"detail-type": ["core.update-account-command"],
	"detail": {"key": [{"exists": True}]},
}

in combination with this message:

{
	"version": "0",
	"id": "<uuid:2>",
	"detail-type": "core.update-account-command",
	"source": "core.update-account-command",
	"account": "111111111111",
	"time": "date",
	"region": "<region>",
	"resources": [],
	"detail": {
	    "key":"value",
		"payload":"baz"
	}
}

does not match on LocalStack, but does correctly match on AWS.

The issue arises from the prefix exists not being considered.

Furthermore, the opposite pattern [("exists"): False] was also not correctly matched

This rule:

{
	"source": ["core.update-account-command"],
	"detail-type": ["core.update-account-command"],
	"detail": {"key": [{"exists": False}]},
}

in combination with this message:

{
	"version": "0",
	"id": "<uuid:2>",
	"detail-type": "core.update-account-command",
	"source": "core.update-account-command",
	"account": "111111111111",
	"time": "date",
	"region": "<region>",
	"resources": [],
	"detail": {
	    "no-key":"no-value",
		"payload":"baz"
	}
}

Changes

Adding a condition to check for the prefix exists and use the boolean value in combination with the condition if there value to return exists for the pattern [("exists"): True].

The pattern [("exists"): False] needs different handling, since per definition, the getter of the message event for the in the pattern defined key will always fail to the fallback object. To still send the message correctly, an additional check is put in place handling this particular instance when the return value is not presented, that is only True in the condition that the pattern prefix equal "exists" see (provider.py line 516).

Fixes #8512 and fixes #7305

Testing

Polling for sqs messages was changed to long poll due to inconsistencies when generating the snapshots against aws with messages not being received.

[github-actions]

LocalStack Community integration with Pro

    2 files      2 suites   1h 12m 42s ⏱️
2 425 tests 2 197 ✅ 228 💤 0 ❌
2 426 runs  2 197 ✅ 229 💤 0 ❌

Results for commit e3283a4.

♻️ This comment has been updated with latest results.

[coveralls]

coverage: 83.974% (-0.02%) from 83.993%
when pulling e3283a4 on bugfix/eventbridge/8512-exists-true-not-matching
into 418a240 on master.

[dominikschubert]

PR is already in a good state to merge, but I have a few suggestions. They can be either tackled in this PR, later or just added as TODOs for future us 👍

Sorry you had to deal with such an annoying test as one of your first bigger AWS tests 😅 Glad we could find a reliable solution in the end.

[dominikschubert]

From the docs: Exists matching only works on leaf nodes. It does not work on intermediate nodes.

Might be something that needs to be covered via a negative test as well at some point

[dominikschubert]

Not sure if AWS behaves the same here with checking truthiness vs. just "not being None". Can be tackled in the future though

[dominikschubert]

E.g.

{
  "detail": {
    "state": [ { "exists": true  } ]
  }
}

with

{
  ...
  "detail": {
    "state": 0
  }
}

I'd assume this should still select but we'd need to this this 🤷‍♂️