Disallow Condition If Sequence Flow Is Not Exclusive or Inclusive Gateway

[jonathanlukas]

The rule should detect the following modeling patterns

Incorrect: Camunda 8.1 will reject this:
converted-c8-conditional-flow.bpmn.txt

'converted-c8-conditional-flow.bpmn': - Element: DoSomethingTask
    - ERROR: Conditional sequence flows are only supported at exclusive or inclusive gateway

Correct: Camunda 8.1 will accept this:
converted-c8-inclusive-gateway.bpmn.txt

In addition, we consider modeling implicit gateways a bad practice, so even if zeebe will support conditional flows, this rule would still apply as warning or info.

How does the rule improve the BPMN diagram?

This rule will prevent users from creating undeployable diagrams.

Rule Details

• Name: no-conditional-flows
• Default notification level: error

What alternatives did you consider?

[marstamm]

The rule makes sense, thanks for suggesting it

[nikku]

In addition, we consider modeling implicit gateways a bad practice, so even if zeebe will support conditional flows, this rule would still apply as warning or info.

This would be "modeling guidance" then. With this plug-in we strictly validated compatibility for execution.

[nikku]

Interestingly enough Zeebe does not fail on default flows, only conditional 🙈. This diagram deploys just fine, but makes no sense without condition support:

[nikku]

Related issue that we do not capture yet (in terms of run-time compatibility):

Conditions must not be empty:

Command 'CREATE' rejected with code 'INVALID_ARGUMENT': Expected to deploy new resources, but encountered the following errors:
'Playground Process.bpmn': - Element: Activity_119f0sp
    - ERROR: Conditional sequence flows are only supported at exclusive or inclusive gateway
- Element: Flow_1f2h1nt > conditionExpression
    - ERROR: Expected expression but found static value ''. An expression must start with '=' (e.g. '=').
[ deploy-error ] 16/5/2023 18:0:38

[nikku]

Closed via #97.

[philippfromme]

• Element: Flow_1f2h1nt > conditionExpression
  • ERROR: Expected expression but found static value ''. An expression must start with '=' (e.g. '=').
    [ deploy-error ] 16/5/2023 18:0:38

How did you end up with an empty expression? The conditionExpression shouldn't exist unless there is a value.

[nikku]

Change a flow into a conditional flow.

[philippfromme]

Change a flow into a conditional flow.

Ah! Yeah, that part is a bit confusing. So any sequence flow can have a condition, but only when the source is an activity it must also be rendered as a conditional sequence flow. I guess we need the empty expression to be able to determine that the sequence flow is conditional and to render it as such.