feat: add ad-hoc-sub-process rule

[jarekdanielak]

Proposed Changes

Add ad-hoc-sub-process rule which validates an ad-hoc sub-process against the BPMN specification.

Constraints:

• Must not include start or end events.
• Every intermediate event must have an outgoing sequence flow.

Additionally with b323933 we make sure existing sub-process rule also applies to an ad-hoc sub-process.

Related to camunda/camunda-modeler#4811

Depends on #164 for 🟢 CI.

Checklist

To ensure you provided everything we need to look at your PR:

• Brief textual description of the changes present
• Visual demo attached
• Steps to try out present, i.e. using the @bpmn-io/sr tool
• Related issue linked via Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}

[nikku]

Added dependency:

Depends on #164 for 🟢 CI.

[nikku]

I'm not sure on the spec intention, but does it feature a blank intermediate catch event or a link catch event as a proposed start? If not, let's not feature these elements as valid, but feature task -> task flows as valid.

Link catch: I'm not sure what semantics that should have. 🙃

[nikku]

Let's consider the spec text:

However, it is possible to specify Sequence Flows between some of the contained Activities. When used, Sequence Flows will provide the same ordering constraints as in a regular Process. To have any meaning, Intermediate Events will have outgoing Sequence Flows and they can be triggered multiple times while the Ad-Hoc Sub-Process is active.

According to it, this, I think, would be a reasonable use of an ad-hoc sub process, with intermediate catch events:

[bastiankoerber]

Let's consider the spec text:

However, it is possible to specify Sequence Flows between some of the contained Activities. When used, Sequence Flows will provide the same ordering constraints as in a regular Process. To have any meaning, Intermediate Events will have outgoing Sequence Flows and they can be triggered multiple times while the Ad-Hoc Sub-Process is active.

According to it, this, I think, would be a reasonable use of an ad-hoc sub process, with intermediate catch events:

I agree with the approach.
Just to double check, i am also allowed to execute multiple times the "Do standalone task" & "Do Work" right?
I can also add a call activity to the bpmn adhoc process right?

[saig0]

@nikku, note that the intermediate events inside the ad-hoc subprocess are not active by default. Instead, they must be explicitly activated before they can be triggered.

In the example, the timer is triggered 10 minutes after its activation, not 10 minutes after the subprocess is entered. The conditional event can only be triggered if it is activated first. Like other activities inside the ad-hoc subprocess, events must be activated first.

Just to double check, i am also allowed to execute multiple times the "Do standalone task" & "Do Work" right?

Yes.

I can also add a call activity to the bpmn adhoc process right?

Yes.

[nikku]

Thanks both. The usual semantics of ad-hoc applies:

• start activities must be explicitly activated
• if activated, then "tasks execute", and "events can be triggered"
• if not activated, then any activity or event is ignored

➡️ This will pose an interesting run-time/introspection challenge, too (ref)

[nikku]

@jarekdanielak as per above discussions I'll update the example in this PR to a simplified version of #160 (comment).

[nikku]

Updated docs via bfbe5c5, squashed.

[nikku]

Great stuff 👏

[nikku]

I agree!

[nikku]

Great stuff 👏

[nikku]

I'm going to release this thing, with the other nit-pics currently worked on.