Output mapping doesn't create an incident if a variable is missing

[saig0]

Describe the bug

I deployed a BPMN process with a task. The task has an output mapping that adds (or updates) a property of a variable a.b.

Now, the job of the task is completed (accidentally) without the variable x that is referenced as the variable assignment value.

If the process instance doesn't have the variable a then an incident is created, as expected. The incident has the following error message:

failed to evaluate expression '{a:if (a = null) then {b: x} else put all(a,{b: x})}': no variable found for name 'x'

But if the process instance has the variable a then no incident is created. Instead, the variable a is set to null and the task is completed.

To Reproduce

1. Deploy the BPMN process: output_mapping.bpmn.txt (without the .txt ending)
2. Create a new process instance with the variables { "a": { "c": 1 } }
3. Complete the task with job type task-a without variables
4. Verify that no incident is created and the task is completed

Expected behavior

An incident is created if a job is completed without a variable that is referenced as the variable assignment value of an output mapping.

The behavior should be consistent. For the case that the variable is present and the case that the variable is not present.

Log/Stacktrace

None.

Environment:

• OS:
• Zeebe Version: 8.0.2
• Configuration:

[saig0]

The issue was reported on the forum: https://forum.camunda.io/t/timer-boundary-event-deletes-variable/38032