camunda/feel-scala

Handle non-existing variables and context entries gracefully

Closed this issue · 1 comments

saig0 commented

Describe the bug
If I access a non-existing variable then the expression fails. To avoid failure, I must do a null check first.

x
// failed to evaluate expression 'x': no variable found for name 'x'

The behavior is the same for path expressions. If I access a non-existing context entry, the expression fails.

{a: 1}.b
// failed to evaluate expression '{a: 1}.b': context contains no entry with key 'b'

Related to #540.
Related to #582.

To Reproduce
Steps to reproduce the behavior:

  1. Evaluate the expression x
  2. Verify that the expression fails to evaluate

Expected behavior
The expression should return null if a variable or a context entry doesn't exist.

x = null

{a: 1}.b = null

{a: 1}.b.c = null

null.b = null

If the path expression is applied to a filter and a context doesn't contain the entry, the resulting list should contain null for this item.

// non-member path filtering
[ { x: 1 }, { y: 2 } ].y = [ null, 2 ]

[ { x: 1 } ].y = [ null ]

The expected behavior is aligned with the DMN spec. It is verified by the TCK test cases:

Environment

  • FEEL engine version: 1.16.0
  • Affects:
    • Camunda Automation Platform 7: [7.x]
    • Zeebe broker: [0.x]
korthout commented

ZPA triage:

  • good issue for an upcoming mob programming session
  • should be resolved before 8.3
  • sizing as medium as it takes the team some time to resolve such issues