The evaluation of `substring()` fails if the length is greater than the given string

[saig0]

Describe the bug If I invoke the substring() function with a length that is greater than the given string then the evaluation fails and reports a Java StringIndexOutOfBoundsException.

To Reproduce Steps to reproduce the behavior:

1. Evaluate the expression substring("abc", 1, 4)
2. Verify that the evaluation fails with the message

failed to evaluate expression 'substring("abc", 1, 4)' :
 java.lang.StringIndexOutOfBoundsException: begin 0, end 4, length 3

Expected behavior

The function invocation should return the whole string if the length is greater than the string.

substring("abc", 1, 4)    // --> "abc"

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However, according to the DMN 1.5 specification, the function invocation should return null.

However, returning null is not the most (business) user-friendly behavior. It could lead to complicated expressions, for example:

if string length(message) < 10 then message else substring(message, 1, 10)

Environment

• FEEL engine version: 1.17.4
• Affects:
  • Camunda Automation Platform 7: [7.x]
  • Zeebe broker: 8.4.0