Feature Request: Small Scale Exception Handling

[MarleTangible]

Hello,

Performance improvements of TBEL over JavaScript is quite good. It is also very capable for a small scripting language. Although it's possible to let the script fail with an exception and use the failure path on the rule engine, more often than not I find myself looking for a small scale exception handling feature. Let me explain with an example.

We're using a small application where some telemetry information being collected, and due to other complexities some conversions and corrections needs to be made at the ThingsBoard level. One of these corrections is that one of the fields needs to be converted to datetime from string.

// 50 lines of code
var pattern = "hh:mm:ss a, EEE M/d/uuuu";
var date = new Date("12:15:30 PM, Sun 10/09/2022", pattern, "en-US");
// another 20 lines of code

The issue is that race conditions might cause malformed text to be sent, so I just would like to wrap it with a try {} catch {} and be done with it. I know it's hard to deal with stack unwinding and all the other complexities of creating a exception system for a scription language. So, maybe something similar to null-safe handling or AutoHotKey style processing can be done. e.g. just return null on exception under certain circumstances, maybe with the help of a keyword, AHK uses the Try keyword at the start of the line or just maybe allow try catch with a single level, but I think it would be really helpful, as so many issues require just a small correction and not a full scale failure of the script. I don't know how much you would like to divert from the MVEL language also.

Thank you.

[MarleTangible]

I'm adding an extended example as a reference to future users and also as a showcase.

The code below first checks if the given text which is already known to be a string matches the regex pattern of the datetime pattern before attempting to process it in order to avoid a runtime exception.

// Set the text value for testing.
msg.text = "Tuesday, November 18, 2025, 1:46:44 PM";

var data = {};

var text = msg.text;

var regex = "^(Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Sunday), " +
            "(January|February|March|April|May|June|July|August|September|October|November|December) " +
            "\\d{1,2}, \\d{4}, \\d{1,2}:\\d{2}:\\d{2} (AM|PM)$";

if (text.matches(regex)) {
    var pattern = "EEEE, MMMM dd, uuuu, h:mm:ss a";
    var date = new Date(text, pattern, "en-US");
    
    data.date = date.toISOString();
}

return {msg: data};