fail Statement

The fail statement terminates the script immediately with a failure status. It accepts an optional string message that must appear on the same line.

fail                                # Failure exit, default message
fail "Invalid input"                # Failure exit with message

Behaviour

• The script stops executing at the fail statement
• The Data context is returned to the host with all modifications made up to that point
• The message is reported to the host as an error
• The host environment treats the script as having failed
• fail terminates the entire script even when called from inside a user-defined function

Message must be on the same line

The message is part of the fail statement syntax. If placed on a separate line, it becomes an independent string expression statement - not a fail message.

# CORRECT
fail "Missing required field"

# INCORRECT - "Missing required field" is a separate statement
fail
"Missing required field"

Intended use

Use fail for business logic validation errors and rule violations - situations where the script cannot produce a valid result.

if Data.orders is null or Data.orders is not array then
    fail "Orders must be an array"
end

if AnyByField(Data.orders, "amount", "<", 0) then
    fail "Negative order amounts are not allowed"
end

Comparison with exit and return

Keyword	Effect	Valid where
fail	Terminate the script with an error (failure)	Anywhere
exit	Terminate the script cleanly (success)	Anywhere
return	Return a value from a function	Inside functions only

All three keywords return the Data context to the host with all mutations applied. See exit for the success counterpart and return for function returns.