fail

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

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. It is not intended for debugging.

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 return

Keyword	Script Succeeds?	Message Severity
return	Yes	Info
fail	No	Error

Both keywords return the Data context to the host with all mutations applied. See return for the success counterpart.