Set a precondition on a task

You can control the execution flow by setting a precondition on a task. A precondition is an if statement for tasks, written in Jython script code.

If the precondition evaluates to True, the task is started. If the precondition evaluates to False, the task is skipped. If an exception is raised or a compilation error occurs when XL Release is evaluating the precondition script, the task is failed. You can fix the script and retry the task.

Manual Task With Precondition

There are two ways of writing preconditions.

Boolean expression

A Boolean expression is restricted to single statement script. For example:

releaseVariables['jobStatus'] == 'Success'

The task will only be started if the variable jobStatus is equal to ‘Success’.

Multi-line script

If you need a more complicated script, you must set the result variable. For example:

if releaseVariables['OS'] == 'Linux' and releaseVariables['pingResult'] == '0':
    result = True
else:
    result = False

Disabling preconditions

You can disable precondition on certain task types. For example, to disable precondition on parallel groups, modify synthetic.xml as follows:

<type-modification type="xlrelease.ParallelGroup">
    <property name="preconditionEnabled" kind="boolean" required="true" default="false" hidden="true"
        description="Whether preconditions should be enabled"/>
</type-modification>