use of start-up tasks in an asynchronous graph

[cylc]

A start-up task (under [scheduling] -> [[special tasks]]) is a non-cycling synchronous task; i.e. it has an associated cycle time, but it only runs once, at suite start up. This is commonly used for a "prep" task that prepares a suite workspace or similar. If you declare a start-up task and then use it in an asynchronous graph, it results in the following run time error:

Cannot create a consistent method resolution order (MRO) for bases oneoff, async_oneoff

This is because cylc has derived a task type from both the oneoff (synchronous) and async_oneoff classes, which is inconsistent.

Cylc should check for task type inconsistencies like this when validating a suite.

[cylc]

This issue was fixed last week. Validation now checks for erroneous use of special synchronous tasks in asynchronous graph sections.