[MESOS-2622] Document the semantic change in decorator return values

• Type: Documentation
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.23.0
• Component/s: documentation
• Labels: mesosphere
• Target Version/s: 0.23.0
• Story Points: 1
• Assignee: Niklas Quarfot Nielsen
• Reporter: Niklas Quarfot Nielsen
• Shepherd: Adam B
• Created: 15/Apr/15 23:36
• Updated: 26/Nov/18 12:20
• Resolved: 26/Nov/18 12:20

Description

In order to enable decorator modules to remove metadata (environment variables or labels), we changed the meaning of the return value for decorator hooks.

The Result<T> return values means:

State	Before	After
Error	Error is propagated to the call-site	No change
None	The result of the decorator is not applied	No change
Some	The result of the decorator is appended	The result of the decorator overwrites the final labels/environment object