How to get a Task's “Unique ID” from a Project Web App via REST?

Question

I'm brand new to MS Project and Project Server / Project Web Apps.

In MS Project Pro, there is a column called "Unique ID" that seems to function like SharePoint's built-in list item "ID" field - an auto-incrementing integer (1 based).

How can I find a task's "Unique ID" from a project that has been saved and published to a Project Web App through Project Server's REST API?

The only "ID" on a Task object retrieved through

https://servername/pwa/_api/projectserver/projects('project-id')/tasks('task-id')

is a GUID, there doesn't seem to be any property associated with an integer ID.

I found this other question and answer over on the MSDN help site. It is about Project Server 2010, and about how to show the "Unique ID" field in a report. But the answer says (emphasis mine):

There are three ID fields in the MSP_EpmTask_UserView; TaskUID, TaskIndex and TaskClientUniqueId. TaskUID is a GUID, TaskIndex corresponds to the Task positional ID and TaskClientUniqueId corresponds to the Unique Id field in Project Professional.

So it appears that this information is stored somewhere within Project Server, but... how do I get it through REST?

Answer 1

So the answer is that the Unique ID property isn't available on tasks retrieved through the Project Server endpoint, but it is available on tasks retrieved through the Project Data endpoint. (Yes, in MS Project Server there are two REST web services.) A request to

https://servername/pwa/_api/ProjectData/Projects(guid'project-id')/Tasks(guid'task-id')

returns an object that has the TaskClientUniqueId property available.