Add xtriggers to GraphQL schema

[kinow]

Describe exactly what you would like to see in an upcoming release

I couldn't find an existing issue in Cylc Flow. Related to

• xtriggers: tree view and beyond cylc-ui#331
• xtriggers (graph view) cylc-ui#131

The UI needs information about the external triggers, so that they can be displayed in the components/views.

Additional context

I tested the UI with the following workflow

[scheduling]
initial cycle point = 2000-01-01

[[xtriggers]]
clock_1 = wall_clock(offset=PT1M):PT20S

[[dependencies]]
[[[P1D]]]
graph = "@clock_1 => foo"

[runtime]
[[foo]]
script = true

Which works fine in the tree view. It shows foo task, but you have no information about the external trigger. I started with the wall_clock as that's the only one I could remember using before.

In GraphQL, with the current schema, the closest I found is the task.proxies.extras field. The query

subscription {
  workflows (ids: ["kinow|xtrigger1"]) {
    id
    tasks {
      id
      proxies {
        id
        extras
      }
    }
  }
}

does return some information about the external trigger of the task

{
  "data": {
    "workflows": [
      {
        "id": "kinow|xtrigger1",
        "tasks": [
          {
            "id": "kinow|xtrigger1|foo",
            "proxies": [
              {
                "id": "kinow|xtrigger1|20030725T0000+1300|foo",
                "extras": {
                  "xtrigger \"clock_1 = wall_clock(offset=PT1M)\"": "satisfied"
                }
              },
              {
                "id": "kinow|xtrigger1|20030724T0000+1300|foo",
                "extras": {
                  "xtrigger \"clock_1 = wall_clock(offset=PT1M)\"": "satisfied"
                }
              },
              {
                "id": "kinow|xtrigger1|20030726T0000+1300|foo",
                "extras": {
                  "xtrigger \"clock_1 = wall_clock(offset=PT1M)\"": "satisfied"
                }
              }
            ]
          }
        ]
      }
    ]
  }
}

But I think we might need more information/structure than what we have at the moment, which is just "xtrigger \"clock_1 = wall_clock(offset=PT1M)\"": "satisfied".

Pull requests welcome!

[hjoliver]

That information in the schema is what powers the old cylc show command, which shows the current state of prerequisites and xtriggers for a task proxy in the task pool:

[scheduling]
   initial cycle point = 2050  # future!
   [[graph]]
      R1 = """
           foo => bar
           @wall_clock => bar
      """

Run this, then:

$ cylc show foo bar.20500101T0000+1300
title: (not given)
description: (not given)
URL: (not given)

prerequisites (- => not satisfied):
  + foo.20500101T0000+1300 succeeded

outputs (- => not completed):
  - bar.20500101T0000+1300 expired
  - bar.20500101T0000+1300 submitted
  - bar.20500101T0000+1300 submit-failed
  - bar.20500101T0000+1300 started
  - bar.20500101T0000+1300 succeeded
  - bar.20500101T0000+1300 failed

other:
  o  xtrigger "wall_clock = wall_clock()" ... NOT satisfied