dont include linked resources already present in the response

[kevinhodges]

What does this PR do? (please provide any background)

https://hxshortbreaks.atlassian.net/browse/FP-1042
Some The Works endpoints now create their own linked resources (see https://github.com/holidayextras/the-works/pull/590 which will consume this work once merged) removing the need for plugin-jsonapi to request them. Plugin-jsonapi now handles this by checking for the presence of linked includes before adding them onto the request array.

This is a performance/optimisation piece.

What tests does this PR have?

One additional test to cover the additional usecase of the getSubResources function

How can this be tested?

On it's own, not so much. Pull down https://github.com/holidayextras/the-works/pull/590 and run a GET /packageRates request with an include of ticketRates,roomRates,hotelProducts. You will then see plugin-jsonapi only request the hotelProducts as the packageRates endpoint will return the ticketRates and roomRates resources itself.

Any tech debt?

None

Screenshots / Screencast

What gif best describes how you feel about this work?

• I have checked our general contributing document and the project specific contributing document (if present) and I'm happy for this to be reviewed.

By approving a review you are confirming you have...

• Witnessed the work behaving as expected (this could be on the author's machine or screencast).
• Checked for coding anti-patterns.
• Checked for appropriate test coverage.
• Checked all the tests are passing.

---

[davobutt]

Not really in your change, but don't think you can get here and resource.links not be truthy.

Given that you could I suppose go with

         if (resource.links[include] && !(stateObject.linked && stateObject.linked[include])) {
          utilities._addSubResourceRequest(stateObject.subResourceRequests, resource.links[include])
        } 

But not sure that adds much to readability.

[davobutt]

Free Gift ;-)
I wrote this test to satisfy myself...

    it('should not attach any already linked sub resources, but still add unlinked ones', function () {
      var stateObject = {
        resources: [
          {
            id: 'ID',
            links: {
              LINK1: {
                ids: ['LINK_ID1'],
                type: 'LINK1'
              },
              LINK2: {
                ids: ['LINK_ID2'],
                type: 'LINK2'
              }
            }
          }
        ],
        includes: ['LINK1', 'LINK2'],
        linked: {
          LINK1: []
        }
      }

      var expected = _.cloneDeep(stateObject)
      expected.subResourceRequests = {
        LINK2: {
          ids: ['LINK_ID2']
        }
      }
      return expect(utilities.getSubResources(stateObject)).to.eventually.deep.equal(expected)
    })