Calling `setDiffDeep` from different models can set duplicate data on a given document in a race condition

const modelA = backend.createModel()
const modelB = backend.createModel()

const $profileInModelA = modelA.at('profiles.profile-id')
const $profileInModelB = modelB.at('profiles.profile-id')

$profileInModelA.fetch((err) => {
  $profileInModelB.fetch((err) => {

  $profileInModelA.set('foo', {bar: []})

    modelA.whenNothingPending(=> {
      modelB.whenNothingPending(=> {

        // These `setDiffDeep`s do not know each other's operations, and would
        // resolve by generating `insert` ops rather than replace on the array.
        // When this is done in quick succession, we set duplicate data
        $profileInModelA.setDiffDeep('foo', {bar: [1,2,3]})
        $profileInModelB.setDiffDeep('foo', {bar: [1,2,3]})

        modelA.whenNothingPending(=> {
          modelB.whenNothingPending(=> {

            $profileInModelA.fetch((err) => {

              console.log($profileInModelA.get('foo.bar'))
              // expect --> [1, 2, 3]
              // result --> [1, 2, 3, 1, 2, 3]
            })
          })
        })
      })
    })
  })
})

derbyjs / racer

Calling `setDiffDeep` from different models can set duplicate data on a given document in a race condition #258