chrome.storage.local.get should return a deep copy of objects

[carbureted]

Presently it's possible for test behavior and real code behavior to differ because changes to objects returned by chrome.storage.local.get can be "persistently" modified in functions that do not save the result to chrome.storage.

interface Thing {
  array: string[]
}

function saveThing(thing: Thing) {
  return new Promise((resolve) => {
    chrome.storage.local.set({ thing: thing }, () => {
      resolve(true)
    })
  })
}

function getThing(): Promise<Thing> {
  return new Promise((resolve) => {
    chrome.storage.local.get('thing', (data: { thing: Thing }) => {
      resolve(data.thing)
    })
  })
}

function doSomethingWithThing(thing: Thing) {
  thing.array = thing.array.map((string) => {
    return 'bar'
  })
}

describe('Thing should work', () => {
  it('thing works', async () => {
    await saveThing({ array: ['foo'] })
    let thing = await getThing()
    expect(thing.array[0]).toEqual('foo')

    doSomethingWithThing(thing)

    thing = await getThing()
    expect(thing.array[0]).toEqual('foo')
  })
})

Expected: "foo"
Received: "bar"