readQueryFromStore using returnPartialData returns an empty object if some fields are empty

[dahjelle]

What should readQueryFromStore return when returnPartialData is true and some requested fields are missing? It currently returns an empty object. I'm not sure what the best approach is. Certainly, for my needs, returning null or even undefined for the missing fields is nicest, and I think makes sense since returnPartialData is expected to get the full data at a later point in time from the server, anyway. Alternatively, perhaps returnPartialData just needs some more clarification.

Here's some code that shows the issue I'm having. The last 2 readQueryFromStore calls demonstrate the issue.

const dataIdFromObject = function(obj) {
  return obj.id;
};
const ID_1 = 'id-1';
const ID_2 = 'id-2';
const NAME = 'Peter Wimsey';
const queryWithId = gql`{
  person {
    id
  }
}`;
const queryWithIdAndName = gql`{
  person {
    id
    name
  }
}`;
let state = store.getState().apollo;

/***************************/
// set up initial store with a person with an id and a name
state.data = writeQueryToStore({
  result: {
    person: [{
      id: ID_1,
      name: NAME
    }]
  },
  query: queryWithIdAndName,
  store: state.data,
  dataIdFromObject
});
/***************************/

/***************************/
// update the store as per https://github.com/apollostack/apollo-client/issues/180#issuecomment-219517006
// NOTE: we don't have name information for this person (yet?)
let people = readQueryFromStore({
  query: queryWithId,
  store: state.data
});
people.person.push({
  id: ID_2
});
state.data = writeQueryToStore({
  result: people,
  query: queryWithId,
  store: state.data,
  dataIdFromObject
});
/***************************/

// read the data back out
// this works as expected
const ids = readQueryFromStore({
  query: queryWithId,
  store: state.data
});
console.log('ids', ids); // { person: [ { id: 'id-1' }, { id: 'id-2' } ] }, like I'd expect
// this DOESN'T work like I'd expect
const getPartialData = readQueryFromStore({
  query: queryWithIdAndName,
  store: state.data,
  returnPartialData: true
});
console.log('getPartialData', getPartialData);
// {}? why? can I get { person: [ { id: 'id-1', name: 'Peter Wimsey' }, { id: 'id-2' } ] } or some such?
// if I don't include `returnPartialData: true`, it throws a `Can't find field name on object` error