Cache invalidation doesn't work on aliased queries

[SavelevMatthew]

Hi, thanks for such a useful library for Apollo-client. Recently I decided to apply it to my project and found the following error:

If you use alias for query, the cache will not be invalidated:

query getMetersByAddressKey($where: MeterWhereInput!, $first: Int!, $skip: Int!) {
    meters: allMeters(
        where: $where
        first: $first
        skip: $skip
    ) {
        id
    }

    meta: _allMetersMeta(where: $where) {
        count
    }
}

I've started digging into why this was happening and discovered the following:

1. When you call super.diff right here it returns result in format like so (aliases as keys):

{
  "meters": [
    {"id": 123, "__typename": "Meter"},
    {"id": 456, "__typename": "Meter"},
  ]
  "meta" {}
}

2. When it goes to cacheResultProcessor.processReadResult and here you obtain fieldName (allMeters in my case) and resultKeyName (meters in my case) and then pass fieldName to processReadSubResult function
3. The first thing processReadSubResult does is extracting field from result. So in my case it tries to get result['allMeters'], which resolved in undefined and processReadSubResult returns Completed status.

I propose to fix this by passing in processReadSubResult in step 2 value like so resultKeyName || fieldName.

What do you think?

[SavelevMatthew]

Implemented a fix:
#84

[pahaz]

Nice catch! I have similar issues

[danReynolds]

lgtm! Merging