HeuristicFragmentMatcher enforces __typename on ROOT_QUERY

[dulakm]

Intended outcome:
When using Fragment on Query warning is not shown and query is executed.

Actual outcome:
When I use query including Fragment defined on Query, HeuristicFragmentMatcher fails on checking the store as ROOT_QUERY doesn't contain __typename.

Stacktrace: https://gist.github.com/dulakm/6ee9d6afb7a730a38bab714875bd3540

How to reproduce the issue:

1. Firstly, make some query, that doesn't contain any fragments. In my scenario, this is the query:

   1.  query GetUserConfig($scope: String!) {
           configs(configsFilter: {
               scopeIs: $scope
           }) {
               id,
               data
           }
       }
      

   2. As roots are not appended with __typename (Don't add fields to the root mutation/query #463) what ends up in cache is this: {"data":{"configs":[{"id":"SOME_ID","data":"SOME_DATA","__typename":"Config"}]}}. Data have its __typename however as expected, ROOT_QUERY doesn't.
2. Secondly, let's make query containing some fragment. In my case:

   1.  query SomeQuery {
           ...EnumsFragment
       }
      
       fragment EnumsFragment on Query {
           supportedOptions {
               name
           }
       }
      

   2. Now in this very exact moment the warning happens (attached stacktrace) and the query is prevented from being sent to server. When debugging the issue what I have found out:
      1. Fragment matcher is called by readFromStore.js#153
      2. Basic look at the parameters:

      rootValue
      {type: "id", id: "ROOT_QUERY", generated: true, typename: "Query"}
      typeCondition
      "Query"
      contextValue
      {store: DepTrackingCache, dataIdFromObject: ƒ, cacheRedirects: {…}}
      

      3. fragmentMatcher.js#13 gets object which is in fact ROOT_QUERY (the one from step 1.)
      4. It passes checks on lines 14 and 17
      5. On line 20 it is affirmed that ROOT_QUERY doesn't contain __typename and warning is thrown.

Versions

  System:
    OS: Windows 10
  Binaries:
    Node: 8.10.0 - C:\Applications\nodejs\node.EXE
    Yarn: 1.13.0 - C:\Users\moro\AppData\Roaming\npm\yarn.CMD
    npm: 6.7.0 - C:\Applications\nodejs\npm.CMD
  Browsers:
    Edge: 42.17134.1.0
  npmPackages:
    apollo-cache-inmemory: 1.3.12 => 1.3.12
    apollo-client: 2.4.8 => 2.4.8
    apollo-link: 1.2.6 => 1.2.6
    apollo-link-context: 1.0.12 => 1.0.12
    apollo-link-error: 1.1.5 => 1.1.5
    apollo-link-http: 1.5.9 => 1.5.9
    react-apollo: 2.3.3 => 2.3.3

[hwillson]

Fragment matchers have been replaced by possibleTypes. Thanks!