Styjun

I am getting the following error when attempting to fetch a query fragment:

"You are using the simple (heuristic) fragment matcher, but your queries contain union or interface types. Apollo Client will not be able to accurately map fragments. To make this error go away, use the IntrospectionFragmentMatcher as described in the docs: https://www.apollographql.com/docs/react/recipes/fragment-matching.html"

This is the call that triggers the error.

const sourceData = cache.readFragment(
 id: `$typename:$idToAdd`,
 fragment: gql`
 $sourceFragment
 `,
 );

where sourceFragment is

fragment series on PriceSeries 
 id
 title
 description
 commodity
 region
 location
 isDiscontinued
 order

Apollo seems to be classing the return value of the fragment as a union or interface. I don't think adding the IntrospectionFragmentMatcher should be necessary as we have no need of unions or interfaces, although maybe I'm wrong. Adding __typename to the fragment didn't help.

• How do I remove this error (I may just be missing some gql syntax for typing?)


• Does using fragments mean we should set up the IntrospectionFragmentMatcher regardless.. (the docs say it should only be needed when using fragments on interfaces or unions which we are not)


• Is the error a bug, should I just be hiding the error (it does work as is if you ignore it)

Update

ApolloClient is created as follows

 client = new ApolloClient(
 link: createLink('MY_URL', Apollo.fetch),
 cache: new InMemoryCache(),
 );

You need to create the apollo cache and setup normalization features with dataIdFromObject.

import InMemoryCache, IntrospectionFragmentMatcher from 'apollo-cache-inmemory';

const fragmentMatcher = new IntrospectionFragmentMatcher(
 // Here you may want to pass your introspection query result data,
);

const cache = new InMemoryCache(
 dataIdFromObject: o => o.id,
 fragmentMatcher,
);