Add Support for Request cancellation

[wgottschalk]

I'm implementing autocomplete right now using apollo-link-rest. Everytime the search term changes, apollo client (useQuery) will kick off a new request. However, I don't want to have my server keep doing expensive search ranking for a result that I'm going to ignore so I'd like to cancel the request.

maybe something like?

const MyComponent  = () => {
  const abortController = useRef(new AbortController());
  const [searchTerm, setSearchTerm] = useState("");
  useEffect(() => {
    abortController.current.abort()
    abortController.current = new AbortController()
  }, [searchTerm])

  const { error, loading, data } = useQuery(SearchQuery, {
    variables: { searchTerm }
    context: { fetchOptions: { signal: abortController.current.signal } }
  })
}

All you really have to do is grab this fetchOptions field from context and make it available in requestOptions and everything should workout correctly

[fbartho]

This seems like a neat feature! Be aware that master includes ApolloClient @ 3.0 code in it, and they've delayed launching that version of ApolloClient so-- adding this feature may be a bit tricky depending on which version you want to ship it for.