Hacked defer support

customNetworkLayer.js

 const defaultNetworkLayer = new Relay.DefaultNetworkLayer(endpoint, {
    fetchTimeout,
    retryDelays,
    headers: {...authHeaders, ...customHeaders}
  });
  defaultNetworkLayer.supports = (...options) => {
    return options.every(option => {
      if (option === 'defer') {
        return true;
      }
      return false;
    });
  };
  
  // I am splitting the the requests into ones I found I could execute in parallel and the ones that need to wait on
  // results. So that would be the ref-queries I suppose. Not sure if checking for it being deferred and it having'request._query.getBatchCall()' 
  // is the best way of doing it, but that seemed to be consistent a consistent way for me.
  // This code is merely a proof of concept and also wouldn't work for nested ref-queries
  // Also I noticed that I still got the 'Deferred queries are not supported' invariant, but everything in my test-case got loaded nevertheless.
  defaultNetworkLayer.sendQueries = (requests) => {
    var deferredFragmentRequests = [];
    var nonDeferredRequests = [];
    requests.forEach(function (request) {
      if (request._query.isDeferred() && request._query.getBatchCall()) {
        deferredFragmentRequests.push(request);
      } else {
        nonDeferredRequests.push(request)
      }
    });

    return Promise.all(nonDeferredRequests.map(request => (
      defaultNetworkLayer._sendQuery(request).then(
        result => result.json()
      ).then(payload => {
        if (payload.hasOwnProperty('errors')) {
          var error = new Error('Server request for query `' + request.getDebugName() + '` ' + 'failed for the following reasons:\n\n' + formatRequestErrors(request, payload.errors));
          error.source = payload;
          request.reject(error);
        } else if (!payload.hasOwnProperty('data')) {
          request.reject(new Error(
            'Server response was missing for query ' +
            `\`${request.getDebugName()}\`.`
          ));
        } else {
          deferredFragmentRequests.forEach((deferredFragmentRequest) => {
            // Match the expected id from the ref query agains the returned request id
            if (deferredFragmentRequest._query.getBatchCall() && deferredFragmentRequest._query.getBatchCall().sourceQueryID == request.getID()) {
              const fullPath = deferredFragmentRequest._query.getBatchCall().sourceQueryPath.slice(4).split('.');
              let deferredFragmentVariable = payload.data[request._query.getFieldName()];
              fullPath.forEach((pathPart) => {
                deferredFragmentVariable = deferredFragmentVariable[pathPart];
              });
              
              // override things in such a way that it this request can be succesfull
              deferredFragmentRequest._query.__batchCall__ = null;
              deferredFragmentRequest._query.__identifyingArg__ = {
                name: "id",
                value: deferredFragmentVariable,
                type: "ID!"
              };
              deferredFragmentRequest._query.__calls__ = [{
                "name": "id",
                "value": deferredFragmentVariable,
                "type": "ID!"
              }];
              deferredFragmentRequest._query.__concreteNode__.fieldName = 'node';

              defaultNetworkLayer._sendQuery(deferredFragmentRequest).then(function (result) {
                return result.json();
              }).then(function (payload) {
                if (payload.hasOwnProperty('errors')) {
                  var error = new Error('Server request for query `' + request.getDebugName() + '` ' + 'failed for the following reasons:\n\n' + formatRequestErrors(request, payload.errors));
                  error.source = payload;
                  request.reject(error);
                } else if (!payload.hasOwnProperty('data')) {
                  request.reject(new Error('Server response was missing for query `' + request.getDebugName() + '`.'));
                } else {
                  request.resolve({response: payload.data});
                }
              })['catch'](function (error) {
                return request.reject(error);
              });
            }
          });
          request.resolve({response: payload.data});
        }
      }).catch(
        error => request.reject(error)
      )
    )));
  };

  Relay.injectNetworkLayer(defaultNetworkLayer);