feat(client): modify Request to accept Query

re #2

packages/client/src/index.ts

@@ -1,2 +1,3 @@
 export * from 'dgraph-js';
 export { Txn } from './txn';
+export { Request } from './request';

packages/client/src/request.ts

@@ -0,0 +1,32 @@
+import { Request } from 'dgraph-js';
+import { paramsToObj } from './common';
+import { Query } from './types';
+
+declare module 'dgraph-js/generated/api_pb' {
+  export interface Request {
+    _setQuery: (query: string) => void;
+
+    setQuery(query: Query | string): void;
+    setQueryWithVars(query: Query | string, vars?: Record<string, string>): void;
+  }
+}
+
+Request.prototype._setQuery = Request.prototype.setQuery;
+
+Request.prototype.setQuery = function (query) {
+  return typeof query === 'string'
+    ? this._setQuery(query)
+    : this.setQueryWithVars(query, {});
+}
+
+Request.prototype.setQueryWithVars = function (query, vars = {}) {
+  this._setQuery(query.toString());
+
+  const varsMap = this.getVarsMap();
+  const params = typeof query === 'string' ? vars
+    : { ...paramsToObj(query.params()), ...vars };
+
+  Object.keys(params).forEach(k => varsMap.set(k, params[k]));
+}
+
+export { Request };