fix(types): stop depending on internal graphql typings

CHANGELOG.md

@@ -1,7 +1,10 @@
 # Changelog and release notes
 
-<!-- ## Unreleased -->
+## Unreleased
 <!-- here goes all the unreleased changes descriptions -->
+### Fixes
+- fix broken compatibility with newer `@types/graphql` due to using removed private types (e.g. `MaybePromise`) (#320)
+
 ## v0.17.2
 ### Features
 - add support for defining `resolveType` function for interfaces and unions (#319)

src/interfaces/Maybe.ts

@@ -0,0 +1,3 @@
+export type Maybe<T> = T | null | undefined;
+
+export type MaybePromise<T> = Promise<T> | T;

src/interfaces/TypeResolver.ts

@@ -1,8 +1,7 @@
 import { GraphQLResolveInfo } from "graphql";
-import { MaybePromise } from "graphql/jsutils/MaybePromise";
-import Maybe from "graphql/tsutils/Maybe";
 
 import { ClassType } from "./ClassType";
+import { MaybePromise, Maybe } from "./Maybe";
 
 export type TypeResolver<TSource, TContext> = (
   value: TSource,

src/interfaces/index.ts

@@ -2,6 +2,7 @@ export { MiddlewareFn, NextFn, MiddlewareInterface } from "./Middleware";
 export * from "./AuthChecker";
 export * from "./ClassType";
 export * from "./Complexity";
+export * from "./Maybe";
 export * from "./Publisher";
 export * from "./ResolverData";
 export * from "./ResolverFilterData";